Author name code: battacharyya
ADS astronomy entries on 2022-09-14
author:"Bhattacharyya, J"
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Title: de Sitterization via Kerr-Schild
Authors: Sharma, Aditya; Banerjee, Kinjal; Bhattacharyya, Jishnu
Bibcode: 2022arXiv220504773S
Altcode:
Spatially homogeneous cosmological spacetimes, evolving in the
presence of a positive cosmological constant and matter satisfying
some reasonable energy conditions, typically approach the de Sitter
geometry asymptotically (at least locally). In this work, we propose an
alternate way to characterize this phenomena. We focus on a subset of
such models admitting a generalized Kerr-Schild representation. We argue
that the functions which define such a representation can be chosen,
such that, their asymptotic behavior make the evolution towards the
de Sitter spacetime manifest through the representation. We verify
our claim for the Kantowski-Sachs family of cosmological spacetimes.
Title: Dynamical obstruction to perpetual motion from
Lorentz-violating black holes
Authors: Benkel, Robert; Bhattacharyya, Jishnu; Louko, Jorma;
Mattingly, David; Sotiriou, Thomas P.
Bibcode: 2018PhRvD..98b4034B
Altcode: 2018arXiv180301624B
Black holes in Lorentz-violating theories have been claimed to
violate the second law of thermodynamics by perpetual motion energy
extraction. We revisit this question for a Penrose splitting process
in a spherically symmetric setting with two species of particles
that move on radial geodesics that extend to infinity. We show that
energy extraction by this process cannot happen in any theory in which
gravity is attractive, in the sense of a geometric inequality that we
describe. This inequality is satisfied by all known Einstein-æther
and Hořava black hole solutions.
Title: Revisiting the cuscuton as a Lorentz-violating gravity theory
Authors: Bhattacharyya, Jishnu; Coates, Andrew; Colombo, Mattia;
Gümrükçüoǧlu, A. Emir; Sotiriou, Thomas P.
Bibcode: 2018PhRvD..97f4020B
Altcode: 2016arXiv161201824B
The cuscuton is a scalar field with infinite speed of propagation. It
was introduced in the context of cosmology but it has also been claimed
to resemble Hořava gravity in a certain limit. Here we revisit the
cuscuton theory as a Lorentz-violating gravity theory. We clarify its
relation with Hořava gravity and Einstein-æther theory, analyze its
causal structure, and consider its initial value formulation. Finally,
we discuss to which extent the cuscuton theory can be used as a proxy
for Hořava gravity in the context of gravitational collapse and
formation of universal horizons.
Title: Simulating Coronal Loop Implosion and Compressible Wave Modes
in a Flare Hit Active Region
Authors: Sarkar, Aveek; Vaidya, Bhargav; Hazra, Soumitra;
Bhattacharyya, Jishnu
Bibcode: 2017ApJ...851..120S
Altcode: 2017arXiv171105273S
There is considerable observational evidence of implosion of magnetic
loop systems inside solar coronal active regions following high-energy
events like solar flares. In this work, we propose that such collapse
can be modeled in three dimensions quite accurately within the framework
of ideal magnetohydrodynamics. We furthermore argue that the dynamics
of loop implosion is only sensitive to the transmitted disturbance
of one or more of the system variables, e.g., velocity generated at
the event site. This indicates that to understand loop implosion,
it is sensible to leave the event site out of the simulated active
region. Toward our goal, a velocity pulse is introduced to model the
transmitted disturbance generated at the event site. Magnetic field
lines inside our simulated active region are traced in real time,
and it is demonstrated that the subsequent dynamics of the simulated
loops closely resemble observed imploding loops. Our work highlights
the role of plasma β in regards to the rigidity of the loop systems
and how that might affect the imploding loops’ dynamics. Compressible
magnetohydrodynamic modes such as kink and sausage are also shown to
be generated during such processes, in accordance with observations.
Title: Causality and black holes in spacetimes with a preferred
foliation
Authors: Bhattacharyya, Jishnu; Colombo, Mattia; Sotiriou, Thomas P.
Bibcode: 2016CQGra..33w5003B
Altcode: 2015arXiv150901558B
We develop a framework that facilitates the study of the causal
structure of spacetimes with a causally preferred foliation. Such
spacetimes may arise as solutions of Lorentz-violating theories,
e.g. Hořava gravity. Our framework allows us to rigorously define
concepts such as black/white holes and to formalize the notion of a
‘universal horizon’, that has been previously introduced in the
simpler setting of static and spherically symmetric geometries. We
also touch upon the issue of development and prove that universal
horizons are Cauchy horizons when evolution depends on boundary data
or asymptotic conditions. We establish a local characterisation of
universal horizons in stationary configurations. Finally, under the
additional assumption of axisymmetry, we examine under which conditions
these horizons are cloaked by Killing horizons, which can act like
usual event horizons for low-energy excitations.
