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Author name code: korzennik
ADS astronomy entries on 2022-09-14
author:"Korzennik, Sylvain"
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Title: Helioseismic Constraints on the Solar Interior Dynamics
and Dynamo
Authors: Kosovichev, A. G.; Brummell, N.; Dikpati, M.; Guerrero,
G.; Kitiashvili, I.; Komm, R.; Korzennik, S.; Pipin, V.; Reiter, J.;
Stejko, A.; Ulrich, R. K.; Warnecke, J.
2020AGUFMSH007..04K Altcode:
Uninterrupted helioseismic observations from the SoHO/MDI, SDO/HMI and
GONG instruments for more than two decades provide unique observational
data for studying the solar-cycle variations of the differential
rotation, large-scale and meridional flows. The data also allows
us to investigate changes in the thermodynamic structure associated
with dynamo-generated magnetic fields. The wealth of global and local
helioseismic data provides theoretical constraints on the solar dynamics
and dynamo models. The synergy of helioseismic inferences with advanced
MHD modeling sheds light on the origin of the solar activity cycles. It
helps to understand better the physical processes that control the
strength and duration of the cyclic magnetic activity and leads to
new physics-based approaches for prediction of the solar cycles. We
briefly overview the current status, discuss the solar dynamical
structure and evolution revealed by helioseismic inversions and the
forward-modeling method, and focus on the most critical points of the
problem. In particular, we discuss recent advances in measurements and
modeling of the solar-cycle variations of the meridional circulation
and migrating zonal flows (torsional oscillations) on the solar surface
and in the subsurface layers, the deep convection zone, and the solar
tachocline. The relationships between the internal dynamics and the
evolution of global magnetic fields lead to new ideas of how magnetic
fields are generated and affect the solar flows and structure.
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Title: On Active Region Emergence Precursors
Authors: Korzennik, Sylvain G.
2020ASSP...57..129K Altcode:
I present intriguing results from a systematic look at possible
indicators of active region emergence precursors using both acoustic
power mapping and time distance travel time anomalies. I analyzed a
set of active regions that have emerged at low latitudes and close to
the central meridian, and were observed with HMI. Such regions, since
they emerged near disk center, could be tracked for days before and
after their emergence. Data cubes of tracked surface observable were
analyzed, using time-series of various length, using HMI's intensity,
velocity and magnetic field data. While each active region displays
its own particularities, this systematic approach allowed me to pick
some interesting statistical properties that will be summarized. Using
different time-series length allowed me to investigate the trade-off
between precision and resolution, whether temporal or spatial. It
also revealed to which extent one sees a tight correlation between
various metric of surface activity and its effect of the measured
acoustic signal, whether seen in raw of filtered power map or travel
time anomalies.
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Title: On the search of active region emergence precursors
using acoustic power maps and travel time anomalies derived from
time-distance analysis of HMI observations
Authors: Korzennik, Sylvain G.
2019AAS...23430505K Altcode:
I present initial results from a systematic look at possible indicators
of active region emergence precursors using acoustic power mapping and
time distance travel time anomalies. Using HMI observations I have
analyzed a set of active regions that have emerged at low latitudes
and close to the central meridian. Since these regions emerged close
to disk center, they could be tracked for days before and after their
emergence. Data cubes of tracked surface images of various lengths
were analyzed using both intensity and velocity observations. While
each active region exhibits particular properties, this systematic
approach allowed me to look at a few statistical properties that will
be summarized. Namely the trade-off between precision and resolution,
both temporal and spatial resolution, and the correlation between
various metric of surface activity and its impact of the measured
acoustic signal, whether seen in power map (filtered or not) or travel
time anomalies derived from a time-distance analysis (also using a
few different filtering).
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Title: New and Improved Mode Fitting Results
Authors: Korzennik, Sylvain G.
2018csc..confE.132K Altcode:
I present the most recent improvements to my mode fitting procedures,
and how they affect inferred properties of the Sun. The fitting has
now been extended to ℓ=0 modes, and in the process to more ℓ=1
modes. Close scrutiny of these low degree modes revealed the need
to change the scaling of the error bars on the derived multiplet
quantities. I fitted a test data set using different leakage matrices,
including one set computed to fit very long time series and therefore
uses for B_o the value of 5.0593^o (or √{|Bo^2|}). I show how that
leakage matrix is different from the one computed in the past for very
long time series (B_o=0) and its impact on the fitted parameters.
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Title: Initial Results from Fitting p -Modes Using Intensity
Observations from the Helioseismic and Magnetic Imager
Authors: Korzennik, Sylvain G.
2017SoPh..292..138K Altcode:
The Helioseismic and Magnetic Imager project recently started processing
the continuum-intensity images following global helioseismology
procedures similar to those used to process the velocity images. The
spatial decomposition of these images has produced time series of
spherical harmonic coefficients for degrees up to ℓ =300 , using a
different apodization than the one used for velocity observations. The
first 360 days of observations were processed and are made available. I
present initial results from fitting these time series using my fitting
method and compare the derived mode characteristics to those estimated
using coeval velocity observations.
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Title: Detailed Image Comparison using MDI, HMI and GONG Co-Eval
Observations
Authors: Korzennik, Sylvain G.
2017SPD....4811302K Altcode:
I present preliminary results from detailed image comparison using
MDI, HMI and GONG co-eval observations taken in 2014, when all three
instruments were operational. This comparison allows me to estimate
both the instrumental image distortion and the instrument PSF, with
respect to HMI. Both intensity and velocity images are compared when
available. The precise observing perspective of each instrument had to
be accounted since it affects the projected image on the instrument
detector at the required level of precision (i.e., a fraction of
an HMI pixel). In the process, it was discovered that the meta data
generated by the respective projects were not accurate enough. While
the inclusion of the image distortion and the instrument PSF in the
spatial decomposition will improve the determination of high degree
modes, it may also benefit other local helioseismic analysis.
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Title: Initial Results from Fitting Resolved Modes using HMI Intensity
Observations
Authors: Korzennik, Sylvain G.
2017SPD....4811301K Altcode:
The HMI project recently started processing the continuum intensity
images following global helioseismology procedures similar to those
used to process the velocity images. The spatial decomposition of these
images has produced time series of spherical harmonic coefficients for
degrees up to l=300, using a different apodization than the one used
for velocity observations. The first 360 days of observations were
processed and made available. I present initial results from fitting
these time series using my state of the art fitting methodology and
compare the derived mode characteristics to those estimated using
co-eval velocity observations.
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Title: Initial Results from Fitting Resolved Modes using HMI Intensity
Observations
Authors: Korzennik, Sylvain G.
2017arXiv170709895K Altcode:
The HMI project recently started processing the continuum intensity
images following global helioseismology procedures similar to those
used to process the velocity images. The spatial decomposition of these
images has produced time series of spherical harmonic coefficients for
degrees up to $\ell=300$, using a different apodization than the one
used for velocity observations. The first 360 days of observations
were processed and made available. In this paper I present initial
results from fitting these time series using my state of the art
fitting methodology and compare the derived mode characteristics to
those estimated using co-eval velocity observations.
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Title: Temporal Changes of pModes Properties Derived from Nearly 20
Year of Observations
Authors: Korzennik, Sylvain G.
2016usc..confE.125K Altcode:
I present a detailed comparison of the temporal changes of the
characteristics of the low and intermediate p-modes oscillations
derived from nearly 20 years of observations acquired from three
instruments: GONG, MDI and HMI. These characteristics were estimated
using three quite different data reduction pipe-lines. The comparisons
are both at the level of mode characteristics (frequency, linewidth,
amplitude and asymmetry) and at the level of inferred properties of
the solar interior (i.e., changes in the solar internal rotation),
and for co-eval observations.
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Title: On the Temporal Changes of Helioseismic Properties Derived
with Different Techniques
Authors: Korzennik, Sylvain G.
2016SPD....4710701K Altcode:
I present a detailed comparison of the temporal changes of the
characteristics of the low and intermediate p-modes oscillations derived
from nearly 20 years of observations acquired from three instruments
(GONG, MDI and HMI) and computed using three quite different data
reduction pipe-lines. The comparisons are both at the level of mode
characteristics (frequency, linewidth, amplitude and asymmetry)
and at the level of inferred properties of the solar interior (i.e.,
changes in the solar internal rotation).
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Title: Fitting medium and high degrees using GONG, MDI and HMI
observations.
Authors: Korzennik, Sylvain G.
2014AAS...22421813K Altcode:
I present results from fitting data from the three major helioseismic
instruments: GONG, MDI, and HMI, both at medium degree (resolved modes)
and at high degrees (ridge fitting). The medium-l fitting was carried
out on time-series of varying lengths (1x, 2x, 4x, 8x, 16x, 32x, 64x
72 day longs, and 36 day long ones), the high-l fitting was carried
out on co-eval time-series that correspond to the 2001, 2002 and 2010
MDI Dynamics runs. I present these results, compare them and discuss
the potential sources of the discrepancies.
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Title: Mode Frequencies from GONG, MDI, and HMI Data
Authors: Korzennik, S. G.
2013ASPC..478..137K Altcode:
I present recent results from fitting all the available data from
the three major helioseismic instruments: GONG, MDI and HMI using
my independent methodology. This method not only fits individual
singlets, but: fits them simultaneously for a given multiplet; uses
an optimal multi-taper spectral estimator; includes the full leakage
matrix and the effect of mode distortion by differential rotation;
and fits an asymmetric mode profile. The mode fitting was carried out
on time series of varying lengths (1×, 2×, 4×, 8×, 16×, 32×,
64× 72 days long), using co-eval epochs for all three instruments. By
fitting time series of varying lengths, one trades off some temporal
resolution for a better precision. I present these results, compare
them and discuss the potential sources of the discrepancies.
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Title: Characterization of High-Degree Modes using MDI, HMI and
GONG Data
Authors: Korzennik, S. G.; Eff-Darwich, A.; Larson, T. P.;
Rabello-Soares, M. C.; Schou, J.
2013ASPC..478..173K Altcode:
We present the first characterization of high-degree modes (i.e.,
ℓ up to 900 or 1000), using three instruments and three epochs
corresponding to the 2001, 2002 and 2010 MDI Dynamics runs. For 2001,
we analyzed MDI full-disk Dopplergrams, while for 2002, we analyzed
MDI and GONG full-disk Dopplergrams, and for 2012 we analyzed
MDI, GONG and HMI full-disk Dopplergrams. These Dopplergrams were
spatially decomposed up to ℓ = 900 or 1000, and power spectra for
all degrees and all azimuthal orders were computed using a high-order
multi-taper, power spectrum estimator. These spectra were then fitted
for all degrees and all azimuthal orders, above ℓ = 100, and for all
orders with substantial amplitude. Fitting at high degrees generates
ridge characteristics, characteristics that do not correspond to
the underlying mode characteristics. We used a sophisticated forward
modeling to recover the best possible estimate of the underlying mode
characteristics (mode frequencies, as well as linewidths, amplitudes
and asymmetries). We present the first attempt to apply this method to
three instruments and three epochs. The derived sets of corrected mode
characteristics (frequencies, line widths, asymmetries and amplitudes)
are presented and compared.
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Title: The Dynamics of the Solar Radiative Zone
Authors: Eff-Darwich, A.; Korzennik, S. G.
2013SoPh..287...43E Altcode: 2012arXiv1205.3143E; 2012SoPh..tmp..149E
The dynamics of the solar radiative interior are still poorly
constrained by comparison to the convective zone. This disparity
is even more marked when we attempt to derive meaningful temporal
variations. Many data sets contain a small number of modes that
are sensitive to the inner layers of the Sun, but we found that the
estimates of their uncertainties are often inaccurate. As a result,
these data sets allow us to obtain, at best, a low-resolution
estimate of the solar-core rotation rate down to approximately
0.2R<SUB>⊙</SUB>. We present inferences based on mode determination
resulting from an alternate peak-fitting methodology aimed at
increasing the amount of observed modes that are sensitive to the
radiative zone, while special care was taken in the determination of
their uncertainties. This methodology has been applied to MDI and GONG
data, for the whole Solar Cycle 23, and to the newly available HMI
data. The numerical inversions of all these data sets result in the
best inferences to date of the rotation in the radiative region. These
results and the method used to obtain them are discussed. The resulting
profiles are shown and analyzed, and the significance of the detected
changes is discussed.
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Title: Accurate Characterization of High-degree Modes Using MDI
Observations
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.; Larson,
T. P.
2013ApJ...772...87K Altcode:
We present the first accurate characterization of high-degree modes,
derived using the best Michelson Doppler Imager (MDI) full-disk
full-resolution data set available. A 90 day long time series of
full-disk 2 arcsec pixel<SUP>-1</SUP> resolution Dopplergrams was
acquired in 2001, thanks to the high rate telemetry provided by the
Deep Space Network. These Dopplergrams were spatially decomposed using
our best estimate of the image scale and the known components of MDI's
image distortion. A multi-taper power spectrum estimator was used to
generate power spectra for all degrees and all azimuthal orders, up to
l = 1000. We used a large number of tapers to reduce the realization
noise, since at high degrees the individual modes blend into ridges and
thus there is no reason to preserve a high spectral resolution. These
power spectra were fitted for all degrees and all azimuthal orders,
between l = 100 and l = 1000, and for all the orders with substantial
amplitude. This fitting generated in excess of 5.2 × 10<SUP>6</SUP>
individual estimates of ridge frequencies, line widths, amplitudes,
and asymmetries (singlets), corresponding to some 5700 multiplets
(l, n). Fitting at high degrees generates ridge characteristics,
characteristics that do not correspond to the underlying mode
characteristics. We used a sophisticated forward modeling to recover
the best possible estimate of the underlying mode characteristics (mode
frequencies, as well as line widths, amplitudes, and asymmetries). We
describe in detail this modeling and its validation. The modeling has
been extensively reviewed and refined, by including an iterative process
to improve its input parameters to better match the observations. Also,
the contribution of the leakage matrix on the accuracy of the
procedure has been carefully assessed. We present the derived set of
corrected mode characteristics, which includes not only frequencies,
but line widths, asymmetries, and amplitudes. We present and discuss
their uncertainties and the precision of the ridge-to-mode correction
schemes, through a detailed assessment of the sensitivity of the model
to its input set. The precision of the ridge-to-mode correction is
indicative of any possible residual systematic biases in the inferred
mode characteristics. In our conclusions, we address how to further
improve these estimates, and the implications for other data sets,
like GONG+ and HMI.
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Title: Mode Frequencies from 17, 15 and 2 Years of GONG, MDI, and
HMI Data
Authors: Korzennik, S. G.; Eff-Darwich, A.
2013JPhCS.440a2015K Altcode:
We present results from fitting all the available data to date from the
three major helioseismic instruments: MDI, GONG and HMI. These data
were fitted using an innovative and independent methodology devised
a few years ago. The mode fitting was carried out on time series of
varying lengths (1×, 2×, 4×, 8×, 16×, 32×, 64 × 72 day-long),
using co-eval epochs for all three data sets. By fitting time series of
varying lengths, one trades off some temporal resolution for a better
precision. We present a comparison of these results, and discuss the
potential sources of the residual small discrepancies. We also present
inferences from these results on the determination of the solar internal
rotation and changes with epoch and thus activity levels.
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Title: Accurate characterization of high-degree modes using MDI data
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.; Larson, T.
2013JPhCS.440a2016K Altcode: 2012arXiv1209.6414K
We present the first accurate characterization of high-degree modes
(i.e., l up to 1000), using the best MDI full-disk full-resolution
data set available (90-day long time series, acquired in
2001). The Dopplergrams were spatially decomposed using our best
estimate of the image scale and the known components of MDI's image
distortion. Multi-tapered power spectra were fitted for all degrees
and all azimuthal orders, between l = 100 and l = 1000, and for all
orders with substantial amplitude. Fitting at high degrees generates
ridge characteristics, characteristics that do not correspond to the
underlying mode characteristics. We used a sophisticated forward
modeling to recover the best possible estimate of the underlying
mode characteristics. We have derived a final set of corrected mode
characteristics (frequencies, line widths, asymmetries and amplitudes)
and their uncertainties.
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Title: Erratum: "On the Determination of Michelson
Doppler Imager High-degree Mode Frequencies" <A
href="/abs/2004ApJ...602..481K">(2004, ApJ, 602, 481)</A>
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.
2012ApJ...760..156K Altcode:
No abstract at ADS
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Title: A Determination of High-degree Mode Parameters Based on
MDI Observations
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.; Larson,
T. P.
2012ASPC..462..189K Altcode:
We present the best to date determination of high-degree mode
parameters obtained from a ninety day long time series of full-disk
full-resolution Michelson Doppler Imager (MDI) Dopplergrams. These
Dopplergrams were decomposed using our best estimate of the image
scale and the known components of MDI's image distortion. The
spherical harmonic decomposition was carried out up to ℓ=1000,
and a high-order sine multi-taper power spectrum estimator was used
to generate power spectra. These power spectra were fitted for all
degrees and all azimuthal orders, for 100 ≤ ℓ ≤ 1000, and
for all radial orders with substantial amplitude, generating some
6 × 10<SUP>6</SUP> estimates of ridge frequencies, line-widths,
amplitudes and asymmetries. We used a sophisticated forward modeling
of the mode to ridge blending, to recover the best possible estimate
of the underlying mode characteristics.
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Title: The Solar Rotation and Its Evolution during Cycle 23
Authors: Korzennik, S. G.; Eff-Darwich, A.
2012ASPC..462..267K Altcode:
We present the most exhaustive and accurate inferences of the internal
solar rotation rate and its evolution during solar cycle 23. A full
solar cycle of Michelson Doppler Imager (MDI) observations has been
analyzed using our state of the art fitting methodology. Time series
of various lengths have been fitted, from a single 4608-day long
epoch (64 × 72 day or 12.6 year) down to 64 separate segments for
the traditional 72-day long epochs. We used time series of spherical
harmonic coefficients computed by the MDI group but using an improved
spatial decomposition. This decomposition now includes our best
estimate of the image plate scale and of the MDI instrumental image
distortion. The leakage matrix used for the fitting includes the effect
of the distortion of the eigenfunctions by the solar differential
rotation, and the undistorted leakage matrix was itself carefully
reviewed and independently recomputed. Rotation inversions were carried
out for all the available mode sets for that epoch and all available
segments, including the MDI and Global Oscillation Network Group (GONG)
pipe-line sets. The improved inversion method we used is an iterative
methodology based on a regularized least-squares. It implements a
model grid optimization derived from the actual information in the
input set. This optimized model grid is itself irregular, namely with a
variable number of latitudes at different depths. We present the most
accurate mean rotation rate, to date. We also focus on the change of
the rotation rate with activity levels and how well these changes are
assessed at high latitudes and below the surface, down to the base of
the convection zone.
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Title: Calibration of an echelle spectrograph with an astro-comb:
a laser frequency comb with very high repetition rate
Authors: Phillips, David F.; Glenday, Alex; Li, Chih-Hao; Furesz,
Gabor; Benedick, Andrew J.; Chang, Guoqing N.; Chen, Li-Jin; Korzennik,
Sylvain; Sasselov, Dimitar; Kaertner, Franz X.; Szentgyorgyi, Andrew;
Walsworth, Ronald L.
2012SPIE.8446E..8OP Altcode:
Searches for extrasolar planets using precision radial velocity (PRV)
techniques are approaching Earth-like planet sensitivity, however
require an improvement of one order of magnitude to identify earth-mass
planets in the habitable zone of sun-like stars. A key limitation is
spectrograph calibration. An astro-comb, an octave-spanning laser
frequency comb and a Fabry-Pérot cavity, producing evenly spaced
frequencies with large wavelength coverage, is a promising tool for
improved wavelength calibration. We demonstrate the calibration of a
high-resolution astrophysical spectrograph below the 1 m/s level in
the 8000-9000 Å and 4200 Å spectral bands.
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Title: Calibration of an astrophysical spectrograph below 1 m/s
using a laser frequency comb
Authors: Phillips, David F.; Glenday, Alexander G.; Li, Chih-Hao;
Cramer, Claire; Furesz, Gabor; Chang, Guoqing; Benedick, Andrew J.;
Chen, Li-Jin; Kärtner, Franz X.; Korzennik, Sylvain; Sasselov,
Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.
2012OExpr..2013711P Altcode:
We deployed two wavelength calibrators based on laser frequency combs
("astro-combs") at an astronomical telescope. One astro-comb operated
over a 100 nm band in the deep red (∼ 800 nm) and a second operated
over a 20 nm band in the blue (∼ 400 nm). We used these red and blue
astro-combs to calibrate a high-resolution astrophysical spectrograph
integrated with a 1.5 m telescope, and demonstrated calibration
precision and stability suffici ent to enable detection of changes in
stellar radial velocity < 1 m/s.
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Title: Comparing Leakage Matrices
Authors: Larson, T. P.; Schou, J.; Korzennik, S. G.
2011sdmi.confE..44L Altcode:
The standard leakage matrix for global mode helioseismology is
calculated assuming a value of zero for the P-angle, B-angle, and CCD
offsets, and value of 1 AU for the observer distance. Since image center
is not constant we vary this parameter so see what effect is has on the
leaks and explore the possibility of using a leakage matrix averaged
over pixel offsets. Since the B-angle and observer distance vary in
a known way with time, we recompute the leakage matrix for realistic
values of these parameters and repeat the fits to find out how the mode
parameters are affected. Since previous studies have indicated certain
systematic errors are associated with the apodization, we also compute
leakage matrices for different apodizations, repeat the spherical
harmonic decomposition with those apodizations, and fit these to see
the effect on mode parameters. Lastly, we compare the leakage matrix
computed at Stanford with a completely independent calculation in order
to both verify our results and discover the source of any discrepancy.
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Title: Results from fitting 13+ years of GONG and MDI data at low
and intermediate degrees
Authors: Korzennik, S. G.
2011sdmi.confE..90K Altcode:
I present the latest results from fitting modes at low and intermediate
degrees (up to l=300 for the f-mode, l=200 for p-modes), using my
state of the art fitting methodology. Time series of various lengths
have been fitted, from a single 4608-day long epoch (64 times 72 day or
12.6 yr) down to 64 separate segments for the "traditional" 72-day long
epochs, and including 32x, 16x, 8x, 4x and 2x 72-day long overlapping
epochs. We used MDI time series of spherical harmonic coefficients
computed using an improved spatial decomposition. This decomposition
now includes our best estimate of the image plate scale and of the
MDI instrumental image distortion. We used the GONG time series of
spherical harmonic coefficients as generated by the GONG pipe-line
(available up to l=200 only). The leakage matrices used for the fitting
includes the distortion of the eigenfunctions by the solar differential
rotation. The undistorted leakage matrices were carefully reviewed and
independently recomputed. The effect of the leakage matrix (and its
residual inadequacy) can be readily observed when using longer time
series than the traditional 72 or 108-day long ones. We compare in
details results from fitting GONG and MDI, using for the first time
the same fitting code, although a different leakage matrix, and the
exact same time span.
---------------------------------------------------------
Title: A determination of high degree mode parameters based on
MDI observations
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.; Larson, T.
2011sdmi.confE..88K Altcode:
We present the best to date determination of high degree mode parameters
obtained from the longest full-disk high-resolution data set available
over the 13 years of MDI operations. A ninety day long time series
of full-disk two arc-second per pixel resolution dopplergrams were
acquired in 2001, thanks to the high rate telemetry provided by the
deep space network. These dopplergrams were decomposed using our best
estimate of the image scale and the known components of MDI's image
distortion. The spherical harmonics decomposition was carried out up
to l=1000, and a sine multi-taper power spectrum estimator was used
to generate power spectra for all degrees and all azimuthal orders up
to l=1000. We used a large number of tapers to reduce the realization
noise. Since at high degrees the individual modes blend into ridges,
there is no reason to preserve a high spectral resolution. These
power spectra were fitted for all degrees and all azimuthal orders,
between l=100 and l=1000, and for all orders with substantial amplitude,
generating in excess of 6 million individual estimate of frequencies,
line-widths amplitudes and asymmetries, corresponding to some 6,000
singlets. Fitting at high degrees generates characteristics of the
blended ridges, characteristics that do not correspond to the underlying
mode characteristics. We used a sophisticated forward modeling of the
mode to ridge blending to recover the best possible estimate of the
underlying mode characteristics for the mode frequency, as well as the
line-width, amplitude and asymmetry. We describe this modeling, as it
has been recently fine tuned, and the iterative process used to refine
its input parameters. Finally not only did we generate corrected mode
characteristics and their uncertainties, but we computed the sensitivity
of the model to its input set to best estimate the precision of the
ridge to mode correction itself. This was carried out to assess the
magnitude of any residual systematic errors in the final estimates of
the mode characteristics.
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Title: High Accuracy Characterization of an Astro-comb with an FTS
Authors: Glenday, Alex; Li, Chih-Hao; Phillips, David; Korzennik,
Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner,
Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald
2011APS..DMP.L1161G Altcode:
Searches for extrasolar planets using the periodic Doppler shift of
stellar lines are approaching Earth-like planet sensitivity. To find
a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude
improvement in state-of-the-art radial velocity spectroscopy is
necessary. An astro-comb, the combination of an ocatve-spanning laser
frequency comb with a Fabry-Perot cavity, producing evenly spaced
frequency markers with the potential for large wavelength coverage
is a promising avenue towards improved wavelength calibration. Key
to achieving high accuracy and long-term stability of the astro-comb
is high-quality suppression of undesired comb laser lines by the
Fabry-Perot filter cavity. Here we present a characterization of a
green astro-comb produced by broadening a Ti:Sapphire laser using
photonic crystal fiber (PCF) and filtered through zero group delay
dispersion mirror sets optimized for the green. The characterization
is performed using a high-resolution FTS constructed in our laboratory.
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Title: Calibration of an Astrophysical Spectrograph with an Astro-comb
in the Visible Spectral Range
Authors: Li, Chih-Hao; Glenday, Alex; Phillips, David; Korzennik,
Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner,
Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald
2011APS..DMP.J5005L Altcode:
Searches for extrasolar planets using the periodic Doppler shift of
stellar lines are approaching Earth-like planet sensitivity. To find
a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude
improvement in state-of-the-art radial velocity spectroscopy is
necessary. An astro-comb, the combination of an ocatve-spanning laser
frequency comb with a Fabry-Perot cavity, producing evenly spaced
frequency markers with the potential for large wavelength coverage
is a promising avenue towards improved wavelength calibration. Here
we demonstrate the calibration of a high-resolution astrophysical
spectrograph below the 50 cm/s level in the visible spectral range
around 420 nm using an octave-spanning Ti:Sapphire laser and an
ultra-low dispersion Fabry-Perot filter cavity adjusted for a mode
spacing of approximately 50 GHz. Modeling of spectrograph response
function and overall system stability and reproducibility will be
described.
