Author name code: ramsey
ADS astronomy entries on 2022-09-14
author:"Ramsey, Lawrence W." OR author:"Ramsey, Larry W."
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Title: TOI-3757 b: A Low-density Gas Giant Orbiting a
Solar-metallicity M Dwarf
Authors: Kanodia, Shubham; Libby-Roberts, Jessica; Cañas, Caleb I.;
Ninan, Joe P.; Mahadevan, Suvrath; Stefansson, Gudmundur; Lin, Andrea
S. J.; Jones, Sinclaire; Monson, Andrew; Parker, Brock A.; Kobulnicky,
Henry A.; Swaby, Tera N.; Powers, Luke; Beard, Corey; Bender, Chad F.;
Blake, Cullen H.; Cochran, William D.; Dong, Jiayin; Diddams, Scott A.;
Fredrick, Connor; Gupta, Arvind F.; Halverson, Samuel; Hearty, Fred;
Logsdon, Sarah E.; Metcalf, Andrew J.; McElwain, Michael W.; Morley,
Caroline; Rajagopal, Jayadev; Ramsey, Lawrence W.; Robertson, Paul;
Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Wisniewski, John;
Wright, Jason T.
Bibcode: 2022AJ....164...81K
Altcode: 2022arXiv220307178K
We present the discovery of a new Jovian-sized planet, TOI-3757
b, the lowest-density transiting planet known to orbit an M dwarf
(M0V). This planet was discovered around a solar-metallicity M dwarf,
using Transiting Exoplanet Survey Satellite photometry and confirmed
with precise radial velocities from the Habitable-zone Planet Finder
(HPF) and NEID. With a planetary radius of 12.0 ${}_{-0.5}^{+0.4}$ R
⊕ and mass of 85.3 ${}_{-8.7}^{+8.8}$ M ⊕, not
only does this object add to the small sample of gas giants (~10) around
M dwarfs, but also its low density ( $\rho ={0.27}_{-0.04}^{+0.05}$
g cm-3) provides an opportunity to test theories of planet
formation. We present two hypotheses to explain its low density; first,
we posit that the low metallicity of its stellar host (~0.3 dex lower
than the median metallicity of M dwarfs hosting gas giants) could have
played a role in the delayed formation of a solid core massive enough
to initiate runaway accretion. Second, using the eccentricity estimate
of 0.14 ± 0.06, we determine it is also plausible for tidal heating to
at least partially be responsible for inflating the radius of TOI-3757b
b. The low density and large scale height of TOI-3757 b makes it an
excellent target for transmission spectroscopy studies of atmospheric
escape and composition (transmission spectroscopy measurement of ~
190). We use HPF to perform transmission spectroscopy of TOI-3757 b
using the helium 10830 Å line. Doing this, we place an upper limit
of 6.9% (with 90% confidence) on the maximum depth of the absorption
from the metastable transition of He at ~10830 Å, which can help
constraint the atmospheric mass-loss rate in this energy-limited regime.
Title: The Active Chromospheres of Lithium-Rich Red Giant Stars
Authors: Sneden, Christopher; Afsar, Melike; Bozkurt, Zeynep; Adamow,
Monika; Mallick, Anohita; Reddy, Bacham E.; Janowiecki, Steven;
Mahadevan, Suvrath; Bowler, Brendan P.; Hawkins, Keith; Lind, Karin;
Dupree, Andrea K.; Ninan, Joe P.; Nagarajan, Neel; Bocek Topcu,
Gamze; Froning, Cynthia S.; Bender, Chad F.; Terrien, Ryan; Ramsey,
Lawrence W.; Mace, Gregory N.
Bibcode: 2022arXiv220905941S
Altcode:
We have gathered near-infrared $zyJ$-band high resolution spectra
of nearly 300 field red giant stars with known lithium abundances
in order to survey their \species{He}{i} $\lambda$10830 absorption
strengths. This transition is an indicator of chromospheric activity
and/or mass loss in red giants. The majority of stars in our sample
reside in the red clump or red horizontal branch based on their
$V-J,M_V$ color-magnitude diagram and their Gaia \teff, \logg\
values. Most of our target stars are Li-poor in the sense of having
normally low Li abundances, defined here as \eps{Li}~$<$~1.25. Over
90\% of these Li-poor stars have weak $\lambda$10830 features. But
more than half of the 83 Li-rich stars (\eps{Li}~$>$~1.25) have strong
$\lambda$10830 absorptions. These large $\lambda$10830 lines signal
excess chromospheric activity in Li-rich stars; there is almost no
indication of significant mass loss. The Li-rich giants also may have a
higher binary fraction than do Li-poor stars, based on their astrometric
data. It appears likely that both residence on the horizontal branch
and present or past binary interaction play roles in the significant
Li-He connection established in this survey.
Title: TOI-3714 b and TOI-3629 b: Two Gas Giants Transiting M Dwarfs
Confirmed with the Habitable-zone Planet Finder and NEID
Authors: Cañas, Caleb I.; Kanodia, Shubham; Bender, Chad F.;
Mahadevan, Suvrath; Stefánsson, Guđhmundur; Cochran, William D.;
Lin, Andrea S. J.; Hwang, Hsiang-Chih; Powers, Luke; Monson, Andrew;
Green, Elizabeth M.; Parker, Brock A.; Swaby, Tera N.; Kobulnicky,
Henry A.; Wisniewski, John; Gupta, Arvind F.; Everett, Mark E.;
Jones, Sinclaire; Anjakos, Benjamin; Beard, Corey; Blake, Cullen H.;
Diddams, Scott A.; Dong, Zehao; Fredrick, Connor; Hakemiamjad, Elnaz;
Hebb, Leslie; Libby-Roberts, Jessica E.; Logsdon, Sarah E.; McElwain,
Michael W.; Metcalf, Andrew J.; Ninan, Joe P.; Rajagopal, Jayadev;
Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita; Ruhle, Jacob;
Schwab, Christian; Terrien, Ryan C.; Wright, Jason T.
Bibcode: 2022AJ....164...50C
Altcode: 2022arXiv220109963C
We confirm the planetary nature of two gas giants discovered by the
Transiting Exoplanet Survey Satellite to transit M dwarfs. TOI-3714
(V = 15.24, J = 11.74) is an M2 dwarf hosting a hot Jupiter (M
p = 0.70 ± 0.03 M J and R p = 1.01
± 0.03 R J ) on an orbital period of 2.154849 ± 0.000001
days with a resolved white dwarf companion. TOI-3629 (V = 14.63, J =
11.42) is an M1 dwarf hosting a hot Jupiter (M p = 0.26
± 0.02 M J and R p =0.74 ± 0.02 R
J ) on an orbital period of ${3.936551}_{-0.000006}^{+0.000005}$
days. We characterize each transiting companion using a combination
of ground-based and space-based photometry, speckle imaging, and
high-precision velocimetry from the Habitable-zone Planet Finder and
the NEID spectrographs. With the discovery of these two systems, there
are now nine M dwarfs known to host transiting hot Jupiters. Among
this population, TOI-3714 b (T eq = 750 ± 20 K and TSM
= 98 ± 7) and TOI-3629 b (T eq = 690 ± 20 K and TSM =
80 ± 9) are warm gas giants amenable to additional characterization
with transmission spectroscopy to probe atmospheric chemistry and,
for TOI-3714, obliquity measurements to probe formation scenarios.
Title: Overview and Current Status of the NEID Data Reduction Pipeline
Authors: Bender, Chad; Ninan, Joe; Terrien, Ryan; Roy, Arpita; Esplin,
Taran; Kaplan, Kyle; Cañas, Caleb; Fulton, Benjamin; Gupta, Arvind;
Halverson, Samuel; Kanodia, Shubham; Laher, Russ; Lin, Andrea; Salazar
Rivera, Noah; Blake, Cullen; Diddams, Scott; Gong, Qian; Hearty,
Frederick; Li, Dan; Logsdon, Sarah; Lubar, Emily; Mahadevan, Suvrath;
McElwain, Michael; Monson, Andrew; Nitroy, Colin; Rajagopal, Jayadev;
Ramsey, Lawrence; Robertson, Paul; Schwab, Christian; Stefansson,
Gudmundur; Wright, Jason
Bibcode: 2022AAS...24040101B
Altcode:
The NEID precision radial velocity spectrometer at the 3.5-m WIYN
Observatory on Kitt Peak began full science operations in summer
2021 and since then has been producing routine data for a wide range
of scientific programs. These include nighttime observations for GO
programs led by PIs across the astronomy community and the GTO program
led by the NEID instrument team, as well as the Sun-as-a-star program
which uses the NEID solar telescope during daytime hours. Data from
these programs are automatically processed by the NEID Data Reduction
Pipeline (DRP), which was developed by the NEID instrument team and
is operated by the NASA Exoplanet Science Center. The DRP processes
raw, uncalibrated two-dimensional images from the spectrometer into
fully calibrated, one-dimensional spectra. It then derives radial
velocities, telluric absorption models, stellar activity metrics, and
other high-level products, and provides these to end users. In stellar
targets with particularly low levels of activity, the DRP has retrieved
radial velocities at the 30 cm/s level. The DRP has also demonstrated
the ability to successfully process targets well outside of the prime
NEID parameter space of main sequence FGK stars, including red M-dwarfs,
observations with low signal-to-noise, solar-system targets, and a
variety of other astrophysical objects. In this presentation, we will
describe the methodology and algorithms behind the DRP, as well as the
data products that are produced and available. We will also provide
details of DRP upgrades that have been implemented subsequent to the
original release in June 2021, and plans for future improvements.
Title: The Warm Neptune GJ 3470b Has a Polar Orbit
Authors: Stefànsson, Guđmundur; Mahadevan, Suvrath; Petrovich,
Cristobal; Winn, Joshua N.; Kanodia, Shubham; Millholland, Sarah
C.; Maney, Marissa; Cañas, Caleb I.; Wisniewski, John; Robertson,
Paul; Ninan, Joe P.; Ford, Eric B.; Bender, Chad F.; Blake, Cullen
H.; Cegla, Heather; Cochran, William D.; Diddams, Scott A.; Dong,
Jiayin; Endl, Michael; Fredrick, Connor; Halverson, Samuel; Hearty,
Fred; Hebb, Leslie; Hirano, Teruyuki; Lin, Andrea S. J.; Logsdon,
Sarah E.; Lubar, Emily; McElwain, Michael W.; Metcalf, Andrew J.;
Monson, Andrew; Rajagopal, Jayadev; Ramsey, Lawrence W.; Roy, Arpita;
Schwab, Christian; Schweiker, Heidi; Terrien, Ryan C.; Wright, Jason T.
Bibcode: 2022ApJ...931L..15S
Altcode: 2021arXiv211101295S
The warm Neptune GJ 3470b transits a nearby (d = 29 pc) bright
slowly rotating M1.5-dwarf star. Using spectroscopic observations
during two transits with the newly commissioned NEID spectrometer
on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the
classical Rossiter-McLaughlin effect, yielding a sky-projected
obliquity of $\lambda ={98}_{-12}^{+15\ \circ }$ and a $v\sin
i={0.85}_{-0.33}^{+0.27}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . Leveraging
information about the rotation period and size of the host star,
our analysis yields a true obliquity of $\psi ={95}_{-8}^{+9\
\circ }$ , revealing that GJ 3470b is on a polar orbit. Using
radial velocities from HIRES, HARPS, and the Habitable-zone
Planet Finder, we show that the data are compatible with a
long-term radial velocity (RV) slope of $\dot{\gamma }=-0.0022\pm
0.0011\,{\rm{m}}\,{{\rm{s}}}^{-1}\,{\mathrm{day}}^{-1}$ over a baseline
of 12.9 yr. If the RV slope is due to acceleration from another
companion in the system, we show that such a companion is capable of
explaining the polar and mildly eccentric orbit of GJ 3470b using
two different secular excitation models. The existence of an outer
companion can be further constrained with additional RV observations,
Gaia astrometry, and future high-contrast imaging observations. Lastly,
we show that tidal heating from GJ 3470b's mild eccentricity has most
likely inflated the radius of GJ 3470b by a factor of ~1.5-1.7, which
could help account for its evaporating atmosphere.
Title: Observing the Sun as a Star: Design and Early Results from
the NEID Solar Feed
Authors: Lin, Andrea S. J.; Monson, Andrew; Mahadevan, Suvrath; Ninan,
Joe P.; Halverson, Samuel; Nitroy, Colin; Bender, Chad F.; Logsdon,
Sarah E.; Kanodia, Shubham; Terrien, Ryan C.; Roy, Arpita; Luhn,
Jacob K.; Gupta, Arvind F.; Ford, Eric B.; Hearty, Fred; Laher, Russ
R.; Hunting, Emily; McBride, William R.; Salazar Rivera, Noah Isaac;
Rajagopal, Jayadev; Wolf, Marsha J.; Robertson, Paul; Wright, Jason T.;
Blake, Cullen H.; Cañas, Caleb I.; Lubar, Emily; McElwain, Michael
W.; Ramsey, Lawrence W.; Schwab, Christian; Stefansson, Gudmundur
Bibcode: 2022AJ....163..184L
Altcode: 2021arXiv211205711L
Efforts with extreme-precision radial velocity (EPRV) instruments
to detect small-amplitude planets are largely limited, on many
timescales, by the effects of stellar variability and instrumental
systematics. One avenue for investigating these effects is the use
of small solar telescopes which direct disk-integrated sunlight to
these EPRV instruments, observing the Sun at high cadence over months
or years. We have designed and built a solar feed system to carry out
"Sun-as-a-star" observations with NEID, a very high precision Doppler
spectrometer recently commissioned at the WIYN 3.5 m Telescope at
Kitt Peak National Observatory. The NEID solar feed has been taking
observations nearly every day since 2020 December; data is publicly
available at the NASA Exoplanet Science Institute NEID Solar Archive:
https://neid.ipac.caltech.edu/search_solar.php. In this paper, we
present the design of the NEID solar feed and explanations behind our
design intent. We also present early radial velocity (RV) results
which demonstrate NEID's RV stability on the Sun over 4 months of
commissioning: 0.66 m s-1 rms under good sky conditions
and improving to 0.41 m s-1 rms under best conditions.
Title: Rotational Modulation of Spectroscopic Zeeman Signatures in
Low-mass Stars
Authors: Terrien, Ryan C.; Keen, Allison; Oda, Katy; Parts(they/them),
Winter; Stefánsson, Guðmundur; Mahadevan, Suvrath; Robertson, Paul;
Ninan, Joe P.; Beard, Corey; Bender, Chad F.; Cochran, William D.;
Cunha, Katia; Diddams, Scott A.; Fredrick, Connor; Halverson, Samuel;
Hearty, Fred; Ickler, Adam; Kanodia, Shubham; Libby-Roberts, Jessica
E.; Lubin, Jack; Metcalf, Andrew J.; Olsen, Freja; Ramsey, Lawrence
W.; Roy, Arpita; Schwab, Christian; Smith, Verne V.; Turner, Ben
Bibcode: 2022ApJ...927L..11T
Altcode: 2022arXiv220111288T
Accurate tracers of the stellar magnetic field and rotation are
cornerstones for the study of M dwarfs and for reliable detection and
characterization of their exoplanetary companions. Such measurements
are particularly challenging for old, slowly rotating, fully convective
M dwarfs. To explore the use of new activity and rotation tracers,
we examined multiyear near-infrared (NIR) spectroscopic monitoring of
two such stars-GJ 699 (Barnard's Star) and Teegarden's Star-carried
out with the Habitable-zone Planet Finder spectrograph. We detected
periodic variations in absorption line widths across the stellar
spectrum, with higher amplitudes toward longer wavelengths. We
also detected similar variations in the strength and width of
the 12435.67 Å neutral potassium (K I) line, a known tracer of
the photospheric magnetic field. Attributing these variations to
rotational modulation, we confirm the known 145 ± 15 day rotation
period of GJ 699, and measure the rotation period of Teegarden's Star
to be 99.6 ± 1.4 days. Based on simulations of the K I line and the
wavelength dependence of the line-width signal, we argue that the
observed signals are consistent with varying photospheric magnetic
fields and the associated Zeeman effect. These results highlight the
value of detailed line profile measurements in the NIR for diagnosing
stellar magnetic field variability. Such measurements may be pivotal for
disentangling activity and exoplanet-related signals in spectroscopic
monitoring of old, low-mass stars.
Title: An Eccentric Brown Dwarf Eclipsing an M dwarf
Authors: Cañas, Caleb I.; Mahadevan, Suvrath; Bender, Chad F.;
Salazar Rivera, Noah Isaac; Monson, Andrew; Beard, Corey; Lubin, Jack;
Robertson, Paul; Gupta, Arvind F.; Cochran, William D.; Fredrick,
Connor; Hearty, Fred; Jones, Sinclaire; Kanodia, Shubham; Lin,
Andrea S. J.; Ninan, Joe P.; Ramsey, Lawrence W.; Schwab, Christian;
Stefánsson, Guđmundur
Bibcode: 2022AJ....163...89C
Altcode: 2021arXiv211203959C
We report the discovery of an M = 67 ± 2M J brown
dwarf transiting the early M dwarf TOI-2119 on an eccentric orbit
(e = 0.3362 ± 0.0005) at an orbital period of 7.200861 ± 0.000005
days. We confirm the brown dwarf nature of the transiting companion
using a combination of ground-based and space-based photometry
and high-precision velocimetry from the Habitable-zone Planet
Finder. Detection of the secondary eclipse with TESS photometry
enables a precise determination of the eccentricity and reveals the
brown dwarf has a brightness temperature of 2100 ± 80 K, a value
which is consistent with an early L dwarf. TOI-2119 is one of the most
eccentric known brown dwarfs with P < 10 days, possibly due to the
long circularization timescales for an object orbiting an M dwarf. We
assess the prospects for determining the obliquity of the host star to
probe formation scenarios and the possibility of additional companions
in the system using Gaia EDR3 and our radial velocities.
Title: High-resolution Near-infrared Spectroscopy of a Flare around
the Ultracool Dwarf vB 10
Authors: Kanodia, Shubham; Ramsey, Lawrence W.; Maney, Marissa;
Mahadevan, Suvrath; Cañas, Caleb I.; Ninan, Joe P.; Monson, Andrew;
Kowalski, Adam F.; Goumas, Maximos C.; Stefansson, Gudmundur;
Bender, Chad F.; Cochran, William D.; Diddams, Scott A.; Fredrick,
Connor; Halverson, Samuel; Hearty, Fred; Janowiecki, Steven; Metcalf,
Andrew J.; Odewahn, Stephen C.; Robertson, Paul; Roy, Arpita; Schwab,
Christian; Terrien, Ryan C.
Bibcode: 2022ApJ...925..155K
Altcode: 2021arXiv211114647K
We present high-resolution observations of a flaring event in the
M8 dwarf vB 10 using the near-infrared Habitable-zone Planet Finder
(HPF) spectrograph on the Hobby-Eberly Telescope. The high stability of
HPF enables us to accurately subtract a vB 10 quiescent spectrum from
the flare spectrum to isolate the flare contributions and study the
changes in the relative energy of the Ca II infrared triplet, several
Paschen lines, the He λ10830 triplet lines, and to select iron and
magnesium lines in HPF's bandpass. Our analysis reveals the presence
of a red asymmetry in the He λ10830 triplet, which is similar to
signatures of coronal rain in the Sun. Photometry of the flare derived
from an acquisition camera before spectroscopic observations and the
ability to extract spectra from up-the-ramp observations with the HPF
infrared detector enable us to perform time-series analysis of part of
the flare and provide coarse constraints on the energy and frequency
of such flares. We compare this flare with historical observations of
flares around vB 10 and other ultracool M dwarfs and attempt to place
limits on flare-induced atmospheric mass loss for hypothetical planets
around vB 10.
Title: Gaia 20eae: A Newly Discovered Episodically Accreting
Young Star
Authors: Ghosh, Arpan; Sharma, Saurabh; Ninan, Joe P.; Ojha, Devendra
K.; Bhatt, Bhuwan C.; Kanodia, Shubham; Mahadevan, Suvrath; Stefansson,
Gudmundur; Yadav, R. K.; Gour, A. S.; Pandey, Rakesh; Sinha, Tirthendu;
Panwar, Neelam; Wisniewski, John P.; Cañas, Caleb I.; Lin, Andrea
S. J.; Roy, Arpita; Hearty, Fred; Ramsey, Lawrence; Robertson, Paul;
Schwab, Christian
Bibcode: 2022ApJ...926...68G
Altcode: 2021arXiv211201717G
The Gaia Alert System issued an alert on 2020 August 28, on Gaia 20eae
when its light curve showed a ~4.25 magnitude outburst. We present
multiwavelength photometric and spectroscopic follow-up observations of
this source since 2020 August and identify it as the newest member of
the FUor/EXor family of sources. We find that the present brightening of
Gaia 20eae is not due to the dust-clearing event but due to an intrinsic
change in the spectral energy distribution. The light curve of Gaia
20eae shows a transition stage during which most of its brightness
(~3.4 mag) has occurred on a short timescale of 34 days with a rise
rate of 3 mag/month. Gaia 20eae has now started to decay at a rate
of 0.3 mag/month. We have detected a strong P Cygni profile in Hα,
which indicates the presence of winds originating from regions close to
the accretion. We find signatures of very strong and turbulent outflow
and accretion in Gaia 20eae during this outburst phase. We have also
detected a redshifted absorption component in all of the Ca II IR
triplet lines consistent with a signature of hot infalling gas in
the magnetospheric accretion funnel. This enables us to constrain the
viewing angle with respect to the accretion funnel. Our investigation of
Gaia 20eae points toward magnetospheric accretion being the phenomenon
for the current outburst.
Title: A Hot Mars-sized Exoplanet Transiting an M Dwarf
Authors: Cañas, Caleb I.; Mahadevan, Suvrath; Cochran, William D.;
Bender, Chad F.; Feigelson, Eric D.; Harman, C. E.; Kopparapu, Ravi
Kumar; Caceres, Gabriel A.; Diddams, Scott A.; Endl, Michael; Ford,
Eric B.; Halverson, Samuel; Hearty, Fred; Jones, Sinclaire; Kanodia,
Shubham; Lin, Andrea S. J.; Metcalf, Andrew J.; Monson, Andrew; Ninan,
Joe P.; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita; Schwab,
Christian; Stefánsson, Guđmundur
Bibcode: 2022AJ....163....3C
Altcode: 2021arXiv211203958C
We validate the planetary nature of an ultra-short-period planet
orbiting the M dwarf KOI-4777. We use a combination of space-based
photometry from Kepler, high-precision, near-infrared Doppler
spectroscopy from the Habitable-zone Planet Finder, and adaptive
optics imaging to characterize this system. KOI-4777.01 is a Mars-sized
exoplanet (R p = 0.51 ± 0.03R ⊕) orbiting the
host star every 0.412 days (~9.9 hr). This is the smallest validated
ultra-short period planet known and we see no evidence for additional
massive companions using our HPF RVs. We constrain the upper 3σ mass
to M p < 0.34 M ⊕ by assuming the planet
is less dense than iron. Obtaining a mass measurement for KOI-4777.01
is beyond current instrumental capabilities.
Title: The HETDEX Instrumentation: Hobby-Eberly Telescope Wide-field
Upgrade and VIRUS
Authors: Hill, Gary J.; Lee, Hanshin; MacQueen, Phillip J.; Kelz,
Andreas; Drory, Niv; Vattiat, Brian L.; Good, John M.; Ramsey,
Jason; Kriel, Herman; Peterson, Trent; DePoy, D. L.; Gebhardt,
Karl; Marshall, J. L.; Tuttle, Sarah E.; Bauer, Svend M.; Chonis,
Taylor S.; Fabricius, Maximilian H.; Froning, Cynthia; Häuser,
Marco; Indahl, Briana L.; Jahn, Thomas; Landriau, Martin; Leck, Ron;
Montesano, Francesco; Prochaska, Travis; Snigula, Jan M.; Zeimann,
Greg; Bryant, Randy; Damm, George; Fowler, J. R.; Janowiecki, Steven;
Martin, Jerry; Mrozinski, Emily; Odewahn, Stephen; Rostopchin, Sergey;
Shetrone, Matthew; Spencer, Renny; Mentuch Cooper, Erin; Armandroff,
Taft; Bender, Ralf; Dalton, Gavin; Hopp, Ulrich; Komatsu, Eiichiro;
Nicklas, Harald; Ramsey, Lawrence W.; Roth, Martin M.; Schneider,
Donald P.; Sneden, Chris; Steinmetz, Matthias
Bibcode: 2021AJ....162..298H
Altcode: 2021arXiv211003843H
The Hobby-Eberly Telescope (HET) Dark Energy Experiment (HETDEX) is
undertaking a blind wide-field low-resolution spectroscopic survey
of 540 deg2 of sky to identify and derive redshifts for a
million Lyα-emitting galaxies in the redshift range 1.9 < z <
3.5. The ultimate goal is to measure the expansion rate of the universe
at this epoch, to sharply constrain cosmological parameters and thus
the nature of dark energy. A major multiyear Wide-Field Upgrade (WFU)
of the HET was completed in 2016 that substantially increased the
field of view to 22' diameter and the pupil to 10 m, by replacing the
optical corrector, tracker, and Prime Focus Instrument Package and by
developing a new telescope control system. The new, wide-field HET
now feeds the Visible Integral-field Replicable Unit Spectrograph
(VIRUS), a new low-resolution integral-field spectrograph (LRS2),
and the Habitable Zone Planet Finder, a precision near-infrared radial
velocity spectrograph. VIRUS consists of 156 identical spectrographs fed
by almost 35,000 fibers in 78 integral-field units arrayed at the focus
of the upgraded HET. VIRUS operates in a bandpass of 3500-5500 Å with
resolving power R ≃ 800. VIRUS is the first example of large-scale
replication applied to instrumentation in optical astronomy to achieve
spectroscopic surveys of very large areas of sky. This paper presents
technical details of the HET WFU and VIRUS, as flowed down from the
HETDEX science requirements, along with experience from commissioning
this major telescope upgrade and the innovative instrumentation suite
for HETDEX.
Title: VizieR Online Data Catalog: Radial velocity follow up of
Barnard's star with HPF (Lubin+, 2021)
Authors: Lubin, J.; Robertson, P.; Stefansson, G.; Ninan, J.;
Mahadevan, S.; Endl, M.; Ford, E.; Wright, J. T.; Beard, C.; Bender,
C.; Cochran, W. D.; Diddams, S. A.; Fredrick, C.; Halverson, S.;
Kanodia, S.; Metcalf, A. J.; Ramsey, L.; Roy, A.; Schwab, C.;
Terrien, R.
Bibcode: 2021yCat..51620061L
Altcode:
Habitable Zone Planet Finder (HPF) is a high-resolution (R~55000)
NIR spectrograph on the 10m Hobby-Eberly Telescope (HET), covering the
Doppler-information-rich z, Y, and J bands from 810 to 1280nm. HPF has
an NIR laser-frequency comb (LFC) calibrator, which has been shown to
enable ~20cm/s calibration precision in 10minute bins and 1.53m/s RV
precision on-sky on Barnard's star over an 3 month baseline. In this
paper, we extend this baseline to 856 days. (1 data file).
Title: A Search for Planetary Metastable Helium Absorption in the
V1298 Tau System
Authors: Vissapragada, Shreyas; Stefánsson, Gudmundur; Greklek-McKeon,
Michael; Oklopčić, Antonija; Knutson, Heather A.; Ninan, Joe P.;
Mahadevan, Suvrath; Cañas, Caleb I.; Chachan, Yayaati; Cochran,
William D.; Collins, Karen A.; Dai, Fei; David, Trevor J.; Halverson,
Samuel; Hawley, Suzanne L.; Hebb, Leslie; Kanodia, Shubham; Kowalski,
Adam F.; Livingston, John H.; Maney, Marissa; Metcalf, Andrew J.;
Morley, Caroline; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita;
Spake, Jessica; Schwab, Christian; Terrien, Ryan C.; Tinyanont,
Samaporn; Vasisht, Gautam; Wisniewski, John
Bibcode: 2021AJ....162..222V
Altcode: 2021arXiv210805358V
Early in their lives, planets endure extreme amounts of ionizing
radiation from their host stars. For planets with primordial
hydrogen and helium-rich envelopes, this can lead to substantial
mass loss. Direct observations of atmospheric escape in young
planetary systems can help elucidate this critical stage of planetary
evolution. In this work, we search for metastable helium absorption-a
tracer of tenuous gas in escaping atmospheres-during transits of three
planets orbiting the young solar analog V1298 Tau. We characterize
the stellar helium line using HET/HPF, and find that it evolves
substantially on timescales of days to months. The line is stable
on hour-long timescales except for one set of spectra taken during
the decay phase of a stellar flare, where absoprtion increased with
time. Utilizing a beam-shaping diffuser and a narrowband filter
centered on the helium feature, we observe four transits with
Palomar/WIRC: two partial transits of planet d (P = 12.4 days), one
partial transit of planet b (P = 24.1 days), and one full transit of
planet c (P = 8.2 days). We do not detect the transit of planet c,
and we find no evidence of excess absorption for planet b, with ΔR
b/R ⋆ < 0.019 in our bandpass. We find
a tentative absorption signal for planet d with ΔR d/R
⋆ = 0.0205 ± 0.054, but the best-fit model requires a
substantial (-100 ± 14 minutes) transit-timing offset on a two-month
timescale. Nevertheless, our data suggest that V1298 Tau d may have
a high present-day mass-loss rate, making it a priority target for
follow-up observations.
Title: VizieR Online Data Catalog: Radial velocities of TOI-1728
with HPF (Kanodia+, 2020)
Authors: Kanodia, S.; Canas, C. I.; Stefansson, G.; Ninan, J. P.;
Hebb, L.; Lin, A. S. J.; Baran, H.; Maney, M.; Terrien, R. C.;
Mahadevan, S.; Cochran, W. D.; Endl, M.; Dong, J.; Bender, C. F.;
Diddams, S. A.; Ford, E. B.; Fredrick, C.; Halverson, S.; Hearty,
F.; Metcalf, A. J.; Monson, A.; Ramsey, L. W.; Robertson, P.; Roy,
A.; Schwab, C.; Wright, J. T.
Bibcode: 2021yCat..18990029K
Altcode:
TOI-1728 was observed by Transiting Exoplanet Survey Satellite
(TESS) in Sector 20 from 2019 December 24 to 2020 January 19 at
two-minute cadence. We observed a transit of TOI-1728b on the
night of 2020 February 22 using the Richard S. Perkin telescope on
the campus of Hobart and William Smith Colleges (Geneva, New York,
United States). The 0.43m (17") f/6.8 Planewave Corrected Dall-Kirkham
(CDK) telescope rests on a Paramount equatorial mount with an SBIG8300M
camera mounted at Cassegrain focus. The camera detector has an array
of 3326x2504, 5.4μm pixels resulting in a ~21x16' field of view. We
obtained a series of 92 consecutive images over 5hr centered on the
target in 1x1 binning mode in the Sloan r' filter. We observed a
transit of TOI-1728b on the night of 2020 February 22 using the 0.6m
telescope located on the roof of the Penn State Davey Laboratory
(University Park, Pennsylvania, United States). The telescope was
installed in 2014 and has an Apogee/Andor Aspen CG42 camera, using a
CCD42-10 2048x2048 pixel chip from e2v with 13.5micron pixels. This
results in a plate scale of ~0.77 per pixel and a field of view of
24'x24'. The observations were made with the Johnson I filter and an
engineered diffuser, with an exposure time of 45s. We observed
TOI-1728 using Habitable Planet Finder (HPF), a high-resolution
(R~55000), NIR (8080-12780Å) precision RVel spectrograph located at
the 10meter Hobby-Eberly Telescope (HET) in Texas. (2 data files).
Title: TOI-532b: The Habitable-zone Planet Finder confirms a Large
Super Neptune in the Neptune Desert orbiting a metal-rich M-dwarf host
Authors: Kanodia, Shubham; Stefansson, Gudmundur; Cañas, Caleb I.;
Maney, Marissa; Lin, Andrea S. J.; Ninan, Joe P.; Jones, Sinclaire;
Monson, Andrew; Parker, Brock A.; Kobulnicky, Henry A.; Rothenberg,
Jason; Beard, Corey; Lubin, Jack; Robertson, Paul; Gupta, Arvind F.;
Mahadevan, Suvrath; Cochran, William D.; Bender, Chad F.; Diddams,
Scott A.; Fredrick, Connor; Halverson, Samuel; Hawley, Suzanne;
Hearty, Fred; Hebb, Leslie; Kopparapu, Ravi; Metcalf, Andrew J.;
Ramsey, Lawrence W.; Roy, Arpita; Schwab, Christian; Schutte, Maria;
Terrien, Ryan C.; Wisniewski, John; Wright, Jason T.
Bibcode: 2021AJ....162..135K
Altcode: 2021arXiv210713670K
We confirm the planetary nature of TOI-532b, using a combination of
precise near-infrared radial velocities with the Habitable-zone Planet
Finder, Transiting Exoplanet Survey Satellite (TESS) light curves,
ground-based photometric follow up, and high-contrast imaging. TOI-532
is a faint (J ~ 11.5) metal-rich M dwarf with Teff = 3957 ±
69 K and [Fe/H] = 0.38 ± 0.04; it hosts a transiting gaseous planet
with a period of ~2.3 days. Joint fitting of the radial velocities
with the TESS and ground-based transits reveal a planet with radius
of 5.82 ± 0.19 R⊕, and a mass of ${61.5}_{-9.3}^{+9.7}$
M⊕. TOI-532b is the largest and most massive super Neptune
detected around an M dwarf with both mass and radius measurements,
and it bridges the gap between the Neptune-sized planets and the
heavier Jovian planets known to orbit M dwarfs. It also follows the
previously noted trend between gas giants and host-star metallicity for
M-dwarf planets. In addition, it is situated at the edge of the Neptune
desert in the Radius-Insolation plane, helping place constraints on
the mechanisms responsible for sculpting this region of planetary
parameter space.
Title: The Habitable-zone Planet Finder Detects a Terrestrial-mass
Planet Candidate Closely Orbiting Gliese 1151: The Likely Source of
Coherent Low-frequency Radio Emission from an Inactive Star
Authors: Mahadevan, Suvrath; Stefánsson, Gudmundur; Robertson, Paul;
Terrien, Ryan C.; Ninan, Joe P.; Holcomb, Rae J.; Halverson, Samuel;
Cochran, William D.; Kanodia, Shubham; Ramsey, Lawrence W.; Wolszczan,
Alexander; Endl, Michael; Bender, Chad F.; Diddams, Scott A.; Fredrick,
Connor; Hearty, Fred; Monson, Andrew; Metcalf, Andrew J.; Roy, Arpita;
Schwab, Christian
Bibcode: 2021ApJ...919L...9M
Altcode: 2021arXiv210202233M
The coherent low-frequency radio emission detected by LOFAR from
Gliese 1151, a quiescent M4.5 dwarf star, has radio emission properties
consistent with theoretical expectations of star-planet interactions for
an Earth-sized planet on a 1- to 5-day orbit. New near-infrared radial
velocities from the Habitable-zone Planet Finder (HPF) spectrometer on
the 10 m Hobby-Eberly Telescope at McDonald Observatory, combined with
previous velocities from HARPS-N, reveal a periodic Doppler signature
consistent with an $m\sin i=2.5\pm 0.5{M}_{\oplus }$ exoplanet on a
2.02-day orbit. Precise photometry from the Transiting Exoplanet Survey
Satellite (TESS) shows no flares or activity signature, consistent with
a quiescent M dwarf. While no planetary transit is detected in the TESS
data, a weak photometric modulation is detectable in the photometry
at a ~2-day period. This independent detection of a candidate planet
signal with the Doppler radial velocity technique adds further weight
to the claim of the first detection of star-exoplanet interactions at
radio wavelengths and helps validate this emerging technique for the
detection of exoplanets.
Title: Stellar Activity Manifesting at a One-year Alias Explains
Barnard b as a False Positive
Authors: Lubin, Jack; Robertson, Paul; Stefansson, Gudmundur; Ninan,
Joe; Mahadevan, Suvrath; Endl, Michael; Ford, Eric; Wright, Jason T.;
Beard, Corey; Bender, Chad; Cochran, William D.; Diddams, Scott A.;
Fredrick, Connor; Halverson, Samuel; Kanodia, Shubham; Metcalf, Andrew
J.; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan
Bibcode: 2021AJ....162...61L
Altcode:
Barnard's star is among the most studied stars given its proximity
to the Sun. It is often considered the radial velocity (RV) standard
for fully convective stars due to its RV stability and equatorial
decl. Recently, an $M\sin i=3.3{M}_{\oplus }$ super-Earth planet
candidate with a 233 day orbital period was announced by Ribas et
al. New observations from the near-infrared Habitable-zone Planet Finder
(HPF) Doppler spectrometer do not show this planetary signal. We ran a
suite of experiments on both the original data and a combined original +
HPF data set. These experiments include model comparisons, periodogram
analyses, and sampling sensitivity, all of which show the signal at
the proposed period of 233 days is transitory in nature. The power in
the signal is largely contained within 211 RVs that were taken within
a 1000 day span of observing. Our preferred model of the system is
one that features stellar activity without a planet. We propose that
the candidate planetary signal is an alias of the 145 day rotation
period. This result highlights the challenge of analyzing long-term,
quasi-periodic activity signals over multiyear and multi-instrument
observing campaigns.
Title: Stellar Activity Manifesting at a One Year Alias Explains
Barnard b as a False Positive
Authors: Lubin, Jack; Robertson, Paul; Stefansson, Gudmundur; Ninan,
Joe; Mahadevan, Suvrath; Endl, Michael; Ford, Eric; Wright, Jason T.;
Beard, Corey; Bender, Chad; Cochran, William D.; Diddams, Scott A.;
Fredrick, Connor; Halverson, Samuel; Kanodia, Shubham; Metcalf, Andrew
J.; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan
Bibcode: 2021arXiv210507005L
Altcode:
Barnard's star is among the most studied stars given its proximity to
the Sun. It is often considered $the$ Radial Velocity (RV) standard
for fully convective stars due to its RV stability and equatorial
declination. Recently, an $M \sin i = 3.3 M_{\oplus}$ super-Earth
planet candidate with a 233 day orbital period was announced by Ribas
et al. (2018). New observations from the near-infrared Habitable-zone
Planet Finder (HPF) Doppler spectrometer do not show this planetary
signal. We ran a suite of experiments on both the original data and
a combined original + HPF data set. These experiments include model
comparisons, periodogram analyses, and sampling sensitivity, all of
which show the signal at the proposed period of 233 days is transitory
in nature. The power in the signal is largely contained within 211
RVs that were taken within a 1000 day span of observing. Our preferred
model of the system is one which features stellar activity without a
planet. We propose that the candidate planetary signal is an alias of
the 145 day rotation period. This result highlights the challenge of
analyzing long-term, quasi-periodic activity signals over multi-year
and multi-instrument observing campaigns.
Title: A Harsh Test of Far-field Scrambling with the Habitable-zone
Planet Finder and the Hobby-Eberly Telescope
Authors: Kanodia, Shubham; Halverson, Samuel; Ninan, Joe P.; Mahadevan,
Suvrath; Stefansson, Gudmundur; Roy, Arpita; Ramsey, Lawrence W.;
Bender, Chad F.; Janowiecki, Steven; Cochran, William D.; Diddams,
Scott A.; Drory, Niv; Endl, Michael; Ford, Eric B.; Hearty, Fred;
Metcalf, Andrew J.; Monson, Andrew; Robertson, Paul; Schwab, Christian;
Terrien, Ryan C.; Wright, Jason T.
Bibcode: 2021ApJ...912...15K
Altcode: 2021arXiv210305148K
The Habitable-zone Planet Finder (HPF) is a fiber-fed precise radial
velocity (RV) spectrograph at the 10 m Hobby-Eberly Telescope (HET). Due
to its fixed-altitude design, the HET pupil changes appreciably
across a track, leading to significant changes of the fiber far-field
illumination. HPF's fiber scrambler is designed to suppress the impact
of these illumination changes on the RVs—but the residual impact on
the RV measurements has yet to be probed on-sky. We use GJ 411, a bright
early type (M2) M dwarf to probe the effects of far-field input trends
due to these pupil variations on HPF RVs. These large changes (∼2x)
in the pupil area and centroid present a harsh test of HPF's far-field
scrambling. Our results show that the RVs are effectively decoupled
from these extreme far-field input changes due to pupil centroid
offsets, attesting to the effectiveness of the scrambler design. This
experiment allows us to test the impact of these changes with large
pupil variation on-sky, something we would not easily be able to do
at a conventional optical telescope. While the pupil and illumination
changes expected at these other telescopes are small, scaling from
our results enables us to estimate and bound these effects, and show
that they are controllable even for the new and next generation of
RV instruments in their quest to beat down instrumental noise sources
toward the goal of a few $\,\mathrm{cm}\,{{\rm{s}}}^{-1}$ .
Title: VizieR Online Data Catalog: Chemical composition of 15 red
giant stars with HPF (Sneden+, 2021)
Authors: Sneden, C.; Afsar, M.; Bozkurt, Z.; Topcu, G. B.; Ozdemir,
S.; Zeimann, G. R.; Froning, C. S.; Mahadevan, S.; Ninan, J. P.;
Bender, C. F.; Terrien, R.; Ramsey, L. W.; Lind, K.; Mace, G. N.;
Kaplan, K. F.; Kim, H.; Hawkins, K.; Bowler, B. P.
Bibcode: 2021yCat..51610128S
Altcode:
The red giants investigated in this Habitable Planet Finder (HPF)
spectroscopic study have been selected from our previous studies. See
those papers for detailed descriptions of the optical observations of
our program stars. HPF is a high-resolution (R~55000) near-infrared (zyJ
photometric bands, 8100-12800Å) spectrograph on the 10m Hobby-Eberly
Telescope (HET) at McDonald Observatory. (4 data files).
Title: Exploring flares around the ultracool M dwarf VB-10 with high
resolution infrared spectroscopy
Authors: Kanodia, Shubham; Ramsey, Lawrence; Ninan, P. Joe; Mahadevan,
Suvrath
Bibcode: 2021csss.confE.286K
Altcode:
Flare activity in late M stars remains an interesting topic since there
is as yet no well tested model of how these convective stars generate
the magnetic field that underlie activity such as flares, and the rate
and strengths of the flare can impact the evolution of the atmospheres
of planets orbiting them We present observations of two flares observed
on the M8 star VB10 with the Habitable zone Planet Finder (HPF) on
the Hobby Eberly Telescope. HPF is designed to be very stable for
precision radial velocities but its NIR coverage (810-1280 nm) and
queue scheduled operations allow us to obtain multiple observations
to analyze the properties of the flares. A combination of the 10 m
telescope aperture with the nondestructive read readout with our H2RG
enables us to obtain a time resolution of ~ minutes on this late type
M dwarf, which helps us resolve the evolution of the flare. We present
our analysis of the Ca II infrared triple lines as well as Pa $\gamma$
and $\delta$ to place constraints on the time behavior and physical
conditions of the emitting material.