Title: Asymptotically Lifshitz spacetimes with universal horizons in
(1 +2 ) dimensions
Authors: Basu, Sayandeb; Bhattacharyya, Jishnu; Mattingly, David;
Roberson, Matthew
Bibcode: 2016PhRvD..93f4072B
Altcode: 2016arXiv160103274B
Hořava gravity theory possesses global Lifshitz space as a solution
and has been conjectured to provide a natural framework for Lifshitz
holography. We derive the conditions on the two-derivative Hořava
gravity Lagrangian that are necessary for static, asymptotically
Lifshitz spacetimes with flat transverse dimensions to contain a
universal horizon, which plays a similar thermodynamic role as the
Killing horizon in general relativity. Specializing to z =2 in 1 +2
dimensions, we then numerically construct such regular solutions over
the whole spacetime. We calculate the mass for these solutions and
show that, unlike the asymptotically anti-de Sitter case, the first
law applied to the universal horizon is straightforwardly compatible
with a thermodynamic interpretation.
Title: Evolution and spherical collapse in Einstein-Æther theory
and Hořava gravity
Authors: Bhattacharyya, Jishnu; Coates, Andrew; Colombo, Mattia;
Sotiriou, Thomas P.
Bibcode: 2016PhRvD..93f4056B
Altcode: 2015arXiv151204899B
We compare the initial value formulation of the low-energy limit of
(nonprojectable) Hořava gravity to that of Einstein-æther theory when
the æther is assumed to be hypersurface orthogonal at the level of the
field equations. This comparison clearly highlights a crucial difference
in the causal structure of the two theories at the nonperturbative
level: in Hořava gravity evolution equations include an elliptic
equation that is not a constraint relating initial data but needs to
be imposed on each slice of the foliation. This feature is absent in
Einstein-æther theory. We discuss its physical significance in Hořava
gravity. We also focus on spherical symmetry, and we revisit existing
collapse simulations in Einstein-æther theory. We argue that they
have likely already uncovered the dynamical formation of a universal
horizon and that they can act as evidence that this horizon is indeed
a Cauchy horizon in Hořava gravity.
Title: Universal horizons in maximally symmetric spaces
Authors: Bhattacharyya, Jishnu; Mattingly, David
Bibcode: 2014IJMPD..2343005B
Altcode: 2014arXiv1408.6479B
Universal horizons in Hořava-Lifshitz gravity and Einstein-æther
theory are the equivalent of causal horizons in general relativity
and appear to have many of the same properties, including a first
law of horizon thermodynamics and thermal radiation. Since universal
horizons are infrared (IR) solutions of a putative power counting
renormalizable quantum gravitational theory, fully understanding
their thermodynamics will shed light on the interplay between black
hole thermodynamics and quantum gravity. In this paper, we provide
a complete classification, including asymptotic charges, of all
four-dimensional static and spherically symmetric universal horizon
solutions with maximally symmetric asymptotics — the equivalents of
the Schwarzschild, Schwarzschild-de Sitter or Schwarzschild-anti-de
Sitter spacetimes. Additionally, we derive the associated first laws for
the universal horizon solutions. Finally, we prove that independent of
asymptotic boundary conditions, any spherically symmetric solution in
Hořava-Lifshitz gravity with a universal horizon is also a solution
of Einstein-æther theory, thereby broadening and complementing the
known equivalence region of the solution spaces.
Title: Towards Thermodynamics of Universal Horizons in Einstein-æther
Theory
Authors: Berglund, Per; Bhattacharyya, Jishnu; Mattingly, David
Bibcode: 2013PhRvL.110g1301B
Altcode: 2012arXiv1210.4940B
Holography grew out of black hole thermodynamics, which relies on
the causal structure and general covariance of general relativity. In
Einstein-æther theory, a generally covariant theory with a dynamical
timelike unit vector, every solution breaks local Lorentz invariance,
thereby grossly modifying the causal structure of gravity. However,
there are still absolute causal boundaries, called “universal
horizons,” which are not Killing horizons yet obey a first law of
black hole mechanics and must have an entropy if they do not violate
a generalized second law. We couple a scalar field to the timelike
vector and show via the tunneling approach that the universal horizon
radiates as a blackbody at a fixed temperature, even if the scalar
field equations also violate local Lorentz invariance. This suggests
that the class of holographic theories may be much broader than
currently assumed.