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Title: Red, Green, and Blue Astro-combs
Authors: Phillips, David; Glenday, Alex; Li, Chih-Hao; Korzennik,
Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner,
Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald
2011APS..DMP.L1162P Altcode:
Searches for extrasolar planets using the periodic Doppler
shift of stellar lines are approaching Earth-like planet
sensitivity. Astro-combs, a combination of an octave spanning
femtosecond laser and a mode-filtering cavity provide a likely route
to increased calibration precision and accuracy. We present results
from three astro-combs operating in the red/near-IR, green and blue
spectral ranges. Light from a 1-GHz, octave-spanning Ti:Sapphire
laser is filtered by a Fabry-Perot Cavity (FPC) constructed from
Doubly-Chirped Mirrors to produce a red astro-comb with 100 nm of
optical bandwidth. This astro-comb has calibrated an astrophysical
spectrograph at the 1 m/s level. In the blue astro-comb, Ti:Sapphire
comb light, doubled in a BBO crystal is filtered to 50 GHz mode spacing
with an FPC. The blue astro-comb has performed 50 cm/s calibrations. In
the “green” astro-comb, light from the 1 GHz Ti:Sapphire comb laser
is broadened in a photonic crystal fiber optimized to produce light in
the green. This 1-GHz spaced green light is then filtered to roughly
40 GHz via an FPC with zero group delay dispersion mirrors, providing
approximately 50 nm of astro-comb light centered near 550 nm.
---------------------------------------------------------
Title: A Comparison Of Solar High-degree p-mode Parameters From HMI
And MDI
Authors: Rabello-Soares, M. Cristina; Bogart, R.; Korzennik, S.;
Larson, T.; Reiter, J.; Rhodes, E.; Schou, J.
2011SPD....42.1606R Altcode: 2011BAAS..43S.1606R
Solar acoustic modes have been successfully used to make inferences
about the solar interior. The comparison of independent contemporaneous
data sets is important to test the reliability of our inferences. Here
we compare helioseismic data from the Michelson Doppler Imager (MDI)
on board SOHO with Helioseismic and Magnetic Imager (HMI) on board SDO
using spherical harmonic decomposition and ring-diagram analysis. We
will focus on the analysis of high-degree modes. They propagate through
the outer layers of the Sun giving valuable information about this
region. This interesting region is the seat of the near-surface shear
layer, where the excitation and damping mechanisms are believed to be
concentrated and where the effects of the equation of state are felt
most strongly.
---------------------------------------------------------
Title: The Solar Rotation and its Evolution During Cycle 23
Authors: Korzennik, Sylvain G.; Eff-Darwich, A.
2011AAS...21822422K Altcode: 2011BAAS..43G22422K
We present the most exhaustive and accurate inferences of the internal
solar rotation rate and its evolution during solar cycle 23. A full
solar cycle of MDI observations have been analyzed using our state of
the art fitting methodology. Time series of various lengths have been
fitted, from a single 4608-day long epoch (64 times 72 day or 12.6
yr) down to 64 separate segments for the "traditional" 72-day long
epochs. We used time series of spherical harmonic coefficients computed
by the MDI group but using an improved spatial decomposition. This
decomposition now includes our best estimate of the image plate scale
and of the MDI instrumental image distortion. The leakage matrix
used for the fitting includes the distortion of the eigenfunctions by
the solar differential rotation, and the undistorted leakage matrix
was itself carefully reviewed and independently recomputed. Rotation
inversions were carried out for all the available mode sets, fitted
for that epoch and all available segments, including the MDI and GONG
"pipe-line" sets. The improved inversions we used is an iterative
methodology based on a least-squares regularization. It also implement
a model grid optimization derived from the actual information in the
input set. This optimized model grid is itself irregular, namely with a
variable number of latitudes at different depths. We not only present
the most accurate mean rotation rate, but also how its derivation may
still be affected by uncertainties in the mode fitting (in particular
the leakage matrix). We also focus on the change of the rotation rate
with activity levels and how well these changes are significantly
assessed at higher latitudes as well as deeper in the solar interior,
down to the base of the convection zone.
---------------------------------------------------------
Title: The solar core as never seen before
Authors: Eff-Darwich, A.; Korzennik, S. G.
2011JPhCS.271a2043E Altcode:
One of the main drawbacks in the analysis of the dynamics of the solar
core comes from the lack of consistent data sets that cover the low
and intermediate degree range (ell = 1,200). It is usually necessary
to merge data obtained from different instruments and/or fitting
methodologies and hence one introduces undesired systematic errors. In
contrast, we present the results of analyzing MDI rotational splittings
derived by a single fitting methodology applied to 4608-, 2304-, etc...,
down to 182-day long time series. The direct comparison of these data
sets and the analysis of the numerical inversion results have allowed
us to constrain the dynamics of the solar core and to establish the
accuracy of these data as a function of the length of the time-series.
---------------------------------------------------------
Title: The rotation rate and its evolution derived from improved
mode fitting and inversion methodology
Authors: Korzennik, S. G.; Eff-Darwich, A.
2011JPhCS.271a2067K Altcode:
We present inferences of the internal solar rotation rate and its
evolution during solar cycle 23. A full solar cycle of MDI observations
have been analyzed using an improved fitting methodology and using
time series of various lengths, up to a single 4,608 day long epoch
(64 times 72 days or 12.6 yr). We used time series of spherical harmonic
coefficients computed by the MDI group, including those resulting from
using their improved spatial decomposition. This decomposition includes
our best estimate of the image plate scale and of the MDI instrumental
image distortion. The leakage matrix used in the fitting includes the
effect of the distortion of the eigenfunctions by the solar differential
rotation, while the undistorted leakage matrix was itself carefully
reviewed and independently recomputed. Rotation inversions were carried
out for all available mode sets, fitted for that epoch, including the
MDI and GONG "pipe-line" values. The improved inversion method uses
an iterative methodology based on a least-squares regularization, but
with an optimal model grid determined by the actual information in the
input set. This method also allows us to use an optimized irregular
grid, with a variable number of latitudes at different depths.
---------------------------------------------------------
Title: Accurate Mapping of the Torsional Oscillations: a Trade-Off
Study between Time Resolution and Mode Characterization Precision
Authors: Eff-Darwich, A.; Korzennik, S. G.
2011JPhCS.271a2078E Altcode:
One salient result of global helioseismology is the mapping of the
so-called torsional oscillations below the solar surface. These
subsurface flows are inferred by inverting rotational frequency
splitting sets of global modes. These flows extend down to a depth
of at least 0.8 R, and are likely associated with the activity cycle
of our star. To better understand the mechanisms that drive the
solar cycle we need to accurately map these flows, and characterize
precisely their penetration depth and their temporal behavior. <P
/>We present a study of the spatial (depth and latitude) and temporal
variations of the solar rotation rate associated with the torsional
oscillation based on state-of-the-art mode fitting of time series
of various lengths of MDI observations, namely 1456-, 728-, 364- and
182-day long time series. Such approach allows us to better estimate
how much significant information can be extracted from the different
time spans and hence trade off time resolution for precision in the
inverted profiles resulting from the different mode sets.
---------------------------------------------------------
Title: Advances in solar rotation rate inferences: Unstructured grid
inversions and improved rotational splittings
Authors: Eff-Darwich, A.; Korzennik, S. G.; García, R. A.
2010AN....331..890E Altcode:
We present a new inversion methodology that adapts the inversion
grid in both radius and co-latitude to the data set and solves the
inversion problem through an iterative procedure. This method was
tested on state-of-the-art global mode frequency splittings to assess
the solar interior rotation rate and its temporal variation. We also
explore the influence of different data sets on the interpretation of
the dynamics of the solar interior, particularly the spatial extend
of the torsional oscillations.
---------------------------------------------------------
Title: New Observational Constraints on the υ Andromedae System
with Data from the Hubble Space Telescope and Hobby-Eberly Telescope
Authors: McArthur, Barbara E.; Benedict, G. Fritz; Barnes, Rory;
Martioli, Eder; Korzennik, Sylvain; Nelan, Ed; Butler, R. Paul
2010ApJ...715.1203M Altcode:
We have used high-cadence radial velocity (RV) measurements from
the Hobby-Eberly Telescope with existing velocities from the Lick,
Elodie, Harlan J. Smith, and Whipple 60” telescopes combined with
astrometric data from the Hubble Space Telescope Fine Guidance
Sensors to refine the orbital parameters and determine the orbital
inclinations and position angles of the ascending node of components
υ And A c and d. With these inclinations and using M <SUB>*</SUB>
= 1.31M <SUB>sun</SUB> as a primary mass, we determine the actual
masses of two of the companions: υ And A c is 13.98<SUP>+2.3</SUP>
<SUB>-5.3</SUB> M <SUB>JUP</SUB>, and υ And A d is 10.25<SUP>+0.7</SUP>
<SUB>-3.3</SUB> M <SUB>JUP</SUB>. These measurements represent the first
astrometric determination of mutual inclination between objects in an
extrasolar planetary system, which we find to be 29fdg9 ± 1°. The
combined RV measurements also reveal a long-period trend indicating a
fourth planet in the system. We investigate the dynamic stability of
this system and analyze regions of stability, which suggest a probable
mass of υ And A b. Finally, our parallaxes confirm that υ And B is
a stellar companion of υ And A. <P />Based on observations made with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555. 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-Universitt
Mnchen, and Georg-August-Universität Göttingen.
---------------------------------------------------------
Title: In-situ determination of astro-comb calibrator lines to better
than 10 cm s^-1
Authors: Li, Chih-Hao; Glenday, Alexander G.; Benedick, Andrew J.;
Chang, Guoqing; Chen, Li-Jin; Cramer, Claire; Fendel, Peter; Furesz,
Gabor; Kärtner, Franz X.; Korzennik, Sylvain; Phillips, David F.;
Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.
2010OExpr..1813239L Altcode: 2010arXiv1006.0492L
Improved wavelength calibrators for high-resolution astrophysical
spectrographs will be essential for precision radial velocity
(RV) detection of Earth-like exoplanets and direct observation of
cosmological deceleration. The astro-comb is a combination of an
octave-spanning femtosecond laser frequency comb and a Fabry-Pérot
cavity used to achieve calibrator line spacings that can be
resolved by an astrophysical spectrograph. Systematic spectral
shifts associated with the cavity can be 0.1-1 MHz, corresponding
to RV errors of 10-100 cm/s, due to the dispersive properties of the
cavity mirrors over broad spectral widths. Although these systematic
shifts are very stable, their correction is crucial to high accuracy
astrophysical spectroscopy. Here, we demonstrate an \emph{in-situ}
technique to determine the systematic shifts of astro-comb lines due to
finite Fabry-Pérot cavity dispersion. The technique is practical for
implementation at a telescope-based spectrograph to enable wavelength
calibration accuracy better than 10 cm/s.
---------------------------------------------------------
Title: New Observational Constraints on the υ Andromedae System
with Data from the Hubble Space Telescope and Hobby Eberly Telescope
Authors: McArthur, Barbara; Benedict, G. F.; Barnes, R.; Martioli,
E.; Korzennik, S.; Nelan, E.; Butler, R. P.
2010AAS...21642510M Altcode:
We have used high-cadence radial velocity measurements from the
Hobby-Eberly Telescope with existing velocities from the Lick, Elodie,
Harlan J. Smith and Whipple 60” telescopes combined with astrometric
data from the Hubble Space Telescope Fine Guidance Sensors to refine
the orbital parameters and determine the orbital inclinations and
position angles of the ascending node of components υ And A c and
d. With these inclinations and using M = 1.31M⊙ as a primary mass
we determine the actual masses of two of the companions: υ And A c
is13.98+2.3 Mjup, and υ And A d is 10.25+0.7 Mjup. These measurements
represent the first astrometric determination of mutual inclination
between objects in an extrasolar planetary system. The combined radial
velocity measurements also reveal a long period trend indicating a
fourth planet in the system. We investigate the dynamic stability
of this system and analyze regions of stability, which suggest a
probable mass of υ And A b. Finally, our parallaxes confirm that
υ And B is a stellar companion of υ And A. Support for this work
was provided by NASA through grants GO-09971, GO-10103, and GO-11210
from the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy (AURA), Inc.,
under NASA contract NAS5-26555.
---------------------------------------------------------
Title: The Asteroseismic Potential of Kepler: First Results for
Solar-Type Stars
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García,
R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki,
W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.;
Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt,
H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan,
G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.;
Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe,
R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic,
M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.;
Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.;
Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.;
Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi,
D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.;
Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.;
Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss,
L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev,
A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.;
Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes,
R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.;
Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre,
V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.;
Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A.
2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C
We present preliminary asteroseismic results from Kepler on three G-type
stars. The observations, made at one-minute cadence during the first
33.5 days of science operations, reveal high signal-to-noise solar-like
oscillation spectra in all three stars: about 20 modes of oscillation
may be clearly distinguished in each star. We discuss the appearance of
the oscillation spectra, use the frequencies and frequency separations
to provide first results on the radii, masses, and ages of the stars,
and comment in the light of these results on prospects for inference
on other solar-type stars that Kepler will observe.
---------------------------------------------------------
Title: Calibration of an Astrophysical Spectrograph with an Astro-comb
Authors: Phillips, David F.; Glenday, Alex; Li, Chih-Hao; Cramer,
Claire; Korzennik, Sylvain; Noah Chang, Guoqing; Chen, Li-Jin;
Benedick, Andrew; Kaertner, Franz X.; Sasselov, Dimitar; Szentgyorgyi,
Andrew; Walsworth, Ronald L.
2010APS..DMP.E1050P Altcode:
Searches for extrasolar planets using the periodic Doppler shift of
stellar lines are approaching Earth-like planet sensitivity. To find
a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude
improvement in state-of-the-art radial velocity spectroscopy is
necessary. An astro-comb, the combination of an ocatve-spanning laser
frequency comb with a Fabry-Perot cavity, producing evenly spaced
frequency markers with the potential for large wavelength coverage
is a promising avenue towards improved wavelength calibration. Here
we demonstrate the calibration of a high-resolution astrophysical
spectrograph below the 1 m/s level in the 800-900 nm spectral band
using an octave-spanning Ti:Sapphire laser and an ultra-low dispersion
Fabry-Perot filter cavity adjusted for a mode spacing of approximately
31 GHz. Modeling of spectrograph response function and overall system
stability and reproducibility will be described.
---------------------------------------------------------
Title: Laboratory Demonstration of a Green Astro-comb
Authors: Li, Chih-Hao; Glenday, Alex; Phillips, David F.; Korzennik,
Sylvain; Noah Chang, Guoqing; Benedick, Andrew; Chen, Li-Jin; Kaertner,
Franz X.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald
2010APS..DMP.E1049L Altcode:
Searches for extrasolar planets using the periodic Doppler
shift of stellar lines are approaching Earth-like planet
sensitivity. Astro-combs, a combination of an octave spanning
femtosecond laser and a mode-filtering cavity provide a likely route
to increased calibration precision and accuracy. Initial astro-comb
demonstrations have been performed in the near infrared where broadband
lasers are available. Here we present initial laboratory results on a
“green” astro-comb providing approximately 50 nm of stable astro-comb
light centered near 550 nm. Light from a 1 GHz, octave-spanning
Ti:Sapphire laser is broadened in a photonic crystal fiber optimized
to produce light in the green. This 1 GHz spaced green light is then
filtered to roughly 30 GHz mode spacing via a Fabry-Perot cavity with
ultra-low dispersion mirrors. Current progress on the characterization
of this green astro-comb will be presented.
---------------------------------------------------------
Title: On the Frequency of Gas Giant Planets in the Metal-Poor Regime
Authors: Sozzetti, A.; Latham, D. W.; Torres, G.; Carney, B. W.;
Laird, J. B.; Stefanik, R. P.; Boss, A. P.; Korzennik, S.
2010IAUS..265..416S Altcode:
We present an analysis of three years of precision radial velocity
measurements of 160 metal-poor stars observed with Keck/HIRES. We report
on variability and long-term velocity trends for each star in our
sample. We identify several long-term, low-amplitude radial-velocity
variables worthy of follow-up with direct imaging techniques. We
place lower limits on the detectable companion mass as a function of
orbital period. None of the stars in our sample exhibits radial-velocity
variations compatible with the presence of Jovian planets with periods
shorter than the survey duration (3 yr). The resulting average frequency
of gas giants orbiting metal-poor dwarfs with -2.0≤[Fe/H]≤ -0.6
is f<SUB>p</SUB> < 0.67%. By combining our dataset with the Fischer
& Valenti (2005) uniform sample, we confirm that the likelihood of
a star to harbor a planet more massive than Jupiter within 2 AU is a
steeply rising function of the host's metallicity. However, the data
for stars with -1.0≤[Fe/H]≤ 0.0 are compatible, in a statistical
sense, with a constant occurrence rate f<SUB>p</SUB>≃1%. Our results
usefully inform theoretical studies of the process of giant planet
formation across two orders of magnitude in metallicity.
---------------------------------------------------------
Title: The Keck metal-poor planet search . On the frequency of gas
giant planets in the metal-poor regime
Authors: Sozzetti, A.; Latham, D. W.; Torres, G.; Boss, A. P.; Carney,
B. W.; Korzennik, S. G.; Laird, J. B.; Stefanik, R. P.
2010MSAIS..14..173S Altcode:
We present an analysis of three years of precision radial velocity
measurements of 160 metal-poor stars observed with Keck/HIRES. We report
on variability and long-term velocity trends for each star in our
sample. We identify several long-term, low-amplitude radial-velocity
variables worthy of follow-up with direct imaging techniques. We
place lower limits on the detectable companion mass as a function of
orbital period. None of the stars in our sample exhibits radial-velocity
variations compatible with the presence of Jovian planets with periods
shorter than the survey duration (3 yr). The resulting average frequency
of gas giants orbiting metal-poor dwarfs with -2.0≲[Fe/H]≲ -0.6
is f_p<0.67%. By combining our dataset with the Fischer &
Valenti (2005) uniform sample, we confirm that the likelihood of a
star to harbor a planet more massive than Jupiter within 2 AU is a
steeply rising function of the host's metallicity. However, the data
for stars with -1.0≲[Fe/H]≲ 0.0 are compatible, in a statistical
sense, with a constant occurrence rate f_p≃1%. Our results usefully
inform theoretical studies of the process of giant planet formation
across two orders of magnitude in metallicity.
---------------------------------------------------------
Title: Search for Structural Variations of the Near-Surface Layers
of the Sun during the Solar Cycle
Authors: Rabello-Soares, M. C.; Korzennik, S. G.
2009ASPC..416..277R Altcode:
Acoustic mode frequencies, with degree up to 900, observed by Michelson
Doppler Imager (MDI) from 1995 to 2005 were analyzed to determine if
there are any changes in the near-surface layers of the solar structure
with the solar cycle. The inclusion of high-degree modes allowed the
determination of the sound speed up to 0.993 R<SUB>sun</SUB>.
---------------------------------------------------------
Title: On the Dependence of our Inferences about the Solar Internal
Rotation on the Frequency Fitting Methodology
Authors: Korzennik, S. G.; Eff-Darwich, A.
2009ASPC..416..221K Altcode:
We show how inferences of the solar internal rotation rate depend on
different aspects of the mode fitting procedure. We study the stability
of the rotation rate and its variation with time through inversions
of frequency splittings data sets computed from fitting 364, 728 and
2088-day long Michelson Doppler Imager (MDI) time series, 72-day long
MDI time series and 108-day long Global Oscillation Network Group
(GONG) time series with different fitting methodologies and acquired
during Cycle 23. <P />The frequency splittings obtained from MDI and
GONG time-series through different fitting techniques are inverted to
analyze the effect of the fitting methodology on the inferred rotation
rate. In particular, we present inversions based on either individual
frequencies (as derived by the fitting technique developed by Korzennik
2005), or frequency splittings parametrized in terms of Clebsh-Gordon
(CG) coefficients. We present the impact of using either individual
frequencies or CG coefficients on the inversion results.
---------------------------------------------------------
Title: Impact of Low-Frequency p Modes on the Inversions of the
Internal Rotation of the Sun
Authors: Salabert, D.; Eff-Darwich, A.; Howe, R.; Korzennik, S. G.
2009ASPC..416..253S Altcode: 2008arXiv0811.1745S
We used the m-averaged spectrum technique ("collapsogram") to
extract the low-frequency solar p-mode parameters of low- and
intermediate-angular degrees (l ≤ 35) in long time series of Global
Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI)
observations. Rotational splittings and central frequencies have been
measured down to ≍850 μHz, including predicted modes which have
not been measured previously. Both GONG and MDI frequency splitting
data sets were numerically inverted to extract the internal solar
rotation rate. The impact of the very low-frequency observables and
the differences between GONG and MDI data sets on the inversion results
are also analyzed.
---------------------------------------------------------
Title: A Tunable Laser System for the Wavelength Calibration of
Multi-Object Spectrographs
Authors: Cramer, Claire; Brown, S.; Dupree, A. K.; Korzennik, S. G.;
Lykke, K. R.; Szentgyorgyi, A.
2009AAS...21361105C Altcode:
High-resolution spectroscopy is an essential technique in the search
for extra-solar earths, time variation of fundamental constants, and
dark matter in the galactic halo. A problem that must be addressed
in order to improve upon existing measurements is the wavelength
calibration of multi-object echelle spectrographs (MOS). Precise MOS
wavelength calibration is largely an unsolved problem. Optimally,
calibration light should illuminate the spectrograph pupil with
the same intensity distribution as a science object. This is best
achieved by making the path of the calibration light and star light
follow the same optical path. For a single object spectrograph, this
is straightforward. The difficulty arises when hundreds of apertures
(fibers) located in different places in the focal plane must be
calibrated in a reasonable amount of time. The ThAr calibration
lamps typically used for high-resolution spectroscopy are too faint
to reflect from a dome screen that acts as a proxy for an infinite
conjugate, and shining lamp light directly onto the focal plane
leads to position- and fiber-dependent shifts and distortions of
the wavelength scale. We present preliminary results from a scheme
we have deployed at the MMT 6.5m telescope to wavelength calibrate
the Hectochelle MOS with tunable lasers. Narrowband tunable lasers
are bright enough to compensate dome screen attenuation, and can be
scanned over a typical MOS free spectral range of 10 nm in under a
minute. We record the wavelengths in each laser calibration scan with
a commercial scanning Michelson interferometer, which gives a precision
and accuracy of 50 m/s for each line, comparable to the photon-limited
Doppler precision of a typical multi-object echelle spectrograph. In
this poster, we describe the tunable laser system, compare wavelength
solutions generated from the tunable laser system and ThAr lamps,
and present examples of astronomical data calibrated with the laser.
---------------------------------------------------------
Title: What Can We Learn on the Structure and the Dynamics of the
Solar Core with g Modes?
Authors: Mathur, S.; Ballot, J.; Eff-Darwich, A.; García, R. A.;
Jiménez-Reyes, S. J.; Korzennik, S. G.; Turck-Chièze, S.
2009ASPC..416..215M Altcode: 2008arXiv0810.2031M
The detection of the signature of dipole gravity modes has opened the
path to study the solar inner radiative zone. Indeed, g modes should
be the best probes to infer the properties of the solar nuclear core
that represents more than half of the total mass of the Sun. Concerning
the dynamics of the solar core, we can study how future observations
of individual g modes could enhance our knowledge of the rotation
profile of the deep radiative zone. Applying inversions on a set of
real p-mode splittings coupled with either one or several g modes,
we have checked the improvement of the inferred rotation profile when
different error bars are considered for the g modes. Moreover, using a
new methodology based on the analysis of the almost constant separation
of the dipole gravity modes, we can introduce new constraints on solar
models. For that purpose, we can compare g-mode predictions computed
from several models including different physical inputs with the g-mode
asymptotic signature detected in Global Oscillations at Low Frequencies
(GOLF) data and calculate the correlation. This work shows the great
consistency between the signature of dipole gravity modes and our
knowledge of p-modes: incompatibility of data with a present standard
model including the Asplund composition.
---------------------------------------------------------
Title: Results from Fitting Long and Very-Long MDI Time-Series at
Low and Intermediate Degrees
Authors: Korzennik, S. G.
2009ASPC..416..315K Altcode:
I present results from fitting long and very-long MDI time series of
spherical harmonics coefficients, at low and intermediate degrees. The
fitting methodology used, initially developed for very-long time series,
incorporates several key aspects not present in the "production"
Michelson Doppler Imager (MDI) (or Global Oscillation Network Group
(GONG)) fitting methodologies. The fitting has since been extended to
higher degrees and applied to shorter time series, resulting in fitting
2088-day long, as well as, 728, 364 and 182-day long time series,
covering nearly 11 years of observations. The 2088-day long time
series has been fitting up to l=125. Nine overlapping 728-day long
time series have been fitted up to l=95, while nineteen and thirty
nine overlapping 364 and 182-day long time series, respectively,
have been fitted up to l=47.
---------------------------------------------------------
Title: A Keck HIRES Doppler Search for Planets Orbiting Metal-Poor
Dwarfs. II. On the Frequency of Giant Planets in the Metal-Poor Regime
Authors: Sozzetti, Alessandro; Torres, Guillermo; Latham, David W.;
Stefanik, Robert P.; Korzennik, Sylvain G.; Boss, Alan P.; Carney,
Bruce W.; Laird, John B.
2009ApJ...697..544S Altcode: 2009arXiv0902.4802S
We present an analysis of three years of precision radial velocity (RV)
measurements of 160 metal-poor stars observed with HIRES on the Keck 1
telescope. We report on variability and long-term velocity trends for
each star in our sample. We identify several long-term, low-amplitude RV
variables worthy of followup with direct imaging techniques. We place
lower limits on the detectable companion mass as a function of orbital
period. Our survey would have detected, with a 99.5% confidence level,
over 95% of all companions on low-eccentricity orbits with velocity
semiamplitude K gsim 100 m s<SUP>-1</SUP>, or M<SUB>p</SUB> sin i
gsim 3.0 M <SUB>J</SUB>(P/yr)<SUP>(1/3)</SUP>, for orbital periods
P lsim 3 yr. None of the stars in our sample exhibits RV variations
compatible with the presence of Jovian planets with periods shorter
than the survey duration. The resulting average frequency of gas giants
orbiting metal-poor dwarfs with -2.0lsim[Fe/H]lsim-0.6 is f<SUB>p</SUB>
< 0.67% (at the 1σ confidence level). We examine the implications
of this null result in the context of the observed correlation between
the rate of occurrence of giant planets and the metallicity of their
main-sequence solar-type stellar hosts. By combining our data set with
the Fischer & Valenti (2005) uniform sample, we confirm that the
likelihood of a star to harbor a planet more massive than Jupiter within
2 AU is a steeply rising function of the host's metallicity. However,
the data for stars with -1.0lsim[Fe/H]lsim0.0 are compatible, in a
statistical sense, with a constant occurrence rate f<SUB>p</SUB> sime
1%. Our results can usefully inform theoretical studies of the process
of giant-planet formation across two orders of magnitude in metallicity.