Title: A Terrestrial-mass Planet Orbiting GJ 1151: The Possible
Source of Coherent Low-frequency Radio Emission from an Inactive Star
Authors: Stefansson, Gudmundur; Mahadevan, Suvrath; Robertson, Paul;
Terrien, Ryan; Ninan, Joe; Holcomb, Rae; Halverson, Samuel; Cochran,
William; Kanodia, Shubham; Ramsey, Lawrence; Wolszczan, Alexander;
Endl, Michael; Bender, Chad; Diddams, Scott; Frederick, Connor;
Hearty, Frederick; Monson, Andrew; Metcalf, Andrew; Roy, Arpita;
Schwab, Christian
Bibcode: 2021csss.confE.107S
Altcode:
The coherent low-frequency radio emission detected by LOFAR from
the quiescent M4.5 dwarf star GJ 1151 is consistent with theoretical
expectations of star-planet interactions for an Earth-sized planet on
a 1-5 day orbit. Using precise near-infrared radial velocities (RVs)
with the Habitable-zone Planet Finder (HPF) on the 10m Hobby-Eberly
Telescope at McDonald Observatory along with literature RVs from
HARPS-N, we reveal a periodic Doppler signature consistent with a
2.5 Earth mass planet in a 2.02-day orbit. Precise photometry from the
Transiting Exoplanet Survey Satellite (TESS) shows no flares or activity
signature, consistent with a quiescent M dwarf. While no planetary
transit is detected in the TESS data, a weak photometric modulation
is detectable in the photometry at a ~2 day period. This independent
detection of a planet signal with the RV technique adds further
weight to the claim to one of the first detection of star-exoplanet
interactions at radio wavelengths, and helps validate this emerging
technique for the detection of exoplanets.<strong> </strong>
Title: Chemical Compositions of Red Giant Stars from Habitable Zone
Planet Finder Spectroscopy
Authors: Sneden, Christopher; Afşar, Melike; Bozkurt, Zeynep; Topcu,
Gamze Böcek; Özdemir, Sergen; Zeimann, Gregory R.; Froning, Cynthia
S.; Mahadevan, Suvrath; Ninan, Joe P.; Bender, Chad F.; Terrien, Ryan;
Ramsey, Lawrence W.; Lind, Karin; Mace, Gregory N.; Kaplan, Kyle F.;
Kim, Hwihyun; Hawkins, Keith; Bowler, Brendan P.
Bibcode: 2021AJ....161..128S
Altcode: 2020arXiv201214742S
We have used the Habitable Zone Planet Finder (HPF) to gather
high-resolution, high signal-to-noise near-infrared spectra of 13
field red horizontal branch (RHB) stars, one open cluster giant,
and one very metal-poor halo red giant. The HPF spectra cover the
0.81-1.28 μm wavelength range of the zyJ bands, partially filling
the gap between the optical (0.4-1.0 μm) and infrared (1.5-2.4 μm)
spectra already available for the program stars. We derive abundances of
17 species from LTE-based computations involving equivalent widths and
spectrum syntheses, and estimate abundance corrections for the species
that are most affected by departures from LTE in RHB stars. Generally
good agreement is found between HPF-based metallicities and abundance
ratios and those from the optical and infrared spectral regions. Light
element transitions dominate the HPF spectra of these red giants, and
HPF data can be used to derive abundances from species with poor or no
representation in optical spectra (e.g., C I, P I, S I, K I). Attention
is drawn to the HPF abundances in two field solar-metallicity RHB stars
of special interest: one with an extreme carbon isotope ratio, and one
with a rare, very large lithium content. The latter star is unique in
our sample in exhibiting very strong He I 10830 Å absorption. The
abundances of the open cluster giant concur with those derived from
other wavelength regions. Detections of C I and S I in HD 122563 are
reported, yielding the lowest metallicity determination of [S/Fe]
from more than one multiplet.
Title: VizieR Online Data Catalog: HPF RVs and TESS photometry of
TOI-1266 (Stefansson+, 2020)
Authors: Stefansson, G.; Kopparapu, R.; Lin, A.; Mahadevan, S.; Canas,
C. I.; Kanodia, S.; Ninan, J. P.; Cochran, W. D.; Endl, M.; Hebb,
L.; Wisniewski, J.; Gupta, A.; Everett, M.; Bender, C. F.; Diddams,
S. A.; Ford, E. B.; Fredrick, C.; Halverson, S.; Hearty, F.; Levi,
E.; Maney, M.; Metcalf, A. J.; Monson, A.; Ramsey, L. W.; Robertson,
P.; Roy, A.; Schwab, C.; Terrien, R. C.; Wright, J. T.
Bibcode: 2021yCat..51600259S
Altcode:
We obtained high-resolution spectra of TOI-1266 with the Habitable
Planet Finder (HPF) Spectrograph to place upper limits on the masses
of both planets and obtain precise spectroscopic parameters of the
host star. The HPF is a fiber-fed near-infrared (NIR) spectrograph on
the 10m Hobby-Eberly Telescope (HET) at McDonald Observatory in Texas,
covering the z, Y, and J bands from 810 to 1260nm at a resolution of
R=55000. The Telescope Encoder and Sky Sensor (TESS) observed
TOI-1266 in 4 sectors: sector 14 (camera4; 2019 July 18--2019 August
15), sector 15 (camera4; 2019 August 15--2019 September 11), sector 21
(camera3; 2020 January 21--2020 February 18), and sector 22 (camera3;
2020 February 18--2020 March 18). (2 data files).
Title: A Mini-Neptune and a Radius Valley Planet Orbiting the
Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the
Habitable-zone Planet Finder
Authors: Stefánsson, Guðmundur; Kopparapu, Ravi; Lin, Andrea;
Mahadevan, Suvrath; Cañas, Caleb I.; Kanodia, Shubham; Ninan, Joe P.;
Cochran, William D.; Endl, Michael; Hebb, Leslie; Wisniewski, John;
Gupta, Arvind; Everett, Mark; Bender, Chad F.; Diddams, Scott A.;
Ford, Eric B.; Fredrick, Connor; Halverson, Samuel; Hearty, Fred;
Levi, Eric; Maney, Marissa; Metcalf, Andrew J.; Monson, Andrew; Ramsey,
Lawrence W.; Robertson, Paul; Roy, Arpita; Schwab, Christian; Terrien,
Ryan C.; Wright, Jason T.
Bibcode: 2020AJ....160..259S
Altcode:
We report on the validation of two planets orbiting the nearby (36
pc) M2 dwarf TOI-1266 observed by the TESS mission. This system is
one of a few M dwarf multiplanet systems with close-in planets where
the inner planet is substantially larger than the outer planet. The
inner planet is sub-Neptune-sized (R = 2.46 ± 0.08 R⊕)
with an orbital period of 10.9 days, while the outer planet has a
radius of ${1.67}_{-0.11}^{+0.09}$ R⊕ and resides in
the exoplanet radius valley—the transition region between rocky and
gaseous planets. With an orbital period of 18.8 days, the outer planet
receives an insolation flux of 2.4 times that of Earth, similar to the
insolation of Venus. Using precision near-infrared radial velocities
with the Habitable-zone Planet Finder Spectrograph, we place upper mass
limits of 15.9 and 6.4 M⊕ at 95% confidence for the inner
and outer planet, respectively. A more precise mass constraint of both
planets, achievable with current radial velocity instruments given the
host star brightness (V = 12.9, J = 9.7), will yield further insights
into the dominant processes sculpting the exoplanet radius valley.
Title: Ghosts of NEID's past
Authors: Kanodia, Shubham; Ninan, Joe P.; Monson, Andrew J.; Mahadevan,
Suvrath; Nitroy, Colin; Schwab, Christian; Halverson, Samuel; Bender,
Chad F.; Terrien, Ryan; Hearty, Frederick R.; Lubar, Emily; McElwain,
Michael W.; Ramsey, Lawrence W.; Robertson, Paul M.; Roy, Arpita;
Stefansson, Gudmundur; Stevens, Daniel J.
Bibcode: 2020SPIE11447E..40K
Altcode: 2020arXiv201200182K
The NEID spectrograph is a R ~ 120,000 resolution fiber-fed and highly
stabilized spectrograph for extreme radial velocity (RV) precision. It
is being commissioned at the 3.5 m WIYN telescope in Kitt Peak National
Observatory with a desired instrumental precision of better than 30 cm
s-1. NEID's bandpass of 380 - 930 nm enables the simultaneous
wavelength coverage of activity indicators from the Ca HK lines in the
blue to the Ca IR triplet in the IR. In this paper we will present
our efforts to characterize and mitigate optical ghosts in the NEID
spectrograph during assembly, integration and testing, and highlight
several of the dominant optical element contributors such as the
cross dispersion prism and input optics. We shall present simulations
of the 2-D spectrum and discuss the predicted ghost features on the
focal plane, and how they may impact the RV performance for NEID. We
also present the mitigation strategy adopted for each ghost which
may be applied to future instrument designs. This work will enable
other instrument builders to potentially avoid some of these issues,
as well as outline mitigation strategies.
Title: VizieR Online Data Catalog: Photometry and RVs of K2-25b with
HPF (Stefansson+, 2020)
Authors: Stefansson, G.; Mahadevan, S.; Maney, M.; Ninan, J. P.;
Robertson, P.; Rajagopal, J.; Haase, F.; Allen, L.; Ford, E. B.;
Winn, J.; Wolfgang, A.; Dawson, R. I.; Wisniewski, J.; Bender, C. F.;
Canas, C.; Cochran, W.; Diddams, S. A.; Fredrick, C.; Halverson, S.;
Hearty, F.; Hebb, L.; Kanodia, S.; Levi, E.; Metcalf, A. J.; Monson,
A.; Ramsey, L.; Roy, A.; Schwab, C.; Terrien, R.; Wright, J. T.
Bibcode: 2020yCat..51600192S
Altcode:
We obtained five transits of K2-25b using the Astrophysical Research
Consortium Telescope Imaging Camera (ARCTIC) imager on the 3.5m
Astrophysical Research Consortium (ARC) 3.5m Telescope at Apache Point
Observatory (APO) on the nights of UT 2017 September 17; 2019 January
4, 18, and 25; and 2019 February 1. All of the transit observations
were performed with the Engineered Diffuser available on ARCTIC, which
we designed specifically to enable very high precision photometric
observations. We used the Sloan Digital Sky Survey (SDSS) i' filter,
except on the night of 2019 January 18, when we used the SDSS z' filter
without the diffuser to minimize background Moon contamination. We observed four transits of K2-25b using the Half-Degree Imager
(HDI) at the WIYN 0.9m telescope at Kitt Peak National Observatory
on the nights of UT 2018 February 7 and 21 and 2018 December 14 and
21. We obtained precision Near Infra Red (NIR) Radial Velocities
(RVs) of K2-25 with the Habitable Zone Planet Finder (HPF) with the
twofold goal to constrain the mass of K2-25b and the obliquity of
the host star. The HPF is a high-resolution (R~55000) NIR fiber-fed
spectrograph on the 10m Hobby-Eberly Telescope (HET) at McDonald
Observatory in Texas. (3 data files).
Title: The Habitable Zone Planet Finder Reveals a High Mass and Low
Obliquity for the Young Neptune K2-25b
Authors: Stefansson, Gudmundur; Mahadevan, Suvrath; Maney, Marissa;
Ninan, Joe P.; Robertson, Paul; Rajagopal, Jayadev; Haase, Flynn;
Allen, Lori; Ford, Eric B.; Winn, Joshua; Wolfgang, Angie; Dawson,
Rebekah I.; Wisniewski, John; Bender, Chad F.; Cañas, Caleb; Cochran,
William; Diddams, Scott A.; Fredrick, Connor; Halverson, Samuel;
Hearty, Fred; Hebb, Leslie; Kanodia, Shubham; Levi, Eric; Metcalf,
Andrew J.; Monson, Andrew; Ramsey, Lawrence; Roy, Arpita; Schwab,
Christian; Terrien, Ryan; Wright, Jason T.
Bibcode: 2020AJ....160..192S
Altcode: 2020arXiv200712766S
Using radial velocity data from the Habitable Zone Planet Finder, we
have measured the mass of the Neptune-sized planet K2-25b, as well as
the obliquity of its M4.5 dwarf host star in the 600-800 Myr Hyades
cluster. This is one of the youngest planetary systems for which
both of these quantities have been measured and one of the very few
M dwarfs with a measured obliquity. Based on a joint analysis of the
radial velocity data, time-series photometry from the K2 mission, and
new transit light curves obtained with diffuser-assisted photometry,
the planet's radius and mass are 3.44 ± 0.12 R⊕ and
${24.5}_{-5.2}^{+5.7}{M}_{\oplus }$ . These properties are compatible
with a rocky core enshrouded by a thin hydrogen-helium atmosphere (5%
by mass). We measure an orbital eccentricity of e = 0.43 ± 0.05. The
sky-projected stellar obliquity is λ = 3° ± 16°, compatible with
spin-orbit alignment, in contrast to other "hot Neptunes" that have
been studied around older stars.
Title: A Warm Jupiter Transiting an M Dwarf: A TESS Single-transit
Event Confirmed with the Habitable-zone Planet Finder
Authors: Cañas, Caleb I.; Stefansson, Gudmundur; Kanodia, Shubham;
Mahadevan, Suvrath; Cochran, William D.; Endl, Michael; Robertson,
Paul; Bender, Chad F.; Ninan, Joe P.; Beard, Corey; Lubin, Jack; Gupta,
Arvind F.; Everett, Mark E.; Monson, Andrew; Wilson, Robert F.; Lewis,
Hannah M.; Brewer, Mary; Majewski, Steven R.; Hebb, Leslie; Dawson,
Rebekah I.; Diddams, Scott A.; Ford, Eric B.; Fredrick, Connor;
Halverson, Samuel; Hearty, Fred; Lin, Andrea S. J.; Metcalf, Andrew
J.; Rajagopal, Jayadev; Ramsey, Lawrence W.; Roy, Arpita; Schwab,
Christian; Terrien, Ryan C.; Wright, Jason T.
Bibcode: 2020AJ....160..147C
Altcode: 2020arXiv200707098C
We confirm the planetary nature of a warm Jupiter transiting the early
M dwarf TOI-1899 using a combination of available TESS photometry;
high-precision, near-infrared spectroscopy with the Habitable-zone
Planet Finder; and speckle and adaptive optics imaging. The data
reveal a transiting companion on an ∼29 day orbit with a mass and
radius of $0.66\pm 0.07\ {M}_{{\rm{J}}}$ and ${1.15}_{-0.05}^{+0.04}\
{R}_{{\rm{J}}}$ , respectively. The star, TOI-1899, is the lowest-mass
star known to host a transiting warm Jupiter, and we discuss the
follow-up opportunities afforded by a warm ( ${T}_{\mathrm{eq}}\sim
362$ K) gas giant orbiting an M0 star. Our observations reveal that
TOI-1899.01 is a puffy warm Jupiter, and we suggest additional transit
observations to both refine the orbit and constrain the true dilution
observed in TESS.
Title: VizieR Online Data Catalog: Flux & RVs of the dwarf G9-40
with K2 & HPF (Stefansson+, 2020)
Authors: Stefansson, G.; Canas, C.; Wisniewski, J.; Robertson, P.;
Mahadevan, S.; Maney, M.; Kanodia, S.; Beard, C.; Bender, C. F.;
Brunt, P.; Clemens, J. C.; Cochran, W.; Diddams, S. A.; Endl, M.; Ford,
E. B.; Fredrick, C.; Halverson, S.; Hearty, F.; Hebb, L.; Huehnerhoff,
J.; Jennings, J.; Kaplan, K.; Levi, E.; Lubar, E.; Metcalf, A. J.;
Monson, A.; Morris, B.; Ninan, J. P.; Nitroy, C.; Ramsey, L.; Roy,
A.; Schwab, C.; Sigurdsson, S.; Terrien, R.; Wright, J. T.
Bibcode: 2020yCat..51590100S
Altcode:
G9-40 was observed by the Kepler spacecraft as part of Campaign 16
of the K2 mission. It was proposed as a K2 Campaign 16 target by the
following programs: GO16005LC (PI: Crossfield), GO16009LC
(PI: Charbonneau), GO16052LC (PI: Stello), and GO16083LC
(PI: Coughlin). The star was monitored in long cadence mode (30 minute
cadence) for 80 days from 2017-December-7 to 2018-February-25. We
obtained four visits of G9-40 with the Habitable-zone Planet Finder
(HPF) Spectrograph with the goal to measure its Radial Velocity (RV)
variation as a function of time. HPF is a high-resolution (R~55000) NIR
spectrograph recently commissioned on the 10m Hobby-Eberly Telescope
(HET) in Texas covering the information-rich z, Y, and J bands from
810 to 1280nm. (2 data files).
Title: TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm
Super-Neptune Orbiting an M-dwarf Host
Authors: Kanodia, Shubham; Cañas, Caleb I.; Stefansson, Gudmundur;
Ninan, Joe P.; Hebb, Leslie; Lin, Andrea S. J.; Baran, Helen; Maney,
Marissa; Terrien, Ryan C.; Mahadevan, Suvrath; Cochran, William D.;
Endl, Michael; Dong, Jiayin; Bender, Chad F.; Diddams, Scott A.;
Ford, Eric B.; Fredrick, Connor; Halverson, Samuel; Hearty, Fred;
Metcalf, Andrew J.; Monson, Andrew; Ramsey, Lawrence W.; Robertson,
Paul; Roy, Arpita; Schwab, Christian; Wright, Jason T.
Bibcode: 2020ApJ...899...29K
Altcode: 2020arXiv200614546K
We confirm the planetary nature of TOI-1728b using a combination
of ground-based photometry, near-infrared Doppler velocimetry and
spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an
old, inactive M0 star with Teff = ${3980}_{-32}^{+31}$ K,
which hosts a transiting super-Neptune at an orbital period of ∼3.49
days. Joint fitting of the radial velocities and TESS and ground-based
transits yields a planetary radius of ${5.05}_{-0.17}^{+0.16}$
R⊕, mass ${26.78}_{-5.13}^{+5.43}$ M⊕,
and eccentricity ${0.057}_{-0.039}^{+0.054}$ . We estimate the
stellar properties, and perform a search for He 10830 Šabsorption
during the transit of this planet and claim a null detection with an
upper limit of 1.1% with 90% confidence. A deeper level of He 10830
Šabsorption has been detected in the planet atmosphere of GJ 3470b, a
comparable gaseous planet. TOI-1728b is the largest super-Neptune—the
intermediate subclass of planets between Neptune and the more massive
gas-giant planets—discovered around an M dwarf. With its relatively
large mass and radius, TOI-1728 represents a valuable data point in
the M-dwarf exoplanet mass-radius diagram, bridging the gap between the
lighter Neptune-sized planets and the heavier Jovian planets known to
orbit M dwarfs. With a low bulk density of ${1.14}_{-0.24}^{+0.26}$
g cm-3, and orbiting a bright host star (J ∼ 9.6, V
∼ 12.4), TOI-1728b is also a promising candidate for transmission
spectroscopy both from the ground and from space, which can be used
to constrain planet formation and evolutionary models.
Title: Persistent Starspot Signals on M Dwarfs: Multiwavelength
Doppler Observations with the Habitable-zone Planet Finder and
Keck/HIRES
Authors: Robertson, Paul; Stefansson, Gudmundur; Mahadevan, Suvrath;
Endl, Michael; Cochran, William D.; Beard, Corey; Bender, Chad F.;
Diddams, Scott A.; Duong, Nicholas; Ford, Eric B.; Fredrick, Connor;
Halverson, Samuel; Hearty, Fred; Holcomb, Rae; Juan, Lydia; Kanodia,
Shubham; Lubin, Jack; Metcalf, Andrew J.; Monson, Andrew; Ninan, Joe
P.; Palafoutas, Jonathan; Ramsey, Lawrence W.; Roy, Arpita; Schwab,
Christian; Terrien, Ryan C.; Wright, Jason T.
Bibcode: 2020ApJ...897..125R
Altcode: 2020arXiv200509657R
Young, rapidly rotating M dwarfs exhibit prominent starspots,
which create quasiperiodic signals in their photometric and
Doppler spectroscopic measurements. The periodic Doppler signals
can mimic radial velocity (RV) changes expected from orbiting
exoplanets. Exoplanets can be distinguished from activity-induced
false positives by the chromaticity and long-term incoherence of
starspot signals, but these qualities are poorly constrained for fully
convective M stars. Coherent photometric starspot signals on M dwarfs
may persist for hundreds of rotations, and the wavelength dependence
of starspot RV signals may not be consistent between stars due to
differences in their magnetic fields and active regions. We obtained
precise multiwavelength RVs of four rapidly rotating M dwarfs (AD Leo,
G227-22, GJ 1245B, GJ 3959) using the near-infrared (NIR) Habitable-zone
Planet Finder and the optical Keck/HIRES spectrometer. Our RVs are
complemented by photometry from Kepler, TESS, and the Las Cumbres
Observatory network of telescopes. We found that all four stars
exhibit large spot-induced Doppler signals at their rotation periods,
and investigated the longevity and optical-to-NIR chromaticity for
these signals. The phase curves remain coherent much longer than is
typical for Sunlike stars. Their chromaticity varies, and one star (GJ
3959) exhibits optical and NIR RV modulation consistent in both phase
and amplitude. In general, though, we find that the NIR amplitudes
are lower than their optical counterparts. We conclude that starspot
modulation for rapidly rotating M stars frequently remains coherent for
hundreds of stellar rotations and gives rise to Doppler signals that,
due to this coherence, may be mistaken for exoplanets.
Title: A Mini-Neptune and a Venus-Zone Planet in the Radius
Valley Orbiting the Nearby M2-dwarf TOI-1266: Validation with the
Habitable-zone Planet Finder
Authors: Stefansson, Gudmundur; Kopparapu, Ravi; Lin, Andrea;
Mahadevan, Suvrath; Cañas, Caleb; Kanodia, Shubham; Ninan, Joe;
Cochran, William; Endl, Michael; Hebb, Leslie; Wisniewski, John;
Gupta, Arvind; Everett, Mark; Bender, Chad; Diddams, Scott; Ford, Eric;
Fredrick, Connor; Halverson, Samuel; Hearty, Fred; Levi, Eric; Maney,
Marissa; Metcalf, Andrew; Monson, Andrew; Ramsey, Lawrence; Robertson,
Paul; Roy, Arpita; Schwab, Christian; Terrien, Ryan; Wright, Jason
Bibcode: 2020arXiv200611180S
Altcode:
We report on the validation of two planets orbiting the nearby (36pc)
M2 dwarf TOI-1266 observed by the TESS mission. The inner planet is
sub-Neptune-sized ($R=2.46 \pm 0.08 R_\oplus$) with an orbital period
of 10.9 days. The outer planet has a radius of $1.67_{-0.11}^{+0.09}
R_\oplus$ and resides in the exoplanet Radius Valley---the transition
region between rocky and gaseous planets. With an orbital period of
18.8 days, the outer planet receives an insolation flux of 2.4 times
that of Earth, similar to the insolation of Venus. Using precision
near-infrared radial velocities with the Habitable-zone Planet
Finder Spectrograph, we place upper mass limits of $15.9 M_\oplus$
and $6.4 M_\oplus$ at 95% confidence for the inner and outer planet,
respectively. A more precise mass constraint of planet c, achievable
with current RV instruments given the host star brightness (V=12.9,
J=9.7), will yield further insights into the dominant processes
sculpting the exoplanet Radius Valley.
Title: Evidence for He I 10830 Å Absorption during the Transit of
a Warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone
Planet Finder
Authors: Ninan, Joe P.; Stefansson, Gudmundur; Mahadevan, Suvrath;
Bender, Chad; Robertson, Paul; Ramsey, Lawrence; Terrien, Ryan; Wright,
Jason; Diddams, Scott A.; Kanodia, Shubham; Cochran, William; Endl,
Michael; Ford, Eric B.; Fredrick, Connor; Halverson, Samuel; Hearty,
Fred; Jennings, Jeff; Kaplan, Kyle; Lubar, Emily; Metcalf, Andrew J.;
Monson, Andrew; Nitroy, Colin; Roy, Arpita; Schwab, Christian
Bibcode: 2020ApJ...894...97N
Altcode: 2019arXiv191002070N
Understanding the dynamics and kinematics of outflowing atmospheres
of hot and warm exoplanets is crucial to understanding the origins
and evolutionary history of the exoplanets near the evaporation
desert. Recently, ground-based measurements of the meta-stable helium
atom's resonant absorption at 10830 Å has become a powerful probe
of the base environment which is driving the outflow of exoplanet
atmospheres. We report evidence for the He I 10830 Å in absorption
(equivalent width ∼0.012 ± 0.002 Å) in the exosphere of a warm
Neptune orbiting the M-dwarf GJ 3470, during three transits using the
Habitable Zone Planet Finder near-infrared spectrograph. This marks the
first reported evidence for He I 10830 Å atmospheric absorption for
a planet orbiting an M-dwarf. Our detected absorption is broad and its
blueshifted wing extends to -36 km s-1, the largest reported
in the literature to date. We modeled the state of helium atoms in the
exosphere of GJ3470b based on assumptions on the UV and X-ray flux of
GJ 3470, and found our measurement of flux-weighted column density of
meta-stable state helium $({N}_{\mathrm{He}{}_{3}^{2}{\rm{S}}}=2.4\times
{10}^{10}\,{\mathrm{cm}}^{-2})$ , derived from our transit observations,
to be consistent with the model, within its uncertainties. The
methodology developed here will be useful to study and constrain the
atmospheric outflow models of other exoplanets like GJ 3470b, which
are near the edge of the evaporation desert.
Title: A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40:
Validation with the Habitable-zone Planet Finder
Authors: Stefansson, Gudmundur; Cañas, Caleb; Wisniewski, John;
Robertson, Paul; Mahadevan, Suvrath; Maney, Marissa; Kanodia, Shubham;
Beard, Corey; Bender, Chad F.; Brunt, Peter; Clemens, J. Christopher;
Cochran, William; Diddams, Scott A.; Endl, Michael; Ford, Eric B.;
Fredrick, Connor; Halverson, Samuel; Hearty, Fred; Hebb, Leslie;
Huehnerhoff, Joseph; Jennings, Jeff; Kaplan, Kyle; Levi, Eric; Lubar,
Emily; Metcalf, Andrew J.; Monson, Andrew; Morris, Brett; Ninan, Joe
P.; Nitroy, Colin; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian;
Sigurdsson, Steinn; Terrien, Ryan; Wright, Jason T.
Bibcode: 2020AJ....159..100S
Altcode: 2019arXiv191200291S
We validate the discovery of a 2-Earth-radii sub-Neptune-sized
planet around the nearby high-proper-motion M2.5 dwarf G 9-40 (EPIC
212048748), using high-precision, near-infrared (NIR) radial velocity
(RV) observations with the Habitable-zone Planet Finder (HPF), precision
diffuser-assisted ground-based photometry with a custom narrowband
photometric filter, and adaptive optics imaging. At a distance of d
= 27.9 $\,\mathrm{pc}$ , G 9-40b is the second-closest transiting
planet discovered by K2 to date. The planet's large transit depth
(∼3500 ppm), combined with the proximity and brightness of the host
star at NIR wavelengths (J = 10, K = 9.2), makes G 9-40b one of the
most favorable sub-Neptune-sized planets orbiting an M dwarf for
transmission spectroscopy with James Webb Space Telescope, ARIEL,
and the upcoming Extremely Large Telescopes. The star is relatively
inactive with a rotation period of ∼29 days determined from the K2
photometry. To estimate spectroscopic stellar parameters, we describe
our implementation of an empirical spectral-matching algorithm
using the high-resolution NIR HPF spectra. Using this algorithm,
we obtain an effective temperature of ${T}_{\mathrm{eff}}=3404\pm
73\,{\rm{K}}$ and metallicity of $[\mathrm{Fe}/{\rm{H}}]=-0.08\pm 0.13$
. Our RVs, when coupled with the orbital parameters derived from the
transit photometry, exclude planet masses above 11.7M⊕
with 99.7% confidence assuming a circular orbit. From its radius,
we predict a mass of $M={5.0}_{-1.9}^{+3.8}{M}_{\oplus }$ and an RV
semiamplitude of $K={4.1}_{-1.6}^{+3.1}\,{\rm{m}}\ {{\rm{s}}}^{-1}$ ,
making its mass measurable with current RV facilities. We urge further
RV follow-up observations to precisely measure its mass, to enable
precise transmission spectroscopic measurements in the future.
Title: Impact of crosshatch patterns in H2RGs on high-precision radial
velocity measurements: exploration of measurement and mitigation
paths with the Habitable-Zone Planet Finder
Authors: Ninan, Joe P.; Mahadevan, Suvrath; Stefansson, Gudmundur;
Bender, Chad; Roy, Arpita; Kaplan, Kyle F.; Fredrick, Connor; Metcalf,
Andrew J.; Monson, Andrew; Terrien, Ryan; Ramsey, Lawrence W.; Diddams,
Scott A.
Bibcode: 2019JATIS...5d1511N
Altcode: 2019arXiv190306614N
Teledyne's H2RG detector images suffer from crosshatch like patterns,
which arise from subpixel quantum efficiency (QE) variation. We present
our measurements of this subpixel QE variation in the Habitable-Zone
Planet Finder's H2RG detector. We present a simple model to estimate
the impact of subpixel QE variations on the radial velocity and how a
first-order correction can be implemented to correct for the artifact
in the spectrum. We also present how the HPF's future upgraded laser
frequency comb will enable us to implement this correction.
Title: Stellar spectroscopy in the near-infrared with a laser
frequency comb
Authors: Metcalf, Andrew J.; Anderson, Tyler; Bender, Chad F.;
Blakeslee, Scott; Brand, Wesley; Carlson, David R.; Cochran, William
D.; Diddams, Scott A.; Endl, Michael; Fredrick, Connor; Halverson,
Sam; Hickstein, Daniel D.; Hearty, Fred; Jennings, Jeff; Kanodia,
Shubham; Kaplan, Kyle F.; Levi, Eric; Lubar, Emily; Mahadevan, Suvrath;
Monson, Andrew; Ninan, Joe P.; Nitroy, Colin; Osterman, Steve; Papp,
Scott B.; Quinlan, Franklyn; Ramsey, Larry; Robertson, Paul; Roy,
Arpita; Schwab, Christian; Sigurdsson, Steinn; Srinivasan, Kartik;
Stefansson, Gudmundur; Sterner, David A.; Terrien, Ryan; Wolszczan,
Alex; Wright, Jason T.; Ycas, Gabriel
Bibcode: 2019Optic...6..233M
Altcode: 2019arXiv190200500M
The discovery and characterization of exoplanets around nearby stars is
driven by profound scientific questions about the uniqueness of Earth
and our Solar System, and the conditions under which life could exist
elsewhere in our Galaxy. Doppler spectroscopy, or the radial velocity
(RV) technique, has been used extensively to identify hundreds of
exoplanets, but with notable challenges in detecting terrestrial
mass planets orbiting within habitable zones. We describe infrared RV
spectroscopy at the 10 m Hobby-Eberly telescope that leverages a 30 GHz
electro-optic laser frequency comb with nanophotonic supercontinuum to
calibrate the Habitable Zone Planet Finder spectrograph. Demonstrated
instrument precision <10 cm/s and stellar RVs approaching 1 m/s
open the path to discovery and confirmation of habitable zone planets
around M-dwarfs, the most ubiquitous type of stars in our Galaxy.
Title: The NEID Doppler spectrometer at WIYN
Authors: Schwab, Christian; Bender, Chad; Blake, Cullen; Gong, Qian;
Halverson, Sam; Hearty, Frederick; Hunting, Emily; Kanodia, Shubham;
Liang, Ming; Logsdon, Sarah E.; Lubar, Emily; Mahadevan, Suvrath;
McElwain, Michael; Monson, Andrew; Rajagopal, Jayadev; Ramsey,
Lawrence; Robertson, Paul; Roy, Arpita; Stefansson, Gudmundur K.;
Terrien, Ryan; Wright, Jason T.
Bibcode: 2019AAS...23340803S
Altcode:
The US exoplanet science community urgently requires a radial velocity
instrument with the sensitivity to observe rocky planets in the
habitable zone, and follow-up the most promising TESS candidates. To
address this need, we are building NEID, the new NN-Explore extreme
precision Doppler spectrometer for the WIYN telescope at Kitt Peak
Observatory. The guiding metric for the complete design was the
instrument’s performance for its primary science goal, the Doppler
observation of Earth-like exoplanets. It is based on a high optical
performance Echelle spectrograph built around a classical white
pupil relay with large beam size, and is fed by a high-scrambling
fiber train. NEID covers the wavelength range from 380 - 930nm
in a single frame with a resolution of ~100.000. The optics bench
is housed in a vacuum chamber for environmental control, reaching
sub-millikelvin temperature stability. Together with a sophisticated
front end to provide excellent atmospheric dispersion correction
and guiding stability, this forms a system with predicted Doppler
precision of <25 cm/s. In this talk, we will present the optical
and optomechanical designs, and discuss the interplay of technical
design choices and science demands.
Title: Ultrastable environment control for the NEID spectrometer:
design and performance demonstration
Authors: Robertson, Paul; Anderson, Tyler; Stefansson, Gudmundur;
Hearty, Frederick R.; Monson, Andrew; Mahadevan, Suvrath; Blakeslee,
Scott; Bender, Chad; Ninan, Joe P.; Conran, David; Levi, Eric; Lubar,
Emily; Cole, Amanda; Dykhouse, Adam; Kanodia, Shubham; Nitroy, Colin;
Smolsky, Joseph; Tuggle, Demetrius; Blank, Basil; Nelson, Matthew;
Blake, Cullen; Halverson, Samuel; Henderson, Chuck; Kaplan, Kyle F.;
Li, Dan; Logsdon, Sarah E.; McElwain, Michael W.; Rajagopal, Jayadev;
Ramsey, Lawrence W.; Roy, Arpita; Schwab, Christian; Terrien, Ryan;
Wright, Jason T.
Bibcode: 2019JATIS...5a5003R
Altcode: 2019arXiv190207729R
Two key areas of emphasis in contemporary experimental exoplanet science
are the detailed characterization of transiting terrestrial planets and
the search for Earth analog planets to be targeted by future imaging
missions. Both of these pursuits are dependent on an order-of-magnitude
improvement in the measurement of stellar radial velocities (RV),
setting a requirement on single-measurement instrumental uncertainty
of order 10 cm / s. Achieving such extraordinary precision on a
high-resolution spectrometer requires thermomechanically stabilizing the
instrument to unprecedented levels. We describe the environment control
system (ECS) of the NEID spectrometer, which will be commissioned on
the 3.5-m WIYN Telescope at Kitt Peak National Observatory in 2019,
and has a performance specification of on-sky RV precision <50 cm /
s. Because NEID's optical table and mounts are made from aluminum,
which has a high coefficient of thermal expansion, sub-milliKelvin
temperature control is especially critical. NEID inherits its ECS from
that of the Habitable-Zone Planet Finder (HPF), but with modifications
for improved performance and operation near room temperature. Our
full-system stability test shows the NEID system exceeds the already
impressive performance of HPF, maintaining vacuum pressures below
10 - 6 Torr and a root mean square (RMS) temperature
stability better than 0.4 mK over 30 days. Our ECS design is fully
open-source; the design of our temperature-controlled vacuum chamber
has already been made public, and here we release the electrical
schematics for our custom temperature monitoring and control system.
Title: Design and Performance of NEID Ultra-Stable Environmental
Control System
Authors: Lubar, Emily; Mahadevan, Suvrath; Robertson, Paul; Stefansson,
Gudmundur K.; Hearty, Frederick; Monson, Andrew; Bender, Chad; Ninan,
Joe; Kanodia, Shubham; Nitroy, Colin; Blake, Cullen; Halverson, Sam;
Logsdon, Sarah E.; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian;
Wright, Jason T.
Bibcode: 2019AAS...23314602L
Altcode:
NEID is an ultra-stable, optical spectrometer designed to achieve Radial
Velocity (RV) precision on the order of 10cm/s. Achieving this level
of measurement precision requires extreme thermo-mechanical stability
within the instrument which we achieve by maintaining a vacuum on the
order of microTorr as well as sub-milliKelvin temperature stability. In
this poster, we will outline NEID's Environmental Control System (ECS)
and Temperature Monitoring and Control (TMC) System, which were both
inherited and improved upon from that of the Habitable-zone Planet
Finder (HPF) infrared spectrograph. We have achieved our target
stability by demonstrating < 0.4mK RMS temperature variability
over the course of a 30 day stability run in the lab. We expect
our stability to improve at the observatory as the WIYN instrument
room is more stable than our instrument development lab. NEID will be
commissioned in midwinter 2019 at Kitt Peak National Observatory on the
3.5m WIYN Telescope. It will serve the exoplanet community as a vital
follow up asset for Earth-like planets targeted by the TESS survey.
Title: Science with NEID Guaranteed Time Observations
Authors: Wright, Jason T.; Bender, Chad; Blake, Cullen; Halverson,
Sam; Hearty, Frederick; Mahadevan, Suvrath; McElwain, Michael; Ramsey,
Lawrence; Roy, Arpita; Schwab, Christian
Bibcode: 2019AAS...23314028W
Altcode:
The NEID spectrograph at the WIYN 3.5m telescope at Kitt Peak will
be a facility instrument available to the precise radial velocity
community via the NN-EXPLORE partnership between NASA and NOAO. The
NEID instrument team will have 270 on-sky hours per year for 5 years
of guaranteed time to conduct some of the novel science enabled by
this instrument. In this poster, I describe the design and goals of
the NEID team's science program with its Guaranteed Time Observations.
Title: Overview of the spectrometer optical fiber feed for the
habitable-zone planet finder
Authors: Kanodia, Shubham; Mahadevan, Suvrath; Ramsey, Larry W.;
Stefansson, Gudmundur K.; Monson, Andrew J.; Hearty, Frederick R.;
Blakeslee, Scott; Lubar, Emily; Bender, Chad F.; Ninan, J. P.; Sterner,
David; Roy, Arpita; Halverson, Samuel P.; Robertson, Paul M.
Bibcode: 2018SPIE10702E..6QK
Altcode: 2018arXiv180800557K
The Habitable-zone Planet Finder (HPF) is a highly stabilized fiber
fed precision radial velocity (RV) spec- trograph working in the Near
Infrared (NIR): 810 - 1280 nm. In this paper we present an overview of
the preparation of the optical fibers for HPF. The entire fiber train
from the telescope focus down to the cryostat is detailed. We also
discuss the fiber polishing, splicing and its integration into the
instrument using a fused silica puck. HPF was designed to be able to
operate in two modes, High Resolution (HR- the only mode mode currently
commissioned) and High Efficiency (HE). We discuss these fiber heads
and the procedure we adopted to attach the slit on to the HR fibers.
Title: The NEID precision radial velocity spectrometer: port adapter
overview, requirements, and test plan
Authors: Logsdon, Sarah E.; McElwain, Michael W.; Gong, Qian; Liang,
Ming; Santoro, Fernando; Schwab, Christian; Bender, Chad; Blake,
Cullen; Halverson, Samuel; Hearty, Fred; Hunting, Emily; Jaehnig,
Kurt P.; Mahadevan, Suvrath; Monson, Andrew J.; Percival, Jeffrey W.;
Rajagopal, Jayadev; Ramsey, Lawrence; Roy, Arpita; Smith, Michael P.;
Terrien, Ryan C.; Timmermann, Erik; Willems, Phil; Wolf, Marsha J.;
Wright, Jason
Bibcode: 2018SPIE10702E..67L
Altcode:
The NEID spectrometer is an optical (380-930 nm), fiber-fed, precision
Doppler spectrometer currently in de- velopment for the WIYN 3.5 m
telescope at Kitt Peak National Observatory as part of the NN-EXPLORE
partnership. Designed to achieve a radial velocity precision of <
30 cm/s, NEID will be sensitive enough to detect terrestrial-mass
exoplanets around low-mass stars. Light from the target stars is focused
by the telescope to a bent Cassegrain port at the edge of the primary
mirror mechanical support. The specialized NEID "Port Adapter" system is
mounted at this bent Cassegrain port and is responsible for delivering
the incident light from the telescope to the NEID fibers. In order to
provide stable, high-quality images to the science instrument, the Port
Adapter houses several sub-components designed to acquire the target
stars, correct for atmospheric dis- persion, stabilize the light onto
the science fibers, and calibrate the spectrometer by injecting known
wavelength sources such as a laser frequency comb. Here we provide an
overview of the overall opto-mechanical design and system requirements
of the Port Adapter. We also describe the development of system error
budgets and test plans to meet those requirements.
Title: The NEID precision radial velocity spectrometer: optical
design of the port adapter and ADC
Authors: Schwab, Christian; Liang, Ming; Gong, Qian; Bender, Chad;
Blake, Cullen; Halverson, Samuel; Harbeck, Daniel; Hearty, Fred;
Hunting, Emily; Jaehnig, Kurt P.; Logsdon, Sarah E.; Mahadevan,
Suvrath; McElwain, Michael W.; Monson, Andrew J.; Percival, Jeffrey W.;
Rajagopal, Jayadev; Ramsey, Lawrence; Robertson, Paul M.; Roy, Arpita;
Santoro, Fernando; Smith, Michael P.; Terrien, Ryan C.; Timmermann,
Erik; Willems, Phil; Wolf, Marsha J.; Wright, Jason
Bibcode: 2018SPIE10702E..71S
Altcode:
NEID is a new extreme precision Doppler spectrometer for the WIYN
telescope. It is fiber fed and employs a classical white pupil Echelle
configuration. NEID has a fiber aperture of only 0.92" on sky in
high-resolution mode, and its tight radial velocity error budget
resulted in very stringent stability requirements for the input
illumination of the spectrograph optics. Consequently, the demands
on the fiber injection are challenging. In this paper, we describe
the layout and optical design of the injection module, including a
broadband, high image quality relay and a high-performance atmospheric
dispersion corrector (ADC) across the bandwidth of 380 - 930 nm.
Title: Completion and performance of the Hobby-Eberly Telescope wide
field upgrade
Authors: Hill, Gary J.; Drory, Niv; Good, John M.; Lee, Hanshin;
Vattiat, Brian L.; Kriel, Herman; Ramsey, Jason; Bryant, Randy; Fowler,
Jim; Landriau, Martin; Leck, Ron; Mrozinski, Emily; Odewahn, Stephen;
Shetrone, Matthew; Westfall, Amy; Terrazas, Eusebio; Balderrama,
Edmundo; Bevins, Emily; Buetow, Brent; Caldwell, John; Damm, George;
MacQueen, Phillip; Martin, Jerry; Martin, Amanda; Pautzke, Justin;
Smither, Katie; Rostopchin, Sergey; Smith, Greg; Spencer, Renny;
Armandroff, Taft; Gebhardt, Karl; Ramsey, Lawrence W.
Bibcode: 2018SPIE10700E..0PH
Altcode:
The Hobby-Eberly Telescope (HET) is an innovative large telescope
with 10 meter aperture, located in West Texas at the McDonald
Observatory. The HET operates with a fixed segmented primary and
has a tracker, which moves the fourmirror corrector and prime focus
instrument package to track the sidereal and non-sidereal motions
of objects. We have completed a major multi-year upgrade of the HET
that has substantially increased the field of view to 22 arcminutes by
replacing the optical corrector, tracker, and prime focus instrument
package and by developing a new telescope control system. The upgrade
has replaced all hardware and systems except for the structure,
enclosure, and primary mirror. The new, reinvented wide-field HET feeds
the revolutionary Visible Integral-field Replicable Unit Spectrograph
(VIRUS‡), fed by 35,000 fibers, in support of the Hobby-Eberly
Telescope Dark Energy Experiment (HETDEX§), a new low resolution
spectrograph (LRS2), the Habitable Zone Planet Finder (HPF), and
the upgraded high resolution spectrograph (HRS2). The HET Wide Field
Upgrade has now been commissioned and has been in science operations
since mid 2016 and in full science operations from mid 2018. This
paper reviews and summarizes the upgrade, lessons learned, and the
operational performance of the new HET.
Title: The Habitable Zone Planet Finder: Precision NIR Radial
Velocities during Testing & Commissioning
Authors: Ninan, Joe Philip; Roy, Arpita; Terrien, Ryan; Kaplan, Kyle;
Bender, Chad; Monson, Andy; Robertson, Paul; Stefansson, Gudmundur;
Kanodia, Shubham; Halverson, Sam; Mahadevan, Suvrath; Hearty, Fred;
Wright, Jason T.; Ramsey, Lawrence; Blakeslee, Scott; Anderson, Tyler;
Schwab, Christian
Bibcode: 2018AAS...23115218N
Altcode:
The Habitable Zone Planet Finder (HPF) is a fiber-fed near-infrared
(0.8 to 1.24 microns) spectrometer designed for high stability for
precision Doppler radial velocity surveys using the 10m Hobby Eberly
Telescope. We discuss results obtained during the lab testing and
commissioning phase that show the solar spectrum and the key parameters
of the instrument, and demonstrate that the HPF fibers track each other
to sub-meter per second relative Doppler radial velocity precision. We
will also discuss the capabilities of HPF, as well as the reduction
challenges in the infrared, and our solutions to these challenges.