Title: Charged dilatonic AdS black branes in arbitrary dimensions
Authors: Berglund, Per; Bhattacharyya, Jishnu; Mattingly, David
Bibcode: 2012JHEP...08..042B
Altcode: 2011arXiv1107.3096B
We study electromagnetically charged dilatonic black brane solutions
in arbitrary dimensions with flat transverse spaces, that are
asymptotically AdS. This class of solutions includes spacetimes which
possess a bulk region where the metric is approximately invariant
under Lifshitz scalings. Given fixed asymptotic boundary conditions,
we analyze how the behavior of the bulk up to the horizon varies with
the charges and derive the extremality conditions for these spacetimes.
Title: Mechanics of universal horizons
Authors: Berglund, Per; Bhattacharyya, Jishnu; Mattingly, David
Bibcode: 2012PhRvD..85l4019B
Altcode: 2012arXiv1202.4497B
Modified gravity models such as Hořava-Lifshitz gravity or
Einstein-æther theory violate local Lorentz invariance and therefore
destroy the notion of a universal light cone. Despite this, in the
infrared limit both models above possess static, spherically symmetric
solutions with “universal horizons”—hypersurfaces that are
causal boundaries between an interior region and asymptotic spatial
infinity. In other words, there still exist black hole solutions. We
construct a Smarr formula (the relationship between the total energy
of the spacetime and the area of the horizon) for such a horizon in
Einstein-æther theory. We further show that a slightly modified first
law of black hole mechanics still holds with the relevant area now
a cross-section of the universal horizon. We construct new analytic
solutions for certain Einstein-æther Lagrangians and illustrate how our
results work in these exact cases. Our results suggest that holography
may be extended to these theories despite the very different causal
structure as long as the universal horizon remains the unique causal
boundary when matter fields are added.
Title: Infrasound from large surf
Authors: Garcés, M.; Aucan, J.; Fee, D.; Caron, P.; Merrifield, M.;
Gibson, R.; Bhattacharyya, J.; Shah, S.
Bibcode: 2006GeoRL..33.5611G
Altcode:
Simultaneous infrasonic, visual, and ocean-bottom pressure sensor
observations of large swells on the island of Kauai and small to
medium-sized surf on the island of Hawaii yielded a clear relationship
between breaking wave height and low-frequency atmospheric sound
amplitudes in the 1-20 Hz frequency range. These experiments confirmed
that infrasound can be generated by barreling waves as well as by
waves crashing against rocky shorelines and exposed ledges. As will
be demonstrated in a companion paper, breaking wave period may also
be extracted from infrasound data. The results of these experiments
demonstrate that low-frequency sound may be used for real-time estimates
of the amplitude, period, and spatial distribution of surf in the
littoral zone, with a potential application to the identification of
breaking wave types.
Title: Different distribution functions of solar x-ray flares
Authors: Das, T. K.; de, B. K.; Bhattacharyya, J.
Bibcode: 2004BASI...32...15D
Altcode:
No abstract at ADS
Title: Neutrino Oscillation as Coupled vibration
Authors: Bhattacharyya, Jyotisekhar; Biswas, Satyabrata
Bibcode: 2002gr.qc....11097B
Altcode:
Neutrino oscillation is visualized as coupled vibrations. Unlike
existing models describing neutrino oscillations, our model involving
a single fundamental mass parameter $m$ and first discussed in the
context of a possible boson oscillation demonstrates that for a self
consistent theory there should be three types of bosons paired with
maximal mixing. The argument is easily extended to neutrinos (fermions)
with the exception that in the case of boson oscillation means periodic
variation of particle number, whereas in the case of fermions the
particle number does not change, only the mass oscillates. The
fermionic vacuum is not really empty but filled with zero energy
fermions. The oscillation length calculated perturbatively conforms to
the experimental findings. Also there is no fermionic number violation
in our model.