---------------------------------------------------------
Title: A New Spectroscopic and Photometric Analysis of the Transiting
Planet Systems TrES-3 and TrES-4
Authors: Sozzetti, Alessandro; Torres, Guillermo; Charbonneau, David;
Winn, Joshua N.; Korzennik, Sylvain G.; Holman, Matthew J.; Latham,
David W.; Laird, John B.; Fernandez, José; O'Donovan, Francis T.;
Mandushev, Georgi; Dunham, Edward; Everett, Mark E.; Esquerdo,
Gilbert A.; Rabus, Markus; Belmonte, Juan A.; Deeg, Hans J.; Brown,
Timothy N.; Hidas, Márton G.; Baliber, Nairn
2009ApJ...691.1145S Altcode: 2008arXiv0809.4589S
We report new spectroscopic and photometric observations of the
parent stars of the recently discovered transiting planets TrES-3
and TrES-4. A detailed abundance analysis based on high-resolution
spectra yields [Fe/H] = -0.19 ± 0.08, T <SUB>eff</SUB> = 5650 ± 75
K, and log g = 4.4 ± 0.1 for TrES-3, and [Fe/H] = +0.14 ± 0.09, T
<SUB>eff</SUB> = 6200 ± 75 K, and log g = 4.0 ± 0.1 for TrES-4. The
accuracy of the effective temperatures is supported by a number of
independent consistency checks. The spectroscopic orbital solution
for TrES-3 is improved with our new radial velocity measurements of
that system, as are the light-curve parameters for both systems based
on newly acquired photometry for TrES-3 and a reanalysis of existing
photometry for TrES-4. We have redetermined the stellar parameters
taking advantage of the strong constraint provided by the light curves
in the form of the normalized separation a/R <SUB>sstarf</SUB> (related
to the stellar density) in conjunction with our new temperatures and
metallicities. The masses and radii we derive are M <SUB>sstarf</SUB>
= 0.928<SUP>+0.028</SUP> <SUB>-0.048</SUB> M <SUB>sun</SUB>,
R <SUB>sstarf</SUB> = 0.829<SUP>+0.015</SUP> <SUB>-0.022</SUB> R
<SUB>sun</SUB>, and M <SUB>sstarf</SUB> = 1.404<SUP>+0.066</SUP>
<SUB>-0.134</SUB> M <SUB>sun</SUB>, R <SUB>sstarf</SUB> =
1.846<SUP>+0.096</SUP> <SUB>-0.087</SUB> R <SUB>sun</SUB> for TrES-3
and TrES-4, respectively. With these revised stellar parameters,
we obtain improved values for the planetary masses and radii. We
find M<SUB>p</SUB> = 1.910<SUP>+0.075</SUP> <SUB>-0.080</SUB> M
<SUB>Jup</SUB>, R<SUB>p</SUB> = 1.336<SUP>+0.031</SUP> <SUB>-0.036</SUB>
R <SUB>Jup</SUB> for TrES-3, and M<SUB>p</SUB> = 0.925 ± 0.082 M
<SUB>Jup</SUB>, R<SUB>p</SUB> = 1.783<SUP>+0.093</SUP> <SUB>-0.086</SUB>
R <SUB>Jup</SUB> for TrES-4. We confirm TrES-4 as the planet with the
largest radius among the currently known transiting hot Jupiters.
---------------------------------------------------------
Title: YAOPBM—II: extension to higher degrees and to shorter
time series
Authors: Korzennik, S. G.
2008JPhCS.118a2082K Altcode:
In 2005, I presented a new fitting methodology (Yet AnOther Peak Bagging
Method -YAOPBM), derived for very-long time series (2088-day-long)
and applied it to low degree modes, ι <= 25. That very-long time
series was also sub-divided into shorter segments (728-day-long) that
were each fitted over the same range of degrees, to estimate changes
with solar activity levels. <P />I present here the extension of this
method in several 'directions': a) to substantially higher degrees
(ι <= 125); b) to shorter time series (364- and 182-day-long);
and c) to additional 728-day-long segments, covering now some 10 years
of observations. <P />I discuss issues with the fitting, namely the
leakage matrix, and the f- and p1 mode at very low frequencies, and
I present some of the characteristics of the observed temporal changes.
---------------------------------------------------------
Title: High degree modes & instrumental effects
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.
2008JPhCS.118a2027K Altcode:
Full-disk observations taken with the Michelson Doppler Imager (MDI)
on board the Solar and Heliospheric Observatory (SOHO) spacecraft, or
the upgraded Global Oscillations Network Group (GONG) instruments, have
enough spatial resolution to resolve modes up to ι = 1000 if not ι =
1500. The inclusion of such high-degree modes (i.e., ι <= 1000)
improves dramatically inferences near the surface. Unfortunately,
observational and instrumental effects cause the characterization
of high degree modes to be quite complicated. <P />Indeed, the
characteristics of the solar acoustic spectrum are such that, for a
given order, mode lifetimes get shorter and spatial leaks get closer
in frequency as the degree of a mode increases. A direct consequence
of this property is that individual modes are resolved only at low
and intermediate degrees. At high degrees the individual modes blend
into ridges and the power distribution of the ridge defines the
ridge central frequency, masking the underlying mode frequency. An
accurate model of the amplitude of the peaks that contribute to the
ridge power distribution is needed to recover the underlying mode
frequency from fitting the ridge. <P />We present a detailed discussion
of the modeling of the ridge power distribution, and the contribution
of the various observational and instrumental effects on the spatial
leakage, in the context of the MDI instrument. We have constructed a
physically motivated model (rather than an ad hoc correction scheme)
that results in a methodology that can produce unbiased estimates of
high-degree modes. This requires that the instrumental characteristics
are well understood, a task that has turned out to pose a major
challenge. <P />We also present our latest results, where most of the
known instrumental and observational effects that affect specifically
high-degree modes were removed. These new results allow us to focus
our attention on changes with solar activity. <P />Finally, we present
variations of mode frequencies resulting from solar activity over
most of solar cycle 23. We present the correlation of medium and high
degree modes with different solar indices. Our results confirm that
the frequency shift scaled by the relative mode inertia is a function
of frequency alone and follows a simple power law.
---------------------------------------------------------
Title: Analysis of MDI High-Degree Mode Frequencies and their
Rotational Splittings
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2008SoPh..251..197R Altcode: 2008arXiv0808.2838R; 2008SoPh..tmp..133R
We present a detailed analysis of solar acoustic mode frequencies and
their rotational splittings for modes with degree up to 900. They were
obtained by applying spherical harmonic decomposition to full-disk
solar images observed by the Michelson Doppler Imager onboard the
Solar and Heliospheric Observatory spacecraft. Global helioseismology
analysis of high-degree modes is complicated by the fact that the
individual modes cannot be isolated, which has limited so far the use
of high-degree data for structure inversion of the near-surface layers
(r>0.97R<SUB>⊙</SUB>). In this work, we took great care to recover
the actual mode characteristics using a physically motivated model
which included a complete leakage matrix. We included in our analysis
the following instrumental characteristics: the correct instantaneous
image scale, the radial and non-radial image distortions, the effective
position angle of the solar rotation axis, and a correction to the
Carrington elements. We also present variations of the mode frequencies
caused by the solar activity cycle. We have analyzed seven observational
periods from 1999 to 2005 and correlated their frequency shift with four
different solar indices. The frequency shift scaled by the relative mode
inertia is a function of frequency alone and follows a simple power law,
where the exponent obtained for the p modes is twice the value obtained
for the f modes. The different solar indices present the same result.
---------------------------------------------------------
Title: Influence of Low-Degree High-Order p-Mode Splittings on the
Solar Rotation Profile
Authors: García, R. A.; Mathur, S.; Ballot, J.; Eff-Darwich, A.;
Jiménez-Reyes, S. J.; Korzennik, S. G.
2008SoPh..251..119G Altcode: 2008SoPh..tmp...43G; 2008arXiv0802.1510G
The solar rotation profile is well constrained down to about
0.25R<SUB>⊙</SUB> thanks to the study of acoustic modes. Since
the radius of the inner turning point of a resonant acoustic mode is
inversely proportional to the ratio of its frequency to its degree,
only the low-degree p modes reach the core. The higher the order of
these modes, the deeper they penetrate into the Sun and thus they carry
more diagnostic information on the inner regions. Unfortunately, the
estimates of frequency splittings at high frequency from Sun-as-a-star
measurements have higher observational errors because of mode blending,
resulting in weaker constraints on the rotation profile in the inner
core. Therefore inversions for the solar internal rotation use only
modes below 2.4 mHz for ℓ≤3. In the work presented here, we used
an 11.5-year-long time series to compute the rotational frequency
splittings for modes ℓ≤3 using velocities measured with the GOLF
instrument. We carried out a theoretical study of the influence of
the low-degree modes in the region from 2 to 3.5 mHz on the inferred
rotation profile as a function of their error bars.
---------------------------------------------------------
Title: Deploying comb and tunable lasers to enable precision radial
velocity surveys
Authors: Szentgyorgyi, Andrew; Cramer, Claire; Benedick, Andrew;
Glenday, Alexander G.; Kaertner, Franz X.; Korzennik, Sylvain; Li,
Chih-Hao; Ordway, Mark P.; Phillips, David F.; Sasselov, Dimitar;
Walsworth, Ronald L.
2008SPIE.7014E..1WS Altcode: 2008SPIE.7014E..64S
We describe recent progress toward developing optical frequency laser
combs and tunable laser to the problem of more precise calibration of
high dispersion astronomical spectra, thus permitting radial velocity
determinations in the few cm/sec regime. We describe two programs in
progress to calibrate both a cross dispersed echelle spectrograph with
a laser comb and to calibrate a multiobject echelle spectrograph with
a tunable laser.
---------------------------------------------------------
Title: Analysis of the Sensitivity of Solar Rotation to Helioseismic
Data from GONG, GOLF, and MDI Observations
Authors: Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S. J.;
García, R. A.
2008ApJ...679.1636E Altcode: 2008arXiv0802.3604E
Accurate determination of the rotation rate in the radiative zone of
the Sun from helioseismic observations requires rotational frequency
splittings of exceptional quality as well as reliable inversion
techniques. Here we present inferences based on mode parameters
calculated from 2088 day MDI, GONG, and GOLF time series that were
fitted to estimate very low frequency rotational splittings (ν <
1.7 mHz). These low-frequency modes provide data of exceptional quality,
since the width of the mode peaks is much smaller than the rotational
splitting, and hence it is much easier to separate the rotational
splittings from the effects caused by the finite lifetime and the
stochastic excitation of the modes. We have also implemented a new
inversion methodology that allows us to infer the rotation rate of the
radiative interior from mode sets that span l = 1 to 25. Our results
are compatible with the Sun rotating like a rigid solid in most of the
radiative zone, and slowing down in the core (r/R<SUB>⊙</SUB> <
0.2). A resolution analysis of the inversion was carried out for the
solar rotation inverse problem. This analysis effectively establishes a
direct relationship between the mode set included in the inversion and
the sensitivity and information content of the resulting inferences. We
show that such an approach allows us to determine the effect of adding
low-frequency and low-degree p-modes, high-frequency and low-degree
p-modes, and some g-modes on the derived rotation rate in the solar
radiative zone, and in particular the solar core. We conclude that the
level of uncertainty that is needed to infer the dynamical conditions
in the core when only p-modes are included is unlikely to be reached
in the near future, and hence sustained efforts are needed toward the
detection and characterization of g-modes.
---------------------------------------------------------
Title: YAOPBM - yet another peak bagging method
Authors: Korzennik, S. G.
2008AN....329..453K Altcode:
I present and discuss the fitting methodology I developed for very-long
time series (2088-day-long). This new method was first used to fit
low degree modes, ℓ ≤25. That time series was also sub-divided in
somewhat shorter segments (728-day-long) and also fitted for these low
degrees, in order to measure changes with the solar activity level. I
have recently extended the fitting in several “directions”: 1) to
substantially higher degrees (ℓ ≤125), 2) to shorter time series
(364- and 182-day-long), and, 3) to additional 728-day-long segments,
covering now some 10 years of observations. I present and discuss
issues related to this expansion, namely problems at low frequencies
affecting the f and p_1 modes, and the inadequacy of the leakage matrix
at higher degrees. I also present some of the characteristics of the
observed temporal changes in the resulting frequencies.
---------------------------------------------------------
Title: Detection and temporal coherence of p-modes below 1.4 mHz
Authors: Eff-Darwich, A.; Régulo, C.; Korzennik, S. G.; Pérez
Hernández, F.; Roca Cortés, T.
2008AN....329..470E Altcode:
Data collected recently by the helioseismic experiments aboard the
SOHO spacecraft have allowed the detection of low degree p-modes
with increasingly lower order n. In particular, the GOLF experiment
is currently able to unambiguously identify low degree modes with
frequencies as low as 1.3 mHz. The detection of p-modes with very low
frequency ({i.e.}, low n), is difficult due to the low signal-to-noise
ratio in this spectral region and its contamination by solar signals
that are not of acoustic origin. To address this problem without using
any theoretical a priory, we propose a methodology that relies only
on the inversion of observed values to define a spectral window for
the expected locations of these low frequency modes. The application
of this method to 2920-day-long GOLF observations is presented and
its results discussed.
---------------------------------------------------------
Title: Analysis of MDI high-degree solar-p mode parameters
Authors: Rabello-Soares, M.; Korzennik, S.; Schou, J.
2008AGUSMSP21A..03R Altcode:
We present a detailed analysis of solar acoustic mode parameters for
modes with degree up to 900. They were obtained by applying spherical
harmonic decomposition to full-disk solar images observed by the
Michelson Doppler Imager (MDI) on board the Solar and Heliospheric
Observatory (SOHO) spacecraft. We have analyzed seven observational
periods (2-3 months long) from 1999 to 2005. A physically motivated
model including a complete leakage matrix was used to recover the
actual high-degree mode characteristics.
---------------------------------------------------------
Title: Variations of the solar acoustic high-degree mode frequencies
over solar cycle 23
Authors: Rabello-Soares, M. C.; Korzennik, Sylvain G.; Schou, J.
2008AdSpR..41..861R Altcode: 2007arXiv0712.3608R
Using full-disk observations obtained with the Michelson Doppler Imager
(MDI) on board the Solar and Heliospheric Observatory (SOHO) spacecraft,
we present variations of the solar acoustic mode frequencies caused by
the solar activity cycle. High-degree (100 < ℓ < 900) solar
acoustic modes were analyzed using global helioseismology analysis
techniques over most of solar cycle 23. We followed the methodology
described in details in [Korzennik, S.G., Rabello-Soares, M.C., Schou,
J. On the determination of Michelson Doppler Imager high-degree mode
frequencies. ApJ 602, 481 515, 2004] to infer unbiased estimates
of high-degree mode parameters ([see also Rabello-Soares, M.C.,
Korzennik, S.G., Schou, J. High-degree mode frequencies: changes
with solar cycle. ESA SP-624, 2006]). We have removed most of the
known instrumental and observational effects that affect specifically
high-degree modes. We show that the high-degree changes are in good
agreement with the medium-degree results, except for years when the
instrument was highly defocused. We analyzed and discuss the effect
of defocusing on high-degree estimation. Our results for high-degree
modes confirm that the frequency shift scaled by the relative mode
inertia is a function of frequency and it is independent of degree.
---------------------------------------------------------
Title: Current status of asteroseismology
Authors: Korzennik, Sylvain G.
2008AdSpR..41..897K Altcode:
Asteroseismology, the extension of helioseismology to stars solar-alike
or not has been an exciting and active field of research for about
two decades. While over that period helioseismology has had great
success in revealing the solar structure and its dynamics, progress in
asteroseismology has been hampered by the observational challenge to
carry out, primarily from the ground, high precision measurements on
unresolved objects with a substantially lower flux. Over the past years,
the field has seen a new golden age, primarily driven by observational
advances and opportunities. With the June 2003 launch of the MOST
spacecraft and the highly anticipated December 2006 launch of the
COROT mission, we have truly entered the space-based observational
era of asteroseismology. The ambitious vision mission like the Stellar
Imager might even one day allow us to spatially resolve oscillations on
not too distant stars. At the same time ground-based observations have
recently seen a quantum leap in precision thanks to the synergy between
asteroseismology and exo-planet detection which both rely primarily
on precise radial velocity techniques. The diagnostic potential of
asteroseismology is clearly demonstrated by the wealth of inferences
collected from helioseismology. Nevertheless the current status of
observations, their interpretations and their implications for our
models remain hotly debated subjects. I review the status of the field,
with an emphasis on solar-like targets, while incorporating my own
healthy scepticism and observational bias.
---------------------------------------------------------
Title: Study of High-Performance Coronagraphic Techniques
Authors: Tolls, Volker; Aziz, M. J.; Gonsalves, R. A.; Korzennik,
S. G.; Labeyrie, A.; Lyon, R. G.; Melnick, G. J.; Somerstein, S.;
Vasudevan, G.; Woodruff, R. A.
2007AAS...20925508T Altcode: 2007BAAS...39..278T
We will provide a progress report about our study of high-performance
coronagraphic techniques. At SAO we have set up a testbed to test
coronagraphic masks and to demonstrate Labeyrie's multi-step speckle
reduction technique. This technique expands the general concept of a
coronagraph by incorporating a speckle corrector (phase or amplitude)
and second occulter for speckle light suppression. The testbed consists
of a coronagraph with high precision optics (2 inch spherical mirrors
with lambda/1000 surface quality), lasers simulating the host star
and the planet, and a single Labeyrie correction stage with a MEMS
deformable mirror (DM) for the phase correction. The correction function
is derived from images taken in- and slightly out-of-focus using phase
diversity. The testbed is operational awaiting coronagraphic masks. The
testbed control software for operating the CCD camera, the translation
stage that moves the camera in- and out-of-focus, the wavefront recovery
(phase diversity) module, and DM control is under development. <P />We
are also developing coronagraphic masks in collaboration with Harvard
University and Lockheed Martin Corp. (LMCO). The development at Harvard
utilizes a focused ion beam system to mill masks out of absorber
material and the LMCO approach uses patterns of dots to achieve the
desired mask performance. We will present results of both investigations
including test results from the first generation of LMCO masks obtained
with our high-precision mask scanner. <P />This work was supported by
NASA through grant NNG04GC57G, through SAO IR&D funding, and by
Harvard University through the Research Experience for Undergraduate
Program of Harvard's Materials Science and Engineering Center. Central
facilities were provided by Harvard's Center for Nanoscale Systems.
---------------------------------------------------------
Title: High-degree Mode Frequencies Using Global Helioseismology
Analysis Of MDI Observations And Their Variation With Solar Cycle.
Authors: Rabello-Soares, M. Cristina; Korzennik, S. G.; Schou, J.
2007AAS...210.2215R Altcode: 2007BAAS...39..126R
Using full-disk observations obtained with the Michelson Doppler
Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO)
spacecraft, we present solar acoustic mode frequencies and their
rotational splitting coefficients for modes with degree up to 900
determined using global helioseismology analysis. Most of the known
instrumental and observational effects that affect specifically the
high-degree modes have been removed. <P />The structural and dynamical
properties of the near-surface layers of the Sun was analyzed through
the study of: (a) the difference between the observed and theoretical
frequencies; and (b) the solar rotation at different latitudes estimated
using a simple analytical method. <P />We also present variations of
the mode frequencies resulting from solar activity over most of solar
cycle 23. We have studied the correlation of medium and high degree
modes with four different solar indices. Our results confirm that the
frequency shift scaled by the relative mode inertia is a function of
frequency alone and follows a simple power law.
---------------------------------------------------------
Title: The cookie cutter test for time-distance tomography of
active regions
Authors: Korzennik, S. G.
2006ESASP.624E..60K Altcode: 2006soho...18E..60K
No abstract at ADS
---------------------------------------------------------
Title: High-degree mode frequencies: changes with solar cycle
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2006ESASP.624E..71R Altcode: 2006soho...18E..71R
No abstract at ADS
---------------------------------------------------------
Title: On the direct determination of sensitivity, resolution
and information content of helioseismic data application to the
inversion of the solar core rotation rate
Authors: Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S. J.;
García, R. A.
2006ESASP.624E..84E Altcode: 2006soho...18E..84E
No abstract at ADS
---------------------------------------------------------
Title: A Keck HIRES Doppler Search for Planets Orbiting Metal-Poor
Dwarfs. I. Testing Giant Planet Formation and Migration Scenarios
Authors: Sozzetti, Alessandro; Torres, Guillermo; Latham, David W.;
Carney, Bruce W.; Stefanik, Robert P.; Boss, Alan P.; Laird, John B.;
Korzennik, Sylvain G.
2006ApJ...649..428S Altcode: 2006astro.ph..5670S
We describe a high-precision Doppler search for giant planets orbiting a
well-defined sample of metal-poor dwarfs in the field. This experiment
constitutes a fundamental test of theoretical predictions, which
will help discriminate between proposed giant planet formation and
migration models. We present details of the survey, as well as an
overall assessment of the quality of our measurements, making use of
the results for stars that show no significant velocity variation.
---------------------------------------------------------
Title: The determination of global high-degree solar p-mode
parameters: challenges and new results
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2006IAUJD..17E...7R Altcode:
We review the challenges of estimating unbiased mode parameters for
global high-degree solar acoustic modes (100 < ℓ < 1000), with
emphasis on the importance of knowing the instrumental characteristics
and how they affect mode parameters determination. We present new
estimates of the global high-degree mode parameters resulting from
incorporating our best knowledge of the MDI instrument on board SOHO
and we also present their dependence with the solar cycle.
---------------------------------------------------------
Title: Study of coronagraphic techniques
Authors: Tolls, Volker; Aziz, Michael; Gonsalves, Robert A.; Korzennik,
Sylvain; Labeyrie, Antoine; Lyon, Richard; Melnick, Gary; Schlitz,
Ruth; Somerstein, Steve; Vasudevan, Gopal; Woodruff, Robert
2006SPIE.6265E..3KT Altcode: 2006SPIE.6265E.107T
Smithsonian Astrophysical Observatory (SAO) has set up a program to
study coronagraphic techniques. The program consists of the development
of new fabrication methods of occulter masks, characterization of the
manufactured masks, and application of the masks to study speckle
reduction technique. Our occulter mask fabrication development
utilizes a focused ion beam system to directly shape mask profiles
from absorber material. Initial milling trials show that we can shape
nearly Gaussian-shaped mask profiles. Part of this development is the
characterization of absorber materials, poly(methyl methacrylate) doped
with light-stable chromophores. For the characterization of the masks we
have built a mask scanner enabling us to scan the transmission function
of occulter masks. The real mask transmission profile is retrieved
applying the maximum entropy method to deconvolve the mask transmission
function from the beam profile of the test laser. Finally, our test
bed for studying coronagraphic techniques is nearing completion. The
optical setup is currently configured as a classical coronagraph and can
easily be re-configured for studying speckle reduction techniques. The
development of the test bed control software is under way. This paper
we will give an update of the status of the individual program elements.
---------------------------------------------------------
Title: Changes Of The Solar Acoustic High-degree Mode Frequencies
Over The Solar Cycle
Authors: Korzennik, Sylvain G.; Rabello-Soares, M. C.; Schou, J.
2006SPD....37.0508K Altcode: 2006BAAS...38..224K
Using full-disk observations obtained with the Michelson Doppler
Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO)
spacecraft, we present frequency and frequency splitting variations
of high-degree (100 < l < 1000) solar acoustic modes over the
solar cycle using global helioseismology analysis techniques. Since we
analyzed high-degree modes, we focus on properties of the near-surface
solar region. We have corrected for most of the known instrumental
effects that affect the characterization of high-degree modes using
the methodology described in Korzennik et al. (2004) as to estimate
unbiased high-degree mode frequencies.
---------------------------------------------------------
Title: Precise Radial Velocities with an Upgraded Advanced Fiber
Optic Echelle (AFOE)
Authors: Walters, M. A.; Korzennik, S. G.; Nisenson, P.; Henry, G. W.
2006AAS...20721108W Altcode:
The Advanced Fiber Optic Echelle (AFOE) has been used to make
precise radial velocity (PRV) observations for some 12 years. The
AFOE spectrograph was initially designed as a test-bed for PRV
techniques for astroseismology and planet detection, and tried
to provide both short term and long term stability. The resulting
trade-offs between spectral resolution, range, and coverage led to
a low efficiency design. In order to optimize PRVs obtained with
the iodine cell technique, the spectrograph was recently upgraded,
increasing the throughput and spectral coverage while reducing the
maximum resolution and range. The instrument was also moved from the
60" Tillinghast telescope at the Fred Lawrence Whipple Observatory,
located at Mt. Hopkins (AZ), to the 100" Hooker telescope, located at
Mt. Wilson (CA). We describe the instrumental changes required for the
spectrograph upgrade as well as those needed to accommodate the 100"
telescope. <P />As a result of the instrumental changes, the data
configuration has changed significantly. One would like to be able
to combine radial velocities obtained before the upgrade with those
obtained after, but one must take care in doing so. We describe the
methodology developed to allow us to use all of the PRVs together. We
also detail the precision achieved for this technique, along with
the inherent precision of the upgraded configuration. <P />Finally,
we present the radial velocities we have obtained for HD 185395 as
an interesting example of our studies. This triple system shows large
radial velocity variations. We compare the RV variations with observed
photometric changes, and present period analyses for both data sets. <P
/>This work is funded by NASA/JPL/SIM (subcontract no. 1259554).
---------------------------------------------------------
Title: Study of Coronagraphic Techniques
Authors: Tolls, Volker; Aziz, Michael; Gonsalves, Robert A.; Korzennik,
Sylvain; Labeyrie, Antoine; Lyon, Richard; Melnick, Gary; Somerstein,
Steve; Vasudevan, Gopal; Woodruff, Robert
2006dies.conf..457T Altcode: 2006IAUCo.200..457T
SAO has set up a testbed to study coronagraphic techniques, starting
with Labeyrie's multi-step speckle reduction technique. This technique
expands the general concept of a coronagraph by incorporating a
speckle corrector (phase and/or amplitude) in combination with
a second occulter for speckle light suppression. The correction
function is derived applying the phase diversity method on images
taken in focus and slightly out-of-focus. The occulter masks for the
testbed will initially be produced lithographically. However, in a
parallel program we are studying a new manufacturing method. This
method utilizes focussed ion beams and will directly mill the mask
shape into absorbing material deposited on a transparent substrate.
---------------------------------------------------------
Title: Variations of the solar acoustic high-degree mode parameters
over solar cycle 23
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2006cosp...36.2668R Altcode: 2006cosp.meet.2668R
The structural and dynamical properties of the Sun as well as the
excitation and damping of the solar acoustic modes change with the solar
cycle The first two manifest themselves as changes in the acoustic mode
frequencies and frequency splittings While the last two are observed
as changes in the mode amplitudes and lifetimes Using full-disk
observations obtained with the Michelson Doppler Imager MDI on board
the Solar and Heliospheric Observatory SOHO spacecraft we present
the amplitude width frequency and frequency splitting variations of
high-degree 100 l 1000 solar acoustic modes over most of solar cycle
23 using global helioseismology analysis techniques By looking at
high-degree modes we focus on the properties of the near-surface solar
region Following the methodology described in detail in Korzennik
et al 2004 we have removed the known instrumental and observational
effects that affect specifically high-degree modes as well as possible
to infer unbiased estimates of high-degree mode parameters
---------------------------------------------------------
Title: Study of Coronagraphic Techniques
Authors: Tolls, V.; Aziz, M.; Gonsalves, R.; Korzennik, S.; Labeyrie,
A.; Lyon, R.; Melnick, G.; Somerstein, S.; Vasudevan, G.; Woodruff, R.