Title: NEID Port Adapter: Design and Verification Plan
Authors: Logsdon, Sarah E.; McElwain, Michael; McElwain, Michael W.;
Gong, Qian; Bender, Chad; Halverson, Samuel; Hearty, Fred; Hunting,
Emily; Jaehnig, Kurt; Liang, Ming; Mahadevan, Suvrath; Monson, A. J.;
Percival, Jeffrey; Rajagopal, Jayadev; Ramsey, Lawrence; Roy, Arpita;
Santoro, Fernando; Schwab, Christian; Smith, Michael; Wolf, Marsha;
Wright, Jason
Bibcode: 2018AAS...23115208L
Altcode:
The NEID spectrograph is an optical (380-930 nm), fiber-fed, precision
Doppler spectrograph currently in development for the 3.5 m WIYN
Telescope at Kitt Peak National Observatory. Designed to achieve a
radial velocity precision of <30 cm/s, NEID will be sensitive enough
to detect terrestrial-mass exoplanets around low-mass stars. Light from
the target stars is focused by the telescope to a bent-Cassegrain port
at the edge of the primary mirror mechanical support. The specialized
NEID “Port Adapter” system is mounted at this bent-Cassegrain
port and is responsible for delivering the incident light from the
telescope to the NEID fibers. In order to provide stable, high-quality
images to the science instrument, the Port Adapter houses several
subcomponents designed to acquire the target stars, correct for
atmospheric dispersion, stabilize the light onto the science fibers,
and calibrate the spectrograph by injecting known wavelength sources
such as a laser frequency comb. Here we describe the overall design
of the Port Adapter and outline the development of calibration tools
and an on-sky test plan to verify the performance of the atmospheric
dispersion corrector (ADC). We also discuss the development of an error
budget and test requirements to ensure high-precision centroiding onto
the NEID science fibers using a system of coherent fiber bundles.
Title: NEID: A High Precision Radial Velocity Spectrograph for the
WIYN 3.5-m Telescope
Authors: Allen, Lori E.; Wright, Jason; Rajagopal, Jayadev; Santoro,
Fernando; Liang, Ming; Timmerman, Erik; Christensen, Robert; Hunting,
Emily; Wolf, Marsha; Jaehnig, Kurt; Percival, Jeffrey; Smith, Michael;
Mahadevan, Suvrath; Hearty, Fred; Bender, Chad; Blake, Cullen; Logsdon,
Sarah E.; Akeson, Rachel; Capps, Richard W.; Callas, John; Willems,
Phillip A.; McElwain, Michael; McElwain, Michael W.; Basten, Fabienne;
Monson, Andy; Stefansson, Gudmundur; Ramsey, Larry; Ninan, Joe;
Blakeslee, Scott; Kaplan, Kyle; Halverson, Sam; Roy, Arpita; Terrien,
Ryan; Robertson, Paul; Schwab, Christian; Rud, Mayer; Kanodia, Shubham
Bibcode: 2018AAS...23124608A
Altcode:
NEID will be an ultra-stable optical high resolution echelle
spectrograph on the 3.5 WIYN telescope at Kitt Peak National
Observatory, with a design goal of < 30 cm/s instrumental
stability. It is part of a joint NSF-NASA initiative (NN-EXPLORE)
to support ground-based Doppler velocimetry of nearby stars for the
detection and characterization of rocky exoplanets around nearby
stars. Here we describe the instrument's design, construction and
commissioning schedule, capabilities, and future opportunities to
apply for public time on this flagship Doppler instrument.
Title: HPF: The Habitable Zone Planet Finder at the Hobby-Eberly
Telescope
Authors: Wright, Jason T.; Mahadevan, Suvrath; Hearty, Fred; Monson,
Andy; Stefansson, Gudmundur; Ramsey, Larry; Ninan, Joe; Bender, Chad;
Kaplan, Kyle; Roy, Arpita; Terrien, Ryan; Robertson, Paul; Halverson,
Sam; Schwab, Christian; Kanodia, Shubham
Bibcode: 2018AAS...23124645W
Altcode:
The Habitable Zone Planet Finder (HPF) is an ultra-stable NIR (ZYJ)
high resolution echelle spectrograph on the 10-m Hobby-Eberly Telescope
capable of 1-3 m/s Doppler velocimetry on nearby late M dwarfs
(M4-M9). This precision is sufficient to detect terrestrial planets
in the Habitable Zones of these relatively unexplored stars. Here we
present its capabilities and early commissioning results.
Title: Proxima Centauri as a Benchmark for Stellar Activity Indicators
in the Near-infrared
Authors: Robertson, Paul; Bender, Chad; Mahadevan, Suvrath; Roy,
Arpita; Ramsey, Lawrence W.
Bibcode: 2016ApJ...832..112R
Altcode: 2016arXiv160806291R
A new generation of dedicated Doppler spectrographs will attempt to
detect low-mass exoplanets around mid- to late M stars at near-infrared
(NIR) wavelengths, where those stars are brightest and have the most
Doppler information content. A central requirement for the success
of these instruments is to properly measure the component of radial
velocity (RV) variability contributed by stellar magnetic activity
and to account for it in exoplanet models of RV data. The wavelength
coverage for many of these new instruments will not include the Ca
II H&K or Hα lines, the most frequently used absorption-line
tracers of magnetic activity. Thus, it is necessary to define and
characterize NIR activity indicators for mid- to late M stars in order
to provide simultaneous activity metrics for NIR RV data. We have used
the high-cadence UVES observations of the M5.5 dwarf Proxima Centauri
from Fuhrmeister et al. to compare the activity sensitivity of eight
NIR atomic lines to that of Hα. We find that equivalent-width-type
measurements of the NIR K I doublet and the Ca II NIR triplet
are excellent proxies for the canonical optical tracers. The Ca II
triplet will be acquired by most of the new and upcoming NIR Doppler
spectrographs, offering a common, reliable indicator of activity.
Title: A Versatile Technique to Enable Sub-milli-Kelvin Instrument
Stability for Precise Radial Velocity Measurements: Tests with the
Habitable-zone Planet Finder
Authors: Stefansson, Gudmundur; Hearty, Frederick; Robertson, Paul;
Mahadevan, Suvrath; Anderson, Tyler; Levi, Eric; Bender, Chad; Nelson,
Matthew; Monson, Andrew; Blank, Basil; Halverson, Samuel; Henderson,
Chuck; Ramsey, Lawrence; Roy, Arpita; Schwab, Christian; Terrien, Ryan
Bibcode: 2016ApJ...833..175S
Altcode: 2016arXiv161006216S
Insufficient instrument thermomechanical stability is one of the many
roadblocks for achieving 10 cm s-1 Doppler radial velocity
precision, the precision needed to detect Earth-twins orbiting
solar-type stars. Highly temperature and pressure stabilized
spectrographs allow us to better calibrate out instrumental
drifts, thereby helping in distinguishing instrumental noise from
astrophysical stellar signals. We present the design and performance of
the Environmental Control System (ECS) for the Habitable-zone Planet
Finder (HPF), a high-resolution (R = 50,000) fiber-fed near-infrared
(NIR) spectrograph for the 10 {{m}} Hobby-Eberly Telescope at McDonald
Observatory. HPF will operate at 180 {{K}}, driven by the choice of
an H2RG NIR detector array with a 1.7 μ {{m}} cutoff. This ECS has
demonstrated 0.6 {mK} rms stability over 15 days at both 180 and 300
{{K}}, and maintained high-quality vacuum (\lt {10}-7
{Torr}) over months, during long-term stability tests conducted
without a planned passive thermal enclosure surrounding the vacuum
chamber. This control scheme is versatile and can be applied as
a blueprint to stabilize future NIR and optical high-precision
Doppler instruments over a wide temperature range from ∼77 {{K}}
to elevated room temperatures. A similar ECS is being implemented
to stabilize NEID, the NASA/NSF NN-EXPLORE spectrograph for the 3.5
{{m}} WIYN telescope at Kitt Peak, operating at 300 {{K}}. A [full SolidWorks
3D-CAD model] and a comprehensive parts list of the HPF ECS are
included with this manuscript to facilitate the adaptation of this
versatile environmental control scheme in the broader astronomical
community. Certain commercial equipment, instruments, or materials
are identified in this paper in order to specify the experimental
procedure adequately. Such identification is not intended to imply
recommendation or endorsement by the National Institute of Standards
and Technology, nor is it intended to imply that the materials or
equipment identified are necessarily the best available for the purpose.
Title: Measuring extended red sensitivity in a 1.7μm-cutoff HgCdTe
detector array
Authors: Terrien, Ryan C.; Monson, Andrew J.; Mahadevan, Suvrath;
Bender, Chad; Halverson, Samuel P.; Ramsey, Larry
Bibcode: 2016SPIE.9915E..1QT
Altcode:
Infrared detectors with cutoff wavelengths of 1.7 μm have much
lower sensitivity to thermal background contamination than those with
longer cutoff wavelengths. This low sensitivity offers the attractive
possibility of reducing the need for fully cryogenic systems for
YJH-band work, offering the potential for "warm-pupil" instrumentation
that nonetheless reduces detected thermal background to the level of
dark current. However, residual sensitivity beyond the cutoff wavelength
is not well characterized, and may preclude the implementation of
such warm-pupil instruments. We describe an experiment to evaluate the
long-wavelength sensitivity tail of a 1.7 µm-cutoff HAWAII-2RG array
using a thermal blocking filter. Our results suggest the possibility
of measurable red sensitivity beyond 2 μm. Ongoing improvements
will confirm and refine this measurement. The thermal blocking filter
offers the prospect of warm-pupil NIR instrument operation, which is
particularly valuable for cost-effective and efficient testing systems:
it has facilitated NIR detector characterization and will enable crucial
laboratory tests of laser frequency comb calibration systems and other
NIR calibration sources.
Title: A comprehensive radial velocity error budget for next
generation Doppler spectrometers
Authors: Halverson, Samuel; Terrien, Ryan; Mahadevan, Suvrath; Roy,
Arpita; Bender, Chad; Stefánsson, Gudmundur K.; Monson, Andrew;
Levi, Eric; Hearty, Fred; Blake, Cullen; McElwain, Michael; Schwab,
Christian; Ramsey, Lawrence; Wright, Jason; Wang, Sharon; Gong, Qian;
Roberston, Paul
Bibcode: 2016SPIE.9908E..6PH
Altcode: 2016arXiv160705634H
We describe a detailed radial velocity error budget for the NASA-NSF
Extreme Precision Doppler Spectrometer instrument concept NEID
(NN-explore Exoplanet Investigations with Doppler spectroscopy). Such
an instrument performance budget is a necessity for both identifying
the variety of noise sources currently limiting Doppler measurements,
and estimating the achievable performance of next generation exoplanet
hunting Doppler spectrometers. For these instruments, no single source
of instrumental error is expected to set the overall measurement
floor. Rather, the overall instrumental measurement precision is
set by the contribution of many individual error sources. We use a
combination of numerical simulations, educated estimates based on
published materials, extrapolations of physical models, results from
laboratory measurements of spectroscopic subsystems, and informed
upper limits for a variety of error sources to identify likely sources
of systematic error and construct our global instrument performance
error budget. While natively focused on the performance of the NEID
instrument, this modular performance budget is immediately adaptable
to a number of current and future instruments. Such an approach is an
important step in charting a path towards improving Doppler measurement
precisions to the levels necessary for discovering Earth-like planets.
Title: Ultra-stable temperature and pressure control for the
Habitable-zone Planet Finder spectrograph
Authors: Stefánsson, Gudmundur K.; Hearty, Frederick R.; Robertson,
Paul M.; Levi, Eric I.; Mahadevan, Suvrath; Anderson, Tyler B.; Monson,
Andrew J.; Bender, Chad F.; Halverson, Samuel P.; Li, Yiting; Ramsey,
Lawrence W.; Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Nelson,
Matthew J.; Blank, Basil
Bibcode: 2016SPIE.9908E..71S
Altcode:
We present recent long-term stability test results of the cryogenic
Environmental Control System (ECS) for the Habitable zone Planet Finder
(HPF), a near infrared ultra-stable spectrograph operating at 180
Kelvin. Exquisite temperature and pressure stability is required for
high precision radial velocity (< 1m=s) instruments, as temperature
and pressure variations can easily induce instrumental drifts of several
tens-to-hundreds of meters per second. Here we present the results from
long-term stability tests performed at the 180K operating temperature
of HPF, demonstrating that the HPF ECS is stable at the 0:6mK level
over 15-days, and <10-7 Torr over months.
Title: The instrument control software package for the Habitable-Zone
Planet Finder spectrometer
Authors: Bender, Chad F.; Robertson, Paul; Stefansson, Gudmundur Kari;
Monson, Andrew; Anderson, Tyler; Halverson, Samuel; Hearty, Frederick;
Levi, Eric; Mahadevan, Suvrath; Nelson, Matthew; Ramsey, Larry; Roy,
Arpita; Schwab, Christian; Shetrone, Matthew; Terrien, Ryan
Bibcode: 2016SPIE.9913E..38B
Altcode:
We describe the Instrument Control Software (ICS) package that we have
built for The Habitable-Zone Planet Finder (HPF) spectrometer. The ICS
controls and monitors instrument subsystems, facilitates communication
with the Hobby-Eberly Telescope facility, and provides user interfaces
for observers and telescope operators. The backend is built around the
asynchronous network software stack provided by the Python Twisted
engine, and is linked to a suite of custom hardware communication
protocols. This backend is accessed through Python-based command-line
and PyQt graphical frontends. In this paper we describe several of the
customized subsystem communication protocols that provide access to
and help maintain the hardware systems that comprise HPF, and show how
asynchronous communication benefits the numerous hardware components. We
also discuss our Detector Control Subsystem, built as a set of custom
Python wrappers around a C-library that provides native Linux access
to the SIDECAR ASIC and Hawaii-2RG detector system used by HPF. HPF
will be one of the first astronomical instruments on sky to utilize
this native Linux capability through the SIDECAR Acquisition Module
(SAM) electronics. The ICS we have created is very flexible, and we
are adapting it for NEID, NASA's Extreme Precision Doppler Spectrometer
for the WIYN telescope; we will describe this adaptation, and describe
the potential for use in other astronomical instruments.
Title: Design of NEID, an extreme precision Doppler spectrograph
for WIYN
Authors: Schwab, C.; Rakich, A.; Gong, Q.; Mahadevan, S.; Halverson,
S. P.; Roy, A.; Terrien, R. C.; Robertson, P. M.; Hearty, F. R.;
Levi, E. I.; Monson, A. J.; Wright, J. T.; McElwain, M. W.; Bender,
C. F.; Blake, C. H.; Stürmer, J.; Gurevich, Y. V.; Chakraborty, A.;
Ramsey, L. W.
Bibcode: 2016SPIE.9908E..7HS
Altcode:
We have developed an optical design for a high resolution spectrograph
in response to NASA's call for an extreme precision Doppler spectrometer
(EPDS) for the WIYN telescope. Our instrument covers a wavelength
range of 380 to 930 nm using a single detector and with a resolution
of 100,000. To deliver the most stable spectrum, we avoid the use of
an image slicer, in favor of a large (195 mm diameter) beam footprint
on a 1x2 mosaic R4 Echelle grating. The optical design is based on
a classic white pupil layout, with a single parabolic mirror that is
used as the main and transfer collimator. Cross dispersion is provided
by a single large PBM2Y glass prism. The refractive camera consists of
only four rotationally symmetric lenses made from i-Line glasses, yet
delivers very high image quality over the full spectral bandpass. We
present the optical design of the main spectrograph bench and discuss
the design trade-offs and expected performance.
Title: A system to provide sub-milliKelvin temperature control at
T 300K for extreme precision optical radial velocimetry
Authors: Robertson, Paul M.; Hearty, Frederick R.; Anderson, Tyler B.;
Stefánsson, Gudmundur K.; Levi, Eric I.; Bender, Chad F.; Mahadevan,
Suvrath; Halverson, Samuel P.; Monson, Andrew J.; Ramsey, Lawrence W.;
Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Nelson, Matthew J.;
Blank, Basil
Bibcode: 2016SPIE.9908E..62R
Altcode:
We present preliminary results for the environmental control system
from NEID, our instrument concept for NASA's Extreme Precision Doppler
Spectrograph, which is now in development. Exquisite temperature
control is a requirement for Doppler spectrographs, as small temperature
shifts induce systematic Doppler shifts far exceeding the instrumental
specifications. Our system is adapted from that of the Habitable Zone
Planet Finder instrument, which operates at a temperature of 180K.We
discuss system modifications for operation at T 300K, and show data
demonstrating sub-mK stability over two weeks from a full-scale
system test.
Title: Deployment of the Hobby-Eberly Telescope wide-field upgrade
Authors: Hill, Gary J.; Drory, Niv; Good, John M.; Lee, Hanshin;
Vattiat, Brian L.; Kriel, Herman; Ramsey, Jason; Bryant, Randy;
Elliot, Linda; Fowler, Jim; Häuser, Marco; Landiau, Martin; Leck, Ron;
Odewahn, Stephen; Perry, Dave; Savage, Richard; Schroeder Mrozinski,
Emily; Shetrone, Matthew; DePoy, D. L.; Prochaska, Travis; Marshall,
J. L.; Damm, George; Gebhardt, Karl; MacQueen, Phillip J.; Martin,
Jerry; Armandroff, Taft; Ramsey, Lawrence W.
Bibcode: 2016SPIE.9906E..06H
Altcode:
The Hobby-Eberly Telescope (HET) is an innovative large telescope,
located in West Texas at the McDonald Observatory. The HET operates with
a fixed segmented primary and has a tracker, which moves the four-mirror
corrector and prime focus instrument package to track the sidereal and
non-sidereal motions of objects. We have completed a major multi-year
upgrade of the HET that has substantially increased the pupil size
to 10 meters and the field of view to 22 arcminutes by replacing the
corrector, tracker, and prime focus instrument package. The new wide
field HET will feed the revolutionary integral field spectrograph called
VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment
(HETDEX§), a new low resolution spectrograph (LRS2), an
upgraded high resolution spectrograph (HRS2), and later the Habitable
Zone Planet Finder (HPF). The upgrade is being commissioned and this
paper discusses the completion of the installation, the commissioning
process and the performance of the new HET.
Title: VizieR Online Data Catalog: Stellar noise for 4529 Kepler
solar-type dwarfs (Gilliland+, 2015)
Authors: Gilliland, R. L.; Chaplin, W. J.; Jenkins, J. M.; Ramsey,
L. W.; Smith, J. C.
Bibcode: 2015yCat..51500133G
Altcode:
The NASA Kepler Mission has left an indelible imprint on the research
of exoplanet and stellar properties for a large number of stars
(~150000), over four years. Our earlier study (Gilliland et al.,
2011ApJS..197....6G; Paper I) provided a discussion about the Kepler
Mission noise properties. The earlier study over the first six quarters
of Kepler data is extended to the full four years ultimately comprising
the mission. A total of 4529 stars (see Table3) brighter than
Kp=12.5 met the selection criteria for solar-type dwarfs
as detailed in Paper I (Gilliland et al., 2011ApJS..197....6G). (1 data file).
Title: Kepler Mission Stellar and Instrument Noise Properties
Revisited
Authors: Gilliland, Ronald L.; Chaplin, William J.; Jenkins, Jon M.;
Ramsey, Lawrence W.; Smith, Jeffrey C.
Bibcode: 2015AJ....150..133G
Altcode: 2015arXiv150805054G
An earlier study of the Kepler Mission noise properties on timescales
of primary relevance to detection of exoplanet transits found that
higher than expected noise followed, to a large extent, from the stars
rather than instrument or data analysis performance. The earlier study
over the first six quarters of Kepler data is extended to the full
four years ultimately comprising the mission. Efforts to improve the
pipeline data analysis have been successful in reducing noise levels
modestly as evidenced by smaller values derived from the current data
products. The new analyses of noise properties on transit timescales
show significant changes in the component attributed to instrument
and data analysis, with essentially no change in the inferred stellar
noise. We also extend the analyses to timescales of several days,
instead of several hours to better sample stellar noise that follows
from magnetic activity. On the longer timescale there is a shift in
stellar noise for solar-type stars to smaller values in comparison to
solar values.
Title: An Efficient, Compact, and Versatile Fiber Double Scrambler
for High Precision Radial Velocity Instruments
Authors: Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath; Ramsey,
Lawrence; Levi, Eric; Schwab, Christian; Hearty, Fred; MacDonald, Nick
Bibcode: 2015ApJ...806...61H
Altcode: 2015arXiv150507463H
We present the design and test results of a compact optical
fiber double-scrambler for high-resolution Doppler radial velocity
instruments. This device consists of a single optic: a high-index n
∼ 2 ball lens that exchanges the near and far fields between two
fibers. When used in conjunction with octagonal fibers, this device
yields very high scrambling gains (SGs) and greatly desensitizes the
fiber output from any input illumination variations, thereby stabilizing
the instrument profile of the spectrograph and improving the Doppler
measurement precision. The system is also highly insensitive to input
pupil variations, isolating the spectrograph from telescope illumination
variations and seeing changes. By selecting the appropriate glass and
lens diameter the highest efficiency is achieved when the fibers are
practically in contact with the lens surface, greatly simplifying
the alignment process when compared to classical double-scrambler
systems. This prototype double-scrambler has demonstrated significant
performance gains over previous systems, achieving SGs in excess of
10,000 with a throughput of ∼87% using uncoated Polymicro octagonal
fibers. Adding a circular fiber to the fiber train further increases
the SG to >20,000, limited by laboratory measurement error. While
this fiber system is designed for the Habitable-zone Planet Finder
spectrograph, it is more generally applicable to other instruments
in the visible and near-infrared. Given the simplicity and low cost,
this fiber scrambler could also easily be multiplexed for large
multi-object instruments.
Title: Toward Understanding Stellar Radial Velocity Jitter as a
Function of Wavelength: The Sun as a Proxy
Authors: Marchwinski, Robert C.; Mahadevan, Suvrath; Robertson, Paul;
Ramsey, Lawrence; Harder, Jerald
Bibcode: 2015ApJ...798...63M
Altcode: 2014arXiv1410.7379M
Using solar spectral irradiance measurements from the SORCE spacecraft
and the F/F' technique, we have estimated the radial velocity (RV)
scatter induced on the Sun by stellar activity as a function of
wavelength. Our goal was to evaluate the potential advantages of
using new near-infrared (NIR) spectrographs to search for low-mass
planets around bright F, G, and K stars by beating down activity
effects. Unlike M dwarfs, which have higher fluxes and therefore greater
RV information content in the NIR, solar-type stars are brightest at
visible wavelengths, and, based solely on information content, are
better suited to traditional optical RV surveys. However, we find that
the F/F' estimated RV noise induced by stellar activity is diminished by
up to a factor of four in the NIR versus the visible. Observations with
the upcoming future generation of NIR instruments can be a valuable
addition to the search for low-mass planets around bright FGK stars
in reducing the amount of stellar noise affecting RV measurements.
Title: Characterizing M dwarf planet hosts and enabling precise
radial velocities in the near-infrared
Authors: Terrien, Ryan; Mahadevan, Suvrath; Deshpande, Rohit; Bender,
Chad F.; Ramsey, Lawrence W.
Bibcode: 2015AAS...22511206T
Altcode:
M dwarfs account for ~70% of the stars in the Solar neighborhood and
represent a rich frontier for upcoming surveys for M dwarf planets,
including the Habitable Zone Planet Finder (HPF) radial velocity
(RV) survey, which will search for planets around nearby M dwarfs
in the near-infrared (NIR). Crucial for the construction of target
lists for these surveys and the interpretation of survey results
is the development of techniques for measuring M dwarf stellar
composition, activity, and age. Measurements of these parameters are
made difficult by the complexity of M dwarf spectra and their slow
evolution once on the main sequence. I will outline our application
of empirically-calibrated techniques for measuring [Fe/H], which has
enabled our development of new activity and age indicators based on NIR
spectra from the low-resolution IRTF-SpeX spectrograph. I will discuss
the implications of these new measurements, which hint at the effects
of alpha element enrichment and youth, and reveal a strong connection
between metallicity and stellar infrared luminosity. These new
techniques allow refinements of existing calibrations, and contribute
to a catalog of the stellar parameters of ~900 M dwarfs that will be
an invaluable resource for the upcoming HPF survey.I will also outline
developments in simulations and design for HPF, which will be among
the first of the next generation of NIR precision RV instruments on
large telescopes. I will describe an end-to-end instrument simulator
that has helped optimize the HPF spectral coverage and instrumental
configuration, the extensive study of vacuum phase holographic grating
cross-disperser that will optimize the efficiency of HPF, and the
precise characterization of the physical properties and behavior of the
HPF H2RG near-infrared detector array. This hardware work will enable
the 1-3m/s precision required for HPF to find Earth-mass planets in
the habitable zones of nearby M dwarfs, and the stellar parameters
in the M dwarf catalog will provide the information necessary to
optimize the scientific yield of HPF by ensuring a large number of
well-characterized planet hosts.
Title: The Habitable-zone Planet Finder (HPF): Achieving high
precision radial velocities and mitigating stellar activity noise
Authors: Mahadevan, Suvrath; Ramsey, Lawrence W.; Terrien, Ryan;
Robertson, Paul; Marchwinski, Robert C.; Hearty, Fred; Levi, Eric;
Kári Stefánsson, Gudmundur; Bender, Chad F.; Halverson, Samuel;
Roy, Arpita; Nelson, Matt; Schwab, Christian
Bibcode: 2015AAS...22525823M
Altcode:
HPF is a stabilized, fiber-fed, near infrared (NIR) spectrograph
currently being built at Penn State for the 10m Hobby-Eberly Telescope
(HET). HPF will be capable of discovering low mass planets in the
Habitable Zones of mid-late M dwarfs via radial velocity (RV). We
discuss the development of critical sub-systems like our high-stability
temperature control system, vacuum cryostat, and implementation of
new wavelength calibration techniques. The design of the HET enables
queue-scheduled operation, but its variable pupil requires attention
to both near- and far-field fiber scrambling, which we accomplish
with double scramblers and octagonal fibers.HPF will provide partial
bandwith coverage of the information-rich z, Y and J NIR bands at a
spectral resolving power of R∼50,000. While stellar activity induced
RV noise is lower in the NIR than at visible wavelengths, we have
carefully included NIR activity indicators in our spectral bandpass
to help discriminate stellar activity from real planet signals, as
has been recently demonstrated for Gliese 581 and Gliese 667C systems.
Title: The habitable-zone planet finder calibration system
Authors: Halverson, Samuel; Mahadevan, Suvrath; Ramsey, Lawrence;
Terrien, Ryan; Roy, Arpita; Schwab, Christian; Bender, Chad; Hearty,
Fred; Levi, Eric; Osterman, Steve; Ycas, Gabe; Diddams, Scott
Bibcode: 2014SPIE.9147E..7ZH
Altcode: 2014arXiv1408.3632H
We present the design concept of the wavelength calibration system for
the Habitable-zone Planet Finder instrument (HPF), a precision radial
velocity (RV) spectrograph designed to detect terrestrial-mass planets
around M-dwarfs. HPF is a stabilized, fiber-fed, R~50,000 spectrograph
operating in the near-infrared (NIR) z/Y/J bands from 0.84 to 1.3
microns. For HPF to achieve 1 m s-1 or better measurement
precision, a unique calibration system, stable to several times better
precision, will be needed to accurately remove instrumental effects at
an unprecedented level in the NIR. The primary wavelength calibration
source is a laser frequency comb (LFC), currently in development
at NIST Boulder, discussed separately in these proceedings. The LFC
will be supplemented by a stabilized single-mode fiber Fabry-Perot
interferometer reference source and Uranium-Neon lamp. The HPF
calibration system will combine several other new technologies developed
by the Penn State Optical-Infrared instrumentation group to improve
RV measurement precision including a dynamic optical coupling system
that significantly reduces modal noise effects. Each component has been
thoroughly tested in the laboratory and has demonstrated significant
performance gains over previous NIR calibration systems.
Title: Scrambling and modal noise mitigation in the Habitable Zone
Planet Finder fiber feed
Authors: Roy, Arpita; Halverson, Samuel; Mahadevan, Suvrath; Ramsey,
Lawrence W.
Bibcode: 2014SPIE.9147E..6BR
Altcode:
We present the baseline fiber feed design for the Habitable-zone
Planet Finder (HPF), a precision radial velocity (RV) spectrograph
designed to detect Earth analogs around M-dwarfs. HPF is a stabilized,
fiber-fed, R∼50,000 spectrograph operating in the near-infrared
(NIR) from 0.82 to 1.3 µm, and will be deployed on the Hobby- Eberly
Telescope (HET) in Texas. While the essential function of the optical
fibers is to deliver high throughput, this mode of light transport also
provides the opportunity to introduce radial and azimuthal scrambling,
which boosts instrument stability and thereby RV precision. Based
on the unique requirements of HPF on the HET, we present initial
tests showing very high scrambling gains via a compact scrambler in
conjunction with octagonal fibers. Conversely, the propagation of light
through the fibers injects modal noise, which can limit achievable RV
precision. Laboratory tests of a custom-built mechanical agitator show
significant gains over a static fiber feed. Overall, the fiber feed
is designed to provide high relative throughput, excellent scrambling,
and reliable modal noise suppression. We will also attempt to minimize
focal ratio degradation (FRD) to the extent possible with the chosen
configuration. HPF inculcates several other new technologies developed
by the Penn State Optical-Infrared instrumentation group, including a
rigorous calibration system, which are discussed separately in these
proceedings.
Title: Near field modal noise reduction using annealed optical fiber
Authors: Osterman, Steven N.; Ycas, Gabriel G.; Donaldson, Chelsea;
Diddams, Scott A.; Mahadevan, Suvrath; Ramsey, Lawrence W.; Plavchan,
Peter P.
Bibcode: 2014SPIE.9147E..5CO
Altcode:
Incomplete and unstable mode population has long complicated the
application of optical fiber for transferring star and calibration
light to high precision spectrographs. The need for improved precision
calibrators in support of radial velocity planet surveys has led to the
introduction of coherent wavelengths sources using single mode fibers
that are then coupled into multi-mode fibers, further exacerbating this
problem. We explore mode scrambling in annealed optical fiber with and
without agitation, as compared to that obtained using octagonal fiber
and using an integrating sphere. We observe improved scrambling with
annealed fibers compared to conventional and octagonal fibers.
Title: Developments in simulations and software for a near-infrared
precision radial velocity spectrograph
Authors: Terrien, Ryan C.; Bender, Chad F.; Mahadevan, Suvrath;
Halverson, Samuel P.; Ramsey, Lawrence W.; Hearty, Frederick R.
Bibcode: 2014SPIE.9152E..26T
Altcode:
We present developments in simulations and software for the Habitable
Zone Planet Finder (HPF), an R~50,000 near-infrared cross-dispersed
radial velocity spectrograph that will be used to search for planets
around M dwarfs. HPF is fiber-fed, operates in the zYJ bands, and uses
a 1.7μm cutoff HAWAII-2RG (H2RG) NIR detector. We have constructed an
end-to-end simulator that accepts as input a range of stellar models
contaminated with telluric features and processes these through a
simulated detector. This simulator accounts for the characteristics of
the H2RG, including interpixel capacitance, persistence, nonlinearities,
read noise, and other detector characteristics, as measured from our
engineering-grade H2RG. It also implements realistic order curvature. We
describe applications of this simulator including optimization of the
fiber configuration at the spectrograph slit and selection of properties
for a laser frequency comb calibration source. The simulator has also
provided test images for development of the HPF survey extraction
and RV analysis pipeline and we describe progress on this pipeline
itself, which will implement optimal extraction, laser frequency comb
and emission lamp wavelength calibration, and cross-correlation based
RV measurement.
Title: Environmental control system for Habitable-zone Planet Finder
(HPF)
Authors: Hearty, Fred; Levi, Eric; Nelson, Matt; Mahadevan, Suvrath;
Burton, Adam; Ramsey, Lawrence; Bender, Chad; Terrien, Ryan; Halverson,
Samuel; Robertson, Paul; Roy, Arpita; Blank, Basil; Blanchard, Ken;
Stefansson, Gudmundur
Bibcode: 2014SPIE.9147E..52H
Altcode:
HPF is an ultra-stable, precision radial velocity near infrared
spectrograph with a unique environmental control scheme. The
spectrograph will operate at a mid-range temperature of 180K,
approximately half way between room temperature and liquid nitrogen
temperature; it will be stable to sub -milli-Kelvin(mK) levels over a
calibration cycle and a few mK over months to years. HPF's sensor is a
1.7 micron H2RG device by Teledyne. The environmental control boundary
is a 9 m2 thermal enclosure that completely surrounds the optical
train and produces a near blackbody cavity for all components. A large,
pressure - stabilized liquid nitrogen tank provides the heat sink for
the system via thermal straps while a multichannel resistive heater
control system provides the stabilizing heat source. High efficiency
multi-layer insulation blanketing provides the outermost boundary of
the thermal enclosure to largely isolate the environmental system
from ambient conditions. The cryostat, a stainless steel shell
derived from the APOGEE design, surrounds the thermal enclosure
and provides a stable, high quality vacuum environment. The full
instrument will be housed in a passive 'meat -locker' enclosure to
add a degree of additional thermal stability and as well as protect
the instrument. Effectiveness of this approach is being empirically
demonstrated via long duration scale model testing. The full scale
cryostat and environmental control system are being constructed for
a 2016 delivery of the instrument to the Hobby-Eberly Telescope. This
report describes the configuration of the hardware and the scale-model
test results as well as projections for performance of the full system.
Title: Deployment of the Hobby-Eberly Telescope wide field upgrade
Authors: Hill, Gary J.; Drory, Niv; Good, John; Lee, Hanshin; Vattiat,
Brian; Kriel, Herman; Bryant, Randy; Elliot, Linda; Landriau, Martin;
Leck, Ron; Perry, David; Ramsey, Jason; Savage, Richard; Allen,
Richard D.; Damm, George; DePoy, D. L.; Fowler, Jim; Gebhardt, Karl;
Haeuser, Marco; MacQueen, Phillip; Marshall, J. L.; Martin, Jerry;
Prochaska, Travis; Ramsey, Lawrence W.; Rheault, Jean-Philippe;
Shetrone, Matthew; Schroeder Mrozinski, Emily; Tuttle, Sarah E.;
Cornell, Mark E.; Booth, John; Moreira, Walter
Bibcode: 2014SPIE.9145E..06H
Altcode:
The Hobby-Eberly Telescope (HET) is an innovative large telescope
located in West Texas at the McDonald Observatory. The HET operates
with a fixed segmented primary and has a tracker, which moves the
four-mirror optical corrector and prime focus instrument package to
track the sidereal and non-sidereal motions of objects. A major upgrade
of the HET is in progress that will substantially increase the pupil
size to 10 meters (from 9.2 m) and the field of view to 22 arcminutes
(from 4 arcminutes) by replacing the corrector, tracker, and prime focus
instrument package. In addition to supporting existing instruments, and
a new low resolution spectrograph, this wide field upgrade will feed a
revolutionary new integral field spectrograph called VIRUS, in support
of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX§). The
upgrade is being installed and this paper discusses the current status.
Title: The Habitable-zone Planet Finder: A status update on the
development of a stabilized fiber-fed near-infrared spectrograph
for the for the Hobby-Eberly telescope
Authors: Mahadevan, Suvrath; Ramsey, Lawrence W.; Terrien, Ryan;
Halverson, Samuel; Roy, Arpita; Hearty, Fred; Levi, Eric; Stefansson,
Gudmundur K.; Robertson, Paul; Bender, Chad; Schwab, Chris; Nelson,
Matt
Bibcode: 2014SPIE.9147E..1GM
Altcode:
The Habitable-Zone Planet Finder is a stabilized, fiber-fed, NIR
spectrograph being built for the 10m Hobby- Eberly telescope (HET) that
will be capable of discovering low mass planets around M dwarfs. The
optical design of the HPF is a white pupil spectrograph layout in a
vacuum cryostat cooled to 180 K. The spectrograph uses gold-coated
mirrors, a mosaic echelle grating, and a single Teledyne Hawaii-2RG
(H2RG) NIR detector with a 1.7-micron cutoff covering parts of the
information rich z, Y and J NIR bands at a spectral resolution of
R∼50,000. The unique design of the HET requires attention to both
near and far-field fiber scrambling, which we accomplish with double
scramblers and octagonal fibers. In this paper we discuss and summarize
the main requirements and challenges of precision RV measurements in the
NIR with HPF and how we are overcoming these issues with technology,
hardware and algorithm developments to achieve high RV precision and
address stellar activity.
Title: Development of Fiber Fabry-Perot Interferometers as Stable
Near-infrared Calibration Sources for High Resolution Spectrographs
Authors: Halverson, Samuel; Mahadevan, Suvrath; Ramsey, Lawrence;
Hearty, Fred; Wilson, John; Holtzman, Jon; Redman, Stephen; Nave,
Gillian; Nidever, David; Nelson, Matt; Venditti, Nick; Bizyaev,
Dmitry; Fleming, Scott
Bibcode: 2014PASP..126..445H
Altcode: 2014arXiv1403.6841H
We discuss the ongoing development of single-mode fiber Fabry-Perot
(FFP) Interferometers as precise astro-photonic calibration sources for
high precision radial velocity (RV) spectrographs. FFPs are simple,
inexpensive, monolithic units that can yield a stable and repeatable
output spectrum. An FFP is a unique alternative to a traditional etalon,
as the interferometric cavity is made of single-mode fiber rather
than an air-gap spacer. This design allows for excellent collimation,
high spectral finesse, rigid mechanical stability, insensitivity to
vibrations, and no need for vacuum operation. The device we have tested
is a commercially available product from Micron Optics. Our development
path is targeted towards a calibration source for the Habitable-Zone
Planet Finder (HPF), a near-infrared spectrograph designed to detect
terrestrial-mass planets around low-mass stars, but this reference could
also be used in many existing and planned fiber-fed spectrographs as
we illustrate using the Apache Point Observatory Galactic Evolution
Experiment (APOGEE) instrument. With precise temperature control
of the fiber etalon, we achieve a thermal stability of 100 $\mu$K
and associated velocity uncertainty of 22 cm s$^{-1}$. We achieve a
precision of $\approx$2 m s$^{-1}$ in a single APOGEE fiber over 12
hours using this new photonic reference after removal of systematic
correlations. This high precision (close to the expected photon-limited
floor) is a testament to both the excellent intrinsic wavelength
stability of the fiber interferometer and the stability of the APOGEE
instrument design. Overall instrument velocity precision is 80 cm
s$^{-1}$ over 12 hours when averaged over all 300 APOGEE fibers and
after removal of known trends and pressure correlations, implying the
fiber etalon is intrinsically stable to significantly higher precision.
Title: Suppression of Fiber Modal Noise Induced Radial Velocity
Errors for Bright Emission-line Calibration Sources
Authors: Mahadevan, Suvrath; Halverson, Samuel; Ramsey, Lawrence;
Venditti, Nick
Bibcode: 2014ApJ...786...18M
Altcode: 2014arXiv1403.1577M
Modal noise in optical fibers imposes limits on the signal-to-noise
ratio (S/N) and velocity precision achievable with the next generation
of astronomical spectrographs. This is an increasingly pressing problem
for precision radial velocity spectrographs in the near-infrared (NIR)
and optical that require both high stability of the observed line
profiles and high S/N. Many of these spectrographs plan to use highly
coherent emission-line calibration sources like laser frequency combs
and Fabry-Perot etalons to achieve precision sufficient to detect
terrestrial-mass planets. These high-precision calibration sources
often use single-mode fibers or highly coherent sources. Coupling light
from single-mode fibers to multi-mode fibers leads to only a very low
number of modes being excited, thereby exacerbating the modal noise
measured by the spectrograph. We present a commercial off-the-shelf
solution that significantly mitigates modal noise at all optical and
NIR wavelengths, and which can be applied to spectrograph calibration
systems. Our solution uses an integrating sphere in conjunction with
a diffuser that is moved rapidly using electrostrictive polymers,
and is generally superior to most tested forms of mechanical fiber
agitation. We demonstrate a high level of modal noise reduction with
a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution
immediately enables spectrographs to take advantage of the innate
precision of bright state-of-the art calibration sources by removing
a major source of systematic noise.
Title: A Y+J Band Laser Frequency Comb for the Habitable Zone
Planet Finder
Authors: Osterman, Steve; Ycas, G. G.; Diddams, S. A.; Bender, C. F.;
Donaldson, C. L.; Mahadevan, S.; Quinlan, F.; Ramsey, L. W.
Bibcode: 2013AAS...22114911O
Altcode:
The Habitable Zone Planet Finder (HPF) scheduled for deployment to the
Hobby-Eberly Telescope in late 2015 will extend the radial velocity
search for exoplanets into the near infrared by providing a high
precision, stabilized near infrared spectrograph spanning the Y+J bands
(0.98-1.3μm) with 50,000 resolution. Working in the near infrared will
allow the HPF to study cooler, lower mass stars than is possible with
the current generation of optical spectrographs. In order to extend the
precision of the HPF to lower minimum RV signatures we are proposing to
develop a deployable, fully autonomous version of the Y+J band laser
frequency comb currently in operation at the NIST Time and Frequency
Division in Boulder, Colorado. The Y+J comb is derived from the H
band (1.45-1.7μm) comb which was successfully demonstrated at the
Hobby-Eberly Telescope in 2010. The deployed version will leverage off
of existing hardware and demonstrated technology. We present instrument
architecture and current performance as well as results of long term
stability tests, filter modeling, modal noise reduction results and
predicted end-to-end performance.
Title: The UKIRT Planet Finder
Authors: Jones, Hugh R. A.; Barnes, John; Bryson, Ian; Adamson, Andy;
Henry, David; Montgomery, David; Ives, Derek; Egan, Ian; Lunney,
David; Rees, Phil; Rayner, John; Ramsey, Larry; Vacca, Bill; Tinney,
Chris; Liu, Mike
Bibcode: 2013ASSP...37..329J
Altcode:
We present a conceptual design for the UKIRT Planet Finder (UPF). It is
a fibre-fed high resolving power (R ∼ 70,000 at 2.5 pixel sampling)
cryogenic echelle spectrograph operating in the near infrared (0.95-1.8
μm) and is designed to provide 1 m/s radial velocity measurements. We
identify the various error sources to overcome in order to achieve
the required stability. We have constructed models simulating likely
candidates and demonstrated the ability to recover exoplanetary
radial-velocity (RV) signals in the infrared. UPF should achieve a
total RV error of around 1 m/s on a typical M6V star. We use these
results as an input to a simulated 5-year survey of nearby M stars,
which has the sensitivity to detect of the order of 30 terrestrial
mass planets in the habitable zone around those stars. UPF will thus
test theoretical planet formation models, which predict an abundance
of terrestrial-mass planets around low-mass stars enabling critical
tests of planet-formation theories and allowing the identification of
nearby planets with conditions potentially suitable for life.
Title: A Large Sample of Magnetically-Active Stars Observed With
Kepler
Authors: Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri,
G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.;
Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.;
Walkowicz, L. M.
Bibcode: 2013AAS...22135415W
Altcode:
We have observed about 325 stars in our Kepler Guest Observer
programs (Cycles 1 through 4). For most of these targets, we are
analyzing extremely high-precision light curves that have been
continuously sampled every 30 minutes for up to 3 years. Our sample
of candidate magnetically-active stars was selected primarily using
GALEX colors. Starspots, pulsations, and variations due to eclipsing
and contact binaries combine to produce a rich variety of light
curves. We have developed semi-automated procedures to characterize
this variability and thus to classify the targets and identify the
physical mechanisms that dominate their Kepler light curves. We will
describe these procedures and discuss the range of physical properties
covered by our final classification scheme. We are using this Kepler
database of variability over timescales of minutes to years to provide
diagnostics of flares, starspot formation, evolution, migration, and
ultimately of stellar cycles in general. This work contains results
obtained using the NASA Kepler satellite and from the Apache Point
Observatory, the MMT (using NOAO community access time), and the
Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants
NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado,
by NSF grant AST-1109695 to the College of Charleston, and by a grant
from the South Carolina Space Grant consortium.