Title: Upper Mantle Shear and Compressional Velocity Structure of
the Central US Craton: Shear Wave Low-Velocity Zone and Anisotropy
Authors: Rodgers, Arthur; Bhattacharyya, Joydeep
Bibcode: 2001GeoRL..28..383R
Altcode:
One-dimensional upper mantle velocity structure is estimated by modeling
P, SV and SH body-waveforms sampling the central United States. The
resulting model features a thick mantle lid with a positive velocity
gradient. A significant shear wave low-velocity zone (6% velocity
reduction) is required below the lid however the compressional
velocities are not reduced. The paths studied lie along the fast axes
of teleseismic shear wave splitting measurements and absolute plate
motion. We observe splitting of upper mantle refracted shear-waves,
with the transverse component slow relative to the radial component. In
order to fit the shear wave arrivals and satisfy teleseismic shear-wave
splitting observations we infer azimuthal anisotropy (maximum 1.6%)
distributed throughout the mantle lid and low-velocity zone, with
increasing anisotropy with depth.
Title: Studies on some aspects of solar X-ray flares.
Authors: Das, T. K.; de, B. K.; Bhattacharyya, J.
Bibcode: 1999InJPB..73..695D
Altcode:
Studies have been made on the solar X-ray flares observed by GOES
during the period July 1993 - June 1994, which encompasses the
post-maximum phase of 22nd solar cycle. It has been examined that N-S
asymmetry remains positive in respect of both latitudinal position
and intensity of X-ray flares and increases with the increase of
intensity. The E-W asymmetry is found to be zero, when longitudinal
distribution is considered; but it remains positive up to a certain
intensity value above which it becomes negative. The duration and
rise time lie respectively in the ranges of values 5 - 15 min and 0 -
5 min. The distribution of impulsiveness of X-ray flares follows an
almost binomial distribution pattern peaking around 0.45.
Title: The Intermediate Polar PQ GEM -- Status of Wet Observations
of 1996
Authors: Marar, T. M. K.; Seetha, S.; Ashoka, B. N.; Kasturirangan,
K.; Mahra, H. S.; Bhattacharyya, J. C.; Leibowitz, E. M.; Hemar, S.;
Mendelson, H.; Ibbetson, P. A.; O'Donoghue, D.; Buckley, D. A. H.;
Breger, M.; Handler, G.; Sperl, M.; Serkowitsch, E.; Reegen, P.;
Moskalik, P.; Zola, S.; Pajdosz, G.; Krzesinski, J.; Silvotti, R.;
Vauclair, G.; Dolez, N.; Solheim, J. -E.; Pfeiffer, B.; Kepler, S. O.;
Kanaan, A.; Provencal, J.; Kawaler, S. D.; O'Brien, M. S.; Nather,
R. E.; Winget, D. E.; Kleinman, S.; Nitta, A.; Bradley, P. A.; Guzik,
J. A.; Clemens, C.; Sullivan, D. J.; Jiang, X.
Bibcode: 1998BaltA...7..287M
Altcode: 1998OAst....7..287M
A summary of the results on PQ Gem based on WET observations conducted
in February 1996 is presented. The 13.9 min spin period of the white
dwarf in the system and the orbital side-band at 14.5 min have been
detected unambiguously. Searches for other periods in the system gave
negative results.
Title: HiRES: the High-Resolution EUV Spectroheliometer
Authors: Timothy, J. Gethyn; Bergamini, Paolo; Bhattacharyya, Jagadish
C.; Huber, Martin H.; Jain, Surendra K.; Naletto, Giampiero; Nicholls,
Ralph W.; Nicolosi, Piergiorgio; Saxena, Ajay K.; Tondello, Giuseppe;
Walker, Arthur B.
Bibcode: 1997SPIE.3114..450T
Altcode:
The high-resolution EUV spectroheliometer (HiRES) is our first step
towards the 0.1 arc sec angular resolution goal at EUV wavelengths. The
HiRES instrument consists of a Gregory telescope with a 45-cm-diameter
primary mirror, and an imaging EUV spectrometer, employing a
single-reflection toric diffraction grating in a Rowland circle mounting
and an imaging pulse-counting multi-anode microchannel array (MAMA)
detector system. The MAMA detector covers the spectral range from 560
to 631 angstrom with a spectral resolution of 70 mAngstrom. A Pt/Ne
lamp impresses a wavelength calibration spectrum on the upper part
of the detector while the solar spectrum is recorded simultaneously
on the lower part. The times-of-arrival and addresses of the detected
photons are transmitted directly to the ground to allow correction of
the SPARCS pointing jitter. The HiRES spectrometer slit is pointed to a
specific location using real-time control of the SPARCS, and SPARCS can
be commanded to execute a linear (push broom) scan across the sun. Two
EUV photodiodes are used to measure the absolute sola irradiances and
the atmospheric extinction profiles in wavelength bands centered at
304 angstrom and 584 angstrom respectively.