2006amos.confE..16T Altcode:
Direct imaging of extra-solar planets is important for determining the
properties of individual planets, for studying multi-planet systems,
and for observing the spatial structure of debris disks. Obtaining
spectra of extra-solar planets enables us to constrain the composition
of planetary atmospheres and surfaces, their climates, and their
rotation periods. The techniques required to isolate and detect
an extra-solar planet next to its host star are quite challenging
and require significant improvement. SAO has set up a testbed to
study coronagraphic techniques, starting with Labeyrie's multi-step
speckle reduction technique. <P />The testbed consists of a classical
coronagraph with high precision optics. A telescope is simulated by
a 2 inch spherical mirror with lambda/1000 surface quality. The focal
length (1 meter) of this mirror was chosen that spherical aberration
can be neglected. A spatially-filtered laser simulates the host star
and an optional attenuated second laser simulates the planet. As an
additional option, we can incorporate apodizing masks to further improve
the performance of the coronagraph. The output signal of the coronagraph
is fed into a single Labeyrie correction stage. It consists of a mirror
to relay the light onto a 140-element MEMS deformable mirror (DM) for
the phase correction. The reflected light is then focused onto a second
occulter to block most of the speckle light and finally imaged onto
a CCD. The phase correction function and, thus, the drive signal for
the DM, is derived from images taken in and slightly out of the focal
plane using phase diversity. The expected performance improvement is
about one order of magnitude. An advanced concept utilizing phase and
amplitude correction promises an even higher degree of speckle light
suppression. <P />In addition, we are using the testbed to characterize
occulter masks developed in collaboration with Harvard University and
Lockheed Martin Corp. At Harvard University we are developing a method
to shape occulter masks out of dye-doped PMMA using a focused ion beam
(FIB) system. Using dye-doped PMMA should enable us to manufacture masks
working at any wavelength from the visible to the near-infrared. It
should also be possible to manufacture masks for the IR if a suitable
mask material can be found. In order to test the absorption profile of
these masks, we are developing a high-precision mask scanner. This work
is supported by NASA through grant NNG04GC57G, SAO IR&D funding,
NSF REU program and Harvard College.
---------------------------------------------------------
Title: Current status of asteroseismology
Authors: Korzennik, S.
2006cosp...36.2553K Altcode: 2006cosp.meet.2553K
Asteroseismology the extension of Helioseismology to stars - solar-alike
or not - has been an exciting and active filed of research for about
two decades While over that period helioseismology has had great
success in revealing the solar structure and it dynamics progress in
asteroseismology has been hampered by the observational challenge to
carry out from the ground high precision measurements on unresolved
objects with a substantial lower flux Over the past years the field
has seen a new golden age primarily driven by new observational
advances and opportunities On one hand with the launch of the MOST
spacecraft and the selection of the COROT mission we have truly entered
the space-based observational era of asteroseismology Moreover the
ambitious vision mission like the Stellar Imager might even one day
allow us to spatially resolve oscillations on not too distant stars On
the other hand ground-based observations have recently seen a quantum
leap in precision -- thanks in some way to the synergy of precise
radial velocity techniques aimed at exo-planet detection The wonderful
diagnostic potential of asteroseismology can clearly be derived from
the wealth of inferences collected from helioseismology Nevertheless
the current status of observations their interpretations and their
implication on our models remain hotly debated subjects I will review
the status of the field with an emphasis on solar-like targets while
incorporating my own healthy scepticism and observational bias
---------------------------------------------------------
Title: Study of Coronagraphic Techniques
Authors: Tolls, V.; Aziz, M. J.; Gonsalves, R. A.; Korzennik, S. G.;
Labeyrie, A.; Lyon, R. G.; Melnick, G. J.; Somerstein, S.; Vasudevan,
G.; Woodruff, R. A.
2005AAS...20719105T Altcode: 2005BAAS...37.1487T
Direct imaging of extra-solar planets is important for determining
the properties of individual planets and to study multi-planet
systems. Obtaining spectra of extra-solar planets enables us to
constrain the composition of planetary atmospheres and surfaces,
their climates, and their rotation periods. The techniques required
to isolate and detect an extra-solar planet next to its host star
are quite challenging and require significant improvement. SAO has
set up a testbed to study coronagraphic techniques, starting with
Labeyrie's multi-step speckle reduction technique. This technique
expands the general concept of a coronagraph by incorporating
a speckle corrector (phase or amplitude) and second occulter for
speckle light suppression. The testbed consists of a coronagraph
with high precision optics (2 inch spherical mirrors with lambda/1000
surface quality), lasers simulating the host star and the planet, and
a single Labeyrie correction stage with a MEMS deformable mirror for
the phase correction. The correction function is derived from images
taken in and slightly out of the focal using phase diversity. In
addition, we are using the testbed for occulter masks developed in
collaboration with Harvard University and Lockheed Martin Corp. This
testing is also supported by a high-precision mask scanner for mask
characterization. This work was supported by NASA through grant
NNG04GC57G.
---------------------------------------------------------
Title: Study of high-performance coronagraphic techniques
Authors: Tolls, Volker; Aziz, Michael; Gonsalves, Robert A.; Korzennik,
Sylvain; Labeyrie, Antoine; Lyon, Richard; Melnick, Gary; Somerstein,
Steve; Vasudevan, Gopal; Woodruff, Robert
2005SPIE.5905..494T Altcode:
SAO has set up a testbed to study coronagraphic techniques, starting
with Labeyrie's multi-step speckle reduction technique. This technique
expands the general concept of a coronagraph by incorporating a speckle
corrector (phase and/or amplitude) in combination with a second occulter
for speckle light suppression. Here we are describing the initial
testbed configuration. In addition, the testbed will be used to test
a new approach of the phase diversity method to retrieve the speckle
phase and amplitude. This method requires measurements of the speckle
pattern in the focal plane and slightly out-of-focus. Then we will
calculate a phase of the wave from which we can derive a correction
function for the speckle corrector. Furthermore we report results
from a parallel program which studies new manufacturing methods of
soft-edge occulter masks. Masks were manufactured using the spherical
caps method. Since the results were not satisfying we also investigated
the method of ion beam milling of masks. Here we will present the
outline of this method. Masks manufactured with both methods will be
fully characterized in our mask tester before their use in the testbed.
---------------------------------------------------------
Title: A Mode-Fitting Methodology Optimized for Very Long Helioseismic
Time Series
Authors: Korzennik, S. G.
2005ApJ...626..585K Altcode:
I describe and present the results of a newly developed fitting
methodology optimized for very long time series. The development of
this new methodology was motivated by the fact that we now have more
than half a decade of nearly uninterrupted observations by the Global
Oscillation Network Group (GONG) and the Michelson Doppler Imager
(MDI), with fill factors as high as 82.2% and 89.8%, respectively. It
was recently prompted by the availability of a 2088 day long time
series of spherical harmonic coefficients produced by the MDI team. The
fitting procedure uses an optimal sine multitaper spectral estimator,
with the number of tapers based on the mode line width, the complete
leakage matrix (i.e., horizontal as well as vertical components), and
an asymmetric mode profile to fit simultaneously all the azimuthal
orders with individually parameterized profiles. This method was
applied to 2088 day long time series of MDI and GONG observations,
as well as 728 day long subsets, and for spherical harmonic degrees
between 1 and 25. The values resulting from these fits are intercompared
(MDI vs. GONG) and compared to equivalent estimates from the MDI team
and the GONG project. I also compare the results from fitting the 728
day subsets to the result of the 2088 day time series. This comparison
shows the well-known change of frequencies with solar activity and how
it scales with a nearly constant pattern in frequency and m/l. This
comparison also shows some changes in the mode line width and the
constancy of the mode asymmetry.
---------------------------------------------------------
Title: New Steps Towards the Unbiased Characterization of High-Degree
Mode Frequencies
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2005AGUSMSP11B..08R Altcode:
Bias in the characterization of high-degree mode frequency results
from the blending of individual modes into ridges as mode lifetimes get
shorter and spatial leaks get closer in frequency at high degrees. To
recover the actual underlying mode frequency from fitting the ridge,
an accurate model of the amplitude of the peaks that contribute to the
ridge power distribution is crucial. Such a model requires that the
instrumental characteristics be very well understood and very precisely
measured. We here present new results from our continuing effort to
estimate unbiased high-degree mode frequencies using full-disk data
from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric
Observatory (SOHO). The methodology is based on the extensive analysis
presented in Korzennik et al (2004) - and will in turn be beneficial
to MDI, GONG and eventually HMI. The key improvement on our previous
work is the re-decomposition of the images onto spherical harmonic
component. This new spatial decomposition incorporates specific MDI
instrumental characteristics, like a more accurate plate scale, our
best model of the image distortion, the image orientation, etc... These
instrumental effects were introduced one at a time and their effect
carefully compared to the predictions of our model. As expected, by
including these corrections in the spatial decomposition, the residual
corrections that must be applied to the ridge frequency are reduced,
leading to a less biased frequency estimation.
---------------------------------------------------------
Title: Study of Coronagraphic Techniques
Authors: Tolls, V.; Nisenson, P.; Aziz, M. J.; Gonsalves, R. A.;
Korzennik, S. G.; Labeyrie, A.; Lyon, R. G.; Melnick, G. J.; Woodruff,
R. A.
2004AAS...20517104T Altcode: 2005BAAS...37..376T
Direct imaging of extra-solar planets is important for determining
the properties of individual planets and to study multi-planet
systems. Obtaining spectra of extra-solar planets enables us to
constrain the composition of planetary atmospheres and surfaces,
their climates, and their rotation periods. The techniques required to
isolate and detect an extra-solar planet next to its host star are quite
challenging and require significant improvement. SAO is setting up a
testbed to study coronagraphic techniques, starting with Labeyrie's
multi-step speckle reduction technique. This technique incorporates
a speckle phase corrector and second occulter for speckle light
suppression. The goal is to study this technique in the testbed for
its application in coronagraphic cameras. In addition, the testbed will
be used to characterize soft-edge occulters. Simulations of soft-edge
occulters with a Gaussian absorption profile show a promising reduction
of the flux in the core of the point spread function in coronagraphs. We
expect this to lead to a reduction in the inner working distance and
to an increase in contrast ratio compared to a Lyot coronagraph. The
occulters for the tests will be developed in Harvard's Department of
Engineering and Applied Sciences and by Lockheed-Martin Corp. This
poster will present the setup of SAO's testbed, simulations for all
developments, and first test results.
---------------------------------------------------------
Title: PCA Inversions for the Rotation of the Solar Radiative Interior
Authors: Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S.;
García, R. A.
2004ESASP.559..420E Altcode: 2004soho...14..420E
No abstract at ADS
---------------------------------------------------------
Title: a Mode Fitting Methodology Optimized for Very Long Time Series
Authors: Korzennik, S. G.
2004ESASP.559..524K Altcode: 2004soho...14..524K; 2004astro.ph..6470K
I describe and present the results of a newly developed fitting
methodology optimized for very long time series. The development of
this new methodology was motivated by the fact that we now have more
than half a decade of nearly uninterrupted observations by GONG and
MDI, with fill factors as high as 89.8% and 82.2% respectively. It was
recently prompted by the availability of a 2088-day-long time series of
spherical harmonic coefficients produced by the MDI team. The fitting
procedure uses an optimal sine-multi-taper spectral estimator --
whith the number of tapers based on the mode linewidth, the complete
leakage matrix (i.e., horizontal as well as vertical components),
and an asymmetric mode profile to fit simultaneously all the azimuthal
orders with individually parametrized profiles. This method was applied
to 2088-day-long time series of MDI and GONG observations, as well as
728-day-long subsets, and for spherical harmonic degrees between 1 and
25. The values resulting from these fits are inter-compared (MDI versus
GONG) and compared to equivalent estimates from the MDI team and the
GONG project. I also compare the results from fitting the 728-day-long
subsets to the result of the 2088-day-long time series. This comparison
shows the well known change of frequencies with solar activity --
and how it scales with a nearly constant pattern in frequency and
m/l. This comparison also shows some changes in the mode linewidth
and the constancy of the mode asymmetry.
---------------------------------------------------------
Title: On the Spatial Dependence of Low-Degree Solar p-Mode Frequency
Shifts from Full-Disk and Resolved-Sun Observations
Authors: Jiménez-Reyes, S. J.; García, R. A.; Chaplin, W. J.;
Korzennik, S. G.
2004ApJ...610L..65J Altcode:
We have analyzed low angular degree (low-l) solar p-mode frequency
shifts extracted from two types of observations, both made by
instruments on board the ESA/NASA Solar and Heliospheric Observatory
satellite during a period that covers the rising phase of activity,
cycle 23 (1995-2002). The first are full-disk (Sun-as-a-star) averages
made in Doppler velocity by the Global Oscillations at Low Frequency
spectrophotometer; the second are Doppler velocity observations made
with high spatial resolution by the Michelson Doppler Imager. We compare
the eigenfrequency shifts from both sets of data and find that they are
consistent at the level of precision of the observations. Furthermore,
the sizes of the shifts uncovered for different mode components are
found to scale in proportion to the corresponding spherical harmonic
components of the observed line-of-sight surface magnetic field, with
the sectoral mode components showing (as expected) the largest shifts.
---------------------------------------------------------
Title: About the rotation of the solar radiative interior
Authors: García, R. A.; Corbard, T.; Chaplin, W. J.; Couvidat, S.;
Eff-Darwich, A.; Jiménez-Reyes, S. J.; Korzennik, S. G.; Ballot,
J.; Boumier, P.; Fossat, E.; Henney, C. J.; Howe, R.; Lazrek, M.;
Lochard, J.; Pallé, P. L.; Turck-Chièze, S.
2004SoPh..220..269G Altcode:
In the modern era of helioseismology we have a wealth of high-quality
data available, e.g., more than 6 years of data collected by the various
instruments on board the SOHO mission, and an even more extensive
ground-based set of observations covering a full solar cycle. Thanks
to this effort a detailed picture of the internal rotation of the Sun
has been constructed. In this paper we present some of the actions
that should be done to improve our knowledge of the inner rotation
profile discussed during the workshop organized at Saclay on June 2003
on this topic. In particular we will concentrate on the extraction of
the rotational frequency splittings of low- and medium-degree modes
and their influence on the rotation of deeper layers. Furthermore,
for the first time a full set of individual |m|-component rotational
splittings is computed for modes ℓ≤4 and 1<ν<2 mHz, opening
new studies on the latitudinal dependence of the rotation rate in the
radiative interior. It will also be shown that these splittings have
the footprints of the differential rotation of the convective zone
which can be extremely useful to study the differential rotation of
other stars where only these low-degree modes will be available.
---------------------------------------------------------
Title: p-mode frequencies in solar-like stars. I. Procyon A
Authors: Martić, M.; Lebrun, J. -C.; Appourchaux, T.; Korzennik, S. G.
2004A&A...418..295M Altcode: 2004astro.ph..3035M
As a part of an on-going program to explore the signature of p-modes
in solar-like stars by means of high-resolution absorption line
spectroscopy, we have studied four stars (α CMi, η Cas A, ζ Her A
and β Vir). We present here new results from two-site observations of
Procyon A acquired over twelve nights in 1999. Oscillation frequencies
for l=1 and 0 (or 2) p-modes are detected in the power spectra of
these Doppler shift measurements. A frequency analysis points out the
difficulties of the classical asymptotic theory in representing the
p-mode spectrum of Procyon A. <P />Based on observations obtained at
the Observatoire de Haute-Provence (CNRS, France) and at the Whipple
Observatory (Arizona, USA).
---------------------------------------------------------
Title: On the Determination of Michelson Doppler Imager High-Degree
Mode Frequencies
Authors: Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.
2004ApJ...602..481K Altcode: 2002astro.ph..7371K
The characteristics of the solar acoustic spectrum are such that mode
lifetimes get shorter and spatial leaks get closer in frequency as
the degree of a mode increases for a given order. A direct consequence
of this property is that individual p-modes are resolved only at low
and intermediate degrees and that at high degrees individual modes
blend into ridges. Once modes have blended into ridges, the power
distribution of the ridge defines the ridge central frequency, and it
will mask the true underlying mode frequency. An accurate model of the
amplitude of the peaks that contribute to the ridge power distribution
is needed to recover the underlying mode frequency from fitting the
ridge. We present the results of fitting high-degree power ridges
(up to l=900) computed from several 2-3 month long time series of
full-disk observations taken with the Michelson Doppler Imager (MDI) on
board the Solar and Heliospheric Observatory between 1996 and 1999. We
also present a detailed discussion of the modeling of the ridge power
distribution, and the contribution of the various observational
and instrumental effects on the spatial leakage, in the context
of the MDI instrument. We have constructed a physically motivated
model (rather than some ad hoc correction scheme) that we believe
results in a methodology that can produce an unbiased determination
of high-degree modes once the instrumental characteristics are well
understood. Finally, we present preliminary estimates of changes in
high-degree mode parameters with epoch and thus solar activity level and
discuss their significance. These estimates are preliminary because they
rely on a simple-if not simplistic-ridge-to-mode correction scheme to
account for errors in the plate scale used for the spherical harmonic
decomposition. Such a correction scheme produced residual systematics
that, as we show, are not always constant with time. These cannot be
properly corrected without reprocessing the data back to the level of
the spherical harmonic decomposition.
---------------------------------------------------------
Title: Calculating Velocity Shifts Between the Pre- and Post-Upgrade
AFOE Data Sets
Authors: Miller, J. K.; Korzennik, S. G.; Nisenson, P.
2003AAS...203.1710M Altcode: 2003BAAS...35.1235M
We present the results of our efforts to develop a procedure to
determine the velocity shifts between the pre- and post-upgrade
stellar reference spectra observed with the Advanced Fiber Optic Echelle
(AFOE). The AFOE spectrograph was upgraded to increase its efficiency in
measuring radial velocities by rearranging the physical set-up of the
optical system. While observing roughly the same wavelength range, the
post-upgrade spectra have a different ratio of wavelength to pixels and
gaps in the data where pieces of the spectrum were not projected onto
the CCD. These differences necessitated taking new stellar references
of each star system. All velocity measurements for a star are made
relative to this reference. However, there is an unknown velocity
shift between every pair of new and old stellar reference spectra
simply because they were observed on different nights. The differences
in the spectra prevent us from recalculating all of the velocities
relative to one reference or the other. To overcome this problem, we
have been developing a procedure that models the new stellar reference
with a parameterized function of the old reference, and the velocity
shift is one parameter of the model. We independently model each
wavelength range of the new spectrum that overlaps the old spectrum,
which gives us twelve measurements of the velocity shift. The spread in
these results gives us an idea of the precision of our calculations,
and our goal precision is ∼ 1 ms<SUP>-1</SUP>. <P />This work was
supported in part by the SAO intern program under NSF grant AST-9731923.
---------------------------------------------------------
Title: The ELODIE survey for northern extra-solar planets. II. A
Jovian planet on a long-period orbit around GJ 777 A
Authors: Naef, D.; Mayor, M.; Korzennik, S. G.; Queloz, D.; Udry,
S.; Nisenson, P.; Noyes, R. W.; Brown, T. M.; Beuzit, J. L.; Perrier,
C.; Sivan, J. P.
2003A&A...410.1051N Altcode: 2003astro.ph..6586N
We present radial-velocity measurements obtained with the ELODIE
and AFOE spectrographs for <ASTROBJ>GJ 777 A</ASTROBJ> (<ASTROBJ>HD
190360</ASTROBJ>), a metal-rich ([Fe/H] = 0.25) nearby (d = 15.9 pc)
star in a stellar binary system. A long-period low radial-velocity
amplitude variation is detected revealing the presence of a Jovian
planetary companion. Some of the orbital elements remain weakly
constrained because of the smallness of the signal compared to our
instrumental precision. The detailed orbital shape is therefore
not well established. We present our best fitted orbital solution:
an eccentric (e = 0.48) 10.7-year orbit. The minimum mass of the
companion is 1.33 M<SUB>Jup</SUB>. <P />Based on observations made
with the ELODIE echelle spectrograph mounted on the 1.93-m Telescope
at the Observatoire de Haute-Provence (CNRS) and with the AFOE
spectrograph mounted on the 1.5-m Telescope at the Fred Lawrence
Whipple Observatory (SAO). <P />The ELODIE and AFOE measurements
discussed in this paper are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/1051
---------------------------------------------------------
Title: VizieR Online Data Catalog: ELODIE survey for northern
extra-solar planets. II. (Naef+, 2003)
Authors: Naef, D.; Mayor, M.; Korzennik, S. G.; Queloz, D.; Udry,
S.; Nisenson, P.; Noyes, R. W.; Brown, T. M.; Beuzit, J. L.; Perrier,
C.; Sivan, J. P.
2003yCat..34101051N Altcode:
Here are the 69 radial-velocity measurements of GJ 777A (HD 190360)
used for deriving the orbital solution of this star. These velocities
were obtained using the ELODIE echelle spectrograph mounted on the
1.93-m Telescope at Observatoire de Haute-Provence (France) and the
AFOE spectrograph mounted on the 1.5-m Telescope at the Fred Lawrence
Whipple Observatory (USA). <P />(1 data file).
---------------------------------------------------------
Title: On the characterization of high-degree modes: a lesson from MDI
Authors: Korzennik, Sylvain G.; Rabello-Soares, Cristina; Schou, Jesper
2003ESASP.517..145K Altcode: 2003soho...12..145K
High degree power ridges (up to l = 900) were computed and fitted for
several two to three-month-long time-series of full-disk observations
taken with the Michelson Doppler Imager (MDI) on-board the Solar and
Heliospheric Observatory between 1996 and 1999. A detailed discussion
of the modeling of the ridge power distribution, and the contribution
of the various observational and instrumental effects on the spatial
leakage, in the context of the MDI instrument, are presented. The result
of this work is a better understanding of the problems associated with
the characterization of high degree modes. We present the instrumental
and observational requirements needed to achieve a determination of high
degree mode frequencies whose residual systematic errors associated
with the accuracy of the ridge to mode correction scheme are smaller
than the uncertainty of the fitting itself.
---------------------------------------------------------
Title: A new upper limit to the temporal variation of the rotation
rate of the tachocline between 1994 and 2002
Authors: Eff-Darwich, A.; Korzennik, S. G.
2003ESASP.517..267E Altcode: 2003soho...12..267E
We have inverted most of the available rotational frequency splittings
at intermediate degrees. Namely, LOWL data from 1994 to 2000, GONG data
from 1995 to 2001, and, MDI data from 1996 to 2002. Our purpose was
to look for any temporal variation of the tachocline and its relation
to the solar activity cycle. However, we did not find any significant
change compatible with the three data sets. From our analysis, we
estimated an upper limit on the temporal variation of Ω/2π of 3
nHz. This value is commensurable with the sensitivity of the present
observational data to changes in the rotation rate of the tachocline.
---------------------------------------------------------
Title: Analysis of rotational frequency splittings sensitive to the
rotation rate of the solar core
Authors: García, R. A.; Eff-Darwich, A.; Korzennik, S. G.; Couvidat,
S.; Henney, C. J.; Turck-Chièze, S.
2003ESASP.517..271G Altcode: 2003soho...12..271G
Updated solar frequency splitting measurements suggest a slight
decrease of the rotation rate below 0.25 R<SUB>solar</SUB> and,
albeit preliminary, rule out a core rotating faster than the upper
radiative zone. The estimates of the rotation rate of the deep solar
layers are based on new rotational frequency splittings computed using
data from the GOLF and MDI instruments on board SoHO. Such results,
provided they are confirmed after further analysis, give additional
insight into the dynamics of the solar core.
---------------------------------------------------------
Title: The Extrasolar Planet Imager (ESPI)
Authors: Nisenson, P.; Melnick, G. J.; Geary, J.; Holman, M.;
Korzennik, S. G.; Noyes, R. W.; Papaliolios, C.; Sasselov, D. D.;
Fischer, D.; Gezari, D.; Lyon, R. G.; Gonsalves, R.; Hardesty, C.;
Harwit, M.; Marley, M. S.; Neufeld, D. A.; Ridgway, S. T.
2003ASPC..294..633N Altcode: 2002astro.ph.10046N
ESPI has been proposed for direct imaging and spectral analysis of
giant planets orbiting solar-type stars. ESPI extends the concept
suggested by Nisenson and Papaliolios (2001) for a square aperture
apodized telescope that has sufficient dynamic range to directly
detect extrasolar planets. With a 1.5-meter square mirror, ESPI can
deliver high dynamic range imagery as close as 0.3 arcseconds to bright
sources, permitting a sensitive search for extrasolar planets around
nearby stars and a study of their characteristics in reflected light.
---------------------------------------------------------
Title: An Upper Limit on the Temporal Variations of the Solar
Interior Stratification
Authors: Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S. J.;
Pérez Hernández, F.
2002ApJ...580..574E Altcode: 2002astro.ph..7402E
We have analyzed changes in the acoustic oscillation eigenfrequencies
measured over the past 7 years by the GONG, MDI, and LOWL
instruments. The observations span the period from 1994 to 2001 that
corresponds to half a solar cycle, from minimum to maximum solar
activity. These data were inverted to look for a signature of the
activity cycle on the solar stratification. A one-dimensional structure
inversion was carried out to map the temporal variation of the radial
distribution of the sound speed at the boundary between the radiative
and convective zones. Such variation could indicate the presence of a
toroidal magnetic field anchored in this region. We found no systematic
variation with time of the stratification at the base of the convection
zone. However, we can set an upper limit to any fractional change of
the sound speed at the level of 3×10<SUP>-5</SUP>.
---------------------------------------------------------
Title: Inversion of the Internal Solar Rotation Rate
Authors: Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S. J.
2002ApJ...573..857E Altcode:
Accurate determination of the rotation rate in the inner radiative
zone (0.2<r/R<SUB>solar</SUB><0.5) of the Sun from helioseismic
observations requires rotational frequency splittings of exceptional
quality. Indeed, only the very low degree modes are sensitive to
the dynamics of the deep interior. Low- and intermediate-degree
splittings have been estimated from a variety of instruments and
different data analysis procedures. Therefore, it is not surprising
that these determinations present significant differences. We have
attempted to build consistent data sets to constrain the dynamics of
the solar core, excluding features in the data that are not common to
all sets as well as excluding modes for frequencies for which such
measurements are not reliable. Our inferences of the solar internal
rotation profile were obtained from a full two-dimensional numerical
inversion based on the optimal mesh distribution methodology, a
variant of the regularized least-squares technique. Our results show
that the radiative zone rotates at a rate of approximately 435 nHz,
slowing down slightly in the core (r/R<SUB>solar</SUB><0.35). We
also did not find any significant angular differential rotation below
the base of the convective zone (r/R<SUB>solar</SUB>~0.7). We can rule
out any departure of the rotation rate in the solar deep interior,
0.2<r/R<SUB>solar</SUB><0.4, by more than 20% of the surface
rotation rate at midlatitude. This result is in clear disagreement with
the theoretical hydrodynamical models that expect a much faster rotation
rate in the solar core, some 10-50 times faster than the surface rate.