Title: Stellar Variability And External Noise Sources With The Kepler
Mission: Can Stellar Cycle Changes Be Revealed?
Authors: Ramsey, Lawrence
Bibcode: 2013adap.prop...39R
Altcode:
We will provide exploration of stellar and instrument noise properties
associated with Kepler Mission data to inform exoplanet detection
capabilities, reveal levels of stellar activity in the Kepler sample
relative to the Sun, and provide a foundation to determine if Kepler
data will support stellar cycle quantifications. Gilliland et al
(2011) provided a study separating observed variations in Kepler time
series into instrumental and stellar components, taking advantage of
the unique way in which the same stars are cycled through different
detectors. The latter study concluded the instrument was noisier
by a small margin on time scales of transits, while the stars were
nearly a factor of two more variable on this few hour time scale
than expected prior to launch. That study used data from the first
six quarters of Kepler observations; this study will extend the same
results by over two additional years (through Quarter 15), and utilize
the latest, updated data products. A more powerful study of intrinsic
stellar variability can focus on longer (activity) time scales; we
will provide such a study in an attempt to resolve a controversy on
variability of the Kepler stars relative to the Sun. Last, but far from
least, in terms of simple signal-to-noise arguments, data from Kepler
should easily reveal stellar cycle variations to well below the 0.1%
amplitude seen for the Sun. However, many instrumental drifts and
systematics have amplitudes well above the multi-year signal levels
expected. We will use Kepler's quietest stars to assess prospects for
extensive stellar cycle studies. The goal of this latter effort is
to perform all necessary calibrations to demonstrate that Kepler is
capable of quantifying stellar cycle variations, or, failing this,
to provide a clear explication of remaining problems that need to
be overcome. Elucidation of cyclic behavior for thousands of stars
would (if feasible) be a future seminal achievement for the Kepler
Mission. This will be a one year program. Actual science on stellar
cycles would benefit immensely from the longer time series that may
be avilable in future proposals. The budget is primarily for research
support of Gilliland -- Science PI on this program -- who will lead
all phases of the research.
Title: Young Star Populations in the Kepler Field
Authors: Brown, Alexander; Neff, J. E.; Wells, M.; Saar, S.; Furesz,
G.; Walkowicz, L. M.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.;
Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.;
Piskunov, N. E.; Ramsey, L. W.
Bibcode: 2013AAS...22135414B
Altcode:
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that routinely
allow detailed studies of stellar magnetic activity on late-type stars
that were difficult previously. Kepler provides multi-year duration
light-curves that allow investigation of how activity phenomena --
such as the growth, migration, and decay of star-spots, differential
rotation, activity cycles, and flaring -- operate on a wide variety of
single and binary stars. The 105 square degree Kepler Field contains
tens of thousands of late-type stars showing rotational modulation due
to star-spots with periods ranging from one day to a ``solar-like''
month. Short rotation periods and high levels of magnetic activity are
strongly correlated. However, there are only two basic reasons why stars
with rotation periods of a few days possess such high angular momentum
--- either they are close binaries or they are young stars. During
Kepler GO Cycles 1 through 4 we have been studying the Long-cadence
(30 minute sampling) photometry of hundreds of active late-type stars
and as an absolutely essential complement we have been obtaining high
resolution optical spectra to understand the physical properties of
these stars. We present results from a spectroscopic survey using the
MMT Hectochelle multi-object echelle of 4 square degrees of the Kepler
Field. We have discovered a significant population of young stars with
Li I absorption indicating ages of ~100 Myr or less at a spatial density
of at least 20 stars per square degree. Our detected young star sample
comprises at least 80 stars and represents a dramatic advance compared
to the previously known sample over the full Kepler Field of three
stars in this age range. Roughly one sixth of the stars observed are
young and a similar number short-period binaries based on 2-4 radial
velocities. We show how the rotational properties of the stars and their
physical properties are related. This work is based on data obtained
with the NASA Kepler satellite and the MMT Hectochelle spectrograph
using NOAO community access time. Support by NASA Kepler grants to the
University of Colorado and by NSF grant to the College of Charleston.
Title: The Metallicity of the CM Draconis System
Authors: Terrien, Ryan C.; Fleming, Scott W.; Mahadevan, Suvrath;
Deshpande, Rohit; Feiden, Gregory A.; Bender, Chad F.; Ramsey,
Lawrence W.
Bibcode: 2012ApJ...760L...9T
Altcode: 2012arXiv1210.4736T
The CM Draconis system comprises two eclipsing mid-M dwarfs of nearly
equal mass in a 1.27 day orbit. This well-studied eclipsing binary
has often been used for benchmark tests of stellar models, since its
components are among the lowest mass stars with well-measured masses
and radii (lsim 1% relative precision). However, as with many other
low-mass stars, non-magnetic models have been unable to match the
observed radii and effective temperatures for CM Dra at the 5%-10%
level. To date, the uncertain metallicity of the system has complicated
comparison of theoretical isochrones with observations. In this Letter,
we use data from the SpeX instrument on the NASA Infrared Telescope
Facility to measure the metallicity of the system during primary and
secondary eclipses, as well as out of eclipse, based on an empirical
metallicity calibration in the H and K near-infrared (NIR) bands. We
derive an [Fe/H] = -0.30 ± 0.12 that is consistent across all orbital
phases. The determination of [Fe/H] for this system constrains a
key dimension of parameter space when attempting to reconcile model
isochrone predictions and observations.
Title: Development of a New, Precise Near-infrared Doppler Wavelength
Reference: A Fiber Fabry-Perot Interferometer
Authors: Halverson, Samuel; Mahadevan, Suvrath; Ramsey, Lawrence;
Redman, Stephen; Nave, Gillian; Wilson, John C.; Hearty, Fred;
Holtzman, Jon
Bibcode: 2012arXiv1209.2704H
Altcode:
We present the ongoing development of a commercially available Micron
Optics fiber-Fabry Perot Interferometer as a precise, stable, easy to
use, and economic spectrograph reference with the goal of achieving
<1 m/s long term stability. Fiber Fabry-Perot interferometers (FFP)
create interference patterns by combining light traversing different
delay paths. The interference creates a rich spectrum of narrow
emission lines, ideal for use as a precise Doppler reference. This
fully photonic reference could easily be installed in existing NIR
spectrographs, turning high resolution fiber-fed spectrographs into
precise Doppler velocimeters. First light results on the Sloan Digital
Sky Survey III (SDSS-III) Apache Point Observatory Galactic Evolution
Experiment (APOGEE) spectrograph and several tests of major support
instruments are also presented. These instruments include a SuperK
Photonics fiber supercontinuum laser source and precise temperature
controller. A high resolution spectrum obtained using the NIST 2-m
Fourier transform spectrometer (FTS) is also presented. We find
our current temperature control precision of the FFP to be 0.15 mK,
corresponding to a theoretical velocity stability of 35 cm/s due to
temperature variations of the interferometer cavity.
Title: Current status of the Hobby-Eberly Telescope wide field upgrade
Authors: Hill, Gary J.; Booth, John A.; Cornell, Mark E.; Good,
John M.; Gebhardt, Karl; Kriel, Herman J.; Lee, Hanshin; Leck, Ron;
Moreira, Walter; MacQueen, Phillip J.; Perry, Dave M.; Rafal, Marc D.;
Rafferty, Tom H.; Ramiller, Chuck; Savage, Richard D.; Taylor, Charles
A.; Vattiat, Brian L.; Ramsey, Lawrence W.; Beno, Joseph H.; Beets,
Timothy A.; Esguerra, Jorge D.; Häuser, Marco; Hayes, Richard J.;
Heisler, James T.; Soukup, Ian M.; Zierer, Joseph J.; Worthington,
Michael S.; Mollison, Nicholas T.; Wardell, Douglas R.; Wedeking,
Gregory A.
Bibcode: 2012SPIE.8444E..0KH
Altcode:
The Hobby-Eberly Telescope (HET) is an innovative large telescope of
9.2 meter aperture, located in West Texas at the McDonald Observatory
(MDO). The HET operates with a fixed segmented primary and has a tracker
which moves the four-mirror corrector and prime focus instrument package
to track the sidereal and non-sidereal motions of objects. A major
upgrade of the HET is in progress that will increase the pupil size
to 10 meters and the field of view to 22' by replacing the corrector,
tracker and prime focus instrument package. In addition to supporting
the existing suite of instruments, this wide field upgrade will feed a
revolutionary new integral field spectrograph called VIRUS, in support
of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEXχ). This
paper discusses the current status of this upgrade.
Title: Near-infrared calibration systems for precise radial-velocity
measurements
Authors: Redman, Stephen L.; Kerber, Florian; Nave, Gillian; Mahadevan,
Suvrath; Ramsey, Lawrence W.; Smoker, Jonathan; Käufl, Hans-Ulrich;
Figueira, P. R. L.
Bibcode: 2012SPIE.8446E..8GR
Altcode:
We present work done to prepare two new near-infrared
calibration sources for use on high-precision astrophysical
spectrographs. Uranium-neon is an atomic calibration source,
commercially available as a hollow-cathode lamp, with over 10 000 known
emission lines between 0.85 and 4 μm. Four gas cells — containing
C2H2, H13CN, 12CO, and
13CO, respectively—are available as National Institute of
Standards and Technology (nist) Standard Reference Materials (SRMs),
and provide narrow absorption lines between 1.5 and 1.65 μm. These
calibration sources may prove useful for wavelength-calibrating the
future near-infrared high-precision radial-velocity spectrometers,
including the Calar Alto high-Resolution search for M dwarfs
with Exo-earths with a Near-infrared Echelle Spectrograph
(CARMENES),1 the SpectroPolarimetre InfraROUge
(SPIRou)∗, and the Habitable-Zone Planet Finder
(HPF).2
Title: The habitable-zone planet finder: a stabilized fiber-fed NIR
spectrograph for the Hobby-Eberly Telescope
Authors: Mahadevan, Suvrath; Ramsey, Lawrence; Bender, Chad; Terrien,
Ryan; Wright, Jason T.; Halverson, Sam; Hearty, Fred; Nelson, Matt;
Burton, Adam; Redman, Stephen; Osterman, Steven; Diddams, Scott;
Kasting, James; Endl, Michael; Deshpande, Rohit
Bibcode: 2012SPIE.8446E..1SM
Altcode: 2012arXiv1209.1686M
We present the scientific motivation and conceptual design for the
recently funded Habitable-zone Planet Finder (HPF), a stabilized
fiber-fed near-infrared (NIR) spectrograph for the 10 meter class
Hobby-Eberly Telescope (HET) that will be capable of discovering low
mass planets around M dwarfs. The HPF will cover the NIR Y and J bands
to enable precise radial velocities to be obtained on mid M dwarfs,
and enable the detection of low mass planets around these stars. The
conceptual design is comprised of a cryostat cooled to 200K, a dual
fiber-feed with a science and calibration fiber, a gold coated mosaic
echelle grating, and a Teledyne Hawaii-2RG (H2RG) *NIR detector with
a 1.7μm cutoff. A uranium-neon hollow-cathode lamp is the baseline
wavelength calibration source, and we are actively testing laser
frequency combs to enable even higher radial velocity precision. We
will present the overall instrument system design and integration
with the HET, and discuss major system challenges, key choices, and
ongoing research and development projects to mitigate risk. We also
discuss the ongoing process of target selection for the HPF survey.
Title: A near-infrared frequency comb for Y+J band astronomical
spectroscopy
Authors: Osterman, Steve; Ycas, Gabriel G.; Diddams, Scott A.; Quinlan,
Franklyn; Mahadevan, Suvrath; Ramsey, Lawrence; Bender, Chad F.;
Terrien, Ryan; Botzer, Brandon; Sigurdsson, Steinn; Redman, Stephen L.
Bibcode: 2012SPIE.8450E..1IO
Altcode: 2012arXiv1209.3295O
Radial velocity (RV) surveys supported by high precision wavelength
references (notably ThAr lamps and I2 cells) have successfully
identified hundreds of exoplanets; however, as the search for
exoplanets moves to cooler, lower mass stars, the optimum wave band
for observation for these objects moves into the near infrared (NIR)
and new wavelength standards are required. To address this need we
are following up our successful deployment of an H band(1.45-1.7μm)
laser frequency comb based wavelength reference with a comb working
in the Y and J bands (0.98-1.3μm). This comb will be optimized for
use with a 50,000 resolution NIR spectrograph such as the Penn State
Habitable Zone Planet Finder. We present design and performance details
of the current Y+J band comb.
Title: Optical fiber modal noise in the 0.8 to 1.5 micron region and
implications for near infrared precision radial velocity measurements
Authors: McCoy, Keegan S.; Ramsey, Lawrence; Mahadevan, Suvrath;
Halverson, Samuel; Redman, Stephen L.
Bibcode: 2012SPIE.8446E..8JM
Altcode: 2012arXiv1209.2906M
Modal noise in fibers has been shown to limit the signal-to-noise
ratio achievable in fiber-coupled, high-resolution spectrographs
if it is not mitigated via modal scrambling techniques. Modal noise
become significantly more important as the wavelength increases and
presents a risk to the new generation of near-infrared precision
radial spectrographs under construction or being proposed to search
for planets around cool M-dwarf stars, which emit most of their light
in the NIR. We present experimental results of tests at Penn State
University characterizing modal noise in the far visible out to 1.5
microns and the degree of modal scrambling we obtained using mechanical
scramblers. These efforts are part of a risk mitigation effort for the
Habitable Zone Planet Finder spectrograph currently under development
at Penn State University.
Title: The SDSS-HET Survey of Kepler Eclipsing Binaries: Spectroscopic
Dynamical Masses of the Kepler-16 Circumbinary Planet Hosts
Authors: Bender, Chad F.; Mahadevan, Suvrath; Deshpande, Rohit; Wright,
Jason T.; Roy, Arpita; Terrien, Ryan C.; Sigurdsson, Steinn; Ramsey,
Lawrence W.; Schneider, Donald P.; Fleming, Scott W.
Bibcode: 2012ApJ...751L..31B
Altcode: 2012arXiv1205.0259B
We have used high-resolution spectroscopy to observe the Kepler-16
eclipsing binary as a double-lined system and measure precise radial
velocities for both stellar components. These velocities yield a
dynamical mass ratio of q = 0.2994 ± 0.0031. When combined with the
inclination, i = 90fdg3401+0.0016 - 0.0019,
measured from the Kepler photometric data by Doyle et al. (D11), we
derive dynamical masses for the Kepler-16 components of MA
= 0.654 ± 0.017 M ⊙ and MB = 0.1959 ± 0.0031
M ⊙, a precision of 2.5% and 1.5%, respectively. Our
results confirm at the ~2% level the mass-ratio derived by D11 with
their photometric-dynamical model (PDM), q = 0.2937 ± 0.0006. These
are among the most precise spectroscopic dynamical masses ever measured
for low-mass stars and provide an important direct test of the results
from the PDM technique. Based on observations obtained with the
Hobby-Eberly Telescope, which is a joint project of the University of
Texas at Austin, the Pennsylvania State University, Stanford University,
Ludwig-Maximilians-Universität München, and Georg-August-Universität
Göttingen.
Title: A High-resolution Atlas of Uranium-Neon in the H Band
Authors: Redman, Stephen L.; Ycas, Gabriel G.; Terrien, Ryan;
Mahadevan, Suvrath; Ramsey, Lawrence W.; Bender, Chad F.; Osterman,
Steven N.; Diddams, Scott A.; Quinlan, Franklyn; Lawler, James E.;
Nave, Gillian
Bibcode: 2012ApJS..199....2R
Altcode: 2011arXiv1112.1062R
We present a high-resolution (R ≈ 50,000) atlas of a uranium-neon
(U/Ne) hollow-cathode spectrum in the H band (1454-1638 nm) for the
calibration of near-infrared spectrographs. We obtained this U/Ne
spectrum simultaneously with a laser-frequency comb spectrum, which we
used to provide a first-order calibration to the U/Ne spectrum. We then
calibrated the U/Ne spectrum using the recently published uranium line
list of Redman et al., which is derived from high-resolution Fourier
transform spectrometer measurements. These two independent calibrations
allowed us to easily identify emission lines in the hollow-cathode
lamp that do not correspond to known (classified) lines of either
uranium or neon, and to compare the achievable precision of each
source. Our frequency comb precision was limited by modal noise and
detector effects, while the U/Ne precision was limited primarily by
the signal-to-noise ratio (S/N) of the observed emission lines and our
ability to model blended lines. The standard deviation in the dispersion
solution residuals from the S/N-limited U/Ne hollow-cathode lamp was 50%
larger than the standard deviation of the dispersion solution residuals
from the modal-noise-limited laser-frequency comb. We advocate the use
of U/Ne lamps for precision calibration of near-infrared spectrographs,
and this H-band atlas makes these lamps significantly easier to use
for wavelength calibration.
Title: An H-band Spectroscopic Metallicity Calibration for M Dwarfs
Authors: Terrien, Ryan C.; Mahadevan, Suvrath; Bender, Chad F.;
Deshpande, Rohit; Ramsey, Lawrence W.; Bochanski, John J.
Bibcode: 2012ApJ...747L..38T
Altcode: 2012arXiv1202.1800T
We present an empirical near-infrared (NIR) spectroscopic method
for estimating M dwarf metallicities, based on features in the H
band, as well as an implementation of a similar published method
in the K band. We obtained R ~ 2000 NIR spectra of a sample of M
dwarfs using the NASA IRTF-SpeX spectrograph, including 22 M dwarf
metallicity calibration targets that have FGK companions with known
metallicities. The H-band and K-band calibrations provide equivalent
fits to the metallicities of these binaries, with an accuracy of
±0.12 dex. We derive the first empirically calibrated spectroscopic
metallicity estimate for the giant planet-hosting M dwarf GJ 317,
confirming its supersolar metallicity. Combining this result with
observations of eight other M dwarf planet hosts, we find that M
dwarfs with giant planets are preferentially metal-rich compared to
those that host less massive planets. Our H-band calibration relies
on strongly metallicity-dependent features in the H band, which will
be useful in compositional studies using mid- to high-resolution NIR
M dwarf spectra, such as those produced by multiplexed surveys like
SDSS-III APOGEE. These results will also be immediately useful for
ongoing spectroscopic surveys of M dwarfs.
Title: Demonstration of on-sky calibration of astronomical spectra
using a 25 GHz near-IR laser frequency comb
Authors: Ycas, Gabriel G.; Quinlan, Franklyn; Diddams, Scott A.;
Osterman, Steve; Mahadevan, Suvrath; Redman, Stephen; Terrien, Ryan;
Ramsey, Lawrence; Bender, Chad F.; Botzer, Brandon; Sigurdsson, Steinn
Bibcode: 2012OExpr..20.6631Y
Altcode: 2012arXiv1201.5125Y
We describe and characterize a 25 GHz laser frequency comb based on
a cavity-filtered erbium fiber mode-locked laser. The comb provides a
uniform array of optical frequencies spanning 1450 nm to 1700 nm, and
is stabilized by use of a global positioning system referenced atomic
clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the
McDonald Observatory where it was used as a radial velocity calibration
source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar
targets were observed in three echelle orders over four nights, and
radial velocity precision of \sim10 m/s (\sim6 MHz) was achieved from
the comb-calibrated spectra.
Title: Precision Rvs In The Nir: First On-sky Velocities With A U/ne
Lamp And A Laser Frequency Comb
Authors: Mahadevan, Suvrath; Ramsey, L.; Redman, S.; Bender, C.;
Terrien, R.; Roy, A.; Botzer, B.; Osterman, S.; Diddams, S.; Ycas,
G.; Quinlan, F.
Bibcode: 2011ESS.....2.0206M
Altcode:
Precision radial velocities in the near infrared (NIR) can help
detect terrestrial mass planets around mid and late M dwarfs that are
typically too faint in the optical for effective monitoring. The NIR
poses a new set of calibration and technology challenges. We will
discuss the current state of the art in NIR spectroscopy, and RV
precision and present ongoing work at Penn State with the Pathfinder
NIR testbed. With the Pathfinder we have demonstrated 10-20 m/s radial
velocity precision in the NIR Y band at the 9m Hobby Eberly telescope
using a Uranium-Neon hollow cathode lamp as a simultaneous wavelength
reference. We shall present these results and also new velocity
results from recent first on-sky observations with an H band laser
frequency comb developed at NIST and CASA. The innate stability and
known frequencies of the comb lines provides an excellent calibrator in
the H band, but numerous systematics like fiber modal noise, tellurics,
and detector calibration need to be overcome. We will discuss progress
made on all these fronts with experiments on the Pathfinder testbed. We acknowledge support from NSF, NASA, NAI, NIST, Penn State, and
the Center for Exoplanets & Habitable Worlds.
Title: Visible and Near-Infrared Properties of Optical Fibers Coupled
to the Pathfinder High-Resolution NIR Spectrograph
Authors: McCoy, K.; Ramsey, L.
Bibcode: 2011amos.confE..69M
Altcode:
The Penn State Astronomy and Astrophysics Department’s Pathfinder
instrument is a fiber-fed, warm-bench echelle spectrograph designed
to explore technical issues that must be resolved in order to measure
precise radial velocities that will allow the detection of exoplanets
in the near-infrared (NIR). In May 2010, Pathfinder demonstrated 10-20
m/s radial-velocity precision in the NIR at the 9 meter Hobby-Eberly
Telescope. To attain even higher precision, we are investigating the NIR
properties of the optical fibers that transmit light from the telescope
to Pathfinder. We conducted a series of modal noise tests with visible
and NIR laser diodes on a 200 micron diameter, fused-silica, multimode
optical fiber as the preliminary step in analyzing the degrading
effects of modal noise on radial-velocity precision. We report these
test results and comment on our future tests to reduce the negative
effects of modal noise and focal ratio degradation (FRD). The lessons
learned from this research and the Pathfinder prototype will be used in
Pathfinder II, which will aim to achieve better than 5 m/s in the NIR.
Title: Laser Frequency Comb Supported Stellar Radial Velocity
Determination in the NIR: Initial Results.
Authors: Osterman, Steve; Diddams, S.; Quinlan, F.; Ycas, G.;
Mahadevan, S.; Ramsey, L.; Bender, C.; Terrien, R.; Botzer, B.;
Redman, S.
Bibcode: 2011ESS.....2.0205O
Altcode:
The laser frequency comb presents the potential for a revolutionary
increase in radial velocity precision by providing a calibration
reference of unprecedented quality in terms of wavelength knowledge,
repeatability, number, density and regularity of lines. Promising first
steps have been taken leading to the derivation of stellar radial
velocities in the NIR H band, a wavelength range well suited to the
observation of M dwarfs. These stars, with low mass and low luminosity,
are the most prevalent class of stars within 10 parsecs and can be
expected to yield a higher reflex velocity for a terrestrial mass
planet in the liquid water habitable zone than would be the case with
a more massive star such as our own. We present the design and both
laboratory and on-sky performance of an H-band laser frequency comb
used in conjunction with the Penn State Pathfinder testbed spectrograph
and discuss lessons learned and plans for follow on testing.
Title: VizieR Online Data Catalog: IR spectrum of Uranium hollow
cathode lamps (Redman+, 2011)
Authors: Redman, S. L.; Lawler, J. E.; Nave, G.; Ramsey, L. W.;
Mahadevan, S.
Bibcode: 2011yCat..21950024R
Altcode:
The observations used for our measurements were made with the 1m Fourier
transform spectrometer (FTS) on Kitt Peak between 1979 and 2002,
and are publicly available on the National Solar Observatory (NSO)
Web site (http://diglib.nso.edu/nso_user.html). (1 data file).
Title: The Infrared Spectrum of Uranium Hollow Cathode Lamps from
850 nm to 4000 nm: Wavenumbers and Line Identifications from Fourier
Transform Spectra
Authors: Redman, Stephen L.; Lawler, James E.; Nave, Gillian; Ramsey,
Lawrence W.; Mahadevan, Suvrath
Bibcode: 2011ApJS..195...24R
Altcode: 2011arXiv1107.4091R
We provide new measurements of wavenumbers and line identifications
of 10, 100 U I and U II near-infrared (NIR) emission lines between
2500 cm-1 and 12, 000 cm-1 (4000-850 nm) using
archival Fourier transform spectrometer spectra from the National Solar
Observatory. This line list includes isolated uranium lines in the Y,
J, H, K, and L bands (0.9-1.1 μm, 1.2-1.35 μm, 1.5-1.65 μm, 2.0-2.4
μm, and 3.0-4.0 μm, respectively), and provides six times as many
calibration lines as thorium in the NIR spectral range. The line lists
we provide enable inexpensive, commercially available uranium hollow
cathode lamps to be used for high-precision wavelength calibration of
existing and future high-resolution NIR spectrographs.
Title: Kepler Observations of Starspot Evolution, Differential
Rotation, and Flares on Late-Type Stars
Authors: Brown, Alexander; Korhonen, H.; Berdyugina, S.; Walkowicz,
L.; Kowalski, A.; Hawley, S.; Neff, J.; Ramsey, L.; Redman, S.; Saar,
S.; Furesz, G.; Piskunov, N.; Harper, G.; Ayres, T.; Tofany, B.
Bibcode: 2011AAS...21820502B
Altcode: 2011BAAS..43G20502B
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that
routinely allow detailed studies of stellar magnetic activity on
late-type stars that were difficult, if not impossible, to attempt
previously. Rotational modulation due to starspots is commonly seen
in the Kepler light-curves of late-type stars, allowing detailed
study of the surface distribution of their photospheric magnetic
activity. Kepler is providing multi-year duration light-curves that
allow us to investigate how activity phenomena -- such as the growth,
migration, and decay of starspots, differential rotation, activity
cycles, and flaring -- operate on single and binary stars with a
wide range of mass and convection zone depth. We present the
first results from detailed starspot modeling using newly-developed
light-curve inversion codes for a range of GALEX-selected stars with
typical rotation periods of a few days, that we have observed as part of
our 200 target Kepler Cycle 1/2 Guest Observer programs. The physical
properties of the stars have been measured using high resolution
optical spectroscopy, which allows the Kepler results to be placed
within the existing framework of knowledge regarding stellar magnetic
activity. These results demonstrate the powerful diagnostic capability
provided by tracking starspot evolution essentially continuously for
more than 16 months. The starspots are clearly sampling the stellar
rotation rate at different latitudes, enabling us to measure the
differential rotation and starspot lifetimes. As would be expected,
stars with few day rotation show frequent flaring that is easily seen
as "white-light" flares in Kepler light-curves. We compare the observed
flare rates and occurrence with the starspot properties. This work
contains results obtained using the NASA Kepler satellite and from the
Apache Point Observatory, the MMT (using NOAO community access time),
and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler
grants NNX10AC51G and NNX11AC79G.
Title: Precision Radial Velocities in the near-infrared Y and H
bands with the Penn State Pathfinder Instrument
Authors: Mahadevan, Suvrath; Ramsey, L.; Redman, S.; Bender, C.;
Botzer, B.; Terrien, R.; Osterman, S.; Diddams, S.; Ycas, G.; Quinlan,
F.; Roy, A.; Zonak, S.
Bibcode: 2011AAS...21740101M
Altcode: 2011BAAS...4340101M
Precision radial velocities in the near infrared can help detect
terrestrial mass planets around mid and late M dwarfs that are
typically too faint in the optical for effective monitoring. We have
demonstrated 10-15 m/s radial velocity precision in the NIR Y band with
our warm-bench fiber-fed Pathfinder instrument at the 9m Hobby Eberly
telescope, and will present these results as well as discuss results
from the first on-sky observations with an H band laser frequency
comb. We will also present the instrumental upgrades and modification
to Pathfinder that have made high NIR velocity precision possible
with the use of new calibration sources like Uranium lamps and laser
combs. The ability to achieve this level of precision with a test bed
bodes well for a stabilized spectrograph built on these principles,
and we discuss progress toward this as well as challenges like modal
noise and telluric absorption correction.
Title: First Stellar Radial Velocities with a Laser Frequency Comb:
Observations in the NIR H Band
Authors: Osterman, Steve; Diddams, S.; Quinlan, F.; Ycas, G.;
Mahadevan, S.; Ramsey, L.; Bender, C.; Redman, S.; Terrien, R.;
Botzer, B.
Bibcode: 2011AAS...21740102O
Altcode: 2011BAAS...4340102O
Advances in high precision radial velocity spectroscopy have been
hindered by the lack of suitable wavelength references. This has been
especially the case in the infrared where until recently radial velocity
precision has been limited to 50-100m/s, hindering investigations
such as the search for extrasolar planets orbiting cooler M stars
at these wavelengths. To redress deficiency this we have developed a
25GHz laser frequency comb spanning the H band and suitable for use
with spectrographs with spectral resolution in the range of 40,000 -
60,000, with RV precision limited by instrument stability and object
S/N rather than by the lack of a suitable wavelength standard. We
will present CU/NIST frequency comb performance and results obtained
using the Pennsylvania State University's Pathfinder Spectrograph on
the Hobby Eberly Telescope and will discuss lessons learned.
Title: A Precision Radial Velocity Pathfinder Instrument in the H
Band with a Laser Frequency Comb
Authors: Terrien, Ryan; Mahadevan, S.; Ramsey, L.; Bender, C.; Redman,
S.; Osterman, S.; Diddams, S.; Ycas, G.; Quinlan, F.; Botzer, B.
Bibcode: 2011AAS...21725309T
Altcode: 2011BAAS...4325309T
We describe changes to the warm-bench, fiber-fed, Penn State Pathfinder
instrument that enabled us to test the ability to recover precision
radial velocities in the H-band. The use of thermal blocking filters
that cut off at 1.7 microns allows us to observe in the H-band by
blocking the overwhelming thermal flux beyond 2 microns. A PK-50 window
provides further suppression of this thermal flux. We also describe the
observations, reduction, and results from an August 2010 test run of
this instrument with a 25 GHz NIST laser frequency comb calibration
system. We obtained radial velocities of several bright stars with
on-sky observation with the laser comb. Our results demonstrate the
potential of our testbed configuration for obtaining precision radial
velocities in the NIR, as well as the utility of laser frequency combs
as wavelength calibrators in this wavelength regime.
Title: The Habitable Zone Planet Finder Project: A Proposed High
Resolution NIR Spectrograph for the Hobby Eberly Telescope (HET)
to Discover Low Mass Exoplanets around M Stars
Authors: Mahadevan, S.; Ramsey, L.; Redman, S.; Zonak, S.; Wright,
J.; Wolszczan, A.; Endl, M.; Zhao, B.
Bibcode: 2010ASPC..430..272M
Altcode:
Radial velocity precision in the NIR is now approaching the level
necessary to detect exoplanets around mid-late M stars that are very
faint in the optical and emit most of their flux in the NIR. The
Penn State Pathfinder prototype instrument has already demonstrated
7-10 ms-1 precision on sunlight, and similar precision
has been reported at the Pathways conference using CRIRES and an
ammonia gas-cell. We discuss the science goals that motivate a stable
cross-dispersed, high-resolution NIR spectrograph on a large telescope,
as well as the path leading from the Pathfinder prototype to one
such possible instrument—the fiber-fed Habitable Zone Planet Finder
(HZPF) on the Hobby Eberly Telescope (HET). We also discuss wavelength
calibration issues specific to the NIR, and our ongoing exploration
with Pathfinder to mitigate these issues.
Title: Uranium-Neon as a Near-Infrared Calibration Source
Authors: Redman, Stephen; Nave, Gillian; Lawler, Jim; Ramsey, Larry;
Mahadevan, Suvrath
Bibcode: 2010aepr.confP..17R
Altcode:
No abstract at ADS
Title: Optical Fibers in Spectrograph Design; A Technical Overview
Authors: Ramsey, Larry
Bibcode: 2010aepr.confE..28R
Altcode: 2010aepr.confE...1R
No abstract at ADS
Title: The habitable zone planet finder: a proposed high-resolution
NIR spectrograph for the Hobby Eberly Telescope to discover low-mass
exoplanets around M dwarfs
Authors: Mahadevan, Suvrath; Ramsey, Larry; Wright, Jason; Endl,
Michael; Redman, Stephen; Bender, Chad; Roy, Arpita; Zonak, Stephanie;
Troupe, Nathaniel; Engel, Leland; Sigurdsson, Steinn; Wolszczan,
Alex; Zhao, Bo
Bibcode: 2010SPIE.7735E..6XM
Altcode: 2010arXiv1007.3235M; 2010SPIE.7735E.227M
The Habitable Zone Planet Finder (HZPF) is a proposed instrument
for the 10m class Hobby Eberly telescope that will be capable of
discovering low mass planets around M dwarfs. HZPF will be fiber-fed,
provide a spectral resolution R~ 50,000 and cover the wavelength
range 0.9-1.65μm, the Y, J and H NIR bands where most of the flux is
emitted by midlate type M stars, and where most of the radial velocity
information is concentrated. Enclosed in a chilled vacuum vessel with
active temperature control, fiber scrambling and mechanical agitation,
HZPF is designed to achieve a radial velocity precision < 3m/s, with
a desire to obtain <1m/s for the brightest targets. This instrument
will enable a study of the properties of low mass planets around M
dwarfs; discover planets in the habitable zones around these stars,
as well serve as an essential radial velocity confirmation tool for
astrometric and transit detections around late M dwarfs. Radial velocity
observation in the near-infrared (NIR) will also enable a search for
close in planets around young active stars, complementing the search
space enabled by upcoming high-contrast imaging instruments like GPI,
SPHERE and PALM3K. Tests with a prototype Pathfinder instrument have
already demonstrated the ability to recover radial velocities at 7-10
m/s precision from integrated sunlight and ~15-20 m/s precision on
stellar observations at the HET. These tests have also demonstrated
the ability to work in the NIR Y and J bands with an un-cooled
instrument. We will also discuss lessons learned about calibration and
performance from our tests and how they impact the overall design of
the HZPF.
Title: The Pathfinder testbed: exploring techniques for achieving
precision radial velocities in the near infrared
Authors: Ramsey, Larry W.; Mahadevan, Suvrath; Redman, Stephen;
Bender, Chad; Roy, Arpita; Zonak, Stephanie; Sigurdsson, Steinn;
Wolszczan, Alex
Bibcode: 2010SPIE.7735E..71R
Altcode: 2010arXiv1009.0477R; 2010SPIE.7735E.231R
The Penn State Pathfinder is a prototype warm fiber-fed Echelle
spectrograph with a Hawaii-1 NIR detector that has already demonstrated
7-10 m/s radial velocity precision on integrated sunlight. The
Pathfinder testbed was initially setup for the Gemini PRVS design study
to enable a systematic exploration of the challenges of achieving
high radial velocity precision in the near-infrared, as well as to
test possible solutions to these calibration challenges. The current
version of the Pathfinder has an R3 echelle grating, and delivers a
resolution of R~50,000 in the Y, J or H bands of the spectrum. We will
discuss the on sky-performance of the Pathfinder during an engineering
test run at the Hobby Eberly Telescope as well the results of velocity
observations of M dwarfs. We will also discuss the unique calibration
techniques we have explored, like Uranium-Neon hollow cathode lamps,
notch filter, and modal noise mitigation to enable high precision
radial velocity observation in the NIR. The Pathfinder is a prototype
testbed precursor of a cooled high-resolution NIR spectrograph capable
of high radial velocity precision and of finding low mass planets
around mid-late M dwarfs.
Title: The Lunar Orbiter Laser Altimeter Investigation on the Lunar
Reconnaissance Orbiter Mission
Authors: Smith, David E.; Zuber, Maria T.; Jackson, Glenn B.;
Cavanaugh, John F.; Neumann, Gregory A.; Riris, Haris; Sun, Xiaoli;
Zellar, Ronald S.; Coltharp, Craig; Connelly, Joseph; Katz, Richard B.;
Kleyner, Igor; Liiva, Peter; Matuszeski, Adam; Mazarico, Erwan M.;
McGarry, Jan F.; Novo-Gradac, Anne-Marie; Ott, Melanie N.; Peters,
Carlton; Ramos-Izquierdo, Luis A.; Ramsey, Lawrence; Rowlands, David
D.; Schmidt, Stephen; Scott, V. Stanley; Shaw, George B.; Smith,
James C.; Swinski, Joseph-Paul; Torrence, Mark H.; Unger, Glenn; Yu,
Anthony W.; Zagwodzki, Thomas W.
Bibcode: 2010SSRv..150..209S
Altcode:
The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the
payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO)
(Chin et al., in Space Sci. Rev. 129:391-419, 2007). The instrument
is designed to measure the shape of the Moon by measuring precisely
the range from the spacecraft to the lunar surface, and incorporating
precision orbit determination of LRO, referencing surface ranges to
the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz,
with a nominal accuracy of 10 cm. Its primary objective is to produce
a global geodetic grid for the Moon to which all other observations
can be precisely referenced.
Title: Extending the Search for Other Earths with Precision Radial
Velocity Measurements in the Near-IR
Authors: Redman, Stephen L.; Ramsey, L.; Mahadevan, S.
Bibcode: 2010AAS...21534804R
Altcode: 2010BAAS...42..530R
M dwarfs, the most common type of star in the Solar neighborhood,
exhibit higher Doppler radial velocities when orbited by a
terrestrial mass planet than F, G, K dwarfs since they have lower
mass. Unfortunately, late M dwarfs have low optical luminosities,
emitting most of their flux in the near-infrared (NIR). The ExoPlanet
Task Force has recommended that NIR RV instruments be made a high
priority. We have been developing such an instrument at Penn State
and preliminary results for our "pathfinder" instrument have been
published in PASP (120:870, 2008, p. 887). These studies have been
extended with a significant upgrade which includes better optimized
gratings and a substantially improved calibration system. We present
recent results from Y- and J-band observations in the near-Infrared
using the Earth's rotational velocity with respect to the Sun as a
test signal and a Hawaii-1K array. We use these results, along with
a high resolution spectrum of Barnard's Star (M4) at red limit of the
CCD to estimate the achievable precision when we move the pathfinder
to the Hobby-Eberly telescope in the Spring of 2010.
Title: The Habitable Zone Planet Finder: A Proposed High Resolution
Nir Spectrograph For The Het To Discover Low Mass Exoplanets Around
M Stars
Authors: Mahadevan, Suvrath; Ramsey, L.; Wolszczan, A.; Wright, J.;
Endl, M.; Redman, S.
Bibcode: 2010AAS...21542123M
Altcode: 2010BAAS...42..290M
The Habitable Zone Planet Finder (HZPF) is a proposed instrument for
the 9m Hobby Eberly telescope that will be capable of discovering
low mass planets around M dwarfs. HZPF will be fiber-fed, provide a
spectral resolution R 50,000 and cover the wavelength range 0.9-1.65mm,
the Y, J and H near infrared (NIR) bands where most of the flux is
emitted by late type M stars, and where most of the radial velocity
information is concentrated. Enclosed in a vacuum tank with active
temperature control, fiber scrambling and mechanical agitation, HZPF
is designed to achieve a radial velocity precision < 3m/s, with a
desire to achieve 1m/s for the brightest targets. This instrument will
enable a study of the properties of low mass planets around M dwarfs;
discover planets in the habitable zones around these stars, and serve
as an essential radial velocity confirmation tool for astrometric and
transit detections around late M dwarfs. Radial velocity observation the
NIR will also enable a search for close in planets around young active
stars, complementing the search space enabled by upcoming high-contrast
imaging instruments. Tests with our laboratory prototype have already
demonstrated the ability to recover radial velocities in the NIR at
7-10 m/s precision from integrated sunlight. We will discuss lessons
learned about calibration and NIR array performance from our tests
and how they impact the design of the HZPF.
Title: Rotational Velocities for M Dwarfs
Authors: Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko,
Y.; Gallardo, J.; Barnes, J. R.; Pinfield, D. J.
Bibcode: 2009ApJ...704..975J
Altcode: 2009arXiv0908.4092J
We present spectroscopic rotation velocities (v sin i) for 56 M dwarf
stars using high-resolution Hobby-Eberly Telescope High Resolution
Spectrograph red spectroscopy. In addition, we have also determined
photometric effective temperatures, masses, and metallicities ([Fe/H])
for some stars observed here and in the literature where we could
acquire accurate parallax measurements and relevant photometry. We
have increased the number of known v sin i values for mid M stars
by around 80% and can confirm a weakly increasing rotation velocity
with decreasing effective temperature. Our sample of v sin is peak
at low velocities (~3 km s-1). We find a change in the
rotational velocity distribution between early M and late M stars,
which is likely due to the changing field topology between partially
and fully convective stars. There is also a possible further change
in the rotational distribution toward the late M dwarfs where dust
begins to play a role in the stellar atmospheres. We also link v
sin i to age and show how it can be used to provide mid-M star age
limits. When all literature velocities for M dwarfs are added to our
sample, there are 198 with v sin i <= 10 km s-1 and 124
in the mid-to-late M star regime (M3.0-M9.5) where measuring precision
optical radial velocities is difficult. In addition, we also search
the spectra for any significant Hα emission or absorption. Forty three
percent were found to exhibit such emission and could represent young,
active objects with high levels of radial-velocity noise. We acquired
two epochs of spectra for the star GJ1253 spread by almost one month
and the Hα profile changed from showing no clear signs of emission,
to exhibiting a clear emission peak. Four stars in our sample appear
to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with
both GJ3129 and Gl802 exhibiting double Hα emission features. The
tables presented here will aid any future M star planet search target
selection to extract stars with low v sin i. Based on observations
obtained with the Hobby-Eberly Telescope, which is a joint project of
the University of Texas at Austin, the Pennsylvania State University,
Stanford University, Ludwig-Maximilians-Universität München, and
Georg-August-Universität Göttingen.
Title: Precision Radial Velocities in the Infrared
Authors: Jones, Hugh R. A.; Rayer, John; Ramsey, Larry; Dent, Bill;
Longmore, Andy; Vacca, Bill; Liu, Mike; Webster, Adrian; Wolscznan,
Alex; Barnes, John
Bibcode: 2009ASSP....9..415J
Altcode: 2009svlt.conf..415J
Over 250 extra-solar planets have been discovered to date using a
variety of techniques. The majority have been discovered at optical
wavelengths from the Doppler shift of F, G and K stars induced by
orbiting planets. We have constructed models simulating likely planets
around M dwarfs and demonstrated the ability to recover their radial
velocity signals in the infrared. We have conducted experiments in the
infrared with a brass-board instrument to explore real-world issues. We
are thus confident that a stabilised radial velocity spectrometer with
a single-shot 1 and 1.7 microns coverage at a resolution of around 70
k can achieve an instrumental radial velocity error of 0.5 m/s. This
enables the efficient measurement of radial velocities for M, L and
T spectral classes.
Title: A Pathfinder Instrument for Precision Radial Velocities in
the Near-Infrared
Authors: Ramsey, L. W.; Barnes, J.; Redman, S. L.; Jones, H. R. A.;
Wolszczan, A.; Bongiorno, S.; Engel, L.; Jenkins, J.
Bibcode: 2008PASP..120..887R
Altcode: 2008arXiv0806.3749R
We have designed and tested an in-plane echelle spectrograph configured
to investigate precision radial velocities from ground-based
near-infrared observations. The spectrograph operates across the
spectral range of 0.9-1.7 μm at a spectral resolution of R = 50,000,
and uses a liquid nitrogen-cooled HAWAII 1 K detector. Repeated
measurements of the Earth’s rotation via integrated sunlight with
two different instrument arrangements in the near-infrared Y band
have produced radial velocities with ∼10 m s-1 rms over
a period of several hours. The most recent instrument configuration
has achieved an unbinned rms of 7 m s-1 and suggests that
infrared radial velocity precisions may be able to approach those
achieved at optical wavelengths.
Title: Precision radial velocity spectrograph
Authors: Jones, Hugh R. A.; Rayner, John; Ramsey, Larry; Henry,
David; Dent, Bill; Montgomery, David; Vick, Andy; Ives, Derek; Egan,
Ian; Lunney, David; Rees, Phil, II; Webster, Adrian; Tinney, Chris;
Liu, Mike
Bibcode: 2008SPIE.7014E..0YJ
Altcode: 2008SPIE.7014E..31J
We present a conceptual design for a Precision Radial Velocity
Spectrograph (PRVS) for the Gemini telescope. PRVS is a fibre fed high
resolving power (R~70,000 at 2.5 pixel sampling) cryogenic echelle
spectrograph operating in the near infrared (0.95 - 1.8 microns) and is
designed to provide 1 m/s radial velocity measurements. We identify the
various error sources to overcome in order to the required stability. We
have constructed models simulating likely candidates and demonstrated
the ability to recover exoplanetary RV signals in the infrared. PRVS
should achieve a total RV error of around 1 m/s on a typical M6V
star. We use these results as an input to a simulated 5-year survey of
nearby M stars. Based on a scaling of optical results, such a survey
has the sensitivity to detect several terrestrial mass planets in the
habitable zone around nearby stars. PRVS will thus test theoretical
planet formation models, which predict an abundance of terrestrial-mass
planets around low-mass stars.We have conducted limited experiments
with a brass-board instrument on the Sun in the infrared to explore
real-world issues achieving better than 10 m/s precision in single
10 s exposures and better than 5 m/s when integrated across a minute
of observing.
Title: The image quality of the Southern African Large Telescope
(SALT)
Authors: O'Donoghue, Darragh E.; Atad-Ettedgui, Eli; Balona, Luis;
Bigelow, Bruce C.; Booth, John A.; Botha, Lucian; Brink, Janus D.;
Buckley, David A. H.; Charles, Phil; Christians, Alrin; Clemens,
J. Christopher; Crause, Lisa A.; Crawford, Steven M.; Evans, Geoffrey
P.; Gajjar, Hitesh; Hashimoto, Yas; Hendricks, Malcolm; Kniazev,
Alexei; Koeslag, Anthony R.; Koorts, Willie P.; Kriel, Herman J.;
Loaring, Nicola S.; Love, Jonathan; Marang, Fred; Metcalfe, Douglas;
Meyer, Brennan; O'Connor, James; du Plessis, Charl A.; Ramsey,
Lawrence W.; Romero-Colmenero, Encarni; Sass, Craig; Scholtz, Johann
C.; Sefako, Ramotholo; Siyengo, Sandisa; Still, Martin; Strydom,
Ockert J.; Swat, Arkadiusz; Du Toit, Johann F.; Vaisanen, Petri;
Wells, Martyn; Worters, Hannah
Bibcode: 2008SPIE.7018E..13O
Altcode: 2008SPIE.7018E..32O
Construction of the Southern African Large Telescope (SALT) was largely
completed by the end of 2005 and since then it has been in intensive
commissioning. This has now almost been completed except for the
telescope's image quality which shows optical aberrations, chiefly
a focus gradient across the focal plane, along with astigmatism and
other less significant aberrations. This paper describes the optical
systems engineering investigation that has been conducted since early
2006 to diagnose the problem. A rigorous approach has been followed
which has entailed breaking down the system into the major sub-systems
and subjecting them to testing on an individual basis. Significant
progress has been achieved with many components of the optical system
shown to be operating correctly. The fault has been isolated to a
major optical sub-system. We present the results obtained so far,
and discuss what remains to be done.
Title: Warm Planets Around Cool Stars: Searches for Habitable Zone
Planets Around Late M Dwarfs
Authors: Ramsey, L.; Wolszczan, A.; Bongiorno, S.; Redman, S.; Engel,
L.; Barnes, J.; Jones, H. R. A.
Bibcode: 2008ASPC..398..505R
Altcode:
The low mass of M stars, less than 0.5 solar masses, combined with
close in orbits yield radial velocity amplitudes for planets in
the habitable zone around these stars that are well within current
limits of 1-2 m/s achieved with visible-light instruments. These
same instruments become significantly challenged when looking at
M5 dwarfs and cooler. However, if one takes advantage of the fact
that M-stars emit most of their energy in the near-infrared (NIR),
hundreds of targets become accessible to 8-meter class telescopes
with instruments such as the Precision Radial Velocity Spectrometer
(PRVS) for Gemini. We present some preliminary laboratory results that
demonstrate the viability and challenges of PRV work in the NIR.
Title: The PRVS Pathfinder
Authors: Ramsey, Lawrence W.; Redman, S.; Wolszczan, A.; Jones, H.;
Barnes, J.
Bibcode: 2007AAS...211.1118R
Altcode: 2007BAAS...39..747R
The Precision Radial Velocity Spectrometer (PRVS) is a fiber coupled
near infrared (NIR) spectrometer being designed for the Gemini
International Observatory specifically to search for planets around
M stars. These stars emit most of their flux at wavelengths between 1
and 2 microns. These low mass stars are the most likely place where PRV
techniques will allow detection of earth mass planets in the so called
"Habitable Zone". The pathfinder instrument has become a significant
tool in mitigating design, performance and cost risks for the PRVS. Last
year we demonstrated the ability to detect radial velocity variations
at the 10-15 meter/sec level. Since then, we have made significant
progress in our understanding of the limitations of the PRVS in the
NIR. In particular, we present the latest improvements we have made to
the calibration spectra, as well as the characterization and suppression
of the modal noise in the optical fibers.
Title: Precision Radial Velocity Spectrometer
Authors: Jones, Hugh; Rayner, J.; Ramsey, L.; Barnes, J.; Vacca, B.;
Tinney, C.; Liu, M.; Dent, B.; Wolszczan, A.; Webster, A.
Bibcode: 2007AAS...211.1701J
Altcode: 2007BAAS...39Q.767J
The Precision Radial Velocity Spectrometer (PRVS) is a 1.0-1.8 micron
R 70,000 second-generation Gemini instrument design resulting from
the Aspen Process. It is designed to deliver short- and long- term
stability of better than 1 m/s. We have constructed models simulating
likely candidates and demonstrated the ability to recover exoplanetary
radial velocity signals in the infrared. In addition we have conducted
limited experiments with a brass-board instrument to explore real-world
issues yielding precisions of better than 10 m/s. The mass-sensitivity
of the Doppler technique around low-mass primaries means that PRVS
will be sensitive to terrestrial-mass planets orbiting in the habitable
zone of M dwarfs. While the design of PRVS is driven by the stability
necessary to achieve long-term precise radial velocity measurements,
as a cross-dispersed infrared spectrograph with a large wavelength
coverage and high dispersion which is always available PRVS should
also be important for a wide range of other science, e.g., gamma-ray
burst follow-up. PRVS is intended to be fully commissioned in 2011.
Title: M-dwarf Target Selection for our PRVS Planet Search Project
Authors: Jenkins, James; Jones, H. R. A.; Ramsey, L.
Bibcode: 2007AAS...211.1702J
Altcode: 2007BAAS...39R.767J
PRVS is a precision radial-velocity spectrometer that aims to attain
1m/s precision in the near-IR. It is scheduled to be added to the Gemini
suite of instruments by 2011. Therefore, we are currently preparing
a number of precursor programs to fully exploit the science that PRVS
will provide. One of the main aims of PRVS will be discovering planets
around cool substellar objects. Therefore, we have selected a candidate
list of cool stars that will provide ideal targets for PRVS. We firstly
have selected a number of bright M-dwarfs and measured their rotation
velocity (v sin i) using HRS on the HET. A deconvolution technique
was used to generate high S/N line profiles using a cool atmosphere
line list from the VALD database. The slowest rotators will be the
high priority targets for our PRVS planet search project since they
will provide the lowest noise thresholds and best sensitivity. I will
discuss both the methodology and initial results from this work and
then explain where the project will lead in the future.
Title: A Planetary-Mass Companion to the K0 Giant HD 17092
Authors: Niedzielski, A.; Konacki, M.; Wolszczan, A.; Nowak, G.;
Maciejewski, G.; Gelino, C. R.; Shao, M.; Shetrone, M.; Ramsey, L. W.
Bibcode: 2007ApJ...669.1354N
Altcode: 2007arXiv0705.0935N
We report the discovery of a substellar-mass companion to the K0
giant HD 17092 with the Hobby-Eberly Telescope. In the absence
of any correlation of the observed 360 day periodicity with the
standard indicators of stellar activity, the observed radial velocity
variations are most plausibly explained in terms of a Keplerian
motion of a planetary-mass body around the star. As the estimated
stellar mass is 2.3 Msolar, the minimum mass of the planet
is 4.6 MJ. The planet's orbit is characterized by a mild
eccentricity of e=0.17 and a semimajor axis of 1.3 AU. This is the
tenth published detection of a planetary companion around a red giant
star. Such discoveries add to our understanding of planet formation
around intermediate-mass stars, and they provide dynamical information
on the evolution of planetary systems around post-main-sequence stars.
Title: Development of A Protype Infrared Exoplanet Tracker for All
Sky Extrasolar Planet Survey
Authors: Guo, Pengcheng; Ge, J.; Mahadevan, S.; Ramsey, L.
Bibcode: 2006AAS...209.8513G
Altcode: 2006BAAS...38.1016G
We present a design of a prototype infrared version of the Exoplanet
Tracker (ET). This instrument is a combination of a fixed-delay
interferometer with a medium resolution near infrared spectrograph
(R 10,000). It inherits the design of the single object optical ET
instrument at the Kitt Peak 2.1m telescope, which has been used for
high precision radial velocity observations since 2004, including
a discovery of ET-1(HD102195b) planet. This IR ET is optimized for
high throughput and Doppler precision in 0.9-1.8 microns. An existing
medium resolution spectrograph available at Penn State will be used for
initial lab testing and telescope demonstration. We will also present
instrument performance simulation results. Once the capability is
demonstrated, we will develop a multiple object version for the Sloan
2.5m telescope for surveying nearby tens of thousands of M dwarfs for
new planets during All Sky Extrasolar Planet Survey.
Title: Exploring Precision Radial Velocities in the NIR: PRVS
Pathfinder
Authors: Ramsey, Lawrence W.; Bongiorno, S.; Engel, L.; Redman, S.;
Wolszczan, A.; Jones, H. R.; Barnes, J.
Bibcode: 2006AAS...209.8514R
Altcode: 2006BAAS...38.1016R
In summer of 2005 we began a program at Penn State to build a test
instrument to explore issues involved with attaining 1 meter/sec
Precision Radial Velocities (PRV) in the near infrared where M and L
stars emit most of their flux. These low mass stars are the most likely
place where PRV techniques will allow detection of earth mass planets in
the “Habitable Zone”. Key issues studied are calibration techniques,
effects of telluric absorption and modal noise in fibers. The instrument
is a standard in-plane echelle spectrograph with a LN2 cooled Hawaii
1K array. It can be set to cover selected regions between 1.0 and 1.7
microns. More recently our experiments were aimed more directly toward
addressing key issues in the design approach to the Gemini Precision
Radial Velocity Spectrometer (PRVS) taken by the UK ATC/Penn State/U
Hawaii/U Hertfordshire team. Tests to date have focused on measuring the
earth’s rotation signature in the integrated sunlight spectrum. We
present results showing 10 meter/sec or better precision and compare
the observed errors with what is expected from the information content
of the solar spectrum in this region.
Title: The First Extrasolar Planet Discovered with a New-Generation
High-Throughput Doppler Instrument
Authors: Ge, Jian; van Eyken, Julian; Mahadevan, Suvrath; DeWitt,
Curtis; Kane, Stephen R.; Cohen, Roger; Vanden Heuvel, Andrew; Fleming,
Scott W.; Guo, Pengcheng; Henry, Gregory W.; Schneider, Donald P.;
Ramsey, Lawrence W.; Wittenmyer, Robert A.; Endl, Michael; Cochran,
William D.; Ford, Eric B.; Martín, Eduardo L.; Israelian, Garik;
Valenti, Jeff; Montes, David
Bibcode: 2006ApJ...648..683G
Altcode: 2006astro.ph..5247G
We report the detection of the first extrasolar planet, ET-1 (HD
102195b), using the Exoplanet Tracker (ET), a new-generation Doppler
instrument. The planet orbits HD 102195, a young star with solar
metallicity that may be part of the local association. The planet
imparts radial velocity variability to the star with a semiamplitude of
63.4+/-2.0 m s-1 and a period of 4.11 days. The planetary
minimum mass (msini) is 0.488MJ+/-0.015MJ. The
planet was initially detected in the spring of 2005 with the Kitt
Peak National Observatory (KPNO) 0.9 m coudé feed telescope. The
detection was confirmed by radial velocity observations with the ET
at the KPNO 2.1 m telescope and also at the 9 m Hobby-Eberly Telescope
(HET) with its High Resolution Spectrograph. This planetary discovery
with a 0.9 m telescope around a V=8.05 magnitude star was made possible
by the high throughput of the instrument: 49% measured from the fiber
output to the detector. The ET's interferometer-based approach is an
effective method for planet detection. In addition, the ET concept
is adaptable to multiple-object Doppler observations or very high
precision observations with a cross-dispersed echelle spectrograph to
separate stellar fringes over a broad wavelength band. In addition
to spectroscopic observations of HD 102195, we obtained brightness
measurements with one of the automated photometric telescopes at
Fairborn Observatory. Those observations reveal that HD 102195 is a
spotted variable star with an amplitude of ~0.015 mag and a 12.3+/-0.3
day period. This is consistent with spectroscopically observed Ca II H
and K emission levels and line-broadening measurements but inconsistent
with rotational modulation of surface activity as the cause of the
radial velocity variability. Our photometric observations rule out
transits of the planetary companion.
Title: Contamination control of space-based laser instruments
Authors: Chen, Philip; Hedgeland, Randy; Ramsey, Larry; Rivera,
Rachel; Houston, Karrie
Bibcode: 2006SPIE.6291E..04C
Altcode: 2006SPIE.6291E...4C
Space based laser missions have gained their popularity in areas
such as: communication, power beaming, ranging, altimetry, and Light
Detection and Ranging. The capabilities of 1.0 micron lasers offer
a host of improvements in the knowledge gaps that exist and help
promote our understanding of our Earth and lunar environments as well as
planetary and space science applications. Some past and present National
Aeronautics and Space Administration missions that have been developed
for increasing our universal knowledge of such environments and
applications include: The Shuttle Laser Altimeter, Mars Orbiter Laser
Altimeter, Geoscience Laser Altimeter System, Mercury Laser Altimeter,
Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, and
Lunar Orbiter Laser Altimeter. The effort of contamination control
depends on the specific performance goals, instrument designs,
and planned operating scenarios of such missions. Trace amounts
of contamination have been shown to greatly reduce the performance
of 1.0 micron space based laser systems. In addition, the type of
contamination plays an important role in the degree of degradation
and helps to define the "contamination sensitivity" of the mission. A
space based laser mission is considered highly contamination sensitive
and therefore requires an unprecedented contamination control effort.
Title: Stellar Astrophysics on the Hobby-Eberly Telescope
Authors: Ramsey, Lawrence W.
Bibcode: 2005AIPC..752....3R
Altcode:
We briefly describe the Hobby-Eberly Telescope (HET) and its present
status and give several examples of successful stellar astrophysics
programs. The HET was primarily driven by a science mission of
conducting spectroscopic surveys. In addition the HET's unique design
derives from considering that telescopes are largely used for exposure
times of an hour or less at moderate zenith distances and modest image
quality that is based on median site seeing which is consistent with a
survey mission. We present results from planet searches, large radial
velocity surveys, and Sloan Digital Sky Survey follow up programs in
this context. The queue-scheduled nature of the HET makes it especially
effective at synoptic programs that require a large aperture.
Title: The Hobby-Eberly Telescope: performance upgrades, status,
and plans
Authors: Booth, John A.; Adams, Mark T.; Barker, Edwin S.; Bash,
Frank N.; Fowler, James R.; Good, John M.; Hill, Gary J.; Kelton,
Philip W.; Lambert, David L.; MacQueen, Phillip J.; Palunas, Povilas;
Ramsey, Lawrence W.; Wesley, Gordon L.
Bibcode: 2004SPIE.5489..288B
Altcode:
The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope
with a spherical primary mirror and a tracker at prime focus to follow
astronomical objects. The telescope was constructed for $13.9M over
the period 1994-1997. A series of extensive engineering upgrades
and corrective actions have been completed recently, resulting in
significantly improved delivered image quality and increased operational
efficiency. The telescope's Spherical Aberration Corrector (SAC) optics
were recoated with a highly reflective and durable broadband coating at
Lawrence Livermore National Laboratory. The software mount model that
maintains optical alignment of the SAC with the 11-m primary mirror
array was recalibrated and improved. The acquisition and guiding optics
for both the High Resolution Spectrograph (HRS) and the Low Resolution
Spectrograph (LRS) were reworked and improved, allowing for better focus
and SAC alignment monitoring and control. Recoating of the primary
mirror segment array was begun. Telescope images of 0.82 arcseconds
have been recorded for sustained periods in preliminary testing
following the engineering upgrade, an improvement of 50% over previous
best performance. Additional engineering upgrades are scheduled to
consolidate these performance gains and to continue improving delivered
image quality, throughput, and telescope operational efficiency. The
HET is now capable of the science performance for which it was designed.
Title: Performance of the Hobby-Eberly Telescope and facility
instruments
Authors: Hill, Gary J.; MacQueen, Phillip J.; Ramsey, Lawrence W.;
Shetrone, Matthew D.
Bibcode: 2004SPIE.5492...94H
Altcode:
The Hobby-Eberly Telescope (HET) is a revolutionary large telescope of
9.2 meter aperture, located in West Texas at McDonald Observatory. The
HET operates with a fixed segmented primary and has a tracker which
moves the four-mirror corrector and prime focus instrument package
to track the sidereal and non-sidereal motions of objects. The HET
has been taking science data for five years, but the image quality
and primary mirror stability have been far from specifications. Work
over the past two years has improved performance significantly, and
demonstrated site-seeing limited images of 0.8 arcsec., showing that
the telescope will meet all specifications. The performance of the HET
is discussed in detail. The first phase of HET instrumentation includes
three facility instruments: the Low Resolution Spectrograph (LRS), the
Medium Resolution Spectrograph (MRS), and High Resolution Spectrograph
(HRS). The current status of the instruments is described. Upcoming
near infrared capabilities for the LRS and MRS are also discussed.
Title: SparsePak: A Formatted Fiber Field Unit for the WIYN Telescope
Bench Spectrograph. I. Design, Construction, and Calibration
Authors: Bershady, Matthew A.; Andersen, David R.; Harker, Justin;
Ramsey, Larry W.; Verheijen, Marc A. W.
Bibcode: 2004PASP..116..565B
Altcode: 2004astro.ph..3456B
We describe the design and construction of a formatted
fiber field unit, SparsePak, and characterize its optical and
astrometric performance. This array is optimized for spectroscopy
of low surface brightness extended sources in the visible and
near-infrared. SparsePak contains 82, 4.7" fibers subtending an area
of 72''×71'' in the telescope focal plane and
feeds the WIYN Bench Spectrograph. Together, these instruments are
capable of achieving spectral resolutions of λ/Δλ~20,000 and an
area-solid angle product of ~140 arcsec2 m2 per
fiber. Laboratory measurements of SparsePak lead to several important
conclusions on the design of fiber termination and cable curvature
to minimize focal ratio degradation. SparsePak itself has throughput
above 80% redward of 5200 Å and 90%-92% in the red. Fed at f/6.3, the
cable delivers an output of 90% encircled energy at nearly f/5.2. This
has implications for performance gains if the WIYN Bench Spectrograph
were to have a faster collimator. Our approach to integral-field
spectroscopy yields an instrument that is simple and inexpensive to
build, yet yields the highest area-solid angle product per spectrum of
any system in existence. An Appendix details the fabrication process
in sufficient detail for others to repeat. SparsePak was funded by the
National Science Foundation and the University of Wisconsin-Madison
Graduate School, and is now publicly available on the WIYN Telescope
through the National Optical Astronomical Observatories.
Title: PW And: a Young, Single, Spotted, and Flare K2-Dwarf
Authors: Montes, D.; López-Santiago, J.; Fernández-Figueroa, M. J.;
Ramsey, L. W.
Bibcode: 2004IAUS..219..915M
Altcode: 2003IAUS..219E..34M
The single K2 dwarf PW And (HD 1405) has been studied using high
resolution echelle spectra taken during eight observing runs from
1999 to 2002. Accurate radial velocity and rotational velocity have
been determined by cross correlation with standards stars. The U V W
velocity components and the age of 30-80 Myr estimated by using the
color magnitude diagram and the LiI line confirm its membership to the
young Local Association moving group. We have analysed the photospheric
activity (starspots) studying the changes in the bisector of the peak
of the cross correlation function (CCF) which are related to changes
in the profile of the photospheric lines. The variations of the radial
velocity up to 2 km/s that we have found are related with the variations
in the CCF bisectors. The chromospheric activity has been analyzed by
applying the spectral subtraction technique to the Halpha
Hbeta NaI D1&D2 HeI D3 MgIb triplet CaII H&K and
CaII IRT lines. Two flares was detected during the 2001 and 2002
observing runs. Variations in the activity seem to be related to the
photospheric ones showing a good correlation between radial velocity
changes in the CCF bisector and equivalent width of different lines.
Title: Rotational modulation of the photospheric and chromospheric
activity in the young, single K2-dwarf PW And
Authors: López-Santiago, J.; Montes, D.; Fernández-Figueroa, M. J.;
Ramsey, L. W.
Bibcode: 2003A&A...411..489L
Altcode: 2003astro.ph..9072L
High resolution echelle spectra of PW And (HD 1405) have been
taken during eight observing runs from 1999 to 2002. The detailed
analysis of the spectra allow us to determine its spectral type
(K2V), mean heliocentric radial velocity (Vhel = -11.15 km
s-1) rotational velocity (vsin i = 22.6 km s-1),
and equivalent width of the lithium line lambda 6707.8 Å (EW(Li I)
= 273 mÅ). The kinematic (Galactic Velocity (U,V,W)) confirms its
membership in the Local Association moving group, in agreement with
the age (30 to 80 Myrs) inferred from the color magnitude diagram
and the lithium equivalent width. Photospheric activity (presence of
cool spots that disturb the profiles of the photospheric lines) has
been detected as changes in the bisectors of the cross correlation
function (CCF) resulting of cross-correlate the spectra of PW And
with the spectrum of a non-active star of similar spectral type. These
variations of the CCF bisectors are related to the variations in the
measured radial velocities and are modulated with a period similar to
the photometric period of the star. At the same time, chromospheric
activity has been analyzed, using the spectral subtraction technique
and simultaneous spectroscopic observations of the Hα , Hβ , Na I
D1 and D2, He I D3, Mg I b triplet,
Ca II H&K, and Ca II infrared triplet lines. A flare was observed
during the last observing run of 2001, showing an enhancement in the
observed chromospheric lines. A less powerful flare was observed on
2002 August 23. The variations of the chromospheric activity indicators
seem to be related to the photospheric activity. A correlation between
radial velocity, changes in the CCF bisectors and equivalent width of
different chromospheric lines is observed with a different behaviour
between epochs 1999, 2001 and 2002. Based on observations made
with the 2.2 m telescope of the German-Spanish Astronomical Centre,
Calar Alto (Almería, Spain), operated by the Max-Planck-Institute for
Astronomy, Heidelberg, jointly with the Spanish National Commission
for Astronomy, with the Nordic Optical Telescope (NOT), operated on
the island of La Palma jointly by Denmark, Finland, Iceland, Norway
and Sweden, in the Spanish Observatorio del Roque de Los Muchachos
of the Instituto de Astrofísica de Canarias, with the Isaac Newton
Telescope (INT) operated on the island of La Palma by the Isaac Newton
Group in the Spanish Observatorio del Roque de Los Muchachos of the
Instituto de Astrofísica de Canarias, with the Italian Telescopio
Nazionale Galileo (TNG) operated on the island of La Palma by the
Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica)
at the Spanish Observatorio del Roque de Los Muchachos of the Instituto
de Astrofisica de Canarias and with the Hobby-Eberly Telescope (HET)
operated by McDonald Observatory on behalf of The University of Texas
at Austin, the Pennsylvania State University, Stanford University,
Ludwig-Maximilians-Universität München, and Georg-August-Universität
Göttingen. Tables 1, 3, 4 and Figs. 4, 7, 8, 14, 16, 18, 19,
21 are only available in electronic form at http://www.edpsciences.org
Title: The Hobby-Eberly Telescope medium resolution spectrograph
and fiber instrument feed
Authors: Ramsey, Lawrence W.; Engel, Leland G.; Sessions, Nicholas;
DeFilippo, Christopher; Graver, Michelle; Mader, Jeffery
Bibcode: 2003SPIE.4841.1036R
Altcode:
The Medium Resolution Spectrograph (MRS) is a versatile, fiber-fed
echelle spectrograph for the Hobby-Eberly Telescope (HET). This
instrument is designed for a wide range of scientific investigations
and includes single-fiber inputs for the study of point-like sources,
synthetic slits of fibers for long slit spectroscopy 9 independently
positionable probes for multi-object spectroscopy, and a circular
fiber integral field unit. The MRS consists of two beams. The visible
beam has wavelength coverage from 450 - 900 nm in a single exposure
with resolving power between 5,300 and 20,000 depending on the fibers
configuration selected. This beam also has capability in the ranges
380 - 950 nm by altering the angles of the cross-disperser gratings. A
second beam operating in the near-infrared has coverage of 900 - 1300
nm with resolving power between 5,300 and 10,000. Both beams can be
used simultaneously and are fed by the HET Fiber Instrument Feed (FIF)
which is mounted at the prime focus of the telescope and positions
the fibers feeding the MRS. The MRS started commissioning summer 2002.
Title: Fiber fed spectral calibration with the Hobby-Eberly telescope
Authors: Tufts, Joseph R.; Hill, Gary J.; Wesley, Gordon L.; MacQueen,
Phillip J.; Ramsey, Lawrence W.
Bibcode: 2003SPIE.4841.1162T
Altcode:
The Hobby-Eberly Telescope (HET) imposes unique constraints on
the design of a spectral calibration system. Its 9.2 m aperture
and queue scheduled operation make traditional dome screens
impractical. Furthermore, the changing pupil of the HET's tilted
Aricebo design is far more drastic than the simple rotation of
traditional alt-azimuth telescopes. Given these constraints we elected
to build an internal spectral calibration system (SCS) common to all
instruments. The SCS can feed all HET instruments from a uniformly
illuminated Lambertian screen located within the spherical abberation
corrector (SAC) at the telescope's second pupil. A moving baffle
installed at the third pupil will reproduce, during calibration, the
actual HET pupil seen in a science exposure. We eliminated all heat
sources at the SAC by locating the lamps in the basement below the
telescope and coupling source to screen through 12 600 μm diameter
35 m long fibers.
Title: Performance of the facility instruments on the Hobby-Eberly
telescope
Authors: Hill, Gary J.; MacQueen, Phillip J.; Ramsey, Lawrence W.
Bibcode: 2003SPIE.4841...43H
Altcode:
The Hobby-Eberly Telescope (HET) is a revolutionary large telescope of
9.2 meter aperture, located in West Texas at McDonald Observatory. Early
scientific operations started on October 8, 1999. The HET operates
with a fixed segmented primary and has a tracker which moves the
four-mirror corrector and prime focus instrument package to track the
sidereal and non-sidereal motions of objects. As of two years ago,
the HET was taking science data but the image quality and primary
mirror stability were far from specifications. We established the HET
Completion Project to identify and fix these problems, and here we
describe the current performance of the HET relative to its goals,
focusing on progress made in the past two years. The first phase
of HET instrumentation includes three facility instruments: the Low
Resolution Spectrograph (LRS) and High Resolution Spectrograph (HRS),
which are in operation, and the Medium Resolution Spectrograph (MRS),
which will be commissioned in the summer and autumn. The current status
of the instruments is described in detail with performance measures.
Title: The Hobby-Eberly Telescope Completion Project
Authors: Booth, John A.; Wolf, Marsha J.; Fowler, James R.; Adams,
Mark T.; Good, John M.; Kelton, Philip W.; Barker, Edwin S.; Palunas,
Povilas; Bash, Frank N.; Ramsey, Lawrence W.; Hill, Gary J.; MacQueen,
Phillip J.; Cornell, Mark E.; Robinson, Edward L.
Bibcode: 2003SPIE.4837..919B
Altcode:
The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope
with a spherical primary mirror and a tracker at prime focus to follow
astronomical objects. The telescope was constructed for $13.9M over
the period 1994-1997. A number of telescope performance deficiencies
were identified and corrected following construction. Remaining
problems included: 1) Dome seeing, 2) inadequate initial mirror segment
alignment accuracy, and 3) mirror segment misalignment with time. The
HET Completion Project was created in May 2001 to attack these problems
and to identify and solve the next tier of problems. To address
dome seeing, large louvers were installed and in operation by May
2002. Efforts are also underway to eliminate or suppress heat sources
within the dome environment. To address segment alignment accuracy, a
prototype Shack-Hartmann device, the Mirror Alignment Recovery System
(MARS), was built and is in routine use at HET. The Segment Alignment
Maintenance System (SAMS) is in early operation and has markedly
improved telescope performance. Two Differential Image Motion Monitor
(DIMM) telescopes were brought into regular operation in July 2001 to
quantify atmospheric seeing at HET. As these improvements have been
implemented, telescope image quality has improved significantly. Plans
are in place to address additional performance issues.
Title: Mirror Alignment Recovery System (MARS) on the Hobby-Eberly
Telescope
Authors: Wolf, Marsha J.; Palunas, Povilas; Booth, John A.; Ward,
Michael H.; Wirth, Allan; Wesley, Gordon L.; O'Donoghue, Darragh;
Ramsey, Lawrence W.
Bibcode: 2003SPIE.4837..714W
Altcode:
The Mirror Alignment Recovery System (MARS) is a Shack-Hartmann based
sensor at the center of curvature (CoC) of the Hobby-Eberly Telescope
(HET) spherical primary mirror used to align the 91 mirror segments. The
instrument resides in a CoC tower next to the HET dome, a location which
provides a challenging set of problems including wind shake and seeing
from two different domes. The system utilizes an internal light source
to illuminate the HET and a reference mirror to provide focused spot
locations from a spherical surface. A custom lenslet array is sized
to the HET pupil image, matching a single hexagonal lenslet to each
mirror segment. Centroids of the HET mirror segment spots are compared
to the reference spot locations to measure tip/tilt misalignments of
each segment. A MARS proof-of-concept (POC) instrument, tested on the
telescope in 2001, utilized a commercial wavefront sensor from Adaptive
Optics Associates. The final system uses the same concept, but is
customized for optimal performance on the HET. MARS replaces previous
burst-antiburst alignment techniques and provides a more intuitive
method of aligning the primary mirror for telescope operators. The POC
instrument has improved median HET stack sizes by 0.3" EE50, measured
at the CoC tower. The current alignment accuracy is 0.14" rms (0.28"
rms on the sky), resolution is 0.014", measurement precision is 0.027"
rms, and segment capture range is +/- 5". With continuing improvements
in HET dome ventilation and the addition of software customized for
removal of tower motion during measurement, the alignment accuracy
is expected to reach approximately 0.04" rms in the final MARS, to be
installed in late 2002.
Title: Doppler high precision extra-solar planet surveys by a fixed
delay interferometer
Authors: Ge, Jian; van Eyken, Julian C.; Mahadevan, Suvrath; DeWitt,
Curtis; Ramsey, Lawrence W.; Shaklan, Stuart B.; Pan, Xiaopei
Bibcode: 2003SPIE.4838..503G
Altcode:
A fixed delay interferometer combined with a post-disperser is a new
technique for high precision radial velocity (RV) measurements. The
Doppler measurements are conducted by monitoring the stellar fringe
phase shifts of the interferometer instead of absorption line centroid
shifts as in the echelle. High Doppler sensitivity is achieved through
optimizing the optical delay in the interferometer and measuring
multiple fringes over a broadband. The broadband operation is achieved
by using the post-disperser for dispersing fringes in different
wavelengths. Comparing to the state-of-the-art cross-dispersed echelle
spectroscopy, this interferometer technique provides almost identical RV
precision based on photon statistics. However, the interferometer method
has a potential for lower systematic noise due to its simpler instrument
response than the echelle. The interferometer can be optimized for
higher throughput than the echelle. The interferometer approach also
allows fringes to be recorded in one dispersion order instead of many
cross-dispersed echelle orders. Therefore, this instrument opens up a
great opportunity for multi-object observations to allow all sky surveys
for extra-solar planets at moderate sized wide field telescopes. Initial
observations with a prototype at the Hobby-Eberly 9 m and Palomar 5 m
telescopes demonstrate ~9 m/s Doppler RV precision with stellar fringe
data recorded on a 1kx1k CCD detector (or 140 Å wavelength coverage),
a S/N ~ 120 per pixel and a post-disperser spectral resolving power
of R = 6,700. This precision is consistent with the photon noise
limit. Future improvement in wavelength coverage and wavelength
calibration can reduce the Doppler error to a few m/s or less.
Title: L Dwarfs Found in Sloan Digital Sky Survey Commissioning
Data. II. Hobby-Eberly Telescope Observations
Authors: Schneider, Donald P.; Knapp, Gillian R.; Hawley, Suzanne L.;
Covey, Kevin R.; Fan, Xiaohui; Ramsey, Lawrence W.; Richards, Gordon
T.; Strauss, Michael A.; Gunn, James E.; Hill, Gary J.; MacQueen,
Phillip J.; Adams, Mark T.; Hill, Grant M.; Ivezić, Željko; Lupton,
Robert H.; Pier, Jeffrey R.; Saxe, David H.; Shetrone, Matthew; Tufts,
Joseph R.; Wolf, Marsha J.; Brinkmann, J.; Csabai, István; Hennessy,
G. S.; York, Donald G.
Bibcode: 2002AJ....123..458S
Altcode: 2001astro.ph.10273S
Low-dispersion optical spectra have been obtained with the Hobby-Eberly
Telescope of 22 very red objects found in early imaging data from the
Sloan Digital Sky Survey (SDSS). The objects are assigned spectral types
on the Two Micron All Sky Survey (2MASS) system and are found to range
from late M to late L. The red and near-infrared colors from SDSS and
2MASS correlate closely with each other, and most of the colors are
closely related to spectral type in this range; the exception is the
i*-z* color, which appears to be independent of spectral type between
about M7 and L4. The spectra suggest that this independence is due
to the disappearance of the TiO and VO absorption in the i band for
later spectral types, the presence of strong Na I and K I absorption
in the i band, and the gradual disappearance of the 8400 Å absorption
of TiO and FeH in the z band. Based on observations obtained with
the Sloan Digital Sky Survey, which is owned and operated by the
Astrophysical Research Consortium, and on observations obtained with
the Hobby-Eberly Telescope, which is a joint project of the University
of Texas at Austin, Pennsylvania State University, Stanford University,
Ludwig-Maximillians-Universität München, and Georg-August-Universität
Göttingen.
Title: Extra-solar Planet Studies with New Instrument Technology at
Penn State
Authors: Ge, J.; van Eyken, J.; Mahadevan, S.; Debes, J.; McDavitt,
D.; Bernecker, J.; De Witt, C.; Chakraborty, A.; Berger, D.; Ramsey,
L.; Shaklan, S.; Pan, X.
Bibcode: 2001AAS...199.3304G
Altcode: 2001BAAS...33.1356G
Several new instruments have been developed at Penn State for
studying extra-solar planets around nearby stars. An optical
dispersed interferometer, a combination of an interferometer and a
medium resolution (R = 10,000) spectrograph, called Exoplanet Tracker
(ET), is designed to provide high Doppler precision ( ~ 2 m/s), high
throughput ( ~20%) measurements of radial velocity. Initial observing
results from the HET 9m and Palomar 5m telescopes with a prototype will
be presented. A Penn State near IR Imaging Spectrometer (PIRIS) has
been used at the Mt. Wilson 100inch telescope with a powerful natural
guide star adaptive optics system. It has an IR coronagraph mode and
a special Gaussian pupil mode for providing high contrast imaging
(104) of nearby stars to allow possible detection of faint
companions and planetary disks within 1-2 arcsec of stars. New observing
results will be reported. An anamorphic silicon immersion grating with
80x40 mm2 etched grating area is being developed at Penn
State Nanofabrication facility using photolithography and anisotropic
chemical etching techniques and will provide a very high spectral
resolution at the diffraction limit (R = 200,000 at 2.3 micron and R
=100,000 at 4.6 micron). This grating will be coupled with existing
IR instruments such as the Arizona Imager and Echelle Spectrograph
(ARIES) at large ground-based telescopes to search for protoplanets
around nearby young stellar objects.
Title: A new Virtual Interferometer technique for Extrasolar Planet
Searches
Authors: Mahadevan, S.; Ge, J.; van Eyken, J.; DeWitt, C.; Berger,
D.; Ramsey, L. W.
Bibcode: 2001AAS...199.0302M
Altcode: 2001BAAS...33.1303M
A new instrument has been designed and developed at Penn State for high
precision Doppler radial velocity measurements using the Moire fringe
technique. The Moire fringes generated by superimposing a digital
comb on two dimensional stellar spectra allow us to translate Doppler
shifts in the dispersion direction into much larger Moire fringe shifts
(3-5 times larger) in the slit direction. The magnification of Moire
fringes and a much simpler phase shift of a sinosoidal pattern enable
precision Doppler velocity measurements. This prototype instrument
using a medium resolution spectrograph( R 10,000) can provide much
higher throughput (5-10 times more) than conventional high resolution
echelle spectrographs. We have demonstrated velocity measurements in
the 30 m/s range with this virtual interferometer and further work will
allow us to improve the accuracy to 5-10 m/s. The Virtual Interferometer
will fill a niche in the 5-50 m/s range allowing a much deeper survey
of stellar objects. This can be important in setting constraints on
SIM grid stars as well as finding companions around fainter stars.
Title: A Moire Fringing Spectrometer for Extra-Solar Planet Searches
Authors: van Eyken, J. C.; Ge, J.; Mahadevan, S.; De Witt, C.; Ramsey,
L. W.; Berger, D.; Shaklan, S.; Pan, X.
Bibcode: 2001AAS...199.0303V
Altcode: 2001BAAS...33.1303V
We have developed a prototype moire fringing spectrometer for high
precision radial velocity measurements for the detection of extra-solar
planets. This combination of Michelson interferometer and spectrograph
overlays an interferometer comb on a medium resolution stellar spectrum,
producing Moire patterns. Small changes in the doppler shift of the
spectrum lead to corresponding large shifts in the Moire pattern (Moire
magnification). The sinusoidal shape of the Moire fringes enables
much simpler measurement of these shifts than in standard echelle
spectrograph techniques, facilitating high precision measurements with
a low cost instrument. Current data analysis software we have developed
has produced short-term repeatability (over a few hours) to 5-10m/s,
and future planned improvements based on previous experiments should
reduce this significantly. We plan eventually to carry out large scale
surveys for low mass companions around other stars. This poster will
present new results obtained in the lab and at the HET and Palomar 5m
telescopes, the theory of the instrument, and data analysis techniques.
Title: The Chandra Deep Survey of the Hubble Deep Field-North
Area. II. Results from the Caltech Faint Field Galaxy Redshift
Survey Area
Authors: Hornschemeier, A. E.; Brandt, W. N.; Garmire, G. P.;
Schneider, D. P.; Barger, A. J.; Broos, P. S.; Cowie, L. L.; Townsley,
L. K.; Bautz, M. W.; Burrows, D. N.; Chartas, G.; Feigelson, E. D.;
Griffiths, R. E.; Lumb, D.; Nousek, J. A.; Ramsey, L. W.; Sargent,
W. L. W.
Bibcode: 2001ApJ...554..742H
Altcode: 2001astro.ph..1494H
A deep X-ray survey of the Hubble Deep Field-North (HDF-N) and its
environs is performed using data collected by the Advanced CCD Imaging
Spectrometer (ACIS) on board the Chandra X-Ray Observatory. Currently
a 221.9 ks exposure is available, the deepest ever presented, and
here we give results on X-ray sources located in the 8.6‧×8.7‧
area covered by the Caltech Faint Field Galaxy Redshift Survey (the
``Caltech area''). This area has (1) deep photometric coverage in
several optical and near-infrared bands; (2) extensive coverage at
radio, submillimeter, and mid-infrared wavelengths; and (3) some of the
deepest and most complete spectroscopic coverage ever obtained. It is
also where the X-ray data have the greatest sensitivity; the minimum
detectable fluxes in the 0.5-2 keV (soft) and 2-8 keV (hard) bands are
~1.3×10-16 and ~6.5×10-16 ergs cm-2
s-1, respectively. More than ~80% of the extragalactic X-ray
background in the hard band is resolved. The 82 Chandra sources detected
in the Caltech area are correlated with more than 25 multiwavelength
source catalogs, and the results of these correlations as well as
spectroscopic follow-up results obtained with the Keck and Hobby-Eberly
Telescopes are presented. All but nine of the Chandra sources are
detected optically with R<~26.5. Redshifts are available for 39%
of the Chandra sources, including 96% of the sources with R<23 the
redshift range is 0.1-3.5, with most sources having z<1.5. Eight of
the X-ray sources are located in the HDF-N itself, including two not
previously reported. A population of X-ray faint, optically bright,
nearby galaxies emerges at soft-band fluxes of <~3×10-16
ergs cm-2 s-1. Our multiwavelength correlations
have set the tightest constraints to date on the X-ray emission
properties of μJy radio sources, mid-infrared sources detected by the
Infrared Space Observatory (ISO), and very red (R-Ks>5.0)
objects. A total of 16 of the 67 1.4 GHz μJy sources in the Caltech
area are detected in the X-ray band, and the detection rates for
starburst-type and AGN-candidate μJy sources are comparable. Only two
of the 17 red, optically faint (I>25) μJy sources are detected
in X-rays. While many of the starburst-type μJy sources appear to
contain obscured active galactic nuclei (AGNs), the Chandra data are
consistent with the majority of the μJy radio sources being powered
by star formation. A total of 11 of the ~100 ISO mid-infrared sources
found in and near the HDF-N are detected in X-rays. In the HDF-N itself,
where both the infrared coverage and the X-ray coverage are deepest,
it is notable that six of the eight Chandra sources are detected by
ISO; most of these are known to be AGNs where the X-ray and infrared
detections reveal both the direct and indirect accretion power being
generated. The high X-ray-to-infrared matching rate bodes well for
future sensitive infrared observations of faint X-ray sources. Four
of the 33 very red objects that have been identified in the Caltech
area are detected in X-rays these four are among our hardest Chandra
sources, and we argue that they contain moderately luminous obscured
AGNs. Overall, however, the small Chandra detection fraction suggests a
relatively small AGN content in the optically selected very red object
population. A stacking analysis of the very red objects not detected
individually by Chandra yields a soft-band detection with an average
soft-band X-ray flux of ~1.9×10-17 ergs cm-2
s-1 the observed emission may be associated with the hot
interstellar media of moderate-redshift elliptical galaxies. Constraints
on AGN candidates, extended X-ray sources, and Galactic objects in the
Caltech area are also presented. Based on observations obtained at the
W. M. Keck Observatory, which is operated jointly by the California
Institute of Technology and the University of California. Based on
observations obtained by the Hobby-Eberly Telescope (HET), which is a
joint project of The University of Texas at Austin, The Pennsylvania
State University, Stanford University, Ludwig-Maximillians-Universität
München, and Georg-August-Universität Göttingen.
Title: High-Redshift Quasars Found in Sloan Digital Sky Survey
Commissioning Data. V. Hobby-Eberly Telescope Observations
Authors: Schneider, Donald P.; Fan, Xiaohui; Strauss, Michael A.; Gunn,
James E.; Richards, Gordon T.; Hill, Gary J.; MacQueen, Phillip J.;
Ramsey, Lawrence W.; Adams, Mark T.; Booth, John A.; Hill, Grant M.;
Knapp, G. R.; Lupton, Robert H.; Saxe, David H.; Shetrone, Matthew;
Tufts, Joseph R.; Vanden Berk, Daniel E.; Wolf, Marsha J.; York,
Donald G.; Anderson, John E., Jr.; Anderson, Scott F.; Bahcall,
Neta A.; Brinkmann, J.; Brunner, Robert; Csabai, István; Fukugita,
Masataka; Hennessy, G. S.; Ivezić, Željko; Lamb, Donald Q.; Munn,
Jeffrey A.; Thakar, Aniruddha R.