---------------------------------------------------------
Title: The Extra-Solar Planet Imager (ESPI): A Proposed MIDEX Mission
Authors: Melnick, G. J.; Fischer, D.; Geary, J. C.; Gezari, D. Y.;
Hardesty, C.; Harwit, M.; Holman, M.; Korzennik, S. G.; Lyon, R. G.;
Marley, M. S.; McElroy, M. B.; Neufeld, D. A.; Nisenson, P.; Noyes,
R. W.; Papaliolios, C.; Ridgway, S. T.; Sasselov, D. D.
2001AAS...199.0910M Altcode: 2002BAAS...34..559M
ESPI is a project that has been proposed as a NASA MIDEX for direct
imaging and spectral analysis of giant planets orbiting solar-type
stars. ESPI extends the concept suggested by Nisenson and Papaliolios
(2001) for a square aperture apodized telescope that has sufficient
dynamic range to directly detect exo-planets. ESPI can deliver high
dynamic range imagery as close as 0.32 arcseconds to bright sources,
permitting a sensitive search for exoplanets around nearby stars and
a study of their characteristics in reflected light. It also permits
unique observations of many Galactic, extragalactic and cosmological
sources. The ESPI Survey will be conducted with a square 1.5 x 1.5-meter
telescope mirror, operated in conjunction with a Jacquinot apodization
mask that has a throughput of more than 30 percent. The system is
capable of detecting Jupiter-like planets in relatively long-period
orbits around as many as 160 to 175 stars with a signal-to-noise
ratio greater than 5. In addition to the survey, ESPI will also
study a few of the brightest discovered planets spectroscopically
and spectrophotometrically to distinguish ice giants like Uranus and
Neptune from gas giants like Jupiter and Saturn, and to determine
whether super-Earth and super-Venus planets exist. Nisenson, P. and
Papaliolios, C. 2001, ApJ, 548, L 201.
---------------------------------------------------------
Title: Energy Distribution of Solar Oscillation Modes Inferred from
Space-Based Measurements
Authors: Woodard, M. F.; Korzennik, S. G.; Rabello-Soares, C.; Kumar,
P.; Tarbell, T. D.; Acton, S.
2001AGUSM..SP21C05W Altcode:
We have measured the energy distribution of solar p- and f-mode
oscillations of angular degree and temporal frequency in the range
100<l<800 and 2<ν (mHz)<4 using helioseismology data from
the SOI/MDI instrument on the SOHO satellite. At temporal frequency ν
≈ 3 mHz, the surface velocity power per oscillation mode increases
slightly with angular degree between l = 100 and l=200, but decreases
rather steeply with l above l=200, in approximate agreement with
earlier findings from ground-based measurements. From this we infer
that the time-averaged energy per mode, which is theoretically related
to the modal surface velocity power, decreases steeply with l at fixed
frequency, over the entire observed l range. Specifically, at ν =3.1
mHz the energy per mode drops by a factor of ≈ 10 between l=150 and
l=650, a circumstance not quantitatively understood at present. This
research was supported by NASA and Stanford University.
---------------------------------------------------------
Title: Time-Distance Inversions: Potential and Limitations
Authors: Korzennik, S. G.; Eff-Darwich, A.
2001AGUSM..SP31A20K Altcode:
Time-distance analysis is emerging as a powerful diagnostic tool in
local helioseismology. By directly measuring propagation times of
wave packets between selected locations at the surface of the sun,
and their variations over specific areas, a directed diagnostic
of the physical properties of the region below these areas can be
achieved. We present and discuss inversion methodologies specific
to time-distance analysis. These have been optimized for sparse
matrices, and include error-bar computation as well as resolution
kernel estimation. Our inversion methodology for velocity flow allow
us to impose a mass-conservation constrain. We show the diagnostic
potential of time-distance inversion and its limitation with various
simulations. We illustrate the inversion resolving power potential
and discuss the trade-off between resolution and error magnification,
including the effect of imposing mass-conservation for velocity flow
inferences. We also show inferences from actual observations obtained
with the MDI experiment on board the SOHO spacecraft.
---------------------------------------------------------
Title: Energy Distribution of Solar Oscillation Modes Inferred from
Space-based Measurements
Authors: Woodard, M. F.; Korzennik, S. G.; Rabello-Soares, M. C.;
Kumar, P.; Tarbell, T. D.; Acton, S.
2001ApJ...548L.103W Altcode:
We have measured the energy distribution of solar p- and f-mode
oscillations of angular degree and temporal frequency in the range
100<l<800 and 2<ν(mHz)<4 using helioseismology data
from the Solar Oscillations Investigation-Michelson Doppler Imager
instrument on the Solar and Heliospheric Observatory satellite. At
temporal frequency ν~3 mHz, the surface velocity power per oscillation
mode increases slightly with angular degree between l=100 and l=200 but
decreases rather steeply with l above l=200, in approximate agreement
with earlier findings from ground-based measurements. From this we
infer that the time-averaged energy per mode, which is theoretically
related to the modal surface velocity power, decreases steeply with l,
at fixed frequency, over the entire observed l-range. Specifically, at
ν=3.1 mHz, the energy per mode drops by a factor of ~10 between l=150
and l=650, a circumstance not quantitatively understood at present.
---------------------------------------------------------
Title: Interdependence of the basis functions of the solar
stratification inversion problem
Authors: Eff-Darwich, A.; Pérez-Hernández, F.; Korzennik, S. G.
2001ESASP.464..503E Altcode: 2001soho...10..503E
In helioseismic inversions, the number of independent pieces of
information that a mode set contains is much less than the actual
number of modes. This is due in part to the similarity between the
basis functions that define the inverse problem, the kernels, while
the observational errors also contribute to the loss of independent
information. We have devised a strategy to assess the amount of
independent and accessible information contained in a given mode
set. It consists in calculating the number of linearly independent
data, that is the number of modes that cannot be obtained as linear
combinations of the others. We have restricted our analysis to the
solar stratification inverse problem. It turns out that within the
present observational errors, only a small amount of modes are linearly
independent. Indeed, if we use a SOI/MDI data set of 1560 modes, only
117 were independent. Although this result might appear discouraging
indicating an apparent substantial loss of useful information, it also
allow us to reparameterize the data set before the inversion is carried
out. Such reparameterization considerably reduce the computation burden
of such inversion.
---------------------------------------------------------
Title: Rotation of the solar interior: compatibility of different
helioseismic data sets
Authors: Eff-Darwich, A.; Thiery, S.; Jiménez-Reyes, S.; Korzennik,
S. G.; Pérez-Hernández, F.
2001ESASP.464..507E Altcode: 2001soho...10..507E
Accurate determination of the rotation rate in the inner radiative zone
(0.2 < r/R<SUB>solar</SUB> < 0.5) of the sun from helioseismic
observations requires rotational frequency splittings of exceptional
quality. Indeed, only low degree modes are sensitive to the dynamics
of the deep interior. Low and intermediate degree splittings have
been estimated from a variety of instruments as well as different
data analysis procedures. It is therefore not surprising that these
determinations present significant differences. We present a study
of the three more common data sets used to infer the solar rotation
rate, namely LOWL, GONG and SOI/MDI. Our purpose is to find the
common features present in the three sets, in order to build a robust
determination of the rotation rate in the solar interior. We also
have analyzed the effect of using rotational splittings estimated by
fitting an asymmetric profile rather than a symmetric Lorentzian as
a model for the limit spectrum.
---------------------------------------------------------
Title: The determination of MDI high-degree mode frequencies
Authors: Rabello-Soares, M. C.; Korzennik, S. G.; Schou, J.
2001ESASP.464..129R Altcode: 2001soho...10..129R
As mode lifetimes get shorter and spatial leaks get closer in frequency,
individual p-modes can only be resolved up to some degree l (around
150). At higher degrees, individual modes blend into ridges and
the power distribution of the ridge masks the true underlying mode
frequency. To recover the underlying mode frequency from fitting the
ridge, an accurate model of the amplitude of the peaks that contribute
to the ridge power distribution is needed. Using full-disk data from the
Michelson Doppler Imager data on the Solar and Heliospheric Observatory,
we present and discuss the differences between the observations and
the spatial leakage calculation (including the horizontal component)
and estimate the horizontal-to-vertical displacement ratio for
medium-degree modes using sectoral modes for different observational
periods. We show how time variations in the instrument calibration
affect the spatial leakage and discuss their importance in the spatial
leakage calculation. By constructing a physically motivated model
(rather than some ad hoc correction scheme) can we hope to produce an
unbiased determination of the high-degree modes in the near future.
---------------------------------------------------------
Title: Sensitivity of oscillation frequencies to temporal variations
in the tachocline region
Authors: Eff-Darwich, A.; Pérez Hernández, F.; Korzennik, S. G.
2001ESASP.464..289E Altcode: 2001soho...10..289E
We have analyzed the differences in the oscillation eigenfrequencies
measured over four years of GONG, SOI/MDI and LOWL observations
(1996 to 1999). We have inverted these data to look for signatures
of the solar activity cycle on the stratification. A one-dimensional
structure inversion code was used to study temporal variations of the
radial distribution of the sound speed at the boundary between the
radiative and convective zones. Such variations could be an indication
of the presence of a toroidal magnetic field anchored in this region. We
have not found systematic variations of the stratification at the base
of the convection zone. However we set an upper limit to fractional
variations of the sound speed of approximately 4×10<SUP>-5</SUP>.
---------------------------------------------------------
Title: On the diagnostic potential of time-distance helioseismology
Authors: Korzennik, Sylvain G.
2001ESASP.464..149K Altcode: 2001soho...10..149K
Time-distance analysis has proven to be a powerful and intuitively
self evident approach for local helioseismology. By directly measuring
propagation times of wave packets between selected locations at the
surface, and their variations over a specific area of the sun, a
directed diagnostic of the physical properties of that region can be
achieved. The empirical approach taken by most investigators appears
to be robust and has produced enticing results. But surprisingly, the
theoretical framework for time-distance seismology remains sketchy. At
the same time, rigorous inversion methodologies need to be further
developed and validated; and, as in any inverse problem, the topology
of the underlying anihilator must be well understood to adequately
interpret the inferred properties. Using simulated observables and
focusing on the inference of the velocity flow, I illustrate the
diagnostic potential of time-distance inversion and its limitation with
simple and realistic simulations. I also present inversions based on
actual observations obtained with the MDI instrument on board SOHO.
---------------------------------------------------------
Title: A self-consistent procedure to detect low-l low-n solar p-modes
Authors: Eff-Darwich, A.; Régulo, C.; Roca Cortés, T.; Pallé,
P. L.; Korzennik, S. G.
2001ESASP.464..511E Altcode: 2001soho...10..511E
Recent data colleted by the helioseismic experiments aboard SOHO have
allowed the detection of low degree p-modes with lower and lower order,
n. In particular, the GOLF experiment is currently able to identify
unambiguously modes as low as n = 8 for l = 0, and l = 1 (e.g., ≍1.3
mHz). To detect p-modes with lower n (hence lower frequeny), where the
signal-to-noise ratio gets small, one needs some guidance. Several
groups use theoretical predictions from a standard solar model as a
guide. But using theoretical predictions has the potential to bias
the mode identification and in turn produce modes that confirm the
features of the model rather than the properties of the actual sun. To
alleviate this, we propose an alternative methodology based on peak
fitting techniques and helioseismic data inversion procedures. This
method allow us to reject many peaks from the spectrum by using the
prediction capability of the inversion. We describe the method and
show resuls from its application to current GOLF spectra.
---------------------------------------------------------
Title: Response of the radial stratification at the base of the
convection zone to the activity cycle
Authors: Eff-Darwich, Antonio; Korzennik, Sylvain G.
2000SoPh..193..365E Altcode:
We have analyzed the differences in the oscillation eigenfrequencies
measured over more than two years of GONG observations (December
1995-April 1998) and SOI/MDI observations (May 1996-July 1998). We
have inverted these data to look for signatures of the solar activity
cycle on the stratification. A one-dimensional (radial) structure
inversion code was used to study temporal variations of the sound speed
distribution at the boundary between the radiative and convective
zones. Such variations could be an indication of the presence of a
toroidal magnetic field anchored in this region.
---------------------------------------------------------
Title: A High-Eccentricity Low-Mass Companion to HD 89744
Authors: Korzennik, Sylvain G.; Brown, Timothy M.; Fischer, Debra A.;
Nisenson, Peter; Noyes, Robert W.
2000ApJ...533L.147K Altcode: 2000astro.ph..3045K
HD 89744 is an F7 V star with a mass of 1.4 M<SUB>solar</SUB>, an
effective temperature of 6166 K, an age of 2.0 Gyr, and metallicity
[Fe/H]=0.18. The radial velocity of the star has been monitored
with the Advanced Fiber-Optic Echelle spectrograph at the Whipple
Observatory since 1996, and evidence has been found for a low-mass
companion. The data were complemented by additional data from the
Hamilton spectrograph at Lick Observatory during the companion's
periastron passage in the fall of 1999. As a result, we have
determined the star's orbital wobble to have a period P=256 days,
an orbital amplitude K=257 m s<SUP>-1</SUP>, and an eccentricity
e=0.7. From the stellar mass, we infer that the companion has a
minimum mass m<SUB>2</SUB>sini=7.2 M<SUB>J</SUB> in an orbit with a
semimajor axis a<SUB>2</SUB>=0.88 AU. The eccentricity of the orbit,
among the highest known for extrasolar planets, continues the trend
that extrasolar planets with semimajor axes greater than about 0.15 AU
tend to have much higher eccentricities than are found in our solar
system. The high metallicity of the parent star reinforces the trend
that parent stars of extrasolar planets tend to have high metallicity.
---------------------------------------------------------
Title: Evidence for Multiple Companions to υ Andromedae
Authors: Butler, R. Paul; Marcy, Geoffrey W.; Fischer, Debra A.;
Brown, Timothy M.; Contos, Adam R.; Korzennik, Sylvain G.; Nisenson,
Peter; Noyes, Robert W.
1999ApJ...526..916B Altcode:
The bright F8 V star υ Andromedae was previously reported to have
a 4.6 day Doppler velocity periodicity, consistent with having a
Jupiter-mass companion orbiting at 0.059 AU. Follow-up observations
by both the Lick and Advanced Fiber-Optic Echelle spectrometer (AFOE)
planet survey programs confirm this periodicity and reveal additional
periodicities at 241 and 1267 days. These periodicities are consistent
with Keplerian orbital motion and imply two additional companions
orbiting at 0.83 and 2.5 AU, with minimum (Msini) masses of 2.0 and
4.6 M<SUB>JUP</SUB>, respectively. Non-Keplerian explanations for the
observed Doppler velocity variations, including radial and nonradial
pulsations, rotational modulation of surface features, and stellar
magnetic cycles, are examined. These explanations seem unlikely
based on the observed photometric and chromospheric stability of the
star. This putative three-planet system is found to be dynamically
stable by both analytic techniques and numerical simulations. The
outer two companions both reside in eccentric orbits, as do all nine
known extrasolar planet candidates in distant orbits. If real, this
multiple-planet system is the first around a main-sequence star, and
its study should offer insights into planet formation, planet-planet
interactions, and the observed eccentricities of planetary orbits. <P
/>Based on observations obtained at Lick Observatory, operated by the
University of California, and at the Whipple Observatory, operated by
the Smithsonian Astrophysical Observatory.
---------------------------------------------------------
Title: Stellar and Planetary Explorer (SPEX)
Authors: Schou, J.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.;
Scherrer, P. H.; Brown, T. M.; Buzasi, D. L.; Horner, S. D.; Korzennik,
S. G.
1999AAS...195.8808S Altcode: 1999BAAS...31.1506S
The Stellar and Planetary Explorer (SPEX) mission will search for
terrestrial inner planets around Sun-like (FGK, main sequence) stars
using photometric techniques as well as provide very long time series
for asteroseismology. If every Sun-like star had a planetary system
similar to ours, the proposed instrumentation would detect at least
100 terrestrial planets similar to the Earth or Venus and be able to
provide statistics on their diameters and orbital periods. SPEX will
accomplish this by continuously observing a large number of field stars
to detect planetary transits. The instrument consists of a fast Schmidt
camera with a mosaic of large CCD detectors. SPEX will observe a field
near the galactic plane from a geosynchronous orbit for a minimum of 3
years. The very long asteroseismic time series will allow inferences
on the interiors of more than 100 Sun-like stars with a variety of
masses and ages. This will allow us to substantially refine stellar
model calculations and in particular improve on the age estimates of
stars. This in turn is of considerable interest for the understanding
of the evolution of our galaxy and the universe as a whole. SPEX will
also provide new data for stellar activity and will be able to detect
the reflected light from large inner planets, such as those detected
using ground based Doppler velocity searches.
---------------------------------------------------------
Title: Evidence for a system of planets orbiting Upsilon Andromedae.
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Holman, M. J.;
Contos, A.; Brown, T. M.
1999BAAS...31.1236N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Upper Limit on the Reflected Light from the Planet Orbiting
the Star τ Bootis
Authors: Charbonneau, David; Noyes, Robert W.; Korzennik, Sylvain G.;
Nisenson, Peter; Jha, Saurabh; Vogt, Steven S.; Kibrick, Robert I.
1999ApJ...522L.145C Altcode: 1999astro.ph..7195C
The planet orbiting τ Boo at a separation of 0.046 AU could produce
a reflected light flux as bright as 1×10<SUP>-4</SUP> relative to
that of the star. A spectrum of the system will contain a reflected
light component which varies in amplitude and Doppler shift as the
planet orbits the star. Assuming the secondary spectrum is primarily
the reflected stellar spectrum, we can limit the relative reflected
light flux to be less than 5×10<SUP>-5</SUP>. This implies an upper
limit of 0.3 for the planetary geometric albedo near 480 nm, assuming a
planetary radius of 1.2 R<SUB>Jup</SUB>. This albedo is significantly
less than that of any of the giant planets of the solar system and is
not consistent with certain published theoretical predictions.
---------------------------------------------------------
Title: Evidence for a System of Planets Orbiting Upsilon Andromedae
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Holman, M. J.;
Contos, A.; Brown, T. M.
1999AAS...194.1404N Altcode: 1999BAAS...31..847N
Using the Advanced Fiber Optic Echelle (AFOE) spectrograph at SAO's
Whipple Observatory, we have monitored the radial velocity of Upsilon
Andromedae since September 1994. Similar observations were made by the
"Lick" group (P. Butler, G. Marcy, D. Fischer; see Paper 14.02).The AFOE
data show, in addition to the already known close-in “hot Jupiter”
in a 4.6-day circular orbit, two additional companions. The middle
companion has a well-defined orbit, with semi-major axis about
0.83 AU, period 243.5 days, eccentricity 0.22, and minimum mass
(M sin i) of 2 Jupiter masses. This is in very close agreement with
independent findings by the Lick group. The AFOE data alone do not
yield well-determined orbital parameters for the outer companion,
because the total observing span encompasses only about one period of
its orbit. However, the data are consistent with parameters derived
for that companion by the Lick group from data with a longer time span,
and when combined with the Lick data yield a semi-major axis of 2.5 AU,
orbital period of 1267 days, eccentricity of 0.41, and minimum mass
about 4.6 Jupiter masses. These results, independently obtained by two
different groups with different instruments and analysis methodologies,
together give strong indications that a true planetary “system” has
now been discovered around a star like our own. We have carried out
numerical integrations which show that this system can be stable, but
only for certain combinations of periods, masses, and eccentricities
of the outer two companions. The stability requirement thus provides
a prediction that can be tested as the orbital elements of the outer
companion are refined. In addition, it imposes an upper limit on the
actual planetary masses, and on the difference in orbital inclination of
the two outer planets. Finally, the numerical integrations imply that
the longitudes of periastron of the two outer companions are locked to
nearly the same value, in accord with the present observations. This
work was supported by NASA, NSF, and the Smithsonian Institution.
---------------------------------------------------------
Title: Doppler Imaging of Stellar Oscillations: Multi-Site
Observations of Epsilon Cephei
Authors: Kennelly, E. J.; Brown, T. M.; Ehrenfreund, P.; Foing,
B.; Hao, J.; Horner, S.; Korzennik, S.; Nisenson, P.; Noyes, R.;
Sonnentrucker, P.
1999ASPC..185..264K Altcode: 1999IAUCo.170..264K; 1999psrv.conf..264K
We investigate the oscillation properties of ɛ Cep using a series of
specialized techniques designed to extract and analyze time variations
in absorption line profiles. To obtain the necessary temporal coverage
for this investigation, multi-site observations were collected at
3 sites (China, France, Arizona) all equipped with high-resolution
echelle spectrographs. From these observations, we find evidence for
a very rich spectrum of modes in ɛ Cep.
---------------------------------------------------------
Title: Solar Rotation Near the Surface: The Outer 1%
Authors: Korzennik, Sylvain G.; Eff-Darwich, Antonio
1999soho....9E..68K Altcode:
We present an estimate of the solar rotation rate near the surface
(i.e., the outer 1%) based on rotational splittings estimated for high
degree modes ( ) from the SOI/MDI dynamics program. We also present and
discuss the nature and magnitude of systematic errors present in the
evaluation of high degrees rotational splittings and their implication
of the inferred rotation profile.
---------------------------------------------------------
Title: The Advanced Fiber-Optic Echelle (AFOE) and Extra-Solar
Planet Searches
Authors: Nisenson, P.; Contos, A.; Korzennik, S.; Noyes, R.; Brown, T.
1999ASPC..185..143N Altcode: 1999IAUCo.170..143N; 1999psrv.conf..143N
The Advanced Fiber-Optic Echelle (AFOE) is a fiber-fed bench-top
spectrograph specifically designed for precise radial velocity
observations. The AFOE is permanently located at the 1.5-m telescope
at Smithsonian's Whipple Observatory in Arizona and is regularly used
for monitoring exo-planet candidate stars and for asteroseismology
observations. In this paper, we discuss the status of the instrument,
as well as an upgrade to the instrument, a Fabry-Perot reference,
which may prove important both for the AFOE and for all precise radial
velocity (PRV) facilities.
---------------------------------------------------------
Title: Response of the Stratification in the Sun to the Solar
Activity Cycle
Authors: Eff-Darwich, A.; Korzennik, S. G.
1999soho....9E..53E Altcode:
We have analyzed the differences in the oscillation eigenfrequencies
measured in the last three years of GONG (From September 1996 to August
1998) observations and 2 years of SOI/MDI (from May 1996 to May 1998)
observations. We have inverted these data to look for signatures
of the solar activity cycle on the stratification. A one-dimensional
(radial) structure inversion code was used to study temporal variations
of the "bump" in the sound speed distribution located in the boundary
between the radiative and convective zones. These variations could be
an indication of a toroidal magnetic field anchored in this region. A
two-dimensional (radial and latitudinal) structure inversion code was
used to analyze surface latitudinal variations of the sound speed
distribution with time. We also attempted to push the inversion to
deeper regions, but we failed to produce well localized solutions due to
the noise present in the data. The most interesting results are those
found for the sound speed distribution in the solar surface. There
is a clear dependence of the angular distribution of sound speed with
time. The relation between this dependence and some physical phenomena
like the rising of the magnetic activity or thermal variations in the
solar surface are explored.
---------------------------------------------------------
Title: The Planet Orbiting ρ Coronae Borealis
Authors: Noyes, R. W.; Contos, A. R.; Korzennik, S. G.; Nisenson,
P.; Brown, T. M.; Horner, S. D.
1999ASPC..185..162N Altcode: 1999IAUCo.170..162N; 1999psrv.conf..162N
Continuing precise radial velocity observations of ρ Coronae Borealis
have allowed the determination of updated parameters of the 40-day
orbit of its Jupiter-mass companion. This confirms the near-zero
eccentricity of the orbit, and provides improved predictions for the
times of possible transit of the companion in front of the star. The
new data provide more stringent upper limits to the mass of a possible
second companion to the system. The orbital parameters are discussed in
the light of several different scenarios for the origin and migration
of extra-solar giant planets.
---------------------------------------------------------
Title: Structure and dynamics of the interior of the Sun and Sun-like
stars. Proceedings.
Authors: Korzennik, S. G.; Wilson, A.
1998sdis.book.....K Altcode:
The following topics were dealt with: resonant mode characterisation;
seismology of Sun-like stars: techniques and strategies; solar
structure: models and inversions; local seismology, active regions and
magnetic effects; solar dynamics: large-scale and small-scale flows;
temporal variations of solar oscillation characteristics: short-
and long-term changes and mode excitation and damping.
---------------------------------------------------------
Title: Helioseismic Studies of Differential Rotation in the Solar
Envelope by the Solar Oscillations Investigation Using the Michelson
Doppler Imager
Authors: Schou, J.; Antia, H. M.; Basu, S.; Bogart, R. S.; Bush,
R. I.; Chitre, S. M.; Christensen-Dalsgaard, J.; Di Mauro, M. P.;
Dziembowski, W. A.; Eff-Darwich, A.; Gough, D. O.; Haber, D. A.;
Hoeksema, J. T.; Howe, R.; Korzennik, S. G.; Kosovichev, A. G.;
Larsen, R. M.; Pijpers, F. P.; Scherrer, P. H.; Sekii, T.; Tarbell,
T. D.; Title, A. M.; Thompson, M. J.; Toomre, J.
1998ApJ...505..390S Altcode:
The splitting of the frequencies of the global resonant acoustic modes
of the Sun by large-scale flows and rotation permits study of the
variation of angular velocity Ω with both radius and latitude within
the turbulent convection zone and the deeper radiative interior. The
nearly uninterrupted Doppler imaging observations, provided by the
Solar Oscillations Investigation (SOI) using the Michelson Doppler
Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft
positioned at the L<SUB>1</SUB> Lagrangian point in continuous sunlight,
yield oscillation power spectra with very high signal-to-noise ratios
that allow frequency splittings to be determined with exceptional
accuracy. This paper reports on joint helioseismic analyses of
solar rotation in the convection zone and in the outer part of the
radiative core. Inversions have been obtained for a medium-l mode set
(involving modes of angular degree l extending to about 250) obtained
from the first 144 day interval of SOI-MDI observations in 1996. Drawing
inferences about the solar internal rotation from the splitting data
is a subtle process. By applying more than one inversion technique
to the data, we get some indication of what are the more robust
and less robust features of our inversion solutions. Here we have
used seven different inversion methods. To test the reliability and
sensitivity of these methods, we have performed a set of controlled
experiments utilizing artificial data. This gives us some confidence
in the inferences we can draw from the real solar data. The inversions
of SOI-MDI data have confirmed that the decrease of Ω with latitude
seen at the surface extends with little radial variation through much
of the convection zone, at the base of which is an adjustment layer,
called the tachocline, leading to nearly uniform rotation deeper
in the radiative interior. A prominent rotational shearing layer in
which Ω increases just below the surface is discernible at low to
mid latitudes. Using the new data, we have also been able to study the
solar rotation closer to the poles than has been achieved in previous
investigations. The data have revealed that the angular velocity
is distinctly lower at high latitudes than the values previously
extrapolated from measurements at lower latitudes based on surface
Doppler observations and helioseismology. Furthermore, we have found
some evidence near latitudes of 75° of a submerged polar jet which
is rotating more rapidly than its immediate surroundings. Superposed
on the relatively smooth latitudinal variation in Ω are alternating
zonal bands of slightly faster and slower rotation, each extending
some 10° to 15° in latitude. These relatively weak banded flows
have been followed by inversion to a depth of about 5% of the solar
radius and appear to coincide with the evolving pattern of “torsional
oscillations” reported from earlier surface Doppler studies.