Bibcode: 2001AJ....121.1232S
Altcode: 2000astro.ph.12083S
We report the discovery of 27 quasars with redshifts between 3.58 and
4.49. The objects were identified as high-redshift candidates based
on their colors in Sloan Digital Sky Survey commissioning data. The
redshifts were confirmed with low-resolution spectra obtained at the
Hobby-Eberly Telescope. The quasars' i* magnitudes range
from 18.55 to 20.97. Nearly 60% of the quasar candidates observed
are confirmed spectroscopically as quasars. Two of the objects are
broad absorption line quasars, and several other quasars appear to
have narrow associated absorption features. Based on observations
obtained with the Sloan Digital Sky Survey, which is owned and
operated by the Astrophysical Research Consortium, and with the
Hobby-Eberly Telescope, which is a joint project of the University of
Texas at Austin, Pennsylvania State University, Stanford University,
Ludwig-Maximillians-Universität München, and Georg-August-Universität
Göttingen.
Title: The AGN content in the HDF-N and flanking fields as seen
by Chandra
Authors: Alexander, D. M.; Brandt, W. N.; Hornschemeier, A. E.;
Garmire, G. P.; Schneider, D. P.; Barger, A. J.; Broos, P. S.; Cowie,
L. L.; Townsley, L. K.; Bautz, M. W.; Burrows, D. N.; Chartas, G.;
Feigelson, E. D.; Griffiths, R.; Lumb, D.; Nousek, J. A.; Ramsey,
L. W.; Sargent, W. L. W.
Bibcode: 2000AAS...197.7402A
Altcode: 2000BAAS...32.1520A
We present a multi-wavelength analysis of the Chandra study in
the Hubble Deep Field (HDF) and its environs (the Caltech region)
obtained using 225 ks of data collected by the Advanced CCD Imaging
Spectrometer (ACIS). We have detected 82 sources within this region and
have positionally cross-correlated these sources with multi-wavelength
source lists. We focus on the possible AGN detections of 5 Chandra
sources. We argue that one of these sources is a high-redshift QSO II
candidate object based on its X-ray, optical and infrared colours. The
other 4 sources are all extremely red objects (EROs, R-K>5) and
have hard X-ray colours. The possible identification of AGN activity in
these objects ( ~10% of the EROs in this region) could prove important
from the viewpoints of understanding the nature of EROs and the nature
of the hard X-ray background. We acknowledge the financial support of
NASA grant NAS 8-38252 and the NSF CAREERS grant AST-998 3783.
Title: Development of high quality silicon grisms at Penn State for
high resolution infrared spectroscopy
Authors: Bernecker, J.; Ge, J.; McDavitt, D.; Hajj, A.; Ramsey, L.;
Fonash, S.; Horn, M.
Bibcode: 2000AAS...197.1510B
Altcode: 2000BAAS...32.1429B
We have developed a new chemical etching process using tetramethyl
ammonium hydroxide (TMAH) instead of the traditional potassium hydroxide
(KOH) to fabricate silicon gratings taking advantage of Penn State's
state-of-the-art Nanofabrication Facility supported by the NSF. The
first set of etched gratings have surface quality comparable to
the best silicon gratings developed by a team led by Jian Ge at
Lawrence Livermore National laboratory (LLNL) using the KOH process
in early 2000. For example, the scattered light level at 0.6238 μ m
is less than 3%. The great advantage of this new approach is that it
significantly simplifies the fabrication process of silicon gratings
on large, thick silicon substrates. This new fabrication technique is
being applied in the development of silicon grisms one inch in size
for several near-IR astronomical instruments including the Gemini
8m telescope IR instruments, the Goddard Space Flight Center (GSFC)
wide field near-IR multi-object spectrograph, and Steward Observatory
PISCES near-IR camera and Arizona Imager and Echelle Spectrograph
(ARIES). Status of the development and performance of the silicon
grisms are reported. The development of silicon grisms is supported
by the Penn State Eberly College of Sciences.
Title: Extra-solar planet searches with a Penn State optical/IR
dispersive interferometer at the Hobby-Eberly Telescope
Authors: McDavitt, D.; Ge, J.; DeWitt, C.; Bernecker, J.; Mellon,
R.; Mahadevan, S.; Ramsey, L.; Wolszczan, A.; Rushford, M.
Bibcode: 2000AAS...197.1504M
Altcode: 2000BAAS...32.1428M
An optical/infrared dispersive interferometer is being developed at Penn
State for extra-solar planet searches at the Hobby-Eberly Telescope
(HET). This instrument is a combination of a wide angle Michelson
type interferometer and an intermediate resolution spectrograph (R
≈ 15000). It is designed to provide very low instrument noise for
sensitive Doppler radial velocity measurements aimed at detecting
extra-solar planets with a velocity perturbation amplitude of a few
m/s around nearby F, G, K and M dwarfs. It is a modified version of a
prototype, developed by Jian Ge and his collaborators earlier at LLNL,
with a much improved detection efficiency to allow observation of faint
stars (V ≈ 11 mag.) in the both optical and near-IR wavelengths. The
prototype with R = 5600 has demonstrated a radial velocity precision
of 7 m/s at the Lick 1 m telescope in 1999. New instrument components
including an imaging slicer and an interferometer cavity control
system are being developed and tested at Penn State. The image slicer
is used to convert the telescope's circular beams to rectangular ones
in order to increase the detection efficiency and also allow convenient
placement of an interferometer fringe comb on stellar absorption lines
for precision fringe phase measurements. The interferometer cavity
control system is used to reduce systematic errors and also control
phase shifts. Reference sources other than iodine absorption are
being studied for calibrating the new instrument at red and near-IR
wavelengths. The instrument's first light at the HET will be spring
2001. Simulations of the instrument's performance show that a Doppler
radial velocity precision of 1 m/s can be achieved for a late type
star with a S/N of 200, a wavelength coverage of 500 Å at 1.55 μ m
and R = 15000. The development of the instrument is supported by the
Penn State Eberly College of Sciences.
Title: The Sources Comprising the X-ray Background in the
HDFN Region observed by the Chandra X-ray Observatory
Authors: Garmire, G. P.; Brandt, N. W.; Hornschemeier, A. E.;
Schneider, D. P.; Broos, P. S.; Townsley, L. K.; Burrows, D. N.;
Chartas, G.; Feigelson, E. D.; Nousek, J. A.; Ramsey, L. W.; Barger,
A. J.; Cowie, L. L.; Bautz, M. W.; Griffiths, R.; Lumb, D.; Sargent,
W. L. W.
Bibcode: 2000AAS...197.7401G
Altcode: 2000BAAS...32R1519G
The Chandra X-ray Observatory (CXC) has observed the HDF-N region
(a 17' by 19' area including the HDF-N) for 224.7 ks as of this
writing. Another 775 ks will be devoted to this region in the next six
months. A total of about 200 sources have been detected in the 0.5 -
8.0 keV energy band. The 2.0 - 8.0 keV Log N(>S) vs Log S plot,
where N is the areal density of sources and S the flux, reveals that the
bulk of the sky flux comes from sources brighter than 10-14
ergs/cm2/s. The majority of these sources lies closer than
a redshift of 1, based on 51 redshifts measured thus far. The X-ray
spectra of the sources show a gradual hardening with decreasing
source intensity, with the fainter sources (3 x 10-15
ergs/cm2/s in the 0.5 - 10.0 keV band) exhibiting a photon
number spectral slope of 1.35+/-0.2. This work is supported in part
by NASA grant NAS 8-38252(GPG PI), NASA GSRP grant NGT5-50247 (AEH),
NSF CAREER award AST-9983783 and the Alfred P. Sloan Foundation (WNB),
and NSF grant AST99-00703 (DPS).
Title: Issues in scaling the ELT up to 100 m
Authors: Ray, Frank B.; Bash, Frank N.; Ramsey, Lawrence W.; Sebring,
Thomas A.
Bibcode: 2000SPIE.4004..405R
Altcode:
The Hobby-Eberly Telescope (HET) has been examined as a prototype for
an Extremely Large Telescope (ELT) with a 33- meter diameter primary
mirror. In this paper we examine the feasibility of scaling the HET/ELT
up to 100-meters in diameter. In this 100-meter telescope design (called
ELTX) the advantages of the tilted Arecibo concept seem to emerge even
more strongly. For example the whole primary mirror is below grade
and extremely well shielded from wind shake and the Stewart platform
which carries the spherical aberration corrector and the instruments
is capable of being scaled up to this massive size without any serious
problems. Such a design is on track for probable science missions in
the next half century.
Title: Performance testing of the Hobby-Eberly Telescope primary
mirror array
Authors: Adams, Mark T.; Booth, John A.; Hill, Grant M.; Ramsey,
Lawrence W.
Bibcode: 2000SPIE.4004..471A
Altcode:
To improve the image quality performance of the Hobby-Eberly Telescope's
(HET) segmented primary mirror and to assist in the requirements
definition for an optical alignment sensing and control system,
multiple engineering tests have been designed and executed. The most
significant of these tests have been the alignment maintenance baseline
and solid mount tests. Together, these engineering tests defined the
complex thermal and non-thermal response modes of the steel HET primary
mirror truss and quantified the performance of the segment support
system. We discuss the configuration and performance of the HET primary
mirror, and discuss our engineering test motivation, goals, design,
implementation and results. We also discuss the implications of our
primary mirror performance test results for conceptually similar next
generation telescope designs, such as the Extremely Large Telescope.
Title: Commissioning experience with the 9.2-m Hobby-Eberly Telescope
Authors: Barnes, Thomas G.; Adams, Mark T.; Booth, John A.; Cornell,
Mark E.; Gaffney, Niall I.; Fowler, James R.; Hill, Gary J.; Hill,
Grant M.; Nance, Craig E.; Piche, Francois; Ramsey, Lawrence W.;
Ricklefs, Randall L.; Spiesman, William J.; Worthington, P. T.
Bibcode: 2000SPIE.4004...14B
Altcode:
The HET is unique among 9-meter class telescopes in featuring an
Arecibo-like design with a focal surface tracker. The focal surface
tracker causes image quality and pointing/tracking performance to
interact in a complex way that has no precedent in astronomical
telescope system design and that has presented unusual demands upon
commissioning. The fixed-elevation, segmented primary-mirror array
offers some simplifications over traditional telescope design in
principle, but has presented challenges in practice. The sky access
characteristics of the HET also place unique demands on observational
planning and discipline. The HET is distinguished by uniquely low
construction and operating costs which affected commissioning. In this
contribution, we describe those aspects of our commissioning experience
that may impact how similar telescopes are designed, especially those
with larger aperture, and review the challenges and lessons learned from
commissioning a 9-meter class telescope with a small technical team.
Title: Hobby-Eberly Telescope operations model
Authors: Adams, Mark T.; Barnes, Thomas G.; Nance, Craig E.; Ramsey,
Lawrence W.
Bibcode: 2000SPIE.4010...16A
Altcode:
The Hobby-Eberly telescope (HET) is an innovative, low cost 9- meter
class telescope that specializes in visible and near- infrared, queue
observing mode spectroscopy. The operations costs for this telescope
follow the capital cost model, being approximately 15 - 20% that of
other 9-meter telescopes. In this contribution we describe the HET
operations model and our early operations and scientific experience with
this telescope, emphasizing those aspects that most directly impact
the scientific productivity of the HET and describing the actions we
have taken to optimize the telescope's scientific return.
Title: The Missing Link: Early Methane (``T'') Dwarfs in the Sloan
Digital Sky Survey
Authors: Leggett, S. K.; Geballe, T. R.; Fan, Xiaohui; Schneider,
Donald P.; Gunn, James E.; Lupton, Robert H.; Knapp, G. R.; Strauss,
Michael A.; McDaniel, Alex; Golimowski, David A.; Henry, Todd J.;
Peng, Eric; Tsvetanov, Zlatan I.; Uomoto, Alan; Zheng, Wei; Hill,
G. J.; Ramsey, L. W.; Anderson, Scott F.; Annis, James A.; Bahcall,
Neta A.; Brinkmann, J.; Chen, Bing; Csabai, István; Fukugita,
Masataka; Hennessy, G. S.; Hindsley, Robert B.; Ivezić, Željko;
Lamb, D. Q.; Munn, Jeffrey A.; Pier, Jeffrey R.; Schlegel, David J.;
Smith, J. Allyn; Stoughton, Chris; Thakar, A. R.; York, Donald G.
Bibcode: 2000ApJ...536L..35L
Altcode: 2000astro.ph..4408L
We report the discovery of three cool brown dwarfs that fall in
the effective temperature gap between the latest L dwarfs currently
known, with no methane absorption bands in the 1-2.5 μm range, and
the previously known methane (T) dwarfs, whose spectra are dominated
by methane and water. The newly discovered objects were detected as
very red objects in the Sloan Digital Sky Survey imaging data and
have JHK colors between the red L dwarfs and the blue Gl 229B-like
T dwarfs. They show both CO and CH4 absorption in their
near-infrared spectra in addition to H2O, with weaker
CH4 absorption features in the H and K bands than those
in all other methane dwarfs reported to date. Due to the presence of
CH4 in these bands, we propose that these objects are early
T dwarfs. The three form part of the brown dwarf spectral sequence and
fill in the large gap in the overall spectral sequence from the hottest
main-sequence stars to the coolest methane dwarfs currently known.
Title: Early science results from the Hobby-Eberly telescope
Authors: Hill, Gary J.; MacQueen, Phillip J.; Ramsey, Lawrence W.;
Robinson, Edward L.
Bibcode: 2000SPIE.4005..240H
Altcode:
We present science results from the first four months of early
operations of the Hobby-Eberly Telescope (HET). During this period the
HET was used for science approximately two weeks per month centered
on new moon. We discuss the types of science program that are bets
suited to the unique nature of the HET and give examples of survey and
synoptic observations that are on-going. The Marcario Low Resolution
Spectrograph is the only facility instrument currently in service,
so the science result from this instrument are emphasized. Future
facility instruments are briefly discussed, along with a description
of current HET performance.
Title: VizieR Online Data Catalog: Library of FOE spectra of late-type
stars (Montes, 1999)
Authors: Montes, D.; Ramsey, L. W.; Welty, A. D.
Bibcode: 2000yCat..21230283M
Altcode:
We present a library of Penn State Fiber Optic Echelle (FOE)
observations of a sample of field stars with spectral types F to M and
luminosity classes V to I. The spectral coverage is from 3800 to 10000Å
with a nominal resolving power of 12,000. These spectra include many
of the spectral lines most widely used as optical and near-infrared
indicators of chromospheric activity such as the Balmer lines (Hα
to Hδ), Ca II H & K, the Mg I b triplet, Na I D1,
D2, He I D3, and Ca II IRT lines. There are also
a large number of photospheric lines, which can also be affected by
chromospheric activity, and temperature-sensitive photospheric features
such as TiO bands. The spectra have been compiled with the goal of
providing a set of standards observed at medium resolution. We have
extensively used such data for the study of active chromosphere stars
by applying a spectral subtraction technique. However, the data set
presented here can also be utilized in a wide variety of ways ranging
from radial velocity templates to study of variable stars and stellar
population synthesis. This library can also be used for spectral
classification purposes and determination of atmospheric parameters
(Teff, logg, [Fe/H]). A digital version of all the fully
reduced spectra is available via ftp and the World Wide Web (WWW)
in FITS format. (1 data file).
Title: Aplanatic Corrector Designs for the Extremely Large Telescope
Authors: Moretto, Gil; Sebring, Thomas A.; Ray, Frank B.; Ramsey,
Lawrence W.
Bibcode: 2000ApOpt..39.2805M
Altcode:
The next century is knocking on our door, bringing with it the
possibility of telescopes even bigger than the 8-10-m-class instruments
that have proliferated over the past decade. The fixed spherical
reflector is the most economical and pragmatic way to construct an
extremely large primary mirror (30-50 m in diameter). Although spherical
mirrors have virtues such as manufacturability and identically figured
segments, they also create great amounts of spherical aberration and
coma. Here we show that there are several catoptric (all-reflecting)
corrector designs that enable a fast telescope based on a spherical
primary mirror.
Title: Spectra of Early and Late(r) Methane Dwarfs in the SDSS
and 2MASS
Authors: Geballe, T. R.; Leggett, S. K.; Fan, X.; Schneider, D. P.;
Knapp, G. K.; McDaniel, A.; Gunn, J. E.; Lupton, R. H.; Strauss,
M. A.; Golimowski, D. A.; Henry, T.; Peng, E.; Tsvetanov, Z. I.;
Uomoto, A.; Zheng, W.; Hill, G. J.; Ramsey, L. W.
Bibcode: 2000AAS...196.0306G
Altcode: 2000BAAS...32..678G
We have obtained high quality 1-2.5 microns spectra of three cool brown
dwarfs, recently identified in the Sloan Digital Sky Survey and one cool
brown dwarf from the Two Micron All Sky Survey. JHK photometry of the
three SDSS objects, which had been photometrically selected from their
i'-z' colors as likely methane dwarfs, suggested that they could be
"transition objects" between the L and T classes of brown dwarfs. Their
spectra, obtained by CGS4 on UKIRT, contain both CO and CH4
features, as well as H2O bands. The CH4 bands
are weaker than those in all other methane dwarfs reported to date. The
strengths of the bands of these three molecules are different in each
object, and together the spectra form a sequence linking the late L-type
dwarfs and previously observed T dwarfs. We propose that these SDSS
objects represent the early subclasses of the T classification. In the
2MASS object, Gl 570D, identified by Burgasser et al. (astro-ph/0001194)
as being significantly cooler than other methane dwarfs, the bands of
CH4 and H2O are deeper and in some cases broader
than in any other known T dwarf, further narrowing the windows short
of 3 microns where radiation can easily escape.
Title: Observations of Faint, Hard-Band X-Ray Sources in the Field
of CRSS J0030.5+2618 with the Chandra X-Ray Observatory and the
Hobby-Eberly Telescope
Authors: Brandt, W. N.; Hornschemeier, A. E.; Schneider, D. P.;
Garmire, G. P.; Chartas, G.; Hill, Gary J.; MacQueen, P. J.; Townsley,
L. K.; Burrows, D. N.; Koch, T. S.; Nousek, J. A.; Ramsey, L. W.
Bibcode: 2000AJ....119.2349B
Altcode: 2000astro.ph..2121B
We present results from a study of 2-8 keV X-ray sources detected by
the Advanced CCD Imaging Spectrometer on the Chandra X-Ray Observatory
in the field of the z=0.516 cluster CRSS J0030.5+2618. In our 63.5
arcmin2 search area, we detect 10 sources with 2-8 keV
fluxes down to ~4×10-15 ergs cm-2 s-1
our lowest flux sources are ~10 times fainter than those previously
available for study in this band. Our derived source density is about
an order of magnitude larger than previous source counts above 2
keV, although this density may be enhanced somewhat because of the
presence of the cluster. We detail our methods for source detection
and characterization, and we show that the resulting source list
and parameters are robust. We have used the Marcario Low-Resolution
Spectrograph on the Hobby-Eberly Telescope to obtain optical spectra
for several of our sources; by combining these spectra with archival
data, we find that the sources appear to be active galaxies, often
with narrow permitted lines, red optical continua, or hard X-ray
spectra. Four of the X-ray sources are undetected to R=21.7; if they
reside in L* galaxies they must have z>0.55-0.75 and
hard X-ray luminosities of L2-8>~4×1042
ergs s-1. We detect all but one of our 2-8 keV sources
in the 0.2-2 keV band as well. This result extends to significantly
lower fluxes the constraints on any large, completely new population
of X-ray sources that appears above 2-3 keV. Based on observations
obtained with the Hobby-Eberly Telescope, which is a joint project
of the University of Texas at Austin, Pennsylvania State University,
Stanford University, Ludwig-Maximillians-Universität München, and
Georg-August-Universität Göttingen.
Title: The Extremely Large Telescope (ELT), a scientific opportunity;
an engineering certainty
Authors: Sebring, T. A.; Moretto, G.; Bash, F. N.; Ray, F. B.; Ramsey,
L. W.
Bibcode: 2000ESOC...57...53S
Altcode: 2000elt..conf...53S
No abstract at ADS
Title: Pennsylvania State University, Astronomy and Astrophysics,
University Park, Pennsylvania 16802-6305. Report for the period 1
Sep 1998 - 31 Aug 1999.
Authors: Sambruna, R.; Ramsey, L.
Bibcode: 2000BAAS...32..418S
Altcode:
No abstract at ADS
Title: The Low-Resolution Spectrograph of the Hobby-Eberly
Telescope. II. Observations of Quasar Candidates from the Sloan
Digital Sky Survey
Authors: Schneider, D. P.; Hill, Gary J.; Fan, X.; Ramsey, L. W.;
MacQueen, P. J.; Weedman, D. W.; Booth, J. A.; Eracleous, M.; Gunn,
J. E.; Lupton, R. H.; Adams, M. T.; Bastian, S.; Bender, R.; Berman,
E.; Brinkmann, J.; Csabai, I.; Federwitz, G.; Gurbani, V.; Hennessy,
G. S.; Hill, G. M.; Hindsley, R. B.; Ivezić, Z.; Knapp, G. R.; Lamb,
D. Q.; Lindenmeyer, C.; Mantsch, P.; Nance, C.; Nash, T.; Pier, J. R.;
Rechenmacher, R.; Rhoads, B.; Rivetta, C. H.; Robinson, E. L.; Roman,
B.; Sergey, G.; Shetrone, M.; Stoughton, C.; Strauss, M. A.; Szokoly,
G. P.; Tucker, D. L.; Wesley, G.; Willick, J.; Worthington, P.; York,
D. G.
Bibcode: 2000PASP..112....6S
Altcode: 1999astro.ph.10306S
This paper describes spectra of quasar candidates acquired during
the commissioning phase of the Low-Resolution Spectrograph of the
Hobby-Eberly Telescope. The objects were identified as possible quasars
from multicolor image data from the Sloan Digital Sky Survey. The 10
sources had typical r' magnitudes of 19-20, except for one extremely red
object with r'~23. The data, obtained with exposure times
between 10 and 25 minutes, reveal that the spectra of four candidates
are essentially featureless and are not quasars, five are quasars
with redshifts between 2.92 and 4.15 (including one broad absorption
line quasar), and the red source is a very late M star or early L
dwarf. Based on observations obtained with the Sloan Digital Sky Survey,
which is owned and operated by the Astrophysical Research Consortium.
Title: Library of Medium-Resolution Fiber Optic Echelle Spectra of F,
G, K, and M Field Dwarfs to Giant Stars
Authors: Montes, David; Ramsey, Lawrence W.; Welty, Alan D.
Bibcode: 1999ApJS..123..283M
Altcode: 1999astro.ph..1411M
We present a library of Penn State Fiber Optic Echelle (FOE)
observations of a sample of field stars with spectral types F to M and
luminosity classes V to I. The spectral coverage is from 3800 to 10000
Å with a nominal resolving power of 12,000. These spectra include many
of the spectral lines most widely used as optical and near-infrared
indicators of chromospheric activity such as the Balmer lines (Hα
to Hɛ), Ca II H & K, the Mg I b triplet, Na I D1,
D2, He I D3, and Ca II IRT lines. There are also
a large number of photospheric lines, which can also be affected by
chromospheric activity, and temperature-sensitive photospheric features
such as TiO bands. The spectra have been compiled with the goal of
providing a set of standards observed at medium resolution. We have
extensively used such data for the study of active chromosphere stars
by applying a spectral subtraction technique. However, the data set
presented here can also be utilized in a wide variety of ways ranging
from radial velocity templates to study of variable stars and stellar
population synthesis. This library can also be used for spectral
classification purposes and determination of atmospheric parameters
(Teff, logg, [Fe/H]). A digital version of all the fully
reduced spectra is available via ftp and the World Wide Web (WWW)
in FITS format.
Title: Supernova 1999bv in MCG +10-25-14
Authors: Hill, G. J.; Bergmann, M. P.; Howell, D. A.; Wheeler, J. C.;
MacQueen, P. J.; Booth, J. A.; Adams, M. T.; Eracleus, M.; Tejada, C.;
Cobos, F.; Garfias, F.; Cuervo, J.; Nicklas, H.; Mitsch, W.; Wesley,
G. W.; Odoms, P. S.; Barczac, G.; Ramsey, L. W.; Barnes, T. G., III;
Roman, B.; Nance, C.; Worthington, T.
Bibcode: 1999IAUC.7186....2H
Altcode: 1999IAUC.7186R...1H; 1999IAUC.7186B...1H
G. J. Hill, McDonald Observatory, University of Texas, reports on behalf
of the Hobby-Eberly Telescope (HET) Low Resolution Spectrograph (LRS)
commissioning team (which also includes M. P. Bergmann, D. A. Howell,
J. C. Wheeler, P. J. MacQueen, J. A. Booth, M. T. Adams, M. Eracleus,
C. Tejada, F. Cobos, F. Garfias, J. Cuervo, H. Nicklas, W. Mitsch,
G. W. Wesley, P. S. Odoms, G. Barczac, L. W. Ramsey, T. G. Barnes
III, B. Roman, C. Nance, G. Hill, T. Worthington): "A low-resolution
spectrogram (range 400- 1000 nm) of SN 1999bv was obtained on Apr. 21.37
UT with the Marcario LRS, during first light commissioning of the
instrument. The broad emission features seen by Jha et al. (IAUC 7150)
at 667, 600, 475, and 402 nm are confirmed, and we note that the broad
emission (FWHM 10 000 km/s) at 667 nm is consistent with slightly
blueshifted H-alpha emission in the rest frame of the supernova. Such
emission was also seen in SN 1993J, and is suspected to be an indication
of transition, or hybrid type-II/type-Ib/c events, sometimes referred
to as type IIb."
Title: Chromospheric Activity of ROSAT-discovered Weak-line T
Tauri Stars
Authors: Montes, D.; Ramsey, L. W.
Bibcode: 1999ASPC..158..302M
Altcode: 1999ssa..conf..302M; 1998astro.ph..9117M
We have started a high resolution optical observation program dedicated
to the study of chromospheric activity in weak-lined T Tauri stars
(WTTS) recently discovered by the ROSAT All-Sky Survey (RASS). It is
our purpose to quantify the phenomenology of the chromospheric activity
of each star determining stellar surface fluxes in the more important
chromospheric activity indicators (Ca II H & K, H_beta, H_alpha,
Ca II IRT) as well as obtain the Li I abundance, a better determination
of the stellar parameters, spectral type, and possible binarity. A
large number of WTTS have been discovered by the RASS in and around
differen star formation clouds.Whether these stars are really WTTS,
or post-TTS, or even young main sequence stars is a matter of ongoing
debate. However, we have centered our study only on objects for which
very recent studies, of Li I abundance (greater than Pleiads of the same
spectral type) or radio properties, clearly confirmed their pre-main
sequence (PMS) nature. In this contribution we present preliminary
results of our January 1998 high resolution echelle spectroscopic
observations at the 2.1m telescope of the McDonald Observatory. We
have analysed, using the spectral subtraction technique, the H_alpha
and Ca II IRT lines of six WTTS (RXJ0312.8-0414NW, SE; RXJ0333.1+1036;
RXJ0348.5+0832; RXJ0512.0+1020; RXJ0444.9+2717) located in and around
the Taurus-Auriga molecular clouds. A broad and variable double-picked
H_alpha emission is observed in RXJ0444.9+2717. Emission above the
continuum in H_alpha and Ca II IRT lines is detected in RXJ0333.1+1036
and a filling-in of these lines is present in the rest of the stars. Our
spectral type and Li I EW deterninations confirm the PMS nature of
these objects.
Title: A Long-Duration Flare on the X-ray/EUV Selected,
Chromospherically Active Binary 2RE J0743+224
Authors: Montes, D.; Ramsey, L. W.
Bibcode: 1999ASPC..158..226M
Altcode: 1999ssa..conf..226M; 1998astro.ph..9118M
2RE J0743+224 (BD +23 1799) is a chromospherically active star selected
by X-rays and EUV emission detected in the Einstein Slew Survey
and ROSAT Wide Field Camera (WFC) all sky survey, and classified
as single-lined spectroscopic binary by (Jeffries et al. 1995). We
present here high resolution echelle spectroscopic observations of
this binary, obtained during a 10 night run 12-21 January 1998 using
the 2.1m telescope at McDonald Observatory. These observations reveal
it is a double-lined spectroscopic binary. A dramatic increase in
the chromospheric emissions (H_alpha and Ca II IRT lines) is detected
during the observations. Several arguments favor the interpretation of
this behavior as an unusual long-duration flare. First the temporal
evolution of the event is similar to the observed in other solar and
stellar flares, with an initial impulsive phase characterized by a
strong increase in the chromospheric lines (the H_alpha EW change in a
factor of 5 in only one day) and thereafter, the line emission decreased
gradually over several days. Second, a broad component in the H_alpha
line profile is observed just at the beginning of the event. Third,
the detection of the He I D_{3} in emission and a filled-in He I 6678
A. We detect a Li I 6708 A line enhancement which is clearly related
with the temporal evolution of the flare. The maximum Li I enhancement
occurs just after the maximum chromospheric emission observed in the
flare. We suggest that this Li I is produced by spallation reactions in
the flare. This is the first time that such Li I enhancement associate
with a stellar flare is reported, and probably the long-duration of
this flare is a key factor for this detection.
Title: The Hobby*Eberly Telescope, a Tool for Spectroscopic
Astrophysics Introduction
Authors: Ramsey, L. W.
Bibcode: 1998AAS...193.2601R
Altcode: 1998BAAS...30Q1285R
The Hobby*Eberly telescope (HET), which is currently in commissioning,
is a special purpose telescope that represents a unique approach to
ground based visible and near infrared astronomy. The US community
will have several weeks per year of queue scheduled nights on the HET
via National Science Foundation support of instrumentation. The focus
of this session is how the Hobby*Eberly telescope is being deployed
to meet the science goals of the partners and the US community at
large. Invited talks will emphasize the scientific promise, as well
as the instrumental and particular scheduling capabilities of the
HET. Poster papers will detail the instrumental capabilities as well
as how one can prepare to best utilize the HET.
Title: Visible and Near-IR Astrophysics at Medium Resolution with
the Hobby-Eberly Telescope
Authors: Ciardullo, R.; Ramsey, L. W.
Bibcode: 1998AAS...193.2604C
Altcode: 1998BAAS...30.1285C
The Medium Resolution Spectrograph (MRS) is a versatile, fiber-fed,
dual beam echelle spectrograph for optical and near-IR observations with
the Hobby-Eberly Telescope. Its high efficiency, excellent velocity
stability, broad wavelength coverage, wide range of resolving power
(3500 < R < 20,000), and many observing modes (including synthetic
long-slit, multi-object, and integral field) make the instrument
ideal for a wide range of scientific investigations. We review some of
the major programs the MRS will undertake during its first few years
of service, paying particular attention to those projects that will
exercise the unique capabilities of the instrument and the telescope.
Title: Li I enhancement during a long-duration stellar flare
Authors: Montes, David; Ramsey, Lawrence W.
Bibcode: 1998A&A...340L...5M
Altcode: 1998astro.ph.10232M
We report the possible detection of a Li I λ6708 Angstroms line
enhancement during an unusual long-duration optical flare in the
recently discovered, X-ray/EUV selected, chromospherically active
binary 2RE J0743+224. The Li I equivalent width (EW) variations follow
the temporal evolution of the flare and large changes are observed in
the intensity of the line. The maximum Li I enhancement (40% in EW)
occurs just after the maximum chromospheric emission observed in the
flare. A significant increase of the (6) Li/(7) Li isotopic ratio is
also detected. No significant simultaneous variations are detected
in other photospheric lines. Neither line blends nor starspots seem
to be the primary cause of the observed Li I line variation. From all
this we suggest that this Li I enhancement is produced by spallation
reactions during the flare.
Title: Hobby-Eberly Telescope: current status
Authors: Barnes, T. G.; Ramsey, L. W.
Bibcode: 1998AAS...193.2602B
Altcode: 1998BAAS...30Q1285B
The Hobby-Eberly telescope (HET) is well into its second year of
commissioning and rapid progress is being made on all HET systems. We
report on the current pointing, tracking and image quality performance
of the HET. We also outline plans for further improvement and estimate
the performance we expect at the commencement of early operations
sometime in the first half of 1999. Finally we will lay out expected
science availability of HET facility instrumentation.
Title: Spider: The Formated Field Unit for the Hobby Eberly Telescope
Authors: Andersen, D. R.; Bershady, M. A.; Ramsey, L. W.
Bibcode: 1998AAS...193.1005A
Altcode: 1998BAAS...30.1263A
We describe the Formated Field Unit (FFU) under construction at Penn
State University for the 9m Hobby-Eberly Telescope's (HET) Medium
Resolution Spectrograph (MRS): Spider. This FFU is an array of fiber
optic cables formatted optimally to spectrally image single, extended,
axi-symmetric sources, such as galaxies and planetary nebulae. The
FFU consists of four, 15 arcsecond long slits with a common center
but at four position angles (like an aserisk, or spider). Each slit
is sampled by 1 arcsec diameter fibers (200 mu m), spaced 1.3 arcsec
apart. Spider will be installed during the commissioning phase of the
MRS (mid 1999). This fiber-fed echelle spectrograph has a resolution
of 10,900 for a 1 arcsec aperture, and initial spectral coverage from
0.5-0.95 mu m in a red beam. The large telescope aperture and fiber
size of Spider yields large etendue (50 m(2) arcsec(2) ). There are
currently no fiber arrays either planned or in existence which are
comparable. Hence this FFU fills a niche for moderate resolution
spectroscopy at low surface-brightness. The FFU is expected to reach
a limiting surface-brightness in V of 22 at S/N = 10 per spectral
resolution element per fiber at R = 10,900 in one hour; this assumes a
peak throughput of 15% for the HET plus MRS system. In this presentation
we outline the expected performance, design and construction progress
to date, and our characterization of fiber packing quality and focal
ratio degradation from test arrays. We also demonstrate how the Spider
FFU can be used for kinematic studies nearby and moderately distant
galaxies. The fiber array will be capable of delivering simultaneous
rotation curves and disk velocity dispersions over a range of look-back
times. This research is supported by NSF/AST 96-18849.
Title: Optical Fiber Evaluation for the Hobby-Eberly Telescope
Authors: McGouldrick, K.; Maywalt, J.; Engel, L.; Rhoads, B.; Andersen,
D. R.; Ramsey, L. W.
Bibcode: 1998AAS...193.1006M
Altcode: 1998BAAS...30.1263M
Two major facility instruments on the Hobby-Eberly telescope
(HET) are fiber coupled: the high and medium resolution
spectrographs. Understanding the behavior of the fibers with the HET is
central to understanding the performance of the telescope/spectrograph
system. We will describe the Penn State fiber evaluation facility
which enables us to measure focal ratio degradation (FRD) and total
throughput. We will present some typical data obtained using the HET
focal ratio at the fiber input. The HET design has a roving pupil that
changes the illumination pattern somewhat during the typical 1 hour
tracking time on a target. We will describe our plans to simulate the
HET input test the degree to which the varying pupil is scrambled by
the fiber.
Title: The Hobby-Eberly Telescope Commissioning Status
Authors: Adams, M. T.; Barnes, T. G.; Booth, J. A.; Ramsey, L. W.
Bibcode: 1998AAS...193.1001A
Altcode: 1998BAAS...30Q1262A
The Hobby-Eberly Telescope (HET) is unique among the new generation of
8 meter class telescopes in that it establishes a new cost paradigm
for large aperture science by making considered trades between cost
and performance. We briefly review the HET optical design and the
as-built facility. We discuss the status and performance of the major
HET systems. We describe the intense commissioning period that has
been underway since September 1997 and outline plans to ramp HET into
science operations this coming year.
Title: The J-band camera system for the Hobby-Eberly telescope
Authors: Beatty, J. J.; Charlton, J. C.; Churchill, C. W.; Ramsey,
L. W.
Bibcode: 1998AAS...193.1002B
Altcode: 1998BAAS...30.1262B
The J-band camera system, or JCAM, is an simple extension to the current
HET commissioning spectrograph to allow moderate resolving power (7,000
< R < 13,000) spectroscopy in the near-infrared. The JCAM system
will replace the current echelle grating, cross disperser, camera,
and detector in the Upgraded Fiber Optic Echelle (UFOE) currently at
the HET site. The camera has a five element all-refracting design. The
detector system is a 1024x1024 Hawaii array housed in an IR Labs
dewar and provides full coverage from 0.98 - 1.34 microns in a single
exposure. The detector electronics utilizes a VME-based PC driving
custom control and signal processing electronics. At the resolution of
JCAM only ~ 10% of the spectrum is contaminated by night sky lines. It
will be possible to obtain S/N ~ 30 per resolution element in one hour
on a J=18 object.
Title: The Medium Resolution Spectrograph for the Hobby Eberly
telescope: Capability and Performance Goals
Authors: Ramsey, L. W.; Engel, L.; Rhoads, B.; Maywalt, J.;
McGouldrick, K.; Andersen, D. R.
Bibcode: 1998AAS...193.1007R
Altcode: 1998BAAS...30.1263R
The Medium Resolution Spectrograph (MRS) is a versatile, fiber-fed dual
beam echelle spectrograph for the Hobby-Eberly Telescope (HET). This
instrument is designed for a wide range of scientific investigations;
it includes single-fiber inputs for the study of point-like sources,
synthetic slits of fibers for long slit spectroscopy, multi-fiber
inputs for multi-object spectroscopy, and an optical fiber integral
field unit. The MRS will have resolving power ranging from 3500 to
20,000 depending on the fiber/slit combination selected. The initial,
visible wavelength beam will have wavelength coverage from 450 -
900 nm in a single exposure. Later, a second beam operating in the
near-infrared will be added which will have coverage of 950-1300 nm in
a single exposure and capability out to 1800 nm. We detail the fiber
input and spectral coverage options on the HET as well as present
performance goals.
Title: Detection of Li i enhancement during a long-duration flare
in the recenltly discovered X-ray selected, chromospherically active
binary 2RE J0743+2 24
Authors: Montes, David; Ramsey, Lawrence W.
Bibcode: 1998AAS...192.8203M
Altcode: 1998BAAS...30Q1155M; 1998astro.ph..6227M
We report the detection of a long-duration optical flare in the
recenltly discovered, X-ray selected, chromospherically binary 2RE
J0743+224. The high resolution echelle spectroscopic observations taken
in 12-21th January 1998 exhibit a dramatic increase in the chromospheric
emissions (Hα and Ca ii IRT lines) that we interpret as a flare based
on: the temporal evolution of the event, the broad component observed
in the Hα line profile, the detection of the He i D3 in
emission and a filled-in He i 6678 Angstroms. During these obsevations
we detect a Li i 6708 Angstroms line enhancement which is clearly
related with the temporal evolution of the flare. The maximum Li i
enhancement (20% in EW) occurs just after the maximum chromospheric
emission observed in the flare. A significant increase of the (6) Li/(7)
Li isotopic ratio is also detected. For all this we suggest that this Li
i enhancement is produced by spallation reactions during the flare. This
is the first time that such Li i enhancement associate with a stellar
flare is reported, and probably the long-duration of this flare is a
key factor for this detection. A large fraction of the stellar surface
seem to be covered by starspots during the event, as we deduce for
the analysis of the TiO 7055 Angstroms band, thus taken into account
the Li i is very temperature sensitive, we can not discard that this
Li i variations was related the presence of starspots. However, the
correlation with the temporal evolution of the flare, the no detection
of changes in the other photospheric absorption lines, and the large
changes observed in the core of the Li i, as predict the models, argue
in favour of the hipothesis that the Li i is produced during the flare.
Title: Early performance and present status of the Hobby-Eberly
Telescope
Authors: Ramsey, Lawrence W.; Adams, M. T.; Barnes, Thomas G.; Booth,
John A.; Cornell, Mark E.; Fowler, James R.; Gaffney, Niall I.;
Glaspey, John W.; Good, John M.; Hill, Gary J.; Kelton, Philip W.;
Krabbendam, Victor L.; Long, L.; MacQueen, Phillip J.; Ray, Frank B.;
Ricklefs, Randall L.; Sage, J.; Sebring, Thomas A.; Spiesman, W. J.;
Steiner, M.
Bibcode: 1998SPIE.3352...34R
Altcode:
The Hobby-Eberly telescope (HET) is a recently completed 9- meter
telescope designed to specialize in spectroscopy. It saw first light in
December 1996 and during July 1997, it underwent its first end-to-end
testing acquiring its first spectra of target objects. We review the
basic design of the HET. In addition we summarize the performance of
the telescope used with a commissioning spherical aberration correlator
and spectrograph, the status of science operations and plans for the
implementation of the final spherical aberration corrector and facility
class instruments.
Title: Extremely large telescope: further adventures in feasibility
Authors: Sebring, Thomas A.; Bash, Frank N.; Ray, Frank B.; Ramsey,
Lawrence W.
Bibcode: 1998SPIE.3352..792S
Altcode:
Should the astronomical community pursue development of telescopes
10 times larger than the 8 and 10 meter individual and arrayed
telescopes currently under development or recently commissioned? The
question devolves into two parts: Is construction of such a telescope
feasible from an engineering and cost standpoint? Does the scientific
benefit justify the probable cost of such development? An Extremely
Large Telescope (ELT) has previously been proposed based on the
Arecibo type design employed in the recently completed Hobby Eberly
Telescope. Analysis of the performance and scientific viability
of the ELT shows that it can have an important role in near and IR
spectroscopy for cosmology providing that stringent image and background
performance requirements are met. Further development of engineering
design and interaction with the manufacturing community conclusively
shows that not only is such a telescope feasible, but that the entire
observatory can be constructed for of order $DLR250 million at a site
likely to provide optimal optical seeing. It remains an issue for the
scientific community to judge whether such capability provides benefits
commensurate with the costs.
Title: Hobby-Eberly Telescope: commissioning experience and observing
plans
Authors: Glaspey, John W.; Adams, M. T.; Booth, John A.; Cornell,
Mark E.; Fowler, James R.; Krabbendam, Victor L.; Ramsey, Lawrence W.;
Ray, Frank B.; Ricklefs, Randall L.; Spiesman, W. J.
Bibcode: 1998SPIE.3349...50G
Altcode:
Experience in bringing into operation the 91-segment primary mirror
alignment and control system, the focal plane tracker system, and
other critical subsystems of the HET will be described. Particular
attention is given to the tracker, which utilizes three linear and
three rotational degrees of freedom to follow sidereal targets. Coarse
time-dependent functions for each axis are downloaded to autonomous
PMAC controllers that provide the precise motion drives to the two
linear stages and the hexapod system. Experience gained in aligning
the sperate mirrors and then maintaining image quality in a variable
thermal environments will also be described. Because of the fixed
elevation of the primary optical axis, only a limited amount of time
is available for observing objects in the 12 degrees wide observing
band. With a small core HET team working with McDonald Observatory
staff, efficient, reliable, uncomplicated methodologies are required
in all aspects of the observing operations.
Title: Hobby-Eberly Telescope medium-resolution spectrograph and
fiber instrument feed
Authors: Horner, Scott D.; Engel, Leland G.; Ramsey, Lawrence W.
Bibcode: 1998SPIE.3355..399H
Altcode:
The Medium Resolution Spectrograph (MRS) is a high throughput,
versatile, fiber-fed echelle spectrograph for the Hobby-Eberly
Telescope (HET). This instrument is designed for a wide range of
scientific investigations; it includes single-fiber inputs for the
study of point-like sources, synthetic slits of fibers for long slit
spectroscopy, multi-fiber inputs for multi- object spectroscopy, and an
optical fiber integral field unit. The MRS will have resolution settings
between 3500 less than (lambda) /(Delta) (lambda) less than 21000 and
will consist of two beams. The initial, visible wavelength beam will
have wavelength coverage from 450 - 900 nm in a single exposure. This
beam will also have capability in the ranges 390 - 450 and 900 -
950 nm by altering the angles of the echelle and/or cross-disperser
gratings. Later, a second beam operating in the near-infrared will be
added which will have coverage of 950 - 1300 nm in a single exposure
and capability out to 1800 nm. The HET Fiber Instrument Feed (FIF) is
mounted at the focal plane of the telescope and positions the fibers
feeding the MRS and the High Resolution Spectrograph (HRS). The unique
and economical design of the FIF enables the HET's versatility in
performing a wide range of scientific investigations with the telescope
operating in a queue-scheduled mode.