---------------------------------------------------------
Title: Exoplanets or Dynamic Atmospheres? The Radial Velocity and
Line Shape Variations of 51 Pegasi and τ Bootis
Authors: Brown, Timothy M.; Kotak, Rubina; Horner, Scott D.;
J. Kennelly, Edward; Korzennik, Sylvain; Nisenson, P.; Noyes, Robert W.
1998ApJS..117..563B Altcode: 1998astro.ph..1166B
The stars 51 Pegasi and τ Bootis show radial velocity variations that
have been interpreted as resulting from companions with roughly Jovian
mass and orbital periods of a few days. Gray and Gray & Hatzes
reported that the radial velocity signal of 51 Peg is synchronous with
variations in the shape of the line λ6253 Fe I; thus, they argue that
the velocity signal arises not from a companion of planetary mass but
from dynamic processes in the atmosphere of the star, possibly nonradial
pulsations. Here we seek confirming evidence for line shape or strength
variations in both 51 Peg and τ Boo, using R = 50,000 observations
taken with the Advanced Fiber Optic Echelle. Because of our relatively
low spectral resolution, we compare our observations with Gray's line
bisector data by fitting observed line profiles to an expansion in terms
of orthogonal (Hermite) functions. To obtain an accurate comparison,
we model the emergent line profiles from rotating and pulsating stars,
taking the instrumental point-spread function into account. We describe
this modeling process in detail. We find no evidence for line profile or
strength variations at the radial velocity period in either 51 Peg or in
τ Boo. For 51 Peg, our upper limit for line shape variations with 4.23
day periodicity is small enough to exclude with 10 σ confidence the
bisector curvature signal reported by Gray & Hatzes; the bisector
span and relative line depth signals reported by Gray are also not seen,
but in this case with marginal (2 σ) confidence. We cannot, however,
exclude pulsations as the source of 51 Peg's radial velocity variation
because our models imply that line shape variations associated with
pulsations should be much smaller than those computed by Gray &
Hatzes; these smaller signals are below the detection limits both for
Gray & Hatzes's data and for our own. τ Boo's large radial velocity
amplitude and v sin i make it easier to test for pulsations in this
star. Again we find no evidence for periodic line shape changes, at a
level that rules out pulsations as the source of the radial velocity
variability. We conclude that the planet hypothesis remains the most
likely explanation for the existing data.
---------------------------------------------------------
Title: The Solar Rotation Rate Ω(R, θ)
Authors: Eff-Darwich, A.; Korzennik, S. G.; Roca Cortés, T.; Pérez
Hernández, F.; Pallé, P.
1998Ap&SS.263..347E Altcode: 1999Ap&SS.263..347E
In recent years, the capability to detect and analyse solar oscillation
acoustic modes has greatly improved. The development of ground based
networks like GONG or BiSON and the use of space platforms like SOHO
has allowed us to study the structure and dynamics of the Sun with
unprecedented precision.
---------------------------------------------------------
Title: The Oscillations of Tau Pegasi
Authors: Kennelly, E. J.; Brown, T. M.; Kotak, R.; Sigut, T. A. A.;
Horner, S. D.; Korzennik, S. G.; Nisenson, P.; Noyes, R. W.; Walker,
A.; Yang, S.
1998ApJ...495..440K Altcode:
We present extensive spectroscopic time series observations of the
multiperiodic, rapidly rotating, δ Scuti star τ Pegasi. Information
about the oscillations is contained within the patterns of line-profile
variation of the star's blended absorption-line spectrum. We introduce
the new technique of Doppler deconvolution with which to extract these
patterns by modeling the intrinsic stellar spectrum and the broadening
functions for each spectrum in the time series. Frequencies and modes
of oscillation are identified from the variations using the technique
of Fourier-Doppler imaging and a two-dimensional least-squares cleaning
algorithm. We find a rich mode spectrum with degrees up to l = 20 and
with frequencies below about 35 cycles day<SUP>-1</SUP>. Those modes
with the largest amplitudes have frequencies that lie within a narrow
band. We conclude that the observed spectrum can be explained if the
modes of τ Peg propagate in the prograde direction with l ~= |m| and
with frequencies that are about equal in the corotating frame of the
star. We discuss the implications of these results for the prospect
of δ Scuti seismology.
---------------------------------------------------------
Title: A Search for Line Shape and Depth Variations in 51 Pegasi
and τ Bootis
Authors: Brown, Timothy M.; Kotak, Rubina; Horner, Scott D.; Kennelly,
Edward J.; Korzennik, Sylvain; Nisenson, P.; Noyes, Robert W.
1998ApJ...494L..85B Altcode: 1997astro.ph.12279B
Spectroscopic observations of 51 Pegasi and τ Bootis show no periodic
changes in the shapes of their line profiles; these results for 51
Peg are in significant conflict with those reported by Gray &
Hatzes. Our detection limits are small enough to rule out nonradial
pulsations as the cause of the variability in τ Boo, but not in 51
Peg. The absence of line shape changes is consistent with these stars'
radial velocity variability arising from planetary mass companions.
---------------------------------------------------------
Title: The Stellar and Planetary Explorer (SPEX) Mission
Authors: Schou, J.; Scherrer, P. H.; Brown, T. M.; Frandsen, S.;
Horner, S. D.; Korzennik, S. G.; Noyes, R. W.; Tarbell, T. D.; Title,
A. M.; Walker, A. B. C., II; Weiss, W. W.; Bogart, R. S.; Bush, R. I.;
Christensen-Dalsgaard, J.; Hoeksema, J. T.; Jones, A.; Kjeldsen, H.
1998ESASP.418..401S Altcode: 1998soho....6..401S
The Stellar and Planetary Explorer (SPEX) is a mission designed
to search for terrestrial sized planets around sun-like stars using
precise photometry. The planets will be detected by searching for the
decrease in brightness associated with transits of the planets in front
of their parent stars. One of the secondary scientific objective of
SPEX is to do asteroseismology on a number of sun-like stars. SPEX
is designed as a secondary payload on a commercial communications
satellite and will have a design life time of three years. We will
provide an overview of the SPEX scientific objectives and design,
with particular emphasis on the prospects for doing asteroseismology.
---------------------------------------------------------
Title: On the Precision of Time/Distance Measurements
Authors: Baudin, F.; Korzennik, S. G.
1998ESASP.418..611B Altcode: 1998soho....6..611B
“Time--distance” analysis is a emerging new tool for local (and
global) helioseismology, pioneered by Duvall et al. (1993). Like for
other seismological analysis techniques, time--distance analysis allow
us to infer internal physical properties of the Sun from measurements
made at the surface, by solving an inverse problem. In the case of
time--distance analysis, the observed quantities are travel times of
acoustic waves from one point of the surface to another (or between
group of points). These travel times are estimated by fitting a wavelet
to the correlation function computed from time-series of velocities
averaged along annuli of given radius. The precision with which these
measurements can be made is a crucial parameter of the inverse problem,
and controls the achievable trade-off between resolution and error
magnification. In the work presented here, we investigate the precision
of these measurements, and how this precision varies with some of the
parameters of the analysis, (like the length of the time-series, the
spatial averaging, etc ldots) as well as the nature of the data used
(i.e., the spatial resolution, the location of the area studied on
the visible disk, etc ldots).
---------------------------------------------------------
Title: The Rotation of the Solar Core: Compatibility of the Different
Data Sets Available
Authors: Eff-Darwich, A.; Korzennik, S. G.
1998ESASP.418..685E Altcode: 1998soho....6..685E
A combination of inverse and forward analysis techniques has
been applied to p-modes rotational splittings in order to infer
the solar rotation rate in the deeper radiative regions (r <
0.45R<SUB>odot</SUB>). In this analysis, we first infer the rotation
distribution down to 0.45R<SUB>odot</SUB> using a 2D inversion
method. We then use that rotation rate to discuss the compatibility
of different low degree splittings sets. These low degree splittings
and the 2D inversion method are also used to infer the rotation rate
in the deeper radiative regions (r < 0.45R<SUB>odot</SUB>). An
exhaustive analysis of the averaging kernels has been carried out in
order to study the resolution and precision of the solution.
---------------------------------------------------------
Title: Structure and Dynamics of the Interior of the Sun and
Sun-like Stars
Authors: Korzennik, S.
1998ESASP.418.....K Altcode: 1998soho....6.....K
No abstract at ADS
---------------------------------------------------------
Title: Exoplanet Research with the Advanced Fiber Optic Echelle
Authors: Korzennik, S. G.; Brown, T. M.; Contos, A. R.; Horner, S.;
Jha, S.; Kennelly, T.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..154.1876K Altcode: 1998csss...10.1876K
The AFOE is a fiber-fed bench-top echelle spectrometer installed
at the Mt. Hopkins 1.5 m telescope for research in exoplanets,
asteroseismology, and other topics requiring precise radial velocity
measurements. Here we describe the instrumentation, observing programs,
and data reduction techniques for exoplanet research with the AFOE. We
also summarize recent results of our search for and characterization
of exoplanets. Further information on the AFOE can be found on the
Web at http://cfa-www.harvard.edu/afoe.
---------------------------------------------------------
Title: Observational Analysis of Asymmetries in Velocity and Intensity
Power Spectra
Authors: Korzennik, S. G.
1998ESASP.418..933K Altcode: 1998soho....6..933K
In order to properly characterize the the limit spectrum of the solar
oscillations, we have computed averaged power spectra of both velocity
and intensity time-series, using SOI/MDI observations. More precisely,
we have computed the 9th order sine multi-tapered power spectrum of
the zonal (m = 0) and sectoral (m = ell) time-series of spherical
harmonic coefficients, for degree up to ell = 200. We computed such
spectra for the 360 day-long velocity time-series and the 61-day-long,
coeval, velocity and intensity time-series. Then, using the set of
eigenfrequencies and rotational splitting coefficients estimated by
the Stanford group and based on the 360-day-long velocity time-series,
we build averaged mode profiles. These profiles were computed by
summing a 200 muHz portion of the (zonal or sectoral) power spectrum,
centered on the eigenfrequency estimated for that mode respectively,
for a set of individual modes that lies within a preset range in degree
and frequency. By averaging only zonal (or sectoral), the resulting
spatial leakage pattern is simple enough to be easily understood. This
averaging was performed independently for the zonal and sectoral power
spectra, and for the 360 day-long velocity time-series, as well as the
61-day-long, coeval, velocity and intensity time-series. We present and
discussed detailed comparisons of these profiles, and show that while
the mode profile displays some intrinsic asymmetry, the amplitude of
the spatial leaks display a similar asymmetry. Indeed, for the velocity
observations and the sectoral profiles, the δ ell = δ m = -1, -2,
-3 leaks (lower frequencies) have more power than the δ ell = δ m =
+1, +2, +3 (higher frequencies), while the opposite is true for the
intensity observations. A direct consequence of such leakage asymmetry
(as opposed to the profile intrinsic asymmetry) is to offset the power
distribution of unresolved power ridges (where the modes are short
lived, i.e., for high frequency and/or high degree modes). It explains
the apparent frequency differences that are measured between velocity
and intensity when these are estimated by fitting unresolved ridges.
---------------------------------------------------------
Title: Temperatures of Cepheids from Line-Depth Ratios
Authors: Krockenberger, M.; Sasselov, D.; Noyes, R.; Korzennik, S.;
Nisenson, P.; Brown, T.; Kennelly, T.; Horner, S.
1998ASPC..154..791K Altcode: 1998csss...10..791K
We present observations of 11 Cepheids and 16 non-variable supergiants
with the Advanced Fiber Optics Echelle (AFOE) spectrograph. We measure
the effective temperatures of Cepheids and supergiants using spectral
line depth ratios and Kurucz's model atmospheres. For the Cepheids we
use the fact that the reddening is constant as a function of phase as an
additional constraint. We find errors in the mean temperature as small
as 10 K for the best sampled Cepheids. Our temperatures and surface
brightnesses disagree with the results of the Barnes-Evans method.
---------------------------------------------------------
Title: 51 Pegasi and Tau Bootis: Planets or Pulsations?
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Kotak, R.; Jha,
S.; Korzennik, S. G.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..135..206H Altcode: 1998hcsp.conf..206H
It has recently been suggested (Gray 1997) that the radial velocity
variations observed in the spectra of 51 Pegasi are the result of
stellar pulsations as opposed to the reflex motion due to an orbital
companion. The AFOE group has confirmed the radial velocity variations
in 51 Pegasi and t Bootis. Here we discuss the results of a search for
evidence of pulsations in the AFOE data for these two stars, as well
as attempt to clear up misconceptions regarding pulsations circulated
as a result of the current debate about the nature of the 51 Pegasi
radial velocity variations.
---------------------------------------------------------
Title: 51 Pegasi and Tau Bootis: Planets or Pulsations?
Authors: Horner, S. D.; Brown, T. M.; Kennedy, E. J.; Kotak, R.; Jha,
S.; Korzennik, S. G.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..154.1860H Altcode: 1998csss...10.1860H
Using data from the AFOE and simulations of pulsating stars, we are able
to rule out pulsations as the cause of the radial velocity variations
seen in tau Bootis and conclude that it is unlikely that pulsations
are the cause of radial velocity variations seen in 51 Pegasi. Orbital
companions are still the most probable causes of the radial velocity
variations observed in these systems.
---------------------------------------------------------
Title: The SOI-MDI High-Latitude Jet: the Evidence For and Against
Authors: Howe, R.; Antia, H.; Basu, S.; Christensen-Dalsgaard, J.;
Korzennik, S. G.; Schou, J.; Thompson, M. J.
1998ESASP.418..803H Altcode: 1998soho....6..803H
The apparent detection of a prograde jet at latitude 75-circ and at a
radius of about 0.95R<SUB>odot</SUB> in some inversions of rotation data
from SOI--MDI (Schou et al., 1998) has excited considerable interest,
but whether the jet really exists in the solar interior is certainly not
yet firmly established. The detection of the feature is sensitive both
to the inversion techniques used and to the methods of mode parameter
estimation used to generate the input data. In particular, the feature
is much more apparent in Regularized Least-Squares inversions than
in inversions using an Optimally Localized Average approach, and is
not detected at all in the present GONG data when analysed with the
GONG peakfinding algorithm, or indeed in SOI data when analysed with
the GONG algorithm. Therefore in this poster we examine critically
the current evidence for the source and existence of this jet in the
light of forward and inverse analyses.
---------------------------------------------------------
Title: Asteroseismology of Procyon with the AFOE
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Korzennik,
S.; Nisenson, P.; Noyes, R. W.
1997AAS...191.4310H Altcode: 1997BAAS...29R1276H
The Advanced Fiber Optic Echelle (AFOE) is a bench-mounted,
fiber-fed echelle spectrograph designed for precision radial velocity
observations. Located at the 1.5m Tillinghast telescope at Whipple
Observatory, the AFOE is used to detect exoplanets and is involved in
several projects in asteroseismology, including asteroseismology of
Sun-like stars. Procyon has been a prime target for asteroseismology
of Sun-like stars due to its proximity and its spectral type
(F5 IV-V). Theory predicts that due to its low surface gravity
and inefficient surface convection, the amplitudes of its p-mode
pulsation modes should be relatively large, though still less than 1
m\ s(-1) . While the velocity of individual modes is extremely small,
observations of Procyon with the AFOE show excess power in the frequency
range between 0.5 to 1.5 MHz. This power may be the result of p-mode
oscillations on Procyon, and is consistent with previous results (Brown
et al. 1991). However, mode identification is required to interpret
the ramifications of the observations for the star's structure, which
is the goal of asteroseismology. These single-site data are limited
in frequency resolution, which may prevent clear identification of
individual modes.
---------------------------------------------------------
Title: Rotation and Zonal Flows in the Solar Envelope from the
SOHO/MDI Observations
Authors: Scherrer, P. H.; Schou, J.; Bogart, R. S.; Bush, R. I.;
Hoeksema, J. T.; Kosovichev, A. G.; Antia, H. M.; Chitre, S. M.;
Christensen-Dalsgaard, J.; Larsen, R. M.; Pijpers, F. P.; Eff-Darwich,
A.; Korzennik, S. G.; Gough, D. O.; Sekii, T.; Howe, R.; Tarbell,
T.; Title, A. M.; Thompson, M. J.; Toomre, J.
1997AAS...191.7310S Altcode: 1997BAAS...29.1322S
We report on the latest inferences concerning solar differential
rotation that have been drawn from the helioseismic data that are now
available from the Solar Oscillations Investigation (SOI) using the
Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory
(SOHO). That spacecraft is positioned in a halo orbit near the Sun-Earth
Lagrangian point L_1, in order to obtain continuous Doppler-imaged
observations of the sun with high spatial fidelity. Doppler velocity,
intensity and magnetic field images are recorded, based on modulations
of the 676.8 nm Ni I solar absorption line. The high spatial resolution
of MDI thereby permits the study of many millions of global resonant
modes of solar oscillation. Determination and subsequent inversion
of the frequencies of these modes, including the degeneracy-splitting
by the rotation of the sun, enables us to infer how the sun's angular
velocity varies throughout much of the interior. The current MDI data
are providing substantial refinements to the helioseismic deductions
that can be made about differential rotation both within the convection
zone and in its transition to the radiative interior. The shearing
layer evident in the angular velocity Omega just below the solar
surface is becoming better defined, as is the adjustment layer or
tachocline near the base of the convection zone. The MDI data are also
revealing a prominent decrease in Omega at high latitudes from the
rotation rate expressed by a simple three-term expansion in latitude
that was originally deduced from surface Doppler measurements. Further,
there are indications that a submerged polar vortex involving somewhat
faster Omega than its surroundings exists at about 75(deg) in latitudes.
---------------------------------------------------------
Title: Erratum: A Planet Orbiting the Star Rho Coronae Borealis:
Authors: Noyes, Robert W.; Jha, Saurabh; Korzennik, Sylvain G.;
Krockenberger, Martin; Nisenson, Peter; Brown, Timothy M.; Kennelly,
Edward J.; Horner, Scott D.
1997ApJ...487L.195N Altcode:
In the Letter, “A Planet Orbiting the Star ρ Coronae Borealis”
by Robert W. Noyes, Saurabh Jha, Sylvain G. Korzennik, Martin
Krockenberger, Peter Nisenson, Timothy M. Brown, Edward J. Kennelly,
and Scott D. Horner (ApJ, 483, L111 [1997]), a software error caused
the sign of the reported radial velocity variations of ρ Coronae
Borealis to be reversed. This error has no effect on the period,
amplitude, or eccentricity of the derived orbit and thus does not
affect the main conclusion of the paper. However, the longitude ω
of periastron reported in Table 1 is off by 180°, and the predicted
time of a possible planetary transit T<SUB>transit</SUB> is off by
approximately 1/2 period. The correct values are ω = 30° +/- 74°
and T<SUB>transit</SUB> = 2,450,657.88 +/- 0.54 HJD.
---------------------------------------------------------
Title: A Planet Orbiting the Star ρ Coronae Borealis
Authors: Noyes, Robert W.; Jha, Saurabh; Korzennik, Sylvain G.;
Krockenberger, Martin; Nisenson, Peter; Brown, Timothy M.; Kennelly,
Edward J.; Horner, Scott D.
1997ApJ...483L.111N Altcode: 1997astro.ph..4248N
We report the discovery of near-sinusoidal radial velocity variations
of the G0V star ρ CrB, with period 39.6 days and amplitude 67 m
s<SUP>-1</SUP>. These variations are consistent with the existence
of an orbital companion in a circular orbit. Adopting a mass of 1.0
M<SUB>solar</SUB> for the primary, the companion has minimum mass
about 1.1 Jupiter masses and orbital radius about 0.23 AU. Such an
orbital radius is too large for tidal circularization of an initially
eccentric orbit during the lifetime of the star, and hence we suggest
that the low eccentricity is primordial, as would be expected for a
planet formed in a dissipative circumstellar disk.
---------------------------------------------------------
Title: A Radial Velocity Search for p-Mode Pulsations in η Bootis
Authors: Brown, Timothy M.; Kennelly, Edward J.; Korzennik, Sylvain
G.; Nisenson, Peter; Noyes, Robert W.; Horner, Scott D.
1997ApJ...475..322B Altcode:
The subgiant η Boo (G5 IV) has been reported to show p-mode pulsations,
as evidenced by variations in the equivalent width of its hydrogen
Balmer lines (reported by Kjeldsen et al.). In an attempt to confirm
this report, we observed η Boo's radial velocity with the AFOE
spectrograph for a total of 22 hours spread over seven successive
nights in 1995 March. We find no evidence for the presence of excess
power at the frequencies reported by Kjeldsen et al.; our upper limit
corresponds to typical mode amplitudes of 0.5 m s<SUP>-1</SUP>, about 3
times smaller than the velocity amplitudes they inferred. Signals with
amplitudes larger than 0.5 m s<SUP>-1</SUP> may be present at other
frequencies within the 0-1000 μHz range, but evidence for such signals
is scanty, and typical mode amplitudes greater than 1.5 m s<SUP>-1</SUP>
are clearly inconsistent with our observations.
---------------------------------------------------------
Title: Internal rotation and dynamics of the Sun from GONG data
Authors: Korzennik, S.; Thompson, M. J.; Toomre, J.; GONG Internal
Rotation Team
1997IAUS..181..211K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The AFOE Program of Extra-Solar Planet Research
Authors: Noyes, R.; Jha, S.; Korzennik, S.; Krockenberger, M.;
Nisenson, P.; Brown, T.; Kennelly, E.; Horner, S.
1997ASPC..119..119N Altcode: 1997pbss.conf..119N
No abstract at ADS
---------------------------------------------------------
Title: The first results of solar observations made in the Crimean
Astrophysical Observatory using a magneto-optical filter
Authors: Didkovskii, L. V.; Dolgushin, A. I.; Kotov, V. A.; Khaneychuk,
V. I.; Tsap, T. T.; Rhodes, E. J.; Korzennik, S. G.; Johnson, N. M.;
Rose, P. J.
1996R&QE...39..916D Altcode:
The results of observations of Doppler velocities and solar magnetic
fields using a magneto- optical filter (MOF) are presented. The
MOF-based instrument was manufactured and supplied to the Crimean
Astrophysical Observatory (CrAO) by the University of Southern
California. It is one of three similar instruments designed to
establish the helioseismology network „Mount Wilson —CrAO —
AFiF” (Fesenkov Astrophysical Institute in Alma- Ata.) Apart from its
main purpose — obtaining a long time series of the Doppler velocity
measurements to study the internal solar structure and recording the
magnetic fields for the ground- based support of the SOHO project —
the instrument allows us to study different structural formations in
the solar atmosphere in Na D1 and D2 spectral lines. This conclusion
relies on the comparison between the magnetic field and beam velocity
maps calculated using the filtergram pairs, which were recorded twice
a minute by 512×512 video-camera (1024×1024 camera will be used in
the future studies).
---------------------------------------------------------
Title: A radial velocity search for p-modes in Procyon.
Authors: Brown, T. M.; Kennelly, E. J.; Noyes, R. W.; Korzennik,
S. G.; Nisenson, P.; Horner, S. D.; Catala, C.
1996BAAS...28..917B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The oscillation modes of ɛ Cep and τ Peg.
Authors: Horner, S. D.; Kennelly, E. J.; Brown, T. M.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Yang, S.; Walker, A. R.
1996BAAS...28..916H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Differential Rotation and Dynamics of the Solar Interior
Authors: Thompson, M. J.; Toomre, J.; Anderson, E. R.; Antia, H. M.;
Berthomieu, G.; Burtonclay, D.; Chitre, S. M.; Christensen-Dalsgaard,
J.; Corbard, T.; De Rosa, M.; Genovese, C. R.; Gough, D. O.; Haber,
D. A.; Harvey, J. W.; Hill, F.; Howe, R.; Korzennik, S. G.; Kosovichev,
A. G.; Leibacher, J. W.; Pijpers, F. P.; Provost, J.; Rhodes, E. J.,
Jr.; Schou, J.; Sekii, T.; Stark, P. B.; Wilson, P. R.
1996Sci...272.1300T Altcode:
Splitting of the sun's global oscillation frequencies by large-scale
flows can be used to investigate how rotation varies with radius
and latitude within the solar interior. The nearly uninterrupted
observations by the Global Oscillation Network Group (GONG) yield
oscillation power spectra with high duty cycles and high signal-to-noise
ratios. Frequency splittings derived from GONG observations confirm
that the variation of rotation rate with latitude seen at the surface
carries through much of the convection zone, at the base of which is
an adjustment layer leading to latitudinally independent rotation at
greater depths. A distinctive shear layer just below the surface is
discernible at low to mid-latitudes.
---------------------------------------------------------
Title: The Oscillation Modes of epsilon CEP and tau Peg
Authors: Horner, S. D.; Kennelly, E. J.; Brown, T. M.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Yang, S.; Walker, A.
1996AAS...188.5901H Altcode: 1996BAAS...28Q.917H
Asteroseismology of delta Scuti stars offers an attractive prospect for
determining the interior properties of main sequence and slightly more
evolved A- and F-type stars. Here we present detailed identifications
of oscillation modes in the rapidly rotating delta Scuti stars epsilon
Cep and tau Peg based on extensive observations carried out at two
North American sites. Using cross-correlation and Fourier techniques
we analyze the line-profile variations and the variations in the
line-profile moments. A solution to the mode spectrum is sought using
a genetic-based search algorithm and a line profile simulation model
to reproduce the observed variations.
---------------------------------------------------------
Title: Use of Temperature-Sensitive Line Ratios for Stellar Seismology
Authors: Noyes, R. W.; Korzennik, S. G.; Krockenberger, M.; Nisenson,
P.; Brown, T.; Kennelly, T.; Horner, S.
1996AAS...188.5906N Altcode: 1996BAAS...28..918N
The line depths of virtually all stellar spectral lines are sensitive
to small changes in stellar temperature T<SUB>eff</SUB> induced by
pulsations, with varying degrees (and signs) depending on the mean
T<SUB>eff</SUB> and the line ionization and excitation state. For
large-amplitude pulsators, such as Cepheids, temperatures obtained
from individual line pairs are sufficiently accurate and invariant
to reddening to play an important role in distance measurements. For
small-amplitude pulsators, this technique is inadequate. However,
by combining the information from a very large number of spectral
lines recorded with high spectral resolution, such as can be provided
by a cross-dispersed echelle spectrograph, it should be possible to
measure temperature changes to a precision considerably greater than
can be obtained by comparing single pairs of lines. We explore this
possibility by using a grid of synthetic stellar spectra to provide the
run of temperature sensitivity as a function of wavelength throughout
the spectrum, and make specific application to spectra obtained with
the Advanced Fiber Optic Echelle (AFOE) spectrograph.
---------------------------------------------------------
Title: The Solar Acoustic Spectrum and Eigenmode Parameters
Authors: Hill, F.; Stark, P. B.; Stebbins, R. T.; Anderson, E. R.;
Antia, H. M.; Brown, T. M.; Duvall, T. L., Jr.; Haber, D. A.;
Harvey, J. W.; Hathaway, D. H.; Howe, R.; Hubbard, R. P.; Jones,
H. P.; Kennedy, J. R.; Korzennik, S. G.; Kosovichev, A. G.; Leibacher,
J. W.; Libbrecht, K. G.; Pintar, J. A.; Rhodes, E. J., Jr.; Schou, J.;
Thompson, M. J.; Tomczyk, S.; Toner, C. G.; Toussaint, R.; Williams,
W. E.
1996Sci...272.1292H Altcode:
The Global Oscillation Network Group (GONG) project estimates
the frequencies, amplitudes, and linewidths of more than 250,000
acoustic resonances of the sun from data sets lasting 36 days. The
frequency resolution of a single data set is 0.321 microhertz. For
frequencies averaged over the azimuthal order m, the median formal
error is 0.044 microhertz, and the associated median fractional error
is 1.6 x 10<SUP>-5</SUP>. For a 3-year data set, the fractional error
is expected to be 3 x 10<SUP>-6</SUP>. The GONG m-averaged frequency
measurements differ from other helioseismic data sets by 0.03 to 0.08
microhertz. The differences arise from a combination of systematic
errors, random errors, and possible changes in solar structure.
---------------------------------------------------------
Title: A Radial Velocity Search for p-modes in Procyon
Authors: Brown, T. M.; Kennelly, E. J.; Noyes, R. W.; Korzennik,
S. G.; Nisenson, P.; Horner, S. D.; Catala, C.
1996AAS...188.5902B Altcode: 1996BAAS...28R.917B
Procyon (alpha CMi F5 IV) has long been a promising candidate for
detection of solar-like p-modes. Although several authors have reported
evidence for low-amplitude (<= 10) m/s pulsations in this star,
none of the existing observations are conclusive. A clear detection
of such pulsations would be a significant step for asteroseismology
of Sun-like stars, allowing refined estimates of the star's properties
and paving the way for the study of fainter stars of similar spectral
type. Identification of oscillation modes in subgiants like Procyon is
expected to be difficult, however, because both the amplitudes and the
frequency separations of the modes are expected to be small. To address
these difficulties, we organized a joint observing campaign involving
the AFOE spectrograph located at the Whipple Observatory (Mt. Hopkins,
AZ) and the MUSICOS spectrograph located at Pic du Midi. Both
instruments are capable of providing Doppler measurements with the
required precision of a few m/s, and the 7 hour longitude separation
between them allows the acquisition of relatively long uninterrupted
data strings. In the event, bad weather prevented more than sporadic
observations from Pic du Midi. At Mt. Hopkins, however, we obtained
good observations on each of 6 consecutive nights 3-8 Feb 1996, for
a total of 47 h of observing time. We discuss here the interpretation
of this data set in terms of possible p-mode oscillations.
---------------------------------------------------------
Title: HD 3346
Authors: Noyes, R.; Korzennik, S.; Nisenson, P.; Jha, S.;
Krockenberger, M.; Brown, T.; Kennelly, T.; Rowland, C.; Horner, S.
1996IAUC.6316....1N Altcode: 1996IAUC.6316Q...1N
R. Noyes, S. Korzennik, P. Nisenson, S. Jha, and M. Krockenberger,
Smithsonian Astrophysical Observatory; T. Brown, T. Kennelly, and
C. Rowland, High Altitude Observatory; and S. Horner, Pennsylvania State
University, report the detection of large short- term radial-velocity
variations in the K5 III star HD 3346 = HR 152. Irregularly spaced
observations were made with the Advanced Fiber Optic Echelle (AFOE)
spectrometer at the 1.5-m telescope of the Whipple Observatory during
the last quarters of 1993, 1994, and 1995, with more intensive
observations in December 1995 and February 1996. A long-period
radial-velocity variation similar to that already reported by McClure
et al. (1985, PASP 97, 740) is seen with amplitude of order 500 m/s
and period of order 650 days. This is consistent with a companion to HD
3346 at orbital distance about 2.5 AU. If the mass of HD 3346 is 5 solar
masses, then this already-reported companion would have projected mass
m sin i about 60 Jupiter masses. The AFOE data reveal the presence of
shorter- term radial-velocity variations superimposed on the 650-day
variation. The amplitude of the variations is in the range 150-300
m/s. Near-nightly observations in December 1995 and February 1996 show
the variations to be consistent with those produced by a second orbital
companion. The window function of the data would allow for its period
to be near 14, 18, 24, or 40 days. Such a short period would imply that
the second companion's orbit would have a semimajor axis between 0.2 and
0.4 AU; the amplitude of the variation implies that (again, if HD 3346
has a mass of 5 solar masses) this second companion has m sin i about
10 Jupiter masses. Acoustic pulsations may be an alternative source of
the short-term radial-velocity variations. However, the fundamental
period of acoustic pulsations in giants is expected to be only a few
days; the present data could be explained by acoustic pulsations only
if the star has a mass much lower than suggested by standard stellar-
evolution theory. Spurious signals due to rotation of starspots appear
to be unlikely because of the low reported rotational velocity for HD
3346. A definitive period for the short-period radial-velocity variation
may be determinable if other contemporaneous precise radial-velocity
observations of this star exist or can be obtained before the star
disappears behind the sun for this observing season.
---------------------------------------------------------
Title: First Results of Solar Oscillations Made in Crimean
Astrophysical Observatory Using Magneto-Optical Filter
Authors: Didkovsky, L. V.; Rhodes, E. J., Jr.; Dolgushin, A. I.;
Haneychuk, V. I.; Johnson, N. M.; Korzennik, S. G.; Kotov, V. A.;
Rose, P. J.; Tasp, T. T.
1996RaF....39...11D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Radial Velocity Search for p-mode Pulsations in eta Bootis
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Brown, T. M.;
Kennelly, E. J.; Horner, S. D.
1995AAS...18710211N Altcode: 1995BAAS...27.1429N
Kjeldsen et al. 1994 (Astron. J 109, 1313 ) have reported the presence
of p-mode pulsations in Balmer line equivalent widths measured in
the spectrum of eta Boo (G5 IV); they give accurate frequencies for
13 modes of oscillation, and estimate velocity amplitudes for these
modes of typically 1.6 m/s. We report here time-series observations of
the radial velocity of eta Boo obtained with the Advanced Fiber Optic
Echelle (AFOE) spectrograph. In March 1995 we obtained 555 spectra
of eta Boo for a total of 21.6 hours of observing time spread over
7 consecutive nights. The radial velocity time series clearly shows
the night-to-night orbital motion of eta Boo; the residual velocities
after removing this motion are typically 10 m/s for single spectra,
a value that is roughly consistent with shot noise limits. The power
spectrum of the time series shows no evidence for Kjeldsen et al.'s
frequencies. With 95 % confidence, we can rule out the presence of these
13 frequencies with typical amplitudes of 0.5 m/s or more. The spectrum
is consistent with pure photon noise, but also with the presence of
pulsations having other frequencies (not those given by Kjeldsen et
al.) and with typical amplitudes as large as about 1.5 m/s. Possible
explanations for the discrepancy between the two results are (a) an
incorrect conversion between the amplitudes of equivalent width and
Doppler pulsations, and (b) a fluke in the noise behavior of one or
both observations.
---------------------------------------------------------
Title: Velocity Fields within the Solar Convection Zone: Evidence
from Oscillation Ring Diagram Analysis of Mount Wilson Dopplergrams
Authors: Patron, J.; Hill, F.; Rhodes, E. J., Jr.; Korzennik, S. G.;
Cacciani, A.
1995ApJ...455..746P Altcode:
A ring-diagram analysis of solar oscillations has been applied to
a 3 day time series of full-disk Doppler images obtained at Mount
Wilson. A model of the three-dimensional power spectrum assuming a
Lorentzian profile in frequency and the advection of the wave front by
horizontal flows has been fitted to the observed spectrum. The model
provides estimates of the two horizontal components of subsurface
flows averaged over depth. These estimates are then input to a
least-squares smoothness-constrained inversion procedure to infer
the depth dependence of the horizontal velocity. The method has been
applied at nine different heliographic positions. The results indicate
the presence of three east-west shear layers at all longitudes and
latitudes, associated in depth with the ionization zones of hydrogen
and helium in the outermost 20 Mm. The direction of the shear with
respect to the average surface rotation rate alternates with depth, with
organized north-south flows apparent between the east-west flows. Thus,
the resultant vector velocity field appears to execute a spiral as
a function of depth. Below ∼30 Mm, the organized character of the
flow disappears, and a chaotic spatial distribution dominates. There
is also an indication of a convergent flow at ∼10° north latitude,
suggesting the presence of a toroidal convective roll. The magnitudes
of the flows are on the order of 100-200 ms<SUP>-1</SUP> in the outer
20 Mm, rising to several hundred ms<SUP>-1</SUP> at 50 Mm.
---------------------------------------------------------
Title: Determining the AFOE's Radial Velocity Precision with Solar
Observations
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Krockenberger, M.
1995AAS...187.7006H Altcode: 1995BAAS...27.1380H
The Advanced Fiber Optic Echelle (AFOE) is an instrument designed
for high precision radial velocity observations to detect extra-solar
planets and study stellar structure through asteroseismology. A 320 mu
m optical fiber is used to obtain solar observations during the day to
determine the precision of the instrument, and to study the relationship
between stellar activity and measured radial velocities. Here we
present the results of our analysis of solar data to determine the
short and long term radial velocity precision of the AFOE.
---------------------------------------------------------
Title: 51 Pegasi
Authors: Mayor, M.; Queloz, D.; Marcy, G.; Butler, P.; Noyes, R.;
Korzennik, S.; Krockenberger, M.; Nisenson, P.; Brown, T.; Kennelly,
T.; Rowland, C.; Horner, S.; Burki, G.; Burnet, M.; Kunzli, M.
1995IAUC.6251....1M Altcode:
M. Mayor and D. Queloz, Geneva Observatory, have reported the discovery
of a Jupiter-mass object in orbit around the solar-type star 51 Peg. The
announcement was made in Florence on Oct. 6 at the Ninth "Cambridge"
Workshop on "Cool Stars, Stellar Systems, and the Sun". The claim is
based on 18 months of precise Doppler measurements made with the ELODIE
spectrograph of the Observatoire de Haute-Provence. The parameters
of the orbital motion are as follows: P = 4.2293 +/- 0.0011 days,
e = 0 (assumed), K = 0.059 +/- 0.003 km/s, T0 = 2449797.773 +/-
0.036. The minimum mass of the companion is 0.47 +/- 0.02 Jupiter
mass. Alternative explanations for the radial-velocity variation
(pulsation or spot rotation) seem to be ruled out by the absence of any
significant corresponding photometric variation. Following the Oct. 6
announcement, confirmation of the 4.2-day radial-velocity variation
was obtained in mid-October by G. Marcy and P. Butler (San Francisco
State University, University of California at Berkeley) at the Lick
Observatory, as well as by a joint team from the Harvard-Smithsonian
Center for Astrophysics (R. Noyes, S. Korzennik, M. Krockenberger and
P. Nisenson), the High Altitude Observatory (T. Brown, T. Kennelly and
C. Rowland) and Pennsylvania State University (S. Horner). G. Burki,
M. Burnet and M. Kuenzli, Geneva Observatory and Lausanne University,
communicate: "Intensive photometric monitoring of 51 Peg has been
carried out at the European Southern Observatory. There is no evidence
for eclipses in the system. The rms of the V magnitude (on 17 nights)
is 0.037, two comparison stars being used. A 4.2-day photometric
variability larger than 0.002 mag can be ruled out."
---------------------------------------------------------
Title: Adjustment and Focus of Solar Images for Magneto-Optical
Filter Observations
Authors: Didkovsky, L. V.; Andreeva, O. A.; Borzyak, P. I.; Dolgushin,
A. I.; Rhodes, E. J.; Johnson, N. M.; Rose, P. J.; Korzennik, S. G.
1995ESASP.376b.201D Altcode: 1995help.confP.201D; 1995soho....2..201D
Provides a more accurate and reliable set of full-disk, high-resolution
helioseismic measurements in the M. Wilson-Crimea-Alma-Ata network
by ensuring the optimum quality of the solar images which will
be generated by each network station. The method of optical layout
adjustment is based on real-time, PC-based programs for improving the
quality of solar images. The best focus is determined through motion
of the camera followed by the checking of the mean inclination angle of
the brightness curves in several equi-spaced azimuthal directions. The
solar limb shape is adjusted to obtain the minimum standard deviation
around the circle through the alignment of the lenses and the video
camera. Finally, the camera and the re-imaging lens are positioned
so as to have a common image size as well as the optimum focus. As a
part of the daily observing procedure, the solar image is focused by
another algorithm which is sensitive to the maximum intensity of some
bright objects on the solar image.
---------------------------------------------------------
Title: Method Optimization for Calculating the Solar-Limb Position
Authors: Didkovsky, L. V.; Andreeva, O. A.; Borzyak, P. I.; Dolgushin,
A. I.; Rhodes, E. J.; Johnson, N. M.; Rose, P. J.; Korzennik, S. G.
1995ESASP.376b.197D Altcode: 1995soho....2..197D; 1995help.confP.197D
The solar limb figure is determined using the middle of linear segments
drawn by a least squares method through brightness profiles and
maximum slopes. The brightness profiles employed are equally spaced
in the azimuthal angle. The authors show that there is an optimal
width for the ring-shaped zone (r/R ≡ 5%) which is used for the
limb determination. In this case the run of standard deviations of
the limb points from a circle has a clear minimum which is 1.3 times
smaller than the standard deviation found with the "activity-based"
algorithm. During iteration cycles the error in determinating the
centre of the solar image gets smaller and reaches a limiting value
which is conditioned by the shape of the image. The proposed method
of solar limb determination is intended to decrease possible errors
in the identification of the degrees of the high-l oscillation modes
and to achieve higher computational efficiency.
---------------------------------------------------------
Title: Looking for Non-Local Features in Horizontal Velocity Flows
Authors: Patrón, J.; Rhodes, E. J., Jr.; Korzennik, S. G.
1995ESASP.376b.133P Altcode: 1995help.confP.133P; 1995soho....2..133P
The tridimensional maps of horizontal velocity flows obtained with ring
diagrams analysis techniques show several common features at given
depths for different horizontal positions. This could be interpreted
as global, rather than local features. Tests have been performed in
order to find large scale horizontal velocity flows under the solar
surface. The procedure, based in a tridimensional analysis of solar
oscillations (ring diagrams), has been applied to a section of the
solar disk of about 45 degrees in latitude and longitude around solar
disk center. The images used in this work correspond to three days
of 1024×1024 pixel Doppler images obtained at Mt. Wilson July 3, 4,
and 5, 1988 using the Magneto-Optical Filter. By using large scale
sections of the solar disk, it is possible to expect an averaging
or filtering effect of the local features of the results (horizontal
velocity flows), giving rise to information about more global features.
---------------------------------------------------------
Title: Restoration of Full-Disk Velocity Maps Obtained with
Magneto-Optical Filter
Authors: Didkovsky, L. V.; Andreeva, O. A.; Borzyak, P. I.; Dolgushin,
A. I.; Rhodes, E. J.; Johnson, N. M.; Rose, P. J.; Korzennik, S. G.
1995ESASP.376b.191D Altcode: 1995soho....2..191D; 1995help.confP.191D
In order to improve the calibration of solar Dopplergrams in the
sense of reducing the standard errors connected with large-scale
nonlinearities, the authors have tested some new algorithms. The
method of the determination of the boundaries between both linear and
non-linear variation of the filtergram signal, as well as the method
of a variable window running mean has been used. The new velocity maps
which result from the application of these methods show good agreement
with velocity maps obtained independently with a spectrograph.
---------------------------------------------------------
Title: Nightly Variations of Nonradial Oscillations in the Delta
Scuti Star upsilon Ursae Majoris
Authors: Korzennik, S. G.; Noyes, R. W.; Brown, T.; Nisenson, P.;
Horner, S.
1995ApJ...443L..25K Altcode:
We obtained spectra of the rapidly rotating Delta Scuti star
upsilon UMa with the Advanced Fiber Optic Echelle Spectrometer
(AFOE) on five successive nights in 1993 April, at a cadence of one
spectrum every 5 minutes over time periods averaging 4 hours on each
night. Cross-correlations of the spectra with a template spectrum from
a slowly rotating star of similar spectral type yielded the pattern
of features propagating across the lines, averaged over all spectral
lines recorded. The spacing of the features in wavelength and their
speed of motion across the line profile depend on the azimuthal order
m and frequency v of propagating oscillation modes. Using a Doppler
imaging analysis, we computed nightly absolute value of m-v diagrams;
these show several resolved modes with effective azimuthal order m
ranging from about 2 up to about 11, and frequencies between 130 and
170 microHz (i.e., periods between 2.1 and 1.6 hours). We identify
the observed modes as propagating prograde modes; the corresponding
retrograde modes are not observed. Viewed in a frame corotating
with the star with rotation speed of 116 km/s as derived from these
data, modes with m approximately 7 and with m approximately 11 have
approximately the same frequency (70 microHz). However, their relative
amplitude changes substantially from night to night, suggesting that
(1) the coherence time of the modes is not longer than about 1 day, or
(2) a possible coupling between modes of similar intrinsic frequencies
causes an alternating pattern of modal amplitude, or (3) beats are being
observed between unresolved modes of similar wavelength and frequency.
---------------------------------------------------------
Title: Compensation of Large-Area Non-Linearities in Solar Velocity
Maps Obtained with a Sodium Magneto-Optical Filter
Authors: Didkovsky, L. V.; Andreeva, O. A.; Borzyak, P. I.; Dolugshin,
A. I.; Rhodes, E. J., Jr.; Johnson, N. M.; Rose, P.; Korzennik, S. G.
1995ASPC...76..536D Altcode: 1995gong.conf..536D
No abstract at ADS
---------------------------------------------------------
Title: Local Helioseismology: Analysis of Localized Time-Distance
Diagrams from Quiet and Active Regions
Authors: Korzennik, S. G.; Noyes, R. W.; Ziskin, V.
1995ASPC...76..268K Altcode: 1995gong.conf..268K
No abstract at ADS
---------------------------------------------------------
Title: Ring Diagram Analysis of Mt. Wilson Data: Velocity Fields
within the Solar Convection Zone
Authors: Patron, J.; Hill, F.; Rhodes, E. J., Jr.; Korzennik, S. G.;
Cacciani, A.
1995ASPC...76..208P Altcode: 1995gong.conf..208P
No abstract at ADS
---------------------------------------------------------
Title: Solar Cycle Dependence of p-Mode Frequencies at Intermediate
and High Degrees
Authors: Rhodes, E. J., Jr.; Johnson, N. M.; Rose, P. J.; Korzennik,
S. G.; Cacciani, A.
1995ASPC...76..227R Altcode: 1995gong.conf..227R
No abstract at ADS
---------------------------------------------------------
Title: Applications of Massively-Parallel Computing in Solar Modeling
Authors: Reiter, J.; Rhodes, E. J., Jr.; Dappen, W.; Korzennik, S. G.
1995ASPC...76..140R Altcode: 1995gong.conf..140R
No abstract at ADS
---------------------------------------------------------
Title: On the Determination of the Solar Internal Rotation
Authors: Korzennik, S. G.; Rhodes, E. J., Jr.; Johnson, N. M.; Rose,
P.; Cacciani, A.
1995ASPC...76...12K Altcode: 1995gong.conf...12K
No abstract at ADS
---------------------------------------------------------
Title: The AFOE: A Spectrograph for Precision Doppler Studies
Authors: Brown, Timothy M.; Noyes, Robert W.; Nisenson, Peter;
Korzennik, Sylvain G.; Horner, Scott
1994PASP..106.1285B Altcode:
The Advanced Fiber Optic Echelle (AFOE) is a fiber-fed echelle
spectrograph designed for the measurement of stellar Doppler
shifts. Using a 2k x 2k CCD detector, it samples about 55% of the
wavelength range between 450 nm and 700 nm (20 echelle orders) at a
single shot, with spectral resolution R = 32000 to 70000 at 500 nm,
depending on the slit width employed. The AFOE employs a number of
devices to assure that the calibrations necessary for accurate Doppler
measurements can be properly performed. The most important of these
are: (1) coupling to the telescope via a double-scrambling optical
fiber system; (2) continuous calibration of the wavelength scale and
point-spread function by means of an atomic emission lamp entering the
spectrograph via a separate fiber and/or a molecular iodine absorption
cell; (3) availability of fiber-coupled sunlight for regular calibration
against the solar spectrum; (4) appropriate mechanical design and active
thermal control, yielding good mechanical stability. The AFOE is coupled
to the Tillinghast 1.5-m telescope at the F. L. Whipple Observatory. It
presently achieves S/N = 500 in the continuum near 500 nm in 60s when
observing Arcturus (alpha-Boo, m_V = -0.04). This noise level sets
a limit of about 0.7 ms^-1 to the Doppler precision attainable in
this length of observing time. Currently, our actual frame-to-frame
repeatability is worse than the photon noise limited value by about a
factor of 3 for this bright star, and about 1.5 for stars with m_V =
4. Work is continuing to refine data processing methods so that the
ultimate noise limit may be approached more closely, and to improve
the spectrograph's relatively low efficiency. (SECTION: Astronomical
Instrumentation )
---------------------------------------------------------
Title: Nightly Variations of Non-Radial Oscillations in the Delta
Scuti Star upsilon UMa
Authors: Korzennik, S.; Noyes, R.; Brown, T.; Nisenson, P.; Horner, S.
1993AAS...183.8405K Altcode: 1993BAAS...25.1423K
We observed the rapidly rotating Delta Scuti star upsilon UMa with the
Advanced Fiber Optic Echelle (AFOE) spectrometer at the Mt. Hopkins
1.5-m telescope on 5 successive nights in April 1993. Spectra covering
a total of 730 Angstroms were obtained at a 5-min cadence over about 4
hours on each night. The rotationally-broadened profiles of unblended
strong lines clearly show previously-seen “bumps" propagating from
the blue side to the red side of the lines. We isolated moving features
for each individual spectrum by subtracting the spectrum from the mean
spectrum for that night, normalizing to the latter. We then calculated
the cross-correlation function between each difference spectrum and
a standard template spectrum, which was a very high signal-to-noise
spectrum of a slowly-rotating star (Procyon) of similar spectral type,
obtained with the same instrument. The cross-correlation combines
the information from all the bumps moving across all spectral lines
(including rotationally-blended lines) into a single function of
displacement from line center, thereby significantly increasing
the signal-to-noise ratio of the moving features. Analysis of
the time-series of cross-correlation functions yields the rate of
propagation of features and their separation in velocity, which may be
interpreted in terms of effective azimuthal wavenumber and oscillation
frequency. Modes are identified by remapping the cross-correlation
functions in terms of longitude and performing two-dimensional Fourier
transforms. For each night a different modal pattern was found, usually
with several modes. The modes have effective azimuthal order m ranging
from about 2 up to about 12, and frequencies between 120 and 170 uHz
(i.e., 2.3 to 1.6 hours), with frequency gradually increasing with
increasing m. The relative amplitude of the different modes changes
substantially from night to night, suggesting either that the coherence
time of the modes is not longer than about a day, or that beats are
being observed between modes of similar wavelength and frequency.
---------------------------------------------------------
Title: Ring Diagram Analysis of Mt. Wilson Data: Current Status
Authors: Hill, F.; Patron, J.; Rhodes, E. J., Jr.; Korzennik, S. G.;
Cacciani, A.
1993BAAS...25R1193H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Confirmation of Solar Cycle--dependent Intermediate-Degree
p-Mode Frequency Shifts
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.; Ulrich, Roger K.
1993ApJ...406..714R Altcode:
Results of intercomparisons of seven different sets of frequencies of
intermediate-degree p-modes obtained at several different locations
between 1981 and 1989 are presented. It is shown that the frequency
shifts exhibited by all of these intermediate-degree p-modes are
consistent with the intermediate-degree frequency shifts presented by
Libbrecht and Woodward (1990) and also with the low-degree frequency
shifts presented by Elsworth et al. (1990). It is also shown that these
frequency shifts correlate with solar cycle-dependent changes in sunspot
number, area, and irradiance. Unbinned and binned differences between
1984 Mount Wilson Observatory and revised 1981 South Pole frequencies
are illustrated.
---------------------------------------------------------
Title: Ring Diagram Analysis of MT.WILSON Data
Authors: Patron, J.; Hill, F.; Rhodes, E. J., Jr.; Korzennik, S. G.;
Cacciani, A.; Brown, T. M.
1993ASPC...42..437P Altcode: 1993gong.conf..437P
No abstract at ADS
---------------------------------------------------------
Title: Preliminary P-Mode Frequencies from a 93-DAY MT.WILSON 60-FOOT
Tower Observing Run
Authors: Rhodes, E. J., Jr.; Cacciani, A.; Korzennik, S. G.
1993ASPC...42..193R Altcode: 1993gong.conf..193R
No abstract at ADS
---------------------------------------------------------
Title: Helioseismology on a Massively Parallel Architecture -
Reduction of 1024-by-1024 Full-Disk Dopplergrams on Intel's
Touchstone-Delta Supercomputer
Authors: Korzennik, S. G.; Rhodes, E. J., Jr.; Johnson, N. M.
1993ASPC...42..461K Altcode: 1993gong.conf..461K
No abstract at ADS
---------------------------------------------------------
Title: Towards a Better Determination of Frequency Splittings at
Intermediate and High Degree Modes - Preliminary Results of Sectoral
Frequency Splittings from a 90-DAY Observing Run
Authors: Korzennik, S. G.; Cacciani, A.; Rhodes, E. J., Jr.
1993ASPC...42..201K Altcode: 1993gong.conf..201K
No abstract at ADS
---------------------------------------------------------
Title: An Advanced Fiber Optic Echelle Spectrograph for
Asteroseismology
Authors: Noyes, R. W.; Brown, T. M.; Horner, S.; Korzennik, S.;
Nisenson, P.
1993ASPC...42..485N Altcode: 1993gong.conf..485N
No abstract at ADS
---------------------------------------------------------
Title: The AFOE - a new instrument for asteroseismology
Authors: Noyes, R. W.; Brown, T. M.; Horner, S.; Korzennik, S.;
Nisenson, P.
1993ASPC...40..752N Altcode: 1993IAUCo.137..752N; 1993ist..proc..752N
No abstract at ADS
---------------------------------------------------------
Title: Measurement of the Phase Relation Between Velocity and
Intensity Fluctuations
Authors: Korzennik, S. G.; Sabbey, C. N.
1993ASPC...42..115K Altcode: 1993gong.conf..115K
No abstract at ADS
---------------------------------------------------------
Title: Plans for MT.WILSON - Crimean Observatory High-Degree
Helioseismology Network
Authors: Rhodes, E. J., Jr.; Cacciani, A.; Dappen, W.; Didkovsky,
L. V.; Hill, F.; Korzennik, S. G.; Kosovichev, A. G.; Kotov, V. A.;
Scherrer, P. H.
1993ASPC...42..477R Altcode: 1993gong.conf..477R
No abstract at ADS
---------------------------------------------------------
Title: Rotation Rate of the Supergranulation Pattern
Authors: Hathaway, D. H.; Rhodes, E. J., Jr.; Korzennik, S.;
Cacciani, A.
1991BAAS...23.1051H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Seismic Analysis of the Sun from Intermediate and High
Degree p-modes
Authors: Korzennik, S. G.
1991BAAS...23Q1032K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: How Deeply Might Sunspots and Supergranules Be Anchored within
the Sun?
Authors: Rhodes, E. J., Jr.; Korzennik, S. G.; Hathaway, D. H.;
Cacciani, A.
1991BAAS...23.1033R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: What We Know about the Sun's Internal Rotation from Solar
Oscillations
Authors: Goode, Philip R.; Dziembowski, W. A.; Korzennik, S. G.;
Rhodes, E. J., Jr.