Title: Multiwavelength Optical Observations of Chromospherically
Active Binary Systems
Authors: Montes, D.; Sanz-Forcada, J.; Fernández-Figueroa, M. J.;
de Castro, E.; Cornide, M.; Ramsey, L. W.
Bibcode: 1998Ap&SS.263..279M
Altcode: 1999Ap&SS.263..279M
We summarize here our ongoing project of multiwavelength optical
observations aimed at studying the chromosphere of active binary
systems, using the information provided for several optical
spectroscopic features, that are formed at different heights in the
chromosphere.
Title: Galaxy Kinematics with Integral-Field Spectroscopy and the
Hobby-Eberly Telescope
Authors: Bershady, M. A.; Andersen, D.; Ramsey, L.; Horner, S.
Bibcode: 1998ASPC..152..253B
Altcode: 1998fopa.proc..253B
No abstract at ADS
Title: Fiber-Optic Instrumentation and the Hobby-Eberly Telescope
Authors: Ramsey, L. W.
Bibcode: 1998ASPC..152..235R
Altcode: 1998fopa.proc..235R
No abstract at ADS
Title: The Hobby-Eberly telescope and facility instrumentation:
a model facility for the Southern African large telescope.
Authors: Ramsey, L. W.
Bibcode: 1998salt.conf...19R
Altcode:
The Hobby-Eberly telescope (HET) is a fundamentally different approach
to building large telescopes. It provides an extremely economical
path to large aperture and thus provides opportunity to scientists in
countries with limited resources. As such it provides an excellent model
for the Southern African Large Telescope (SALT) project. Central to the
HET approach is specialization: the HET is tailored for spectroscopy,
and in particular, fibre-coupled spectroscopy. By limiting observational
flexibility, cost-effective technical approaches have made it possible
for the HET to break traditional cost vs. aperture laws. I will outline
the science missions and capabilities of the HET facility instruments
currently under construction.
Title: The Hobby-Eberly Telescope Fiber-Instrument Feed
Authors: Horner, S. D.; Engel, L. G.; Ramsey, L. W.
Bibcode: 1998ASPC..152..247H
Altcode: 1998fopa.proc..247H
No abstract at ADS
Title: Integral Field Spectroscopy with the Hobby-Eberly Telescope
Authors: Andersen, D. R.; Bershady, M. A.; Ramsey, L. W.; Horner, S. D.
Bibcode: 1997AAS...191.4105A
Altcode: 1997BAAS...29.1270A
We describe two fiber-optical arrays (IFUs) under construction
at Penn State University for the 9m Hobby-Eberly Telescope's
(HET) Medium Resolution Spectrograph (MRS). These arrays optimize
integral-field spectroscopy for kinematic studies of individual,
nearby and moderately distant galaxies, but will have more general
application to moderate spectral resolution studies of extended
sources at low surface-brightness. Once in place, the fiber arrays
will be capable of delivering simultaneous rotation curve and disk
velocity dispersion measurements over a range of look-back times. These
measurements can be used to separately estimate the disk mass and
total mass of galaxies. Such surveys would have important implications
for the nature of dark matter. One array spans over 30 arcsec using 2
arcsec (400 mu m) fibers to densely sample slits at 4 position angles
at resolution from 5500 to 11000. The second array spans 15 arcsec
using 1 arcsec fibers to densely sample a core area of ~ 60 arcsec(2)
at resolution of 11000 to 14500. In contrast, fiber arrays planned
for other 10m-class telescopes generally are optimized for smaller
areas and higher angular resolution, but are commensurately limited to
higher surface-brightness at fixed spectral resolution. Our 400 micron
array will be installed during the commissioning phase of the MRS when
this fiber-fed echelle spectrograph will have a resolution of 10,900
for a 1 arcsec slit and spectral coverage from 0.5-0.95 mu m in a red
beam. In this presentation we outline the expected performance, design
and construction progress to date, and our initial characterization
of fiber packing quality and focal ratio degradation from test arrays
already completed. This research is supported by NSF/AST 96-18849.
Title: Hobby-Eberly Telescope: a progress report
Authors: Sebring, Thomas A.; Ramsey, Lawrence W.
Bibcode: 1997SPIE.2871...32S
Altcode:
The Hobby-Eberly Telescope, nearing completion at McDonald Observatory
in west Texas is an optical Arecibo-type telescope utilizing an 11-meter
primary mirror and a 9.2-meter effective aperture. Innovative approaches
have been employed to provide this large modern telescope at a total
cost of $13.5 million. A joint project of the University of Texas,
The Pennsylvania State University, Stanford University, the University
of Munich, and the University of Goettingen, the telescope will be
completed in mid 1997. First light is expected in mid 1996.
Title: Extremely large telescope: a twenty-five meter aperture for
the twenty-first century
Authors: Bash, Frank N.; Sebring, Thomas A.; Ray, Frank B.; Ramsey,
Lawrence W.
Bibcode: 1997SPIE.2871..576B
Altcode:
The 10-meter class Hobby-Eberly telescope (HET), now nearing completion,
provides technology for optical Arecibo-type telescopes which can be
extrapolated to even larger apertures. Utilizing a fixed elevation angle
and a spherical segmented primary mirror provides cost effective and
pragmatic solutions to mirror mounting and fabrication. Arecibo-type
tracking implies a greatly reduced tracking mass and no change to the
gravity vector for the primary mirror. Such a telescope can address
70 percent of the available sky and exhibit optical quality easily
sufficient for effective spectroscopy and photometry. The extremely
large telescope takes advantage of several key engineering approaches
demonstrated by the HET project to achieve a cost comparable to
similarly-sized radio rather than optical telescopes. These engineering
approaches include: bolted pre-manufactured primary mirror truss,
factory manufactured geodesic enclosure dome, air bearing rotation
of primary mirror, tracker, and dome systems directly on concrete
piers, and tracking via a hexapod system. Current estimates put the
cost of the ELT at $200 million for a 25-meter aperture utilizing a
33-meter primary mirror array. Construction of the ELT would provide
the astronomy community with an optical telescope nearly an order
of magnitude larger than even the largest telescopes in operation or
under construction today.
Title: The Upgraded Fiber Optic Echelle Spectrograph
Authors: Harlow, J. J. B.; Ramsey, L. W.; Andersen, D. R.; Fleig,
J. D.; Rhoads, B. T.; Engel, L. G.
Bibcode: 1996AAS...189.4207H
Altcode: 1996BAAS...28R1324H
The Upgraded Fiber Optic Echelle (UFOE) is a fiber-fed, white pupil
echelle spectrograph to be implemented at the Hobby-Eberly Telescope
(HET) in the spring of 1997. It will serve as the commissioning
spectrograph until HET facility instruments come on line in early
1998. This instrument is a quick, cost effective upgrade of the
Fiber Optic Echelle, resident at KPNO for a decade. The UFOE will be
capable of R = 13,900 (Nyquist limited 2 pixels/resel), with complete
spectral coverage from 530 nm to 850 nm and about 90% coverage to 900
nm with adequate order separation. It utilizes a 2.5 meter radius 400
mm diameter spherical mirror to reimage an ``average'' pupil between
the echelle and the cross-dispersing grating onto the entrance pupil
of a 200 mm f/2 camera lens. Due to the reduction of vignetting made
possible with the pupil mirror, it is estimated that the UFOE will
have an efficiency of 13% on the sky when used on the HET, whereas
the FOE had an efficiency of 8%. This efficiency, combined with the 9
meter aperture of the HET, should allow a limiting magnitude of V =
18.9 for a 3000 second exposure with S/N = 30 per 1/2 resel. This
spectrograph has been designed and constructed at Penn State and we
present results of characterization of image quality, vignetting,
and focal plane characteristics.
Title: A Performance Model for the Hobby-Eberly Telescope
Authors: Ramsey, L.; Gressler, W.; Hill, G. J.; Sebring, T.
Bibcode: 1995AAS...187.7401R
Altcode: 1995BAAS...27.1389R
The Hobby-Eberly telescope's (HET) unique optical design makes
deliberate trades between science performance and cost. To optimize the
use of the telescope we require reliable modeling of the performance
in order to efficiently plan observations. We describe the HET optical
system design and present a performance model that gives the photon
flux in the HET focal plane for sample targets under different seeing
conditions. In addition we utilize this model and similar models of
a focal plane and fiber spectrograph to estimate the HET limiting
magnitudes at anticipated instrument spectral resolutions.
Title: The Hobby-Eberly Telescope: A Progress Report
Authors: Sebring, T. A.; Adams, M. T.; Ramsey, L. W.
Bibcode: 1995AAS...18712103S
Altcode: 1995BAAS...27.1453S
The Hobby-Eberly Telescope (HET) Project has made substantial progress
in design and construction of an 11-meter primary, 9-meter pupil,
optical Arecibo-type telescope. Construction of the facility will be
complete by early 1996 and will be followed by systems integration
leading to engineering first light in the third quarter of 1996. The
telescope structure and primary mirror truss are already in place and
the telescope azimuth rotation system has been tested. The first dozen
of the 91 identical mirror segments are complete.
Title: Beyond 10 Meter Apertures: The Extremely Large Telescope
Authors: Bash, F. N.; Sebring, T. A.; Ray, F. B.; Ramsey, L. W.
Bibcode: 1995AAS...187.7201B
Altcode: 1995BAAS...27.1387B
An overview of a design concept for a highly cost effective telescope
is presented which features an order of magnitude increase in
light gathering power relative to the 10-meter class telescopes
recently completed or currently under construction. The telescope
is an Arecibo-type employing a segmented primary mirror 35 meters
in diameter with a 28-meter pupil. The primary mirror array and the
tracker system are supported on separate structures which mount to a
common foundation. Azimuth rotation is achieved utilizing air bearings
between observations. The total estimated cost for this telescope
is on the order of \$100 million, making it far less expensive than
full-sky designs previously proposed. The ELT employs technology
which has been successfully demonstrated in the construction of the
Hobby-Eberly Telescope.
Title: The Activity of Weak-Lined T Tauri Stars. I. V410 Tauri
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1995AJ....110..336W
Altcode:
From two intensive series of spectra we have studied the phenomenology
of magnetic activity and its distribution on and around V410
Tau. Large-amplitude, quasisinusoidal radial velocity variations at the
stellar rotation period appear to be due to large-scale photospheric
temperature inhomogeneity that has been present at least since 1988,
and not to orbital motion. Other radial velocity variations imply
more localized spot groups. The radial velocity variations highlight
the point that radial velocity searches for brown dwarfs and planets
orbiting cool stars must take stellar activity into account. The
activity-related radial velocity variations seen in V410 Tau are
thousands of times larger than expected radial velocity reflex
motion of low-mass stars due to planets. Variations of absorption
linewidths are consistent with surface temperature inhomogeneities
implied by the radial velocity variations. The implied temperature
distribution is in qualitative with Doppler images made from one
of our series of spectra. We found that the cooler regions of the
photosphere were associated with greater Balmer emission during the
first observing run, but about 90° out of phase 13 months later. The
level of Balmer emission increased from one season to the next,
and flares were observed only during the later season, suggesting
an activity cycle. The net Balmer emission apparently has two strong
contributors: a global chromospheric component and a variable asymmetric
"halo." Prominence-like structures appear not to be a large contributor
to the nonphotospheric Balmer features. Transient absorption features
probably are due to an infall of previously ejected material.
Title: Hobby-Eberly telescope medium-resolution spectrograph
Authors: Ramsey, Lawrence W.
Bibcode: 1995SPIE.2476...20R
Altcode:
We present a concept design for a versatile, high throughput fiber
couple spectrograph for the 9-meter Hobby-Eberly telescope. This
instrument, designated the medium resolution spectrograph (MRS) will
cover the visible spectrum from 350 nm to 1100 nm and have a resolution
range 300 < (lambda) /(Delta) (lambda) < 20000. It will reside
in an environmentally controlled spectrograph room. Operating modes of
the spectrograph will include single object, synthetic long slit, and
multiple object spectroscopy. The dual requirements of spectral coverage
and high resolution mandate that the MRS be a dual beam instrument.
Title: The Hobby-Eberly Telescope; Status and Science Capability
Authors: Ramsey, Lawrence W.
Bibcode: 1995AAS...186.4401R
Altcode: 1995BAAS...27..874R
The Hobby-Eberly Telescope (HET), currently under construction at
McDonald Observatory, is a unique approach to large telescope system
design. The HET, formerly called the Spectroscopic Survey Telescope
before its groundbreaking in March 1994, has a number of unique
features that allow it to meet its science mission with unusual cost
effectiveness. This fixed altitude design has a spherical primary mirror
consisting of 91 identical hexagonal segments made of low expansion
glass with a total collecting area of 77.6 square meters. The pupil
of the HET varies from a maximicrons diameter of 9 meters as an all
reflecting spherical aberration corrector tracks the astronomical target
on the spherical focal surface of the primary mirror. This tracking
is accomplished with a multi-axis system that provides precision
motions and minimal pupil obstruction. A final focal plane field of
view of 4 arc minutes at f/4.7 will deliver seeing limited images at
the McDonald site. A combination of a 35 degree tilt from zenith. The
HET is well suited to spectroscopic follow-up of objects from wide
field ground based and space based surveys. Instrumentation planned
for the HET include a low resolution imaging spectrograph in the focal
plane and fiber coupled medium and high resolution instruments. The
fiber feeds allow rapid switching of instruments compatible with a
queue scheduled observing mode. Anticipated performance of the HET
with such instruments will be present along with the current status
of the project. First light is expected in 1996.
Title: On the Role of Mass Transfer in X-Ray Emission of RS CVN
Systems
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1995AJ....109.2187W
Altcode:
We explore the possible role of mass transfer in generating x rays
in RS CVn binary systems. We have used system properties from the
published literature. We also present results of our ROSAT PSPC pointed
observations of RT Lacertae and SS Boötis. We find the evidence
that mass transfer is responsible for significant x-ray emission to
be suggestive, but not conclusive. Fundamental stellar and orbital
parameters and distances must be determined to good precision for more
RS CVn systems before progress on this question can be made.
Title: The Activity of Weak-Lined T Tauri Stars
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1995AAS...186.0904W
Altcode: 1995BAAS...27..824W
We have conducted intensive spectroscopic observing campaigns on
several weak-lined and classical T Tauri stars (WTTS, CTTS). The data
were obtained with the Penn State Fiber Optic Echelle spectrograph in
three observing runs at the KPNO 2.1m telescope. We wish to understand
the phenomenology of stellar and circumstellar activity of our targets,
and to quantify the activity where possible. Here we present results
for our WTTS targets, V410 Tau in particular. The first step in our
analysis is to determine the spectral type of each target by fitting a
grid of standard star spectra to the target star spectra. Byproducts of
this process are values for radial and projected rotational velocities
and veiling for each observation. We find no veiling (from Hβ to
Hα ) in any of our targets. Results for V410 Tau are dramatic. The
photospheric temperature distribution (recently Doppler imaged by
Strassmeier, Welty, & Rice 1994 and Hatzes 1995) causes line
profile variations which cause apparent radial velocity changes. The
amplitude of this variability is 500 times the Sun's orbital motion due
to Jupiter. Although this is an extreme case, it serves to illustrate
the point that radial velocity searches for low mass companions,
especially planets, must take stellar activity into account. Three
of our other WTTS targets show similar radial velocity variation. We
also feature flare observations of V410 Tau. One event was observed
rising and declining during one observing night. Its total duration was
about 15 hours. It released ~ 10(35) erg in optical line emission. He
D_3 radial velocities enable us to locate the flare with respect to
features in the Doppler images. Our results suggest that V410 Tau has
entered a state of relatively high activity after a decline indicated
by various observations made during the 1980s. We will also be pleased
to discuss results on our CTTS targets with interested parties.
Title: The Shape of FK Comae Berenices: Evidence for a Recently
Coalesced Binary
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1994ApJ...435..848W
Altcode:
To explain its great rotational speed, it has been argued that
FK Comae Berenices is either a recently coalesced binary or has
been spun up by angular momentum transfer via mass transfer from
an unseen companion. Upper limits on radial velocity variation put
severe constraints on any binary model. A series of 51 spectroscopic
observations of FK Com during an eight night observing run in 1989
revealed regular variation of projected rotational speed with rotational
phase. These variations are suggestive of strong nonradial pulsations
at about half the rotational period. We postulate that the pulsations
were excited by a recent binary merger. Less extensive data obtained in
1987 and 1992 show different patterns of line-width variation. Thus
it appears that the pulsation spectrum is changing on timescales
significantly less than two years.
Title: ROSAT Observations of FK Comae Berenices
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1994AJ....108..299W
Altcode:
We obtained ROSAT PSPC observations of FK Com over a period of 24.4 h,
or 0.42 rotation. During the observations the x-ray flux increased by
a factor of at least 5 before declining toward its previous level. A
single temperature Raymond-Smith model is adequate to model the low
signal-to-noise ratio spectrum from each observation interval. Initially
the spectrum was that of a 8.5 x 106 K plasma, with L9sub
x)=0.66 x 1031 erg s-1. When the x-ray flux was
greatest, the model plasma temperature rose to 2.5 x 107
K, and Lx=3.46 x 1031 ergs-1. During
the post-maximum decline in luminosity the plasma temperature was
approximately 12 x 106 K. We conclude that the increase of
x-ray flux recorded by ROSAT was due to an x-ray flare with a 1.5 h
decline time scale.
Title: Spectroscopic survey telescope project
Authors: Ramsey, Lawrence W.; Sebring, Thomas A.; Sneden, Christopher
A.
Bibcode: 1994SPIE.2199...31R
Altcode:
We describe the concept, basic design and capability of an eight
meter class telescope currently being constructed by a international
consortium of universities led by The Pennsylvania State University
and The University of Texas at Austin. This unique telescope concept
represents a deliberate trade between the science mission and technical
cost drives. The basic science driver for the Spectroscopic Survey
Telescope has traditionally been the need to obtain a large number of
spectroscopic exposures in a short time. An efficient design that meets
this need is a tilted Arecibo type telescope with a large segmented
primary mirror. The SST has a number of other unique features that
allow it to meet its science mission with unusual cost effectiveness.
Title: Design and status of the Spectroscopic Survey Telescope
Authors: Sebring, Thomas A.; Booth, John A.; Good, John M.; Krabbendam,
Victor L.; Ray, Frank B.; Ramsey, Lawrence W.
Bibcode: 1994SPIE.2199..565S
Altcode:
The Spectroscopic Survey Telescope is being constructed by a consortium
of universities at McDonald Observatory in the Davis Mountains of
Texas. Principal partners are the University of Texas at Austin and
the Pennsylvania State University. Also participating are Stanford
University and the University of Munich and University of Gottingen in
Germany. We describe the specific design attributes which enable the SST
to be constructed for a fraction of the cost of astronomical telescopes
of comparable size. Such unique features as identical spherical mirror
segments, selective figuring for constant mirror mount deformation,
air bearing azimuth rotation system, and pre-fabricated architectural
type domes are employed. Emphasis is on simplification of design,
reduction of part count and mass, and utilization of lessons learned
from other recent large telescope projects.
Title: Eclipse Observations of RS CVN Binaries II. A Parametric
Model of Extended Matter
Authors: Hall, Jeffrey C.; Ramsey, Lawrence W.
Bibcode: 1994AJ....107.1149H
Altcode:
We have surveyed ten RS CVn binary systems and have detected large
regions of extended, prominencelike material which we have shown to be
a common feature in these systems. These extended regions are apparent
as anomalous absorption features in the spectra when they obscure the
disk of the eclipsed star and as weak emission features when they
appear with no disk behind. We have constructed a first-generation
model to verify the general prominencelike nature of the material and to
estimate its extent and its most basic physical characteristics. In this
paper we present our results of our modeling on four of the systems in
our survey that showed clear signatures of extended material: AW Her,
MM Her, SS Boo, and UV Psc. We find that these stellar prominencelike
structures are very much larger than their solar counterparts, though
their gross physical characteristics (i.e., their electron density
and temperature and their general appearance as tenuous, vertically
oriented, magnetically confined structures) are similar to those seen
in solar prominences. These features appear to evolve fairly rapidly,
since moderate- to high-velocity flows ranging from several tens of
km/s to 170 km/s are apparent. However, in at least one case (SS Boo)
they are recurrent over a time scale of at least a year. We conclude
by discussing the implications of this work regarding the nature of
close binary star active structures and their evolution.
Title: Sleuthing the Dynamo: HST/FOS Observations of UV Emissions
of Solar-Type Stars in Young Clusters
Authors: Ayres, T.; Basri, G.; Simon, T.; Stauffer, J.; Stern, R.;
Antiochos, S.; Bookbinder, J.; Brown, A.; Doschek, G.; Linsky, J.;
Ramsey, L.; Walter, F.
Bibcode: 1994ASPC...64...53A
Altcode: 1994csss....8...53A
No abstract at ADS
Title: A Far-Ultraviolet Flare on a Pleiades G Dwarf
Authors: Ayres, T. R.; Stauffer, J. R.; Simon, Theodore; Stern, R. A.;
Antiochos, S. K.; Basri, G. S.; Bookbinder, J. A.; Brown, A.; Doschek,
G. A.; Linsky, J. L.; Ramsey, L. W.; Walter, F. M.
Bibcode: 1994ApJ...420L..33A
Altcode:
The Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) recorded
a remarkable transient brightening in the C IV lambda lambda 1548,50
emissions of the rapidly rotating Pleiades G dwarf H II 314. On the one
hand the 'flare' might be a rare event luckily observed; on the other
hand it might be a bellwether of the coronal heating in very young
solar-mass stars. If the latter, flaring provides a natural spin-down
mechanism through associated sporadic magnetospheric mass loss.
Title: ROSAT Observations of FK Comae Berenices
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1994ASPC...64..146W
Altcode: 1994csss....8..146W
No abstract at ADS
Title: Spectroscopic Monitoring of V410 Tauri
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1994ASPC...64..495W
Altcode: 1994csss....8..495W
No abstract at ADS
Title: The Spectroscopic Survey Telescope: Concept and Performance
Authors: Ramsey, Lawrence W.
Bibcode: 1994ASPC...55...35R
Altcode: 1994oaem.conf...35R
No abstract at ADS
Title: A Long-Term Study of H-alpha Line Variations in FK Comae
Berenices
Authors: Welty, Alan D.; Ramsey, Lawrence W.; Iyengar, Mrinal; Nations,
Harold L.; Buzasi, Derek L.
Bibcode: 1993PASP..105.1427W
Altcode:
We present observations of H-alpha V/R ratio variations in FK Comae
Berenices obtained during several observing seasons from 1981 to
1992. The raw H-alpha emission profile is always observed to be
double-peaked due to the stellar absorption component. During most
years the V/R ratio varies regularly with the period of the photometric
light curve. The V/R periodicity is most obvious when time spans
no longer than several stellar rotations are considered. We propose
that the bulk of the emission component of the H-alpha line arises
in corotating circumstellar material that may be similar to that of a
quiescent solar prominence. The lifetime of these structures appears
to be on the order of weeks. A weak contribution from a circumstellar
disk is evident and chromospheric emission may also be present. The
appearance or disappearance of circumstellar structures over periods
longer than a few weeks, or the total absence of such structures, blurs
the more regular variations in H-alpha seen over short timescales. Other
more stochastic activity, such as flares, also clearly occurs. Phase
shifts of the V/R ratio from year to year rule out the hypothesis
that mass transfer in a close binary system is responsible for the
V/R variations. (SECTION: Stars)
Title: The Shape of FK Comae
Authors: Welty, Alan D.; Ramsey, Lawrence W.
Bibcode: 1993AAS...18311109W
Altcode: 1993BAAS...25.1458W
FK Comae is an evolved G giant rotating at vsin i = 164.5 +/- 2.1kms(-1)
and exhibits a very strong Hα emission line. In addition, it has long
been known to have other signatures of magnetic activity characteristic
of RS CVn systems and Weak-lined T Tauri stars such as Delta V ~ 0.1
photometric variability indicative of spots, and strong X-ray and
UV line emission. Our recent detailed analysis of the spectrum of
this star have turned up variations in vsin i that we attribute to
changes in the shape of the star of order 2.5%. We present the data
for several seasons to support this interpretation and discuss three
possible explanations for this highly unusual observed behavior.
Title: Some Statistics for Measuring Large-Scale Structure
Authors: Brandenberger, Robert H.; Kaplan, David M.; A, Stephen; Ramsey
Bibcode: 1993astro.ph.10004B
Altcode:
Good statistics for measuring large-scale structure in the Universe
must be able to distinguish between different models of structure
formation. In this paper, two and three dimensional ``counts in cell"
statistics and a new ``discrete genus statistic" are applied to toy
versions of several popular theories of structure formation: random
phase cold dark matter model, cosmic string models, and global texture
scenario. All three statistics appear quite promising in terms of
differentiating between the models.
Title: A Remarkable FUV Flare on the Pleiades G Dwarf HZ 314
Authors: Ayers, T.; Basri, G.; Simon, T.; Stauffer, J.; Stern, R.;
Antiochon, S.; Bookbinger, J.; Brown, A.; Doschek, G.; Linsky, J.;
Ramsey, L.; Walter, F.
Bibcode: 1993AAS...182.4611A
Altcode: 1993BAAS...25..875A
No abstract at ADS
Title: ROSAT X ray survey observations of active chromospheric binary
systems and other selected sources
Authors: Ramsey, Lawrence W.
Bibcode: 1993psu..rept.....R
Altcode:
The connection between processes that produce optical chromospheric
activity indicators and those that produce x-rays in RS CVn binary
systems by taking advantage of the ROSAT All-Sky Survey (RASS) results
and our unique ground-based data set was investigated. In RS CVn
systems, excess emission in the Ca 2 resonance (K & H) and infrared
triplet (IRT) lines and in the Balmer lines of hydrogen is generally
cited as evidence for chromospheric activity, which is usually modeled
as scaled up solar-type activity. X-ray emission in RS CVn systems is
believed to arise from coronal loop structures. Results from spectra
data obtained from RASS observations are discussed and presented.
Title: Lithium Line Variations in Weak-Lined T Tauri Stars
Authors: Patterer, Robert J.; Ramsey, Lawrence; Welty, Alan D.;
Huenemoerder, David P.
Bibcode: 1993AJ....105.1519P
Altcode:
We have observed seven weak-lined T Tauri stars to examine the
effects of magnetic activity on the Li I 6707 A equivalent width
and line profile. Six of the seven program stars were observed at
least twice per evening on four consecutive nights. Variable Li I
equivalent width is certainly present in two targets, which are the
only known binaries (single-lined spectroscopic) in our sample, and
likely in three others. The amplitude of the variability is consistent
with previous estimates of activity effects. The variability itself
supports hypotheses that observed spread in Li I equivalent widths
may be explained by magnetic activity. It is unclear whether or not
the binary nature of our two detections is significant. We find no
indication that similarity to RS CVn systems, other than rapid rotation,
is responsible for the variable activity detected.
Title: A Spectroscopic and Photometric Study of FK Comae in 1989
Authors: Huenemoerder, David P.; Ramsey, Lawrence W.; Buzasi, Derek
L.; Nations, Harold L.
Bibcode: 1993ApJ...404..316H
Altcode:
Results of an observational campaign, coordinated between visual
photometry, optical spectroscopy, and UV spectroscopy, to elucidate
the characteristics of FK Comae are presented. The photometry showed
complicated but systematic behavior. Photospheric absorption lines
were distorted by a Doppler-shifted bump caused by dark starspots
resulting in small apparent radial velocity variations. No radial
velocity variations characteristic of orbital motion were seen to
a level of 3 km/s. Broad emission in H-alpha was modulated at the
photospheric rotational amplitude, implying an origin no farther from
the rotational axis than 1 stellar radius. The strengths of Ca II lines
are modulated in phase with H-alpha but do not have velocity-modulated
wings like H-alpha.
Title: The Spectroscopic Survey Telescope
Authors: Cordova, France A.; Ramsey, Lawrence W.
Bibcode: 1993ASPC...43..283C
Altcode: 1993sspp.conf..283C
The scientific goals and technical character of the eight meter
Spectroscopic Survey Telescope are described. The project to build this
optical telescope in west Texas by the middle of this decade is a joint
collaboration between The Pennsylvania State University, The University
of Texas at Austin, and others. The strategy of this project is to limit
the scientific mission to spectroscopy, emphasizing survey science. This
results in an inexpensive, yet powerful facility for astronomy.
Title: A versatile fiber coupled CCD/echelle spectrograph system
(in Instrumentation in Astronomy VI 1986)
Authors: Ramsey, L. W.; Huenemoerder, D. P.
Bibcode: 1993inas.book..195R
Altcode:
No abstract at ADS
Title: Scrambling Properties of Optical Fibers and the Performance
of a Double Scrambler
Authors: Hunter, Todd R.; Ramsey, Lawrence W.
Bibcode: 1992PASP..104.1244H
Altcode:
Optical fibers have become increasingly commonplace in astronomical
instrumentation during the past decade; especially in coupling
telescopes to spectrographs. In addition to the astrophysical results
there is also a growing literature on the properties of optical fibers
as they pertain to astronomical observations but this has tended to
emphasize transmission and focal ration degradation. This paper looks
at the scrambling properties of optical fibers which are particularly
important in precision radial velocity observations. We find that
a single multimode step index fiber, such as is commonly used in
astronomical applications, is deficient as a scrambler; that is the
output beam has some memory of the input object position and incident
angle. We go on to characterize a solution to this problem which is a
prototype double scrambler using two fibers coupled by an afocal lens
system. (SECTION: Instrumentation and Data Analysis)
Title: Eclipse Observations of RS CVn Binaries. I. A Survey for
Extended Matter
Authors: Hall, Jeffrey C.; Ramsey, Lawrence W.
Bibcode: 1992AJ....104.1942H
Altcode:
We survey a number of RS CVn systems to determine the frequency and
nature of circumstellar matter in these chromospherically active
binaries. A growing body of data suggests that large extended regions
of cool, prominence-like matter may be a common phenomenon in these
systems. Our targets are eclipsing systems as the established geometries
and occultations are useful probes for such extended material. In this
paper we discuss our methods and present the results of our survey and
our spectroscopic phase monitoring of these systems. We find extended
material in eight of the ten systems on our present survey.
Title: The Spectroscopic Survey Telescope: A Different Approach to
8 Meter Class Instruments
Authors: Ramsey, L. W.
Bibcode: 1992AAS...180.2105R
Altcode: 1992BAAS...24Q.758R
No abstract at ADS
Title: A Low-Resolution Spectrograph for Stellar Radial Velocity
Measurements
Authors: Ratcliff, S. J.; Ramsey, L. W.
Bibcode: 1992AAS...180.0904R
Altcode: 1992BAAS...24..740R
No abstract at ADS
Title: BF Orionis: Evidence for an Infalling Circumstellar Envelope
Authors: Welty, Alan D.; Barden, Samuel C.; Huenemoerder, David P.;
Ramsey, Lawrence W.
Bibcode: 1992AJ....103.1673W
Altcode:
Analysis of the optical magnitudes and Balmer lines of the Herbig Ae/Be
star BF Orionis confirm that the object is an early to mid A-type
star, but appears to be below the zero-age main sequence. Enhanced
metal-line strengths (once thought to link BF Ori with the Am stars),
line asymmetries, and radial velocities are shown to be signatures of
an infalling circumstellar envelope. The possibility that BF Ori has
a late-type companion is examined, and it is concluded that it does not.
Title: Optical Spectroscopy of Chromospherically Active Binary
Systems in Conjunction with the ROSAT All-Sky Survey
Authors: Welty, A. D.; Hall, J. C.; Patterer, R. J.; Ramsey, L. W.;
Huenemoerder, D. P.
Bibcode: 1992ASPC...26..116W
Altcode: 1992csss....7..116W
No abstract at ADS
Title: A Study of Extended Matter in RS CVn Systems
Authors: Hall, J. C.; Ramsey, L. W.
Bibcode: 1992ASPC...26..359H
Altcode: 1992csss....7..359H
No abstract at ADS
Title: Robotic Telescopes with Fiber-Coupled Spectrographs
Authors: Ramsey, Lawrence W.
Bibcode: 1992ASPC...34..227R
Altcode: 1992robt.proc..227R; 1992rote.proc..227R
We address the scientific need for a Robotic Spectroscopic Telescope
(RST) and discuss some of the issues that must be considered in the
design of the telescope, the fiber couplings, and the spectroscopic
instrumentation. Performance modeling based on experience with fiber
coupled spectrographs indicates that a one-meter class telescope
can provide the capability to carry out a wide variety of scientific
programs, as well as most economically demonstrate the feasibility of
the RST concept.
Title: Fk-Comae and the Evolution of Close Binaries
Authors: Huenemoerder, D. P.; Ramsey, L. W.; Buzasi, D. L.; Nations,
H. L.
Bibcode: 1992IAUS..151..403H
Altcode:
No abstract at ADS
Title: Short-Term Variability in the RS Canum Venaticorum System
HR 1099
Authors: Buzasi, Derek L.; Huenemoerder, David P.; Ramsey, Lawrence W.
Bibcode: 1991PASP..103.1077B
Altcode:
Observations of the RS CVn system HR 1099 made during the 1988 season
are discussed. A dramatic reduction in extraphotospheric emission
occurred on the primary during the observing period; this reduction
is ascribed to the disappearance of a prominence on the K star. In
addition, the system shows evidence for the process of mass transfer
similar to those seen in the RS CVn system UX Ari.
Title: Detection of Possible p-Mode Oscillations on Procyon
Authors: Brown, Timothy M.; Gilliland, Ronald L.; Noyes, Robert W.;
Ramsey, Lawrence W.
Bibcode: 1991ApJ...368..599B
Altcode:
In the course of a search for solar-like oscillations in bright
late-type stars, Doppler variability was observed in the F5 subgiant
Procyon. The variations have frequencies within a 1.1 mHz range
centered at 0.9 mHz, and a total rms amplitude within that range
of 2.5 m/s. Observations of Arcturus and scattered sunlight made
with the same equipment during the same time interval show no such
variation, indicating that the variations seen on Procyon are of stellar
origin. The Doppler signal seen is entirely consistent with solar-like
p-modes on Procyon, with maximum mode amplitudes of about 50 cm/s
and periods around 20 minutes. Several statistical tests support the
identification for the signal with narrow-band oscillations, but none
does so conclusively. Assuming that the signal does arise from p-modes,
there is evidence that the frequency splitting nu(0) is 71 micro-Hz. The
data do not permit a definite estimate of this quantity, and other
values of nu(0) fit the observations about equally well. In order to
clarify the sources of ambiguity in this and similar observations,
the data acquisition, reduction, and interpretation are described.
Title: A new technique for study of radial velocity changes.
Authors: Ramsey, L.; Brown, T.; Gilliand, R.; Noyes, R.
Bibcode: 1991ASPC...20..614R
Altcode:
No abstract at ADS
Title: Quiescent Prominences in Eclipsing RS CVns
Authors: Ramsey, Lawrence W.
Bibcode: 1991iue..prop.4022R
Altcode:
We propose to observe two eclipsing RS CVn binaries, SS Bootis and AR
Monocerotis, to study large extended regions which we believe to be
responsible for much of the emission in these systems. Ground-based
observations show attenuation of the emission from the eclipsed
component in both systems at a point near but not in eclipse. As the
eclipse ends, the emission level returns to its average out-of-eclipse
value, indicating that a large, obscuring, off-limb feature on the
eclipsing component is present. IUE LWPLo observations of the Mg II
lines in both systems at the proper phases will provide important
data regarding the structure of the emitting regions as well as the
degree to which they are responsible for the emission. With combined
optical and UV data on these systems we will be able to constrain the
size and possibly the optical depth of these structures.
Title: Fixed Phase Observations of RS CVn Stars
Authors: Hall, J. C.; Huenemoerder, D. P.; Ramsey, L. W.; Patterer,
R. J.; Chester, M. M.
Bibcode: 1990BAAS...22.1292H
Altcode:
No abstract at ADS
Title: A Computer Model of Echelle Spectrograph Efficiency
Authors: Horner, S. D.; Brown, T. M.; Ramsey, L. W.
Bibcode: 1990BAAS...22.1260H
Altcode:
No abstract at ADS
Title: Fiber-optic Echelle CCD Observations of SS Bootis
Authors: Hall, Jeffrey C.; Huenemoerder, David P.; Ramsey, Lawrence
W.; Buzasi, Derek L.
Bibcode: 1990ApJ...358..610H
Altcode:
The faint RS CVn system SS Bootis was observed over two seasons, and the
most prominent surface activity indicators in this spectroscopically
understudied object were examined. The first two Balmer lines are
consistently strong in emission, as are the Ca II infrared triplet and
Ca II H line; there is no significant modulation with phase in any of
these lines. No excess emission is evident in He I D3. The ratio of
energy emitted in H-alpha to that in H-beta is typically between three
and six for the more active subgiant primary, and between two and five
for the dwarf secondary. Of special interest is an excess absorption
feature in the Balmer lines near primary eclipse in both seasons. The
feature lies near the velocity of the secondary, and as there is no
similar feature in secondary eclipse, it is suggested that it arises
from obscuring material associated with the primary. From the extent
of the feature and the system's geometry, limits were placed on the
parameters of such material.
Title: Coordinated Optical and Ultraviolet Observations of DH Leo
Authors: Newmark, Jeffrey S.; Buzasi, Derek L.; Huenemoerder, David
P.; Ramsey, Lawrence W.; Barden, Samuel C.; Nations, Harold L.; Seeds,
Michael A.
Bibcode: 1990AJ....100..560N
Altcode:
Results are reported from contemporaneous KPNO optical spectroscopy,
IUE UV spectroscopy, and KPNO R photometry of the DH Leo triple
system in spring 1987. The data are presented in tables, graphs,
and spectral phase images and discussed in detail. The H-alpha,
H-beta, H-gamma, H-delta, and Ca II H and IRT lines are found to
have excess emission, and the phase modulation in H-alpha, H-beta,
and Ca II is well correlated with the photometric modulation. This
result is attributed to the combination of (1) a small amount of
global chromospheric emission and (2) emission from plagelike regions
associated with cool starspots. The (H-alpha)/(H-beta) ratio is found
to be significantly lower than that in longer-period RS CVn systems.
Title: Coordinated Optical and Ultraviolet Observations of IM Pegasi
Authors: Huenemoerder, David P.; Ramsey, Lawrence W.; Buzasi, Derek L.
Bibcode: 1990ApJ...350..763H
Altcode:
IUE spectra and optical observations of IM Peg obtained during the
summers of 1985 and 1986 are analyzed. The modulations of the UV
emission lines and the H-alpha, H-beta, and the CaII IR triplet (IRT)
optical lines are examined. It is observed that: the UV emissin-line
modulation increases as a function of height, H-alpha variability
is related to stochastic events, H-beta displays excess absorption
relative to a standard star, and the Ca IRT reveals a clear modulation
with phase. It is noted that IM Peg corresponds to the solar paradigm
used to explain RS CVn activity.
Title: The Disappearance of a Prominence on HR1099
Authors: Buzasi, D. L.; Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1990ASPC....9..233B
Altcode: 1990csss....6..233B
No abstract at ADS
Title: Optical and Ultraviolet Spectra of Rs-Canum Stars
Authors: Ramsey, Lawrence W.
Bibcode: 1990ASPC....9..195R
Altcode: 1990csss....6..195R
The observed phenomenology in RS CVn and related binary systems is
considered in terms of its modeling according to solar activity by
examining UV and optical spectroscopy. Current data are examined
to validate the existence of cool starspots, plage, prominences, and
flares, as well as to determine the consistency of spatial correlations
given by these data. RS CVn stars show spots at or near the poles,
contrasting the low latitudes of solar spots; plage appears to be
associated with cool spots on BY Draconis-like systems; plage and
prominences, although identified as distinct phenomena, are theorized
to be the same event in some cases. More spectroscopic and photometric
observations are proposed to identify the detailed structure and
locations of spots. UV and visible data are also required to distinguish
plage regions from flare variations as well as determine the relation of
extended structures to starspot and plage phenomena in RS CVn systems.
Title: Evidence for Extended Material in the Eclipsing RS CVn System
SS Bootis
Authors: Hall, J. C.; Huenemoerder, D. P.; Ramsey, L. W.; Buzasi, D. L.
Bibcode: 1990BAAS...22..739H
Altcode:
No abstract at ADS
Title: Optical Spectroscopy of ER Vul
Authors: Newmark, J. S.; Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1990BAAS...22..739N
Altcode:
No abstract at ADS
Title: Echelle Observations of V410 Tau
Authors: Patterer, R.; Huenemoerder, D.; Ramsey, L.; Buzasi, D.
Bibcode: 1990BAAS...22..749P
Altcode:
No abstract at ADS
Title: Flares and Other Optical Emission Line Variations in II-Peg
Authors: Huenemoerder, David P.; Ramsey, Lawrence W.; Buzasi, Derek L.
Bibcode: 1990ASPC....9..236H
Altcode: 1990csss....6..236H
Spectroscopic observations of II Pegasi are reported with particular
attention given to flares observed in the He D3 emission, Balmer line
ratios, and in comparisons of H-alpha and H-beta. A flare in progress
was detected, and comparisons with an earlier harder flare shows that
large flares can reach maximum intensity in optical lines after more
than six hours. The possibility of small amplitude variations of the
minimum emission and random emission events is set forth to describe
the Balmer line modulation.
Title: Titanium Oxide Variations in II Pegasi
Authors: Huenemoerder, David P.; Ramsey, Lawrence W.; Buzasi, Derek L.
Bibcode: 1989AJ.....98.2264H
Altcode:
TiO 8860 A band variations were detected in the RS CVn star II Pegasi
during the fall of 1988. UBV photometry shows that the variations are
correlated with the star's brightness. The TiO is stronger when the
star is fainter. The results are used to estimate cool photospheric
spot sizes of 2030 deg, with equivalent spectral types similar to an
M4 to M6 star.
Title: Fiber-Optic-Echelle-CCD Spectral Monitoring of UX ARIETIS
Authors: Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W.
Bibcode: 1989AJ.....98.1398H
Altcode:
Results are presented on 30 fiber-optic-echelle-CCD spectra for the UX
Ari system, covering one orbit in the spring and two orbits in the fall
of 1987. The spectra obtained have a resolution of about 12,000 over the
range of the Ca II H lines in the near UV to the Ca II triplet in the
near IR, covering several activity sensitive lines. The most striking
features observed were strong H-alpha and H-beta absorption near phase
0.8, which were present at epochs eight months apart. The geometry of
the system, as determined from the mass ratio, rotational velocities,
and the assumption of synchronous rotation, gives a radius for the K
star that is approximately filling its Roche lobe. It is suggested that
the excess absorption seen is due to mass-transfer activity resulting
from Roche lobe overflow of the K star and accretion onto the G star.
Title: Coordinated Observations of FK Comae
Authors: Ramsey, Lawrence W.
Bibcode: 1989iue..prop.3470R
Altcode:
This proposal requests IUE time to obtain SWP low dispersion spectra
during ten US2 half shifts. The target is FK Comae. The research
goal is to obtain a complete UV and optical data set over just a few
rotational periods of this star. In an attempt to better understand
this peculiar object we will correlate the activity indicators in the
visible region with those in the UV. Ground based observations will
be obtained contemporaneously and simultaneously where possible. The
IUE data will primarily provide information on activity in the stellar
transition region through transitions of N V, C IV and Si IV in the SWP
spectral region. Lines such as C II sample the high chromosphere whereas
the ground based data will supply information on the low chromosphere
and photosphere. Mg II data will also be obtained to supplement the
ground based data and to provide velocity resolution within the observed
profile. The proposed program will lead to a unique data set on this
interesting star and will allow progress toward understanding it and
similar systems.