1991ApJ...367..649G Altcode:
In this paper, a uniform approach of inversion was used to determine
the internal rotation rate of the sun from each of the six available
sets of solar oscillation data, which included the data of Duvall et
al. (1986), Rhodes et al. (1987, 1990), Tomczyk (1988), Brown and Morrow
(1987), and Libbrecht (1989). The technique chosen for inverting the
solar oscillation data was the discretized least-squares technique. The
results indicate that the rotation rate of the sun in the equatorial
plane declines going inward between the surface and 0.6 of the radius
and that the polar rate increases going inward (i.e., the surfacelike
differential rotation decreases with depth).
---------------------------------------------------------
Title: The Supergranulation Spectrum
Authors: Hathaway, David H.; Rhodes, Edward J.; Cacciani, Alessandro;
Korzennik, Sylvain G.
1991LNP...388..163H Altcode: 1991ctsm.conf..163H
Full-disk Dopplergram observations obtained at the 60-foot
tower of the Mount Wilson Observatory with the Cacciani sodium
magneto-optical filter were analyzed to determine the spectrum of
the solar supergranulation. Individual Dopplergrams were averaged
together using a weighted average over 20-minute intervals to remove
the p-mode oscillations. The Doppler signals due to the motion of the
observer, the solar rotation, differential rotation, and limb shift
were then removed from the data to produce Dopplergrams dominated
by the supergranular flows. These data were mapped to heliographic
coordinates and projected onto the spherical harmonics. The resulting
spectrum exhibits a peak at spherical harmonic degree } 100, which
corresponds to typical cell diameters of about 40 Mm. Synthetic data
were constructed and passed through the same analysis procedures to
determine the actual spectrum required to reproduce the results. A
good fit was obtained with a kinetic energy spectrum which peaks at }
100 and decreases exponentially out to } 500 with an e-folding range
of } 90. A power law fit to the spectrum over this range in yields an
exponent of about -2.75. No corrections for seeing were included in
the analysis. Although the image was sampled at 8 arcsec resolution,
the effects of seeing may alter the actual slope of the spectrum and
make it somewhat flatter. The spectrum does not exhibit any evidence
for a distinct mesogranulation component out to } 500 (corresponding
to cell diameters of about 8 Mm).
---------------------------------------------------------
Title: Solar Oscillation Ring Diagrams from Mt. Wilson Full-Disk
Magneto-Optical Dopplergrams
Authors: Hill, Frank; Rhodes, Edward J.; Korzennik, Sylvain G.;
Cacciani, Alessandro; Brown, Timothy M.
1991LNP...388..271H Altcode: 1991ctsm.conf..271H
Three-dimensional power spectra of solar oscillations have been
computed from moderate-resolution full disk Doppler images obtained
with the Magneto-Optical Filter at Mt. Wilson. Slices of the spectra
at constant frequency reveal the ring structures that are analogous
to the ridges in two-dimensional spectra. Ring diagrams obtained
at different heliographic positions show large differences in the
structure of the rings. These variations can be attributed to the
changing effective spatial resolution of the observations across the
disk. After correction for this effect, and .for terrestrial seeing,
the rings will be used to map the horizontal flows in the convection
zone as a function of position and depth.
---------------------------------------------------------
Title: Observations of intermediate- and high-degree p-mode
oscillations during sunspot cycles 21 and 22
Authors: Rhodes, E. J.; Cacciani, A.; Korzennik, S. G.
1991AdSpR..11d..17R Altcode: 1991AdSpR..11...17R
Extensive time series of resolved solar images have been available
for helioseismological studies since the late 1970s. We will first
review the temporal coverage that has been built up over the past
11 years at several different observatories. Next, we will present
examples of the frequencies, power levels, modal energies, and widths
of solar intermediate-(5< l <120) and high-degree (120< l
<600) p-modes which were obtained at the Mount Wilson Observatory's
60-Foot Solar Tower Telescope during the rising phase of the current
sunspot cycle. We will demonstrate that the inclusion of frequency
splittings from the high-degree p-modes has allowed us to demonstrate
that the sun's internal equatorial angular velocity is not constant
with radius but rather varies systematically with radius throughout
the solar convection zone and below. Lastly, we will show that, by
intercomparing many of the available p-mode frequency datasets, we have
been able to confirm the recent suggestion by Libbrecht and Woodard
/1/ that the frequencies of the intermediate-degree p-modes do vary
systematically with varying levels of solar activity. In particular,
we will demonstrate that such frequency shifts have been occurring in
every year that observations have been obtained since 1980 and that
such variations are also consistent with similar variations that have
been recently noted in low-degree p-mode frequencies.
---------------------------------------------------------
Title: Measurements of Intermediate- and High-Degree (20<1<600)
p-Mode Solar Oscillation Power and Energy
Authors: Rhodes, Edward J.; Brown, Timothy M.; Cacciani, Alessandro;
Korzennik, Sylvain G.; Ulrich, Roger K.
1991LNP...388..277R Altcode: 1991ctsm.conf..277R
We present measurements of the total modal power and energy of
both intermediate- and high-degree (20< l <600) solar p-mode
oscillations which have been corrected to first order for the combined
effects of atmospheric seeing, image motion due to imperfect tracking,
and the point spread function of our optics. These power and energy
estimates have been obtained from an average of 20 separate zonal l -
n power spectra, which were obtained from observations obtained at the
60-Foot Solar Tower of the Mt. Wilson Observatory between July 1 and 20,
1988. The raw total power values were obtained from a least-squares
fitting of Lorentzian profiles to the p-mode ridges in the average
zonal power spectrum. As an initial method of correcting the observed
power levels, we adopted the procedure described by Kaufman (1988)
and deconvolved measurements of the observed limb profiles from one
of our images using two slightly different theoretical unblurred limb
profiles in order to obtain two estimates of the modulation transfer
function (mtf) of our experiment. The corrected power values which
resulted show systematic variations with both frequency and degree
which are similar to those obtained by Kaufman. For example, between
l = 100 and 600 our corrected power values drop by a factor of at
least 4.5, although the magnitude of our correction becomes less
certain as the degree is increased above 300. We also convert these
power values into estimates of the total energy of the modes to show
that the modal energies decrease by a factor of at least 15 over the
same range in l. Even given the uncertainty of our correction at the
higher degrees, the consistency of the l-dependent decrease in the
modal energies with similar results by Kaufman (1990) suggests that,
at least above l = 100, the modes are not in energy equipartition with
turbulent convective eddies.
---------------------------------------------------------
Title: Further Evidence for Radial Variations in the Solar Equatorial
Angular Velocity Profile
Authors: Rhodes, Edward J.; Cacciani, Alessandro; Korzennik, Sylvain
G.; Ulrich, Roger K.
1991LNP...388..285R Altcode: 1991ctsm.conf..285R
One year ago we presented evidence that the rotationally-induced
frequency splittings of intermediate- and high-degree sectoral p-mode
oscillations vary systematically as a function of the degree, l,
of the modes (Rhodes, Cacciani, and Korzennik, 1989. Recently, we
confirmed the results presented there in three different ways. First,
we extended our earlier 5-day sequence of Dopplergrams to one of 20 days
which ran from July 1 through 20, 1988. We then repeated our earlier
cross-correlation analysis using the intrinsically higher frequency
resolution sectoral power spectra which resulted from the longer
data string. This analysis also showed the same l-dependence of the
frequency splittings which we had found in our earlier work. Second,
we computed a separate pair of 1024-minute long sectoral power
spectra for each of the 20 days and then averaged the 20 prograde
and 20 retrograde spectra into two average sectoral spectra. We
next computed the frequencies of the centers of both the prograde
and retrograde sectoral ridges at each even-l by fitting Lorentzian
profiles using a standard non-linear least-squares method and we then
simply subtracted the central frequencies of the corresponding prograde
and retrograde ridges at those same values of l. The splittings which
resulted from averaging these frequency differences over both l and
the radial overtone, n, showed the same l-dependence as did those
obtained from the cross-correlation analysis. Thirdly, we computed
Legendre coefficient expansions to the m - v frequency shifts of both
the high- and low-resolution tesseral power spectra. We then normalized
the sums of the odd Legendre expansion coefficients to obtain additional
estimates of the sectoral frequency splittings. Finally, we carried out
an inversion of the sectoral frequency splittings. This inversion shows
a rapid rise in the solar equatorial angular velocity from its surface
value to a value of 476 nHz at a depth of 0.07 to 0.08 solar radii below
the photosphere. The inverted profile also shows that the inner half
of the solar convection zone may be rotating at the magnetic feature
rate and that the equatorial angular velocity decreases inwardly of
the base of the convection zone to a depth of at least 0.50 solar radii.
---------------------------------------------------------
Title: Further Evidence for Radial Variations in the Solar Equatorial
Angular Velocity Profile
Authors: Rhodes, E. J., Jr.; Cacciani, A.; Korzennik, S.; Ulrich, R. K.
1990BAAS...22..896R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Depth and Latitude Dependence of the Solar Internal Angular
Velocity
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.
1990ApJ...351..687R Altcode:
One of the design goals for the dedicated helioseismology observing
state located at Mount Wilson Observatory was the measurement of the
internal solar rotation using solar p-mode oscillations. In this paper,
the first p-mode splittings obtained from Mount Wilson are reported
and compared with those from several previously published studies. It
is demonstrated that the present splittings agree quite well with
composite frequency splittings obtained from the comparisons. The
splittings suggest that the angular velocity in the solar equatorial
plane is a function of depth below the photosphere. The latitudinal
differential rotation pattern visible at the surface appears to persist
at least throughout the solar convection zone.
---------------------------------------------------------
Title: Has the sun's internal rotation changed through this activity
cycle ?
Authors: Goode, P. R.; Dziembowski, W. A.; Rhodes, E. J., Jr.;
Korzennik, S.
1990LNP...367..349G Altcode: 1990psss.conf..349G
The internal rotation of the Sun is determined from each of the
six available sets of solar oscillation splitting data. These data
span this activity cycle and best sample the region near the base of
the convection zone. Going inwards through the convection zone into
the outer radiative interior, the robust results are a decrease in
the rotation rate in the equatorial plane and a trend away from the
surface-like differential rotation toward solid body rotation. In
the equatorial plane of the radiative interior, the rotation rate
seems to systematically increase through the solar cycle. If true,
this suggests that the interior has a role in the activity cycle.
---------------------------------------------------------
Title: Contribution of High-Degree Frequency Splittings to the
Inversions of the Solar Rotation Rate
Authors: Korzennik, Sylvain G.; Cacciani, Alessandro; Rhodes, Edward
J.; Ulrich, Roger K.
1990LNP...367..341K Altcode: 1990psss.conf..341K
We present the contribution of high degree rotational splittings to
the inversion of the internal rotation rate around the equator. The
extention of the input data set to l of 500, allow us to improve the
resolution of the solution mainly in the outermost 15% of the solar
radius. The rotational profile obtained in the regions below the
surface leads to an attractive picture that could reconcile different
non-seismic estimates of the surface rotation rate.
---------------------------------------------------------
Title: Seismic Analysis of the Sun from Intermediate and High-Degree
P-Modes
Authors: Korzennik, Sylvain Gereon
1990PhDT........11K Altcode:
Solar oscillations provide a unique tool to investigate the internal
structure and dynamics of the Sun. While accurate measurements of the
solar acoustic spectrum characteristics have been performed for low-
and intermediate-degree modes, only a limited set of short time baseline
measurements for high-degree modes has been available (l > 120). The
purpose of this work is to provide an accurate and more reliable set
of measurements for these high-degree modes. High spatial resolution
(2.2 arc sec per pixel) full-disk dopplergrams of the solar surface
have been acquired at the Mt. Wilson 60-feet solar tower during the
summer of 1988, using a doppler analyzer based on the sodium magneto
-optical filter. Twenty consecutive days of observations have been
reduced to spherical harmonic coefficient time series, for degrees
l<=q 600. The time series were then Fourier transformed in order
to estimate the corresponding power spectra. From these power spectra,
frequency splittings have been estimated for degree 20 <=q l <=q
600. At low and intermediate degree (l <=q 120), individual modes
could be isolated, and hence reliable tesseral measurements have been
obtained. At high-degree (l > 120), the presence of mode blending
introduced systematic errors in the tesseral frequency splitting
determination. The nature of these systematics has been carefully
studied, but our simulations were unable to reproduce in detail the
observed systematics, and therefore, an ad hoc procedure was developed
to correct for them. Alternatively, sectoral frequency splittings, shown
to be less sensitive to mode blending systematics, have provided a more
reliable estimate of the frequency splitting for these high-degree
modes. From collapsed < m = 0>^ectra modal frequencies,
amplitudes and lifetimes have been estimated for 20 <=q l <=q
600. The required corrections for mode blending, point spread function
attenuation, and finite observing run have been applied. These new
measurements are compared with previous determinations and theoretical
predictions. Finally, based on the frequency splittings obtained from
the present study, as well as contemporaneous independent measurements,
we have inferred the internal rotation rate as a function of depth
in the equatorial regions, and discuss some of the implications of
such a profile in relation to solar dynamo, global circulation and
evolutionary models of rotating stars.
---------------------------------------------------------
Title: Evidence for Radial Variations in the Equatorial Profile of
the Solar Internal Angular Velocity
Authors: Rhodes, Edward J.; Cacciani, Alessandro; Korzennik, Sylvain G.
1990LNP...367..163R Altcode: 1990psss.conf..163R
We present evidence that the solar internal angular velocity, at least
as measured in the equatorial plane, shows systematic radial variations
in the outer half (by radius of the solar interior. Specifically,
we employ the rotationally-induced frequency splittings of both high-
and intermediate-degree sectoral p-mode oscillations to demonstrate
that the internal angular velocity rises inwardly from the observed
spectroscopic rotation rate of the photospheric gas to a higher value
that is at least equal to the observed rotation rate of sunspots, if
not higher, in the outer third of the convection zone before decreasing
inward of the convection zone to a value which is at least two percent
below the photospheric gas rotation rate. By making the assumption that
the observed splittings are sensitive to solar rotation at the midpoints
of the p-mode eigenfunctions we obtain an angular velocity profile which
rises from 452 nHz at the photosphere to 462 nHz at a depth of about
five percent of the solar radius below the photosphere. A comparison of
this inferred angular velocity profile with that obtained from a formal
inversion of these splittings (which is reported elsewhere in these
proceedings by Korzennik et al.) suggests that the angular velocity
might actually exceed the magnetic rotation rate over much of the
convection zone before decreasing inwardly toward the center of the sun.
---------------------------------------------------------
Title: Seismic Analysis of the Solar Interior. I. Can Opacity Changes
Improve the Theoretical Frequencies?
Authors: Korzennik, Sylvain G.; Ulrich, Roger K.
1989ApJ...339.1144K Altcode:
The paper describes the application of seismic inverse theory to
the deduction of properties of the solar interior using presently
available measured frequencies of the solar oscillations. Only the
solar opacity is included in this application. This study has used the
spectral expansion method of Lanczos and Jackson to derive changes to
the opacity which improve ageement between the theoretical and observed
frequencies of oscillation. It is found that a family of opacity changes
exists which yields models that improve the frequency agreement by
amounts that are indistinguishable among the family members.
---------------------------------------------------------
Title: Evidence for Degree-Dependent Variations in the Frequency
Splittings of Solar Sectoral p-Modes
Authors: Rhodes, E. J., Jr.; Cacciani, A.; Korzennik, S.
1989BAAS...21..831R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrum Lifetime, and Rotation Rate of Supergranules
Authors: Hathaway, D. H.; Rhodes, E. J., Jr.; Cacciani, A.;
Korzennik, S.
1989BAAS...21..829H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Luminosity Oscillation Telescope (SLOT).
Authors: Andersen, Bo Nyborg; Domingo, V.; Jones, A. R.; Korzennik,
Sylvain G.; Jimenez, A.; Palle, Pere L.; Regulo, C.; Roca Cortés,
Teodoro
1988ESASP.286..175A Altcode: 1988ssls.rept..175A
Low degree l = 0-2 solar p-modes have been detected with the
SLOT instruments at Izaña and Baja California. The main source
of noise for these ground based observations is in the terrestrial
atmosphere. However, the data acquisition system still has to have very
slow intrinsic noise. The authors describe how this is achieved in the
SLOT instruments. They also give a general description of the design
and operating principles of the photometers and data acquisition system.
---------------------------------------------------------
Title: Measurement of the rotational frequency splitting of the solar
five-minute oscillations from magneto-optical filter observations.
Authors: Tomczyk, Steven; Cacciani, Alessandro; Korzennik, Sylvain G.;
Rhodes, Edward J., Jr.; Ulrich, Roger K.
1988ESASP.286..141T Altcode: 1988ssls.rept..141T
Observations of the solar five-minute oscillations in the photospheric
velocity field were obtained during the summer of 1984 at the 60-foot
solar tower of the Mt. Wilson Observatory with a magneto-optical
filter. The magneto-optical filter employs magneto-optical effects in
an atomic vapor to isolate narrow bandpasses in alternate wings of
a spectral line. Time series of full disk velocity images having a
resolution of about 10 arcseconds and a noise level of 15 m/s/pixel
were obtained on 92 days between the months of May and September of
1984. A subset of two time series from this data of 16 and 19 days
duration having a total of 25744 doppler images were analyzed to provide
estimates of the rotational frequency splitting for spherical harmonic
degrees between 5 and 120. The results of this analysis indicate a
decrease in the rate of solar rotation with increasing depth inside
the sun. Also, a decrease in the rate of differential rotation with
increasing depth is observed.
---------------------------------------------------------
Title: Inversion of the solar rotation rate versus depth and latitude.
Authors: Korzennik, Sylvain G.; Cacciani, Alessandro; Rhodes, Edward
J., Jr.; Tomczyk, Steven; Ulrich, Roger K.
1988ESASP.286..117K Altcode: 1988ssls.rept..117K
The authors have used three different inversion techniques to compute
the internal solar rotation rate from several sets of n-averaged
frequency splittings. They have used an iterative variation of the
spectral expansion method, the optimal averaging kernel method and
a piecewise constant constrained least square method to invert the
data. Each computation was carried out independently. While they
present similar trends, each of the solutions differs in detail. A
consistent feature in all the inversions is the disappearance of
differential rotation below the base of the convection zone. Also,
a strong differential signature in the deeper part of the convection
zone is present in most of the solutions. A slow decrease of the
rotation rate with depth for the equatorial and mid-latitude curves
is significant in the spectral expansion and the least square results
but only marginally apparent in the averaging kernel results.
---------------------------------------------------------
Title: Radial and latitudinal gradients in the solar internal
angular velocity.
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.
1988ESASP.286...73R Altcode: 1988ssls.rept...73R
The authors recently presented the results of an analysis of the
frequency splittings of intermediate-degree (3 < degree ≤ 170)
p-mode oscillations which were obtained from a 16-day subset of our 1984
Mt. Wilson 60-foot tower observations. These results showed evidence
for both radial and latitudinal gradients in the solar internal
angular velocity. In particular, the results indicated that, from
0.6 R<SUB><SUB>sun</SUB></SUB> to 0.95 R<SUB><SUB>sun</SUB></SUB>,
the solar internal angular velocity increases systematically from
440 to 463 nHz, corresponding to a positive radial gradient of ≍66
nHz/R<SUB><SUB>sun</SUB></SUB> for that portion of the solar interior. A
previous analysis indicated that the latitudinal differential rotation
gradient which is seen at the solar surface persists throughout
the convection zone, although there was some indication that the
differential rotation might disappear entirely below the base of the
convection zone. Here the authors extend their previous analysis to
include comparisons with additional observational studies and they
also present comparisons between our earlier results and the results
of additional inversions of several of the observational datasets. All
of these comparisons reinforce the previous conclusions regarding
the existence of radial and latitudinal gradients in the internal
angular velocity.
---------------------------------------------------------
Title: Initial high-degree p-mode frequency splittings from the 1988
Mt. Wilson 60-foot tower solar oscillation program.
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.
1988ESASP.286...81R Altcode: 1988ssls.rept...81R
The authors present here the initial frequency splitting results
of solar p-mode oscillations which they have obtained from their
1988 helioseismology at the Mt. Wilson Observatory. These frequency
splittings correspond to the rotational splittings of sectoral harmonics
which range in degree between 10 and 598. They were obtained from a
cross-correlation analysis of the prograde and retrograde portions
of a two-dimensional (l-ν) power spectrum. This power spectrum was
computed from an eight-hour sequence of full-disk Dopplergrams which
were obtained on July 2, 1988, at the 60-foot tower telescope with
a Na magneto-optical filter and a 1024×1024 pixel CCD camera. These
frequency splittings have an inherently larger scatter than did the
splittings obtained from earlier 16-day power spectra. Consequently,
the best one can say now is that these splittings are consistent with an
internal solar rotational velocity which is independent of radius along
the equatorial plane. The normalized frequency splittings averaged
449±3 nHz, a value which is very close to the observed equatorial
rotation rate of the photospheric gas of 451.7 nHz.
---------------------------------------------------------
Title: Diurnal photometric conditions at Teide observatory and
long-term solar irradiance variations
Authors: Andersen, B.; Domingo, V.; Jiménez, A.; Jones, A.; Korzennik,
S.; Pallé, P. L.; Pérez Hernández, F.; Régulo, C.; Roca Cortés,
T.; Tomás, L. L.
1988SoPh..116..391A Altcode:
Monochromatic extinction coefficients at four wavelengths have been
obtained over a period of more than two years at the Observatorio del
Teide (Izaña Tenerife) using a full disc, direct sunlight, quadruple
photometer devoted to the detection of integral luminosity oscillations
of the Sun. The mean extinction coefficients (0.13 at 500 nm) show
a seasonal variation of about 15%, the best atmospheric conditions
being in winter and autumn. Moreover, in anyone day the extinction
coefficient in the afternoon is always lower than the one in the
morning by ∼ 7%. A one-year period fluctuation, with an amplitude
of ∼ 0.035 mag, has been identified in the instrumental magnitudes
outside the atmosphere, and is interpreted as the variation produced
by the different Sun-Earth distance from winter to summer. Finally,
the study made to detect periodic time fluctuations in both, Sun's
magnitude and extinction coefficients, has given null results at levels
of ∼ 0.04 and ∼ 1.8%, respectively.
---------------------------------------------------------
Title: On the Constancy of Intermediate-Degree p-Mode Frequencies
during the Declining Phase of Solar Cycle 21
Authors: Rhodes, Edward J., Jr.; Woodard, Martin F.; Cacciani,
Alessandro; Tomczyk, Steven; Korzennik, Sylvain G.; Ulrich, Roger K.
1988ApJ...326..479R Altcode:
A comparison of two sets of frequencies of intermediate-degree (6 ≤ l
≤ 89) solar p-mode oscillations obtained in late 1981 and in mid-1984
shows agreement at the level of 0.02 μHz, or better than one part in
10<SUP>5</SUP>. In particular, the frequencies of 573 modes obtained
at the South Pole during 1981 December 24 - 25, (reported by Duvall,
Harvey, and Pomerantz in 1987) were compared with the frequencies of
the same modes as observed at the Mount Wilson Observatory 60 foot
Solar Tower from 1984 July 29 through August 13. It is concluded that
the data are consistent with no change in intermediate-degree p-mode
frequencies between late 1981 and mid-1985.
---------------------------------------------------------
Title: Measurements of Solar Internal Rotation Obtained with the
Mt-Wilson 60-FOOT Solar Tower
Authors: Rhodes, E. J., Jr.; Cacciani, A.; Woodard, M.; Tomczyk, S.;
Korzennik, S.; Ulrich, R. K.
1988IAUS..123...41R Altcode:
The authors have obtained estimates of the solar internal rotational
velocity from measurements of the frequency splittings of p-mode
oscillations. Specifically, they have analyzed a 10-day time series
of full-disk Dopplergrams obtained during July and August 1984 at the
60-Foot Tower Telescope of the Mt. Wilson Observatory.
---------------------------------------------------------
Title: Earthbased Observations of Solar Luminosity Oscillations
Authors: Jimenez, A.; Palle, P. L.; Perez-Hernandez, F.; Regulo, C.;
Roca-Cortes, T.; Domingo, V.; Korzennik, S.
1988IAUS..123...71J Altcode:
Earth based multichannel photometry of integral sunlight has been
obtained at Izaña (Tenerife) during 1984 - 1986. Power spectra of the
solar luminosity variations of individual days show power in the 5
minute interval above noise at a level comparable to SMM data. When
combining contigous days of data the signature of p mode solar
oscillations spectrum appears, although individual peak identification
is difficult.
---------------------------------------------------------
Title: Constancy of Intermediate-degree p-Mode Frequencies During
the Declining Phase of Solar Cycle 21
Authors: Rhodes, E. J., Jr.; Woodard, M. F.; Cacciani, A.; Tomczyk,
S.; Korzennik, S.; Ulrich, R. K.
1987BAAS...19Q.933R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Angular Velocity of the Solar Interior Obtained by an
Asymptotic Inversion of P-Mode Frequency Shifts
Authors: Woodard, M. F.; Rhodes, E. J., Jr.; Tomczyk, S.; Korzennik,
S.; Cacciani, A.; Ulrich, R. K.
1987BAAS...19..934W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Estimates of the solar internal angular velocity obtained
with the Mt. Wilson 60-foot solar tower
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Woodard,
Martin; Tomczyk, Steven; Korzennik, Sylvain; Ulrich, R. K.
1987ASSL..137...75R Altcode: 1987isav.symp...75R
Estimates are obtained of the solar internal angular velocity from
measurements of the frequency splittings of p-mode oscillations. A
16-day time series of full-disk Dopplergrams obtained during July and
August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory
is analyzed. Power spectra were computed for all of the zonal, tesseral,
and sectoral p-modes from l = 0 to 89 and for all of the sectoral
p-modes from l = 90 to 200. A mean power spectrum was calculated for
each degree up to 89. The frequency differences of all of the different
nonzonal modes were calculated for these mean power spectra.
---------------------------------------------------------
Title: Ground-based measurements of solar intensity oscillations
Authors: Jimenez, A.; Palle, P. L.; Roca Cortes, T.; Domingo, V.;
Korzennik, S.
1987A&A...172..323J Altcode:
Ground-based multichannel photometry of integral sunlight has been
obtained at Izaña (Tenerife) during three months in 1984 with a
photometer built at ESTEC. Power spectra of solar irradiance variations
of individual days show power in the 5 min band just above noise at
a level comparable to the one found from the SMM data (Woodard and
Hudson, 1983). Previous similar ground work had never achieved the
signal level required at the 5 min interval. When combining the best
7 contiguous days of data, the signature of p mode solar oscillations
spectra appears, but individual identification is difficult due to a
low signal-to-noise ratio.
---------------------------------------------------------
Title: Inversion of Perturbed Solar Models for Improved Solar
Oscillation Frequencies Agreement
Authors: Korzennik, S. G.; Yaari, A.; Ulrich, R. K.
1986BAAS...18..990K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evidence for Radial Gradients in the Solar Internal Rotational
Velocity
Authors: Rhodes, E. J., Jr.; Tomczyk, S.; Woodard, M. F.; Cacciani,
A.; Korzennik, S.; Ulrich, R. K.
1986BAAS...18Q1010R Altcode:
No abstract at ADS