Title: A Progress Report on the Spectroscopic Survey Telescope
Authors: Ramsey, L. W.; Weedman, D. W.; Ray, F. B.; Sneden, C.
Bibcode: 1988ESOC...30..119R
Altcode: 1988vlti....1..119R; 1988vltt.conf..119R
The Penn State/University of Texas Spectroscopic Survey Telescope is
an eight meter aperture special purpose telescope. The authors report
here on the final configuration and progress on the optical train as
well as the anticipated performance of the instrument.
Title: The HAO/Lowell/AFGL Solar-Stellar Spectrophotometer
Authors: Fisher, R. R.; Ramsey, L. W.; Gilliland, R. L.; Radick, R.;
Lockwood, G. W.; Mihalas, D.
Bibcode: 1988BAAS...20..994F
Altcode:
No abstract at ADS
Title: Radiative Transfer Modeling of Spectral Subtraction
Authors: Buzasi, D. L.; Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1988BAAS...20R.994B
Altcode:
No abstract at ADS
Title: Fiber-Optic-Echelle-CCD Spectral Monitoring of UX Aretis
Authors: Huenemoerder, D. P.; Buzasi, D. L.; Ramsey, L. W.
Bibcode: 1988BAAS...20..993H
Altcode:
No abstract at ADS
Title: Detection of Supergiant Variability with the HAO/Lowell/AFGL
Solar Stellar Spectrophotometry Project(S3)
Authors: Ramsey, L. W.; Mihalas, D.; Radick, R.; Gilliland, R. L.;
Lockwood, G. W.; Fisher, R.; Gallagher, J.
Bibcode: 1988BAAS...20.1012R
Altcode:
No abstract at ADS
Title: The Stellar Observing Program of the HAO/Lowell/AFGL
Solar-Stellar Spectrophotometry Project (S3)
Authors: Gilliland, R. L.; Mihalas, D.; Ramsey, L. W.; Radick, R.;
Lockwood, G. W.
Bibcode: 1988BAAS...20..994G
Altcode:
No abstract at ADS
Title: The Life and Times of FK Com
Authors: Nations, H. L.; Buzasi, D. L.; Huenemoerder, D. P.; Ramsey,
L. W.
Bibcode: 1988BAAS...20Q1023N
Altcode: 1988BAAS...20Z1023N
No abstract at ADS
Title: Detection of supergiant variability with the HAO/Lowell/AFGL
solar-stellar spectrophotometry project (S3).
Authors: Mihalas, D.; Ramsey, L. W.; Radick, R.; Gilliland, R. L.;
Lockwood, G. W.; Fisher, R.; Gallagher, J.
Bibcode: 1988BAAS...20.1012M
Altcode:
No abstract at ADS
Title: Use of optical fibers in spectrophotometry
Authors: Ramsey, Lawrence W.
Bibcode: 1988itp..work..277R
Altcode:
The use of single or small numbers of fiber optic fibers in astronomical
spectroscopy with the goal of greater spectrophotometric and radial
velocity accuracy is discussed. The properties of multimode step index
fibers which are most important for this application are outlined,
as are laboratory tests of currently available fibers.
Title: The Solar Observing Program of the HAO/Lowell/AFGL
Solar-Stellar Spectrophotometry Project (S3)
Authors: Mihalas, D.; Radick, R.; Lockwood, G. W.; Gilliland, R. L.;
Ramsey, L. W.; Fisher, R.; Livingston, W.; White, O. R.
Bibcode: 1988BAAS...20Q1008M
Altcode:
No abstract at ADS
Title: Focal ratio degradation in optical fibers of astronomical
interest.
Authors: Ramsey, Lawrence W.
Bibcode: 1988ASPC....3...26R
Altcode: 1988fopa.proc...26R
This paper discusses the sources of the focal ratio degradation (FRD)
of step index fused silica core optical fibers, and describes the
measurements of FRD properties. It is concluded that, although the FRD
does not appear to be sensitive to the large scale bending of the fiber,
this bending might induce stress which causes microbends. It was found
that larger core fibers appear to have better FRD characteristics than
smaller core fibers of identical construction, and that soft buffered
fibers have better FRD features than hard buffered fibers. The best
f-ratios to feed typical glass-clad fibers appears to be from about
f/3.0 to about f/7.0, depending on the fiber diameter. Finally,
it was found that good FRD characteristics are not compatible with
the good radial image scrambling needed for high-precision radial
velocity observations.
Title: Use of optical fibers in spectrophotometry.
Authors: Ramsey, L. W.
Bibcode: 1988NASCP......277R
Altcode:
The author discusses the use of a single or small numbers of fibers
in astronomical spectroscopy with the goal of achieving greater
spectrophotometric and radial velocity accuracy. The properties
of multimode step index fibers which are most important for this
application are outlined as are the laboratory tests of currently
useful commercially available fibers.
Title: A Flare Event on the Long-Period RS Canum Venaticorum System
IM Pegasi
Authors: Buzasi, Derek L.; Ramsey, Lawrence W.; Huenemoerder, David P.
Bibcode: 1987ApJ...322..353B
Altcode:
The characteristics of a flare event detected on the long-period RS
CVn system IM Pegasi are reported. The low-resolution spectrum show
enhancements of up to a factor of five in some emission lines. All
of the ultraviolet emission lines normally visible are enhanced
significantly more than the normal 30 rotational modulation. Emission
fluxes of both the quiescent and flare event are used to construct
models of the density and temperature variation with height. These
models reveal a downward shift of the transition region during the
flare. Scaled models of the quiet and flaring solar outer atmosphere
are used to estimate the filling factor of the flare event at about
30 percent of the stellar surface. The pattern of line enhancements
in the flare is the same as a previous event in Lambda Andromeda
observed previously.
Title: Fiber Coupled Instrumentation for the Spectroscopic Survey
Telescopes
Authors: Ramsey, L. W.
Bibcode: 1987BAAS...19.1098R
Altcode:
No abstract at ADS
Title: Performance of the Penn State Fiber Optic Echelle at KPNO
Authors: Barden, S. C.; Ramsey, L. W.; Huenemoerder, D. P.; Buzasi, D.
Bibcode: 1987BAAS...19.1099B
Altcode:
No abstract at ADS
Title: Transient Features on FK Comae
Authors: Buzasi, D. L.; Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1987BAAS...19Q1026B
Altcode: 1987BAAS...19.1026B
No abstract at ADS
Title: CCD Echelle Observations of the Active RS CVn System II Pegasi
Authors: Huenemoerder, David P.; Ramsey, Lawrence W.
Bibcode: 1987ApJ...319..392H
Altcode:
Optical spectra were obtained of II Peg on eight different nights in
1984 and 1985 to assess the strength and variability of surface activity
indicators in this very active RS CVn system. These cross-dispersed
echelle spectra covered the range from 390 nm to 900 to 900 nm at a
resolution of 12,000. EMission was seen in the first four Balmer lines,
in the Ca II infrared triplet, Ca II H lines, and in one observation,
in He I D3. The ratio of energy emitted in the H-alpha line to that
in H-beta is similar to that in solar prominences, except during
enhancements when the ratio decreases toward values more typical
of solar flares. The H-alpha lines varied both in strength and in
profile. There were slight variations in the Ca II infrared triplet
lines. Exposure levels were too weak to assess the variations in
H-gamma, H-delta, or Ca II H. Relative to comparison star spectra,
the TiO bands at 896 nm and 710 nm were slightly deeper in II Peg,
which is indicative of cool spots.
Title: Improvements in spectroscopic continuum noise with fiber-optics
illumination of a RETICON array.
Authors: Smith, Myron A.; Graves, J. E.; Jaksha, David B.; Plymate,
Claud L.; Ramsey, Lawrence W.
Bibcode: 1987PASP...99..654S
Altcode:
It is shown that under certain observing conditions the pixel-to-pixel
spectroscopic noise of a Reticon detector can be reduced somewhat
by the uniform illumination of the pixels by a fiber-optic image
scrambler. These gains can nearly offset the transmission losses in
the fiber imaging system. The optical layer of the 'solar stellar
spectrograph' at the McMath Solar Telescope is also described.
Title: Development of high stability fiber optic spectrophotometric
systems for study of solar/stellar magnetic activity
Authors: Ramsey, Lawrence W.
Bibcode: 1987psu..reptQ....R
Altcode:
A program to study magnetic activity cycles in solar-type stars,
including the Sun, is described. The goal is to establish the
relationships between a star's magnetic cycle morphology (i.e.,
amplitude, period, shape, regularity, etc.) and its age, rotation
rate, and if possible, differential rotation rate, for a variety
of solar like stars. Basic empirical input will be provided for the
construction of a viable dynamical dynamo theory for the Sun and the
stars, leading to a deeper understanding of the ultimate origins of
solar and stellar magnetism. Only when a realistic theory of magnetic
field generation is available can one understand fully the physics of
magnetic activity, which manifests itself on all temporal and spatial
scales, from transients such as flares to long-lived structures
such as quiescent prominences, from flux-tubes at the limit of
resolution to complex groups of sunspots. A critical first step in
this effort was the development of an appropriate instrument. What
follows describes an advanced-design, special-purpose, fiber fed
spectrograph carefully optimized to make the required observations
with maximum efficiency. This contract designs, fabricates and tests
the breadboard instrument.
Title: Coordinated Optical and UV Observations of the Short Period
RS CVn System DH Leo
Authors: Ramsey, Lawrence
Bibcode: 1987iue..prop.2837R
Altcode:
We propose to observe the short-period RS CVn system DH Leo with IUE
to investigate the presence of "prominence-like" material surrounding
the secondary component. Observations will be made with the SWP camera
in low dispersion outside and during primary conjunction. If the
chromospheric lines in the SWP region arise from the same plasma as
H-alpha we should see decreased emission at conjunction. The behavior
of the hotter lines (N V, Si IV, C IV) should allow us to constrain
somewhat the location of the occulting material. The IUE observations
will be accompanied by ground based spectroscopic and photometric
observations to better define the state of the surface activity at
that time.
Title: Spectroscopic monitoring of RS CVn stars at Kitt Peak using
the Penn State Fiber Optic Echelle.
Authors: Ramsey, L. W.; Huenemoerder, D. P.; Buzasi, D. L.; Barden,
S. C.
Bibcode: 1987LNP...291..514R
Altcode:
No abstract at ADS
Title: Spectroscopic Monitoring of RS CVn Stars at Kitt Peak Using
the Penn State Fiber Optic Echelle
Authors: Ramsey, Lawrence W.; Huenemoerder, David P.; Buzasi, Derek
L.; Barden, Samuel C.
Bibcode: 1987LNP...291..515R
Altcode: 1987LNP87.291..515R; 1987csss....5..515R
The Penn State Fiber Optic Echelle has been moved to Kitt Peak and
works with either the coude feed telescope or 2.1 meter. It is about
twice as efficient as the coude Camera No. 5 for similar bandpass at
600 nm and is comparable at 400 nm using the coude feed telescope. The
high illumination stability afforded by the fiber is a decided advantage
where spectrophotometric and radial velocity stability are at a premium,
as in the study of active stars. We are using this instrument to
intensively monitor about 10 regular RS CVn systems and about six short
period and W UMa systems for a two week period each observing semester.
Title: Hα observations of RS Canum Venaticorum stars. II. 1981
observations for UX Arietis, HR 1099, and BD +61°1211.
Authors: Nations, Harold L.; Ramsey, Lawrence W.
Bibcode: 1986AJ.....92.1403N
Altcode:
H-alpha line observations made during 1981 of the highly active RS
CVn stars UX Ari, HR 1099, and BD +61 deg 1211 are presented and
discussed. Excess H-alpha emission profiles derived by subtracting
synthesized comparison-star spectra are analyzed to find that the UX Ari
and HR 1099 systems differ significantly in the strength of the excess
emission from their secondaries. Specifically, it is found that in UX
Ari the H-alpha emission of the K subgiant completely dominates that of
the G V secondary. In HR 1099, however, the K1 IV primary is responsible
for 86 percent of the total emission and the G5 IV secondary 14 percent,
with the smaller secondary showing the higher surface flux. H-alpha
spectra from the single-lined system BD +61 deg 1211 show a strong,
broad emission line which is variable by over a factor of 3 during
the observational period. The data for these systems are discussed in
terms of the L(H-alpha)/L(bol) vs log P relation for the RS CVn stars.
Title: The Spectroscopic Survey Telescope
Authors: Weedman, D.; Ramsey, L.; Ray, F.; Sneden, C.
Bibcode: 1986BAAS...18..956W
Altcode:
No abstract at ADS
Title: An Ultraviolet Flare on the RS CVn System IM Pegasus
Authors: Ramsey, L. W.; Buzasi, D. L.
Bibcode: 1986BAAS...18..954R
Altcode:
No abstract at ADS
Title: The Penn-State Fiber Coupled CCD / Echelle Spectrograph
Authors: Ramsey, L. W.
Bibcode: 1986tswo.work...80R
Altcode:
The author describes a versatile echelle spectrograph which is coupled
to their 1.6 meter telescope via an optical fiber. Observations obtained
since winter 1985 have shown the instrument to have excellent flat-field
and radial velocity performance properties with quite respectable
throughput.
Title: Report of the Instrumentation Subpanel
Authors: Dunn, R.; Ramsey, L.; Smith, M. A.
Bibcode: 1986tswo.work...93D
Altcode:
No abstract at ADS
Title: The Spectroscopic Survey Telescope
Authors: Ramsey, L. W.; Weedman, D. W.
Bibcode: 1986tswo.work..117R
Altcode:
The authors describe the motivation for and general design of a large
special purpose spectroscopic survey telescope (SST). The telescope
is based on an array of 73 spherically figured segments about a
meter in diameter with a radius of curvature of 26 meters making up
a primary mirror with an effective aperture exceeding 7 meters. All
tracking motions are in a lightweight focal surface system that can
track objects for up to 40 minutes using a two element reflecting
corrector for spherical aberration. The telescope has a fixed tilt to
the vertical which allows access to a 48 degree strip of declination
through an azimuth angle rotation. Instrumentation is coupled to the
focus by means of fiber optics. Multiple object tracking over the 50
deg2 field is possible.
Title: The Light Curve, H-α Modulation, and Possible Prominences
of the Short-Period Binary DH Leo
Authors: Barden, S. C.; Fried, R. E.; Ramsey, L. W.; Guinan, E. F.;
Wacker, S. W.
Bibcode: 1986LNP...254..241B
Altcode: 1986csss....4..241B
No abstract at ADS
Title: A versatile fiber coupled CCD/echelle spectrograph system.
Authors: Ramsey, Lawrence W.; Huenemoerder, David P.
Bibcode: 1986SPIE..627..282R
Altcode:
A versatile echelle spectrograph capable of moderate to high
resolution precision spectroscopy has been developed. This highly
stable instrument is in a temperature- and humidity-controlled room,
and is coupled to a 1.6-m telescope via an optical fiber. Moderate
resolution spectra with near-total spectral coverage from 400-900 nm
are done at a Quasi-Littrow focus with no anamorphic magnification. A
200 mm f/2 camera focuses thirty-four orders of prism cross dispersed
spectra onto a CCD. A simple grating tilt can switch the beam to a
cross-dispersing grating and long focus cameras allowing resolutions
up to 80,000. The high resolution beam has a more typical geometry with
anamorphic magnification greater than one. Observations conducted since
winter, 1985 have shown the system to have excellent photometric and
radial velocity characteristics; it is especially suited to long term,
high SNR monitoring programs.
Title: A CCD/Echelle Spectroscopy System for Study of Active Cool
Stars
Authors: Ramsey, L. W.; Huenemoerder, D. P.
Bibcode: 1986LNP...254..238R
Altcode: 1986csss....4..238R
No abstract at ADS
Title: Echelle Spectroscopy of the RS CVn System II Pegasus
Authors: Ramsey, L. W.; Huenemoerder, D. P.
Bibcode: 1985BAAS...17..880R
Altcode:
No abstract at ADS
Title: Hα Observations of RS CVn Stars: 1981 Spectra of UX Ari,
HR 1099, BD +61 1211 and HD 155638
Authors: Nations, H. L.; Ramsey, L. W.
Bibcode: 1985BAAS...17..754N
Altcode:
No abstract at ADS
Title: Hα Activity and the Light Curve of the RS Canum
Venaticorun Star DH Leo (HD86590)
Authors: Barden, S. C.; Ramsey, L. W.; Fried, R. E.
Bibcode: 1985BAAS...17R.597B
Altcode:
No abstract at ADS
Title: The Penn State Fiber Coupled-CCD Spectrograph System
Authors: Ramsey, L. W.; Brungardt, C.; Huenemoerder, D. P.;
Rosenthal, S.
Bibcode: 1985BAAS...17..574R
Altcode:
No abstract at ADS
Title: CCD-Echelle Reduction with the Charles River Super-micro
Authors: Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1985BAAS...17..575H
Altcode:
No abstract at ADS
Title: Coordinated Observations of Rotational Modulation in Long
Period RS CVn Systems
Authors: Ramsey, Lawrence
Bibcode: 1985iue..prop.2211R
Altcode:
This proposal requests IUE time to obtain SWP low dispersion spectra
during 10 US2 shifts during the Fall of 1985. The targets are all
late G or early K giants in long period active chromosphere RS Canum
Venaticorum binary systems. The research goal is to discern the
spatial relationship and extent of the surface active regions in both
the horizontal and vertical directions. Ground based observations
will be obtained contemporaneously over the fall season. We will
use the C IV line as the primary activity indicator in the stellar
transition region, whereas ground based observations will supply
information on the chromosphere and photosphere. We will particularly
be seeking information on the relative shape and phase lead or lag
of the transition region emission relative to the chromospheric and
photospheric rotational phase behavior.
Title: Balmer Decrements in Active Chromosphere Stars
Authors: Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1984BAAS...16..912H
Altcode: 1984BAAS...16T.912H
No abstract at ADS
Title: A spectroscopic study of the peculiar giant FK Comae. I. The
radial velocity variation and its implications.
Authors: McCarthy, J. K.; Ramsey, L. W.
Bibcode: 1984ApJ...283..200M
Altcode:
The authors present observations of the radial velocity behavior of
the peculiar, rapidly rotating late-type giant FK Comae. Observations
of the Na D lines in FK Comae and several well-studied radial
velocity standards were obtained on 15 nights during late winter
and spring 1982. Using cross-correlation techniques to search for
variations against the standards, the authors set an upper limit of
5 km s-1. The implications of this limit on models for
FK Comae extant in the literature are discussed in detail, with the
conclusion that models requiring accretion from a binary companion
are inconsistent with the current data.
Title: Hydrogen-alpha observations of RS Canum Venaticorum
stars. III. The eclipsing systems AR Lacertae and SZ Piscium.
Authors: Huenemoerder, D. P.; Ramsey, L. W.
Bibcode: 1984AJ.....89..549H
Altcode:
The authors have spectroscopically monitored two eclipsing double-lined
RS CVn binaries, AR Lacertae and SZ Piscium, over many orbital periods
at the wavelength of Hα. Excess Hα emission profiles were derived by
subtracting composite comparison spectra synthesized from observations
of single inactive stars. AR Lac showed no excess Hα emission. SZ Psc
was highly active with emission from the cooler stellar component. SZ
Psc also underwent a large Hα outburst during and after which profiles
were suggestive of a circumstellar origin.
Title: New Estimates on Rotational Velocity of FK Comae and Other
FK Comae-Type Objects
Authors: Ramsey, L. W.; Barden, S. C.; Huenemoerder, D. H.; McGarthy,
J. K.
Bibcode: 1984BAAS...16..511R
Altcode:
No abstract at ADS
Title: Hydrogen alpha observations of RS Canum Venaticorum
stars. I. II Peg.
Authors: Ramsey, L. W.; Nations, H. L.
Bibcode: 1984AJ.....89..115R
Altcode:
The authors present observations of the active RS CVn variable II
Peg made during the 1981 observing season. A marked change in the
emission line behavior with phase over that observed several years ago
is noted. In addition a unique decrease in the H-alpha emission flux
to unprecedented sustained low levels was observed during the summer
of 1981.
Title: The Penn State spectroscopic survey telescope
Authors: Ramsey, L. W.; Weedman, D. W.
Bibcode: 1984vlti.conf..851R
Altcode: 1984IAUCo..79..851R
A design is presented for a telescope which is large enough to obtain
spectra to about 20th magnitude in under 20 minutes' integration time
and which is devoted to spectroscopic surveys in dark time to map the
distribution of galaxies and quasars in the universe. During bright
time the telescope will be used to monitor large numbers of G-M stars
with high-resolution spectroscopy to search for solarlike activity. The
instrument consists of 73 segments, each of 0.9 m diameter and 26 m
radius of curvature. The effective aperture exceeds 7 m. The focal
plane system can track objects for 40 minutes, and sky coverage of
48 deg is obtained by using a fixed tilt for the primary and making
the entire telescope and dome rotatable. The focal plane system is
lightweight and precisely pointable because spectrographs are coupled
to the focus by fiber optic cables.
Title: Hα Activity in the RS CVn System, SZ Psc
Authors: Huenemoerder, D. P.; Ramsey, L. W.; Barden, S. C.
Bibcode: 1983BAAS...15..663H
Altcode:
No abstract at ADS
Title: Hα spectroscopy of the FK Comae type HD 199178: a progress
report.
Authors: Huenemoerder, D. P.; Barden, S. C.; Ramsey, L. W.
Bibcode: 1983BAAS...15..616H
Altcode:
No abstract at ADS
Title: New radial velocity limits for FK Comae.
Authors: McCarthy, J. K.; Ramsey, L. W.
Bibcode: 1982BAAS...14..780M
Altcode:
No abstract at ADS
Title: Stellar analogs of solar activity
Authors: Ramsey, L. W.
Bibcode: 1982psu..rept.....R
Altcode:
A fiber-coupled spectrograph (FSC) for moderate-resolution
stellar observations has been designed, fabricated, and tested. The
excellent shortand long-term stability of this instrument represents a
significant advance in the state-of-the-art for high precision stellar
spectrophotometry. A preliminary observational survey of the greatly
enhanced analogs of solar activity that exist in flare stars and the
RS CVn binaries has been performed using this instrument, and the
starspot model for explaining the photometric variability of these
latter stars has been verified spectroscopically.
Title: Emission-line widths in galactic nuclei.
Authors: Feldman, F. R.; Weedman, D. W.; Balzano, V. A.; Ramsey, L. W.
Bibcode: 1982ApJ...256..427F
Altcode:
Line width measures for the forbidden O III emission lines have been
obtained for 116 galactic nuclei with instrumental resolution of 165
km/sec. Galaxies observed include 53 Seyfert 1 galaxies, 16 Seyfert 2
galaxies, and 47 star-burst galaxies for which the nuclear emission
lines are attributed to ionization by hot, short-lived stars. The
median FWHM for the forbidden O III lines is 375 km/sec for Seyfert 1,
510 km/sec for Seyfert 2, and 160 km/sec for star-burst nuclei. It is
suggested that an empirical criterion for dividing Seyfert galaxies
from other emission line galaxies is a FWHM greater than 250 km/sec for
the forbidden O III lines. From dynamical arguments, the star-burst
nuclei are determined to have the star formation activity restricted
to a nuclear disk with radius less than a few hundred parsecs.
Title: BF Orionis-A Peculiar Pre-Main Sequence A Star
Authors: Barden, S. C.; Nousek, J. A.; Ramsey, L. W.
Bibcode: 1982BAAS...14..614B
Altcode:
No abstract at ADS
Title: A flare event in the peculiar giant FK Comae.
Authors: Ramsey, L. W.; Nations, H. L.
Bibcode: 1982SAOSR.392A.225R
Altcode: 1982csss....2..225R
Observations are presented of a very energetic flare event in the
peculiar rapidly rotating star FK Comae. During this event on June
18th 1981 the usual asymmetrical double peaked H alpha emission feature
with an equivalent width (EW) approx 3-4 A changed to a broad emission
feature with EW approx 13 A. Sixteen spectra were obtained over 2
hours. Some changes in the emission profile are apparent on this time
scale. The following night the enhanced emission persisted but at lower
levels and it was substantially redshifted. This event is interpreted
in terms of a model where material is injected into a disk co-rotating
with the angular velocity of the stellar surface. A localized region
of surface activity is conjectured to be the source of the event.
Title: Regular variations in the alf profile of FK Com.
Authors: Ramsey, L. W.; Nations, H. L.; Barden, S. C.
Bibcode: 1981ApJ...251L.101R
Altcode:
A series of observations of the rapidly rotating G type giant FK
Comae are presented. The unusually broad H-alpha profile is seen to
vary regularly in the sense that the violet-to-red emission ratio is
correlated with photometric phase and presumably with rotation. These
observations are described by an excretion disk model with substantial
density inhomogeneities driven at the angular velocity of the star by
an imbedded magnetic field. That sufficient magnetic flux is available
is suggested by both the high observed v sin i of about 120 km/s and
photometric evidence of starspots.
Title: On the nature of H alf outbursts in the RS CVn binary SZ Psc.
Authors: Ramsey, L. W.; Nations, H. L.
Bibcode: 1981PASP...93..732R
Altcode:
An H-alpha emission episode on the RS CVn binary SZ Psc was observed
in 1979. These observations are compared with a recently reported
1978 outburst, and both data are discussed and interpreted in terms of
the surface phenomena or star-spot model. Bopp (1981) had attributed
the 1978 H-alpha outburst as due to a mass-transfer or mass-loss
event caused by the cooler primary expanding on a short-time scale
and overfilling its Roche lobe. This interpretation appeared to be
inconsistent with the surface phenomena model. Evidence is presented
which supports the bizarre behavior of the H-alpha emission line as
being due to the existence of a disk fed by flare-like eruptions. Bopp's
1978 observations can also be explained in terms of such a model,
only more material would be involved in that event, since its H-alpha
emission is about twice as strong.
Title: NGC 7714 - The prototype star-burst galactic nucleus
Authors: Weedman, D. W.; Feldman, F. R.; Balzano, V. A.; Ramsey,
L. W.; Sramek, R. A.; Wuu, C. -C.
Bibcode: 1981ApJ...248..105W
Altcode:
New X-ray, ultraviolet (IUE), optical, and radio (VLA) observations
are presented for the bright nucleus galaxy NGC 7714. All data are
explainable as resulting from intense star-formation activity in
this nucleus - a star burst. The X-ray and radio luminosities are
explained by supernova remnants arising from the massive stars, and
approximately 10,000 supernova remnants are required in a volume of
280 pc radius. It is thought that NGC 7714 is typical of a significant
class of emission-line galaxies. It is pointed out that individual
supernovae should be observable in this, or similar nuclei, because
they are expected to occur at rates approaching one per year.
Title: On the ionization equilibrium in late-type supergiants.
Authors: Ramsey, L. W.
Bibcode: 1981ApJ...245..984R
Altcode:
We have studied the ionization balance in late-type supergiants of
spectral types G5 to M2 using the Ca I 6573 A and forbidden Ca I 7324
A lines as a probe. An increasing discrepancy is found between the
observed and calculated line strengths setting in for an effective
temperature less than approximately 4250 K. This is interpreted in terms
of increased ionization relative to local thermodynamic equilibrium.
Title: Observations of the TiO 8860 band in M giants
Authors: Ramsey, L. W.
Bibcode: 1981AJ.....86..557R
Altcode:
Observations are presented of the TiO δ(0,0) R-branch bandhead at 8860
Å, which were obtained with the CID camera on the main spectrograph
at the McMath solar telescope. At a spectral resolution of 0.25 Å,
a bandhead index is defined which is calibrated as a function of
effective temperature for spectral types K4 to M6. This feature is a
potentially useful tool for study of surface inhomogeneities on active
stars as well as a diagnostic for cool stellar atmospheres.
Title: Near-Infrared TiO Band Observations of RS CVn Stars
Authors: Nations, H.; Ramsey, L. W.
Bibcode: 1981BAAS...13..803N
Altcode:
No abstract at ADS
Title: BVRI photometry of the RS CVn binary II Peg
Authors: Nations, H. L.; Ramsey, L. W.
Bibcode: 1981AJ.....86..433N
Altcode:
BVRI photometric observations of the RS CVn binary II Peg are
presented and interpreted in terms of the starspot model for RS CVn
binaries. Observations were obtained in the Johnson B and Cousins VRI
systems with a 16-in. telescope in conjunction with a single-channel
pulse-counting photometer. The present light curves are observed to
differ dramatically from those observed in 1977, in exhibiting two
unequal maxima separated by approximately 0.55 in. orbital phase and
a mean V magnitude of 7.52. When interpreted in terms of the starspot
model, the light curves obtained indicate a temperature difference
between the spots and the surrounding photosphere of 1100 + or - 450 K
and 0.27 + or - 0.10 of the visible disk to be covered by the spots. The
Barnes-Evans visual surface brightness relation is used to derive a
minimum radius of 2.19 + 0.37 or - 0.31 solar radii for the primary,
confirming a previous finding that the star is located considerably
above the main sequence. It is recommended that II Peg be observed
every season in order to determine the time evolution of the spot groups
Title: Evaluation of some fiber optical waveguides for astronomical
instrumentation
Authors: Barden, S. C.; Ramsey, L. W.; Truax, R. J.
Bibcode: 1981PASP...93..154B
Altcode:
Fused silica optical fibers were examined with a view toward use in
fiber-coupled spectrographs. The emphasis of the investigation was on
how well the input focal ratio was preserved during transmission down
a long fiber. The best overall performance was given by the Galite
4000 series and the Maxlight 150 micron fibers. The Valtec products
also yielded good results when cabled so that stress could not be
easily induced. It was found that the smaller fibers yielded better
performance with respect to focal ratio preservation.
Title: Telescope Performance of a Fiber Coupled Spectrograph
Authors: Ramsey, L. W.; Barden, S. C.; Nations, H. L.; Truax, R. J.
Bibcode: 1980BAAS...12..836R
Altcode:
No abstract at ADS
Title: HR 1099 and the starspot hypothesis for RS CVn binaries.
Authors: Ramsey, L. W.; Nations, H. L.
Bibcode: 1980ApJ...239L.121R
Altcode:
Observations of the RS CVn binary HR 1099 (V711 Tau) have been
made using the CCD camera at KPNO to test the starspot hypothesis
spectroscopically. A TiO band system near 8860 A is shown to strengthen
greatly at phases when starspots have been predicted to be present on
the visible hemisphere. Data from other spectral regions support this
result. A minimum temperature difference of 1000 K between the spot
and photosphere is indicated.
Title: Spectrum variability in HR 8752.
Authors: Barden, S. C.; Ramsey, L. W.
Bibcode: 1980PASP...92..497B
Altcode:
Observations in the region of H-alpha are presented for the luminous
supergiant HR 8752. Two time scales for the variation of emission
features are detected. Substantial changes in H-alpha appear to take
months or years. More subtle changes can occur in a matter of days. The
photospheric spectrum also shows evolution on both long and short time
scales as has been noted by previous observers.
Title: H alf variability in HR 1099 and other RS CVn stars.
Authors: Nations, H. L.; Ramsey, L. W.
Bibcode: 1980AJ.....85.1086N
Altcode:
Observations of the RS CVn stars HR 1099, UX Ari, HD 224085, AR Lac,
and SZ Psc have been carried out with a CCD detector at KPNO to study
the variability of the Hα line. The Hα equivalent width in HR 1099
is shown to undergo a modulation over the orbital period of this
spectroscopic binary with the modulation being in antiphase with the
photometric distortion wave of the system. Profile and/or intensity
variations of Ha with time scales of a few days are also demonstrated
for the other systems studied here.
Title: Comparing Infrared Fluxes and Emission Line Widths for
Galactic Nuclei
Authors: Weedman, D.; Balzano, Y.; Feldman, F.; Ramsey, L.
Bibcode: 1980BAAS...12..504W
Altcode:
No abstract at ADS
Title: Implementation of a Fiber Coupled Spectrograph
Authors: Barden, S. C.; Ramsey, L. W.; Truax, R. J.
Bibcode: 1980BAAS...12Q.460B
Altcode:
No abstract at ADS
Title: New BVRI Light Curves of HD 224085
Authors: Nations, H. L.; Ramsey, L. W.
Bibcode: 1980BAAS...12Q.530N
Altcode:
No abstract at ADS
Title: A High Dispersion Temperature Index for Cool Stars
Authors: Ramsey, L. W.
Bibcode: 1980BAAS...12..527R
Altcode:
No abstract at ADS
Title: Spectroscopic Evidence for Starspots on HR1099
Authors: Ramsey, L. W.; Nations, H. L.
Bibcode: 1980SAOSR.389...97R
Altcode: 1980csss....1...97R
No abstract at ADS
Title: HR 8752
Authors: Barden, S.; Ramsey, L. W.
Bibcode: 1980IAUC.3446....1B
Altcode:
S. Barden and L. W. Ramsey, Department of Astronomy, Pennsylvania
State University, write: "SIT spectra (dispersion 0.15 x 10**-6)
obtained with the eche1le spectrograph on the 1.6-m telescope indicate
a rapid change in the emission-line spectrum of HR 8752. A spectrum
obtained on Jan. 8.00 UT shows conspicuous Ca I 657.2-nm and Fe I
657.4-nm emission. About 48 hr later (Jan. 9.95 UT) the Ca I emission
was entirely absent. More subtle changes were also apparent in the
H-alpha profile."
Title: Observations of Emission-Line Galaxies
Authors: Feldman, F.; Balzano, V.; Ramsey, L.; Weedman, D.
Bibcode: 1979BAAS...11..637F
Altcode:
No abstract at ADS
Title: Variable mass loss in the metal deficient giant HDE 232078.
Authors: Ramsey, L. W.
Bibcode: 1979PASP...91..252R
Altcode:
High-dispersion echelle spectra taken of the metal-deficient red
giant HDE 232078 indicate that the mass loss rate of this star is
highly variable. The time scale of the variability and the rate of
mass loss is similar to Population I objects of similar temperature
and luminosity. The nature of the variability also calls into question
previous conclusions which indicate that the mass loss rate of globular
cluster giants is independent of metallicity.
Title: Limits on the short-period variability of the Halpha emission
in AD Leo.
Authors: Ramsey, L. W.
Bibcode: 1979AJ.....84..413R
Altcode:
High-time-resolution SIT spectra of the flare star AD Leo are
analyzed in an effort to detect any short-period variation that might
be present. Upper limits are set on the magnitude of any variation
down to a time scale of 5 min. No significant short-term variation was
observed at the 2-sigma level of + or - 12%. Variation of nightly means
on a longer time scale is clearly evident in excess of a 2-sigma level.
Title: Ionization Equilibrium in Bright Supergiants
Authors: Ramsey, L. W.; Balzano, V.
Bibcode: 1978BAAS...10..682R
Altcode:
No abstract at ADS
Title: An Economical Cassegrain High Dispersion Spectrophotometry
System.
Authors: Ramsey, L. W.
Bibcode: 1978BAAS...10..451R
Altcode:
No abstract at ADS
Title: Observed departures from LTE ionization equilibrium in
late-type giants.
Authors: Ramsey, L. W.
Bibcode: 1977ApJ...215..827R
Altcode:
Photoelectric scans of the Ca I line at 6572 A and the forbidden
Ca II transition at 7323 A are studied in the K giant alpha Tau,
the M supergiant alpha Ori, and the M giants beta And, alpha Cet,
mu Gem, and beta Peg. The relative strengths of these lines are
shown to be indicative of the ratio of the relative number densities
of the neutral and ionized species in the photosphere. The analysis
indicates an overionization relative to LTE in qualitative agreement
with the theoretical calculations of Auman and Woodrow for the K and
M giants. The M supergiant alpha Ori exhibits a large overionization
relative to LTE.
Title: A semiempirical atmosphere for alpha Tauri from neutral
iron lines.
Authors: Ramsey, L. W.
Bibcode: 1977ApJ...215..603R
Altcode:
A semiempirical model photosphere is constructed for the K5 III star
Alpha Tau. The technique employed is based on measurements of the
central fluxes in a series of lines in multiplets. Observations of four
multiplets having a range in excitation potential yield the excitation
temperature as a function of the optical depth in a reference line. If
the temperature structure of an assumed starting model is changed
to force agreement between the observed and predicted line source
functions under the assumption that excitation and electron kinetic
temperatures are equal, the final semiempirical model is cooler by
150 K in the outer layers and warmer by 150 K in deeper layers than
the theoretical model with the parameters adopted for Alpha Tau.
Title: Spectrophotometry of cool angular-diameter stars.
Authors: Honeycutt, R. K.; Ramsey, L. W.; Warren, W. H., Jr.; Ridgway,
S. T.
Bibcode: 1977ApJ...215..584H
Altcode:
Wide-band photometry and spectrophotometric scans are combined to
obtain incident flux curves for 26 late-type stars. The wavelength
range covered for most stars is from 0.4 to 3.0 microns with a typical
resolution of approximately 200. Nineteen of these stars have published
angular diameters, so that the emergent flux may be computed from the
incident flux.
Title: Emission Line Variability of AD Leo in the Non-Flaring State.
Authors: Ramsey, L. W.
Bibcode: 1977BAAS....9..311R
Altcode:
No abstract at ADS
Title: High dispersion spectroscopy of quiescent prominences. II:
Vertical structure of the line-of-sight velocity field.
Authors: Ramsey, L. W.
Bibcode: 1977SoPh...51..307R
Altcode:
A systematic study of the internal horizontal (line-of-sight) motions
of quiescent prominences which were observed at the limb has been made
by using fourier techniques to analyse the shift of the Ca II K line
as a function of height above the limb. The results indicate that a
characteristic size for the velocity elements is present in ∼70%
of the 13 prominences studied. This size of ∼4700 km is attributed
to Alfvén waves induced by horizontal convective motions in the
photosphere as previously suggested by Malville. The qualitative aspects
of the observations are described by a simple model which is based on
this hypothesis.
Title: An Observational Study of the Physical Conditions in Red
Giant Atmospheres.
Authors: Ramsey, L. W.
Bibcode: 1976PhDT.........6R
Altcode:
The temperature structure and ionization balance in the atmospheres
of red giant stars was investigated. Particular attention was given
to the giant star Aldebaran (K5 III). The observational basis for all
studies was moderate to high resolution photoelectric spectrophotometry
of various atomic lines. A technique was developed to obtain the run
of excitation temperature (Texc) with height in a stellar atmosphere
from the central fluxes of atomic lines in a single multiplet. Source
function equality for all lines in a multiplet and the dominance
of the line over the continuous opacity were assumed. A test of the
method for the sun using lines in Fe I multiplet (553) yielded good
agreement with independently determined solar model atmospheres.
Title: Observed Departures from LTE Ionization Equilibrium in
Cool Giants
Authors: Ramsey, L. W.
Bibcode: 1976BAAS....8Q.308R
Altcode:
No abstract at ADS
Title: A test of solar atmospheric structure.
Authors: Ramsey, L. W.
Bibcode: 1976BAAS....8Q.293R
Altcode:
No abstract at ADS
Title: A Method for Empirical Determination of Stellar Atmospheric
Structure
Authors: Ramsey, L. W.; Johnson, H. R.
Bibcode: 1975SoPh...45....3R
Altcode:
A technique for obtaining information on the temperature structure of a
stellar atmosphere from spectral line data where only flux observations
are available is discussed. The direct inversion of the flux integral
to obtain the line source function can be circumvented by making the
physically plausible assumptions of (1) source function equality in
a multiplet and (2) the dominance of line absorption over continuum
absorption at line center. Consistency of the technique is demonstrated
by treating a synthetic spectrum as input data and attempting to recover
the temperature structure of the input atmosphere. Using high quality
solar spectrum scans obtained from K.P.N.O. we demonstrate the accuracy
of source function equality for several Fe I multiplets and use one
of these multiplets to obtain an empirical outer atmosphere for the
Sun. Our empirical atmosphere agrees well with current solar models.
Title: On the Spatial Structure of Prominence Velocity Fields
Authors: Ramsey, L. W.
Bibcode: 1975BAAS....7Q.524R
Altcode:
No abstract at ADS
Title: Macroturbulence broadening of solar lines with implications
for stellar studies.
Authors: Evans, J. C.; Ramsey, L. W.; Testerman, L.
Bibcode: 1975A&A....42..237E
Altcode:
This paper reports results of numerical studies of macroturbulence
broadening on solar LTE intensity profiles with a view toward applying
the results toward other solar-type stars. The results are compared
for five different velocity models with spatially and temporally
averaged center-to-limb observations. The comparisons are made through
the curve of the line-width correlation and through the curve of the
line-shape diagram. For mildly saturated lines (about 120 mA), the
solar macrovelocities are the most important of the velocity scale
sizes in determining the shape of the line core. The unsaturated weak
lines and the curve of the line-width correlation do not discriminate
between the two scale sizes of broadening, as suggested by other
studies. High-accuracy photoelectric data for Procyon used in the curve
of the line-shape indicates that macroturbulence broadening dominates
and that the microturbulence component is about 1 km/s.
Title: High-resolution profiles of sodium and potassium lines in
Alpha Orionis.
Authors: Goldberg, L.; Ramsey, L.; Testerman, L.; Carbon, D.
Bibcode: 1975ApJ...199..427G
Altcode:
Profiles of the K I resonance line at 7698.98 A and of the D1
and D2 lines of Nai in the spectrum of a Ori have been recorded
photoelectrically using the main beam of the McMath solar telescope
at KPNO. The Na lines were observed in the fourth order of the
spectrograph and the K iline in the third order, providing a resolving
power of approximately 50 mA. The observed profiles are consistent with
a model in which radiation from the stellar photo sphere is scattered
and reemitted by an expanding envelope or envelopes of radius large
compared with that of the photosphere. Each blueshifted absorption
core appears to consist of two components of approximately the same
intensity. The first has a heliocentric radial velocity of + 11-13 km ,
which agrees very well with measurements of other resonance lines by
other observers, whereas the second is in the range + 6 km 1 and appears
not to have been detected previously. Subject headings: circumstellar
shells - late-type stars - stellar winds - stars, individual
Title: High Resolution Profiles of Sodium and Potassium Lines in
α Orionis.
Authors: Goldberg, L.; Ramsey, L.; Testerman, L.; Carbon, D.
Bibcode: 1975BAAS....7..233G
Altcode:
No abstract at ADS
Title: Atmospheric Structure from Spectral Line Intensities.
Authors: Ramsey, L. W.; Johnson, H. R.
Bibcode: 1975BAAS....7..257R
Altcode:
No abstract at ADS
Title: Formation of the Luminosity-Sensitive 0 I Multiplet at 7774 A
Authors: Johnson, H. R.; Milkey, R. W.; Ramsey, L. W.
Bibcode: 1974ApJ...187..147J
Altcode:
We have calculated line profiles and equivalent widths for the 7774 A
multiplet of 0 i for model atmospheres in the range = K for surface
gravities in the range log g = 4. .0. A kinetic equilibrium (KE)
treatment of line formation can partially account for the observed
luminosity sensitivity of these lines and considerably modifies the
derived microturbulent broadening parameter. Line profiles obtained
from KE line-formation theory are much deeper than LTE profiles, and
we present new observations of Canopus (F0 Ib) to verify the essential
correctness of our treatment. Subject headings: atmospheres, stellar -
line formation - spectra, infrared
Title: Telluric lines in the vicinity of λ5250 and λ6562å
Authors: Livingston, W.; Ramsey, L.
Bibcode: 1973SoPh...31..317L
Altcode:
No abstract at ADS
Title: The San Manuel Effect -- A Progress Report
Authors: Livingston, W.; Ramsey, L.
Bibcode: 1973BAAS....5R.276L
Altcode:
No abstract at ADS
Title: A program for monitoring the abundances of atmospheric
constituents using the McMath infrared spectrograph.
Authors: Hall, D. N.; Ramsey, L. W.
Bibcode: 1973PASP...85Q.532H
Altcode:
No abstract at ADS
Title: Line Broadening by Macroturbulence.
Authors: Evans, J. C.; Ramsey, L. W.; Gray, D. F.
Bibcode: 1972BAAS....4..333E
Altcode:
No abstract at ADS