Title: My encounter with astronomy : early years
Authors: Bhattacharyya, J. C.
Bibcode: 1997BASI...25...19B
Altcode:
No abstract at ADS
Title: My encounter with astronomy : later years
Authors: Bhattacharyya, J. C.
Bibcode: 1997BASI...25...29B
Altcode:
No abstract at ADS
Title: Structures in Saturn's Magnetosphere
Authors: Bhattacharyya, J. C.
Bibcode: 1995JApAS..16..377B
Altcode:
No abstract at ADS
Title: Detection of optical pulsations from RX J0558.0+5353.
Authors: Ashoka, B. N.; Marar, T. M. K.; Seetha, S.; Kasturirangan,
K.; Bhattacharyya, J. C.
Bibcode: 1995A&A...297L..83A
Altcode:
We report the detection of optical pulsations at a period of
272.785+-0.003s from the newly discovered intermediate polar RX
J0558.0+5353. This period nearly coincides with the X-ray period
reported by Haberl et al. (1994). In the optical band the folded light
curve of the star reveals a non-sinusoidal pulse with a pulsed fraction
of 10.8%.
Title: A Personal Computer-Based Imaging Stokes Polarimeter for
Solar Observations
Authors: Ananth, A. V.; Venkatakrishnan, P.; Narayanan, R. S.;
Bhattacharyya, J. C.
Bibcode: 1994SoPh..151..231A
Altcode:
For measurements of vector magnetic field over solar active regions,
a Stokes polarimeter for studying the polarisation profiles on
selected spectral lines is described. This paper gives details of
the relevant CCD imaging system and the personal computer (PC)-based
acquisition, together with the image analysis techniques necessary
for the task. Field trials and tests of the system are also described.
Title: Report of IAU Commission 9: Instruments and techniques
(Instruments et techniques).
Authors: Bhattacharyya, J. C.
Bibcode: 1994IAUTA..22...39B
Altcode:
No abstract at ADS
Title: Inner Core Attenuation From Short-Period Pkp(Bc) Versus
Pkp(Df) Waveforms
Authors: Bhattacharyya, Joydeep; Shearer, Peter; Masters, Guy
Bibcode: 1993GeoJI.114....1B
Altcode:
No abstract at ADS
Title: The High Resolution Extreme-Ultraviolet Spectroheliometer
(HiRES) Experiment: Capabilities and Observing Goals
Authors: Berger, T. E.; Timothy, J. G.; Walker, A. B. C., Jr.; Jain,
S. K.; Saxena, A. K.; Bhattacharyya, J. C.; Huber, M. C. E.; Tondello,
G.; Naletto, G.
Bibcode: 1993BAAS...25.1209B
Altcode:
No abstract at ADS
Title: HiRES: High Resolution Extreme Ultraviolet Spectroheliometer.
Authors: Berger, T.; Bergamini, P.; Kirby, H.; Timothy, J. G.; Walker,
A. B. C.; Bhattacharyya, J. C.; Jain, S. K.; Saxena, A. K.; Huber,
M. C. E.; Naletto, G.; Tondello, G.
Bibcode: 1993uxrs.conf..289B
Altcode: 1993uxsa.conf..289B
The HiRES sounding rocket payload is designed to obtain very high
spatial, spectral, and temporal resolution images of the solar
chromospheric and coronal plasmas in the extreme ultraviolet (EUV)
wavelength range from 500 to 650 Å. The instrument consists of a 450
mm f/15 Gregorian telescope feeding a 1-m normal incidence stigmatic
spectrometer. The stigmatic spectrometer utilizes a toroidal diffraction
grating formed by a unique elastic substrate deformation technique
in order to achieve simultaneous spatial and spectral focusing at
two points on the detector plane. Spatial resolution on the order
of 0.4 arcsecond across a 3×3 arcmin2 field of view is
obtained. Temporal resolution of the order of milliseconds is achieved
by the use of an advanced imaging Multi-Anode Microchannel Array
(MAMA) detector. A hydrogen-alpha 6562.8 Å camera and a 0.25-m EUV
solar irradiance spectrometer are also included in the payload.
Title: Vainu Bappu Telescope
Authors: Bhattacharyya, J. C.; Rajan, K. T.
Bibcode: 1992BASI...20..319B
Altcode:
No abstract at ADS
Title: Design and test of a High-Resolution EUV Spectroheliometer
Authors: Berger, Thomas E.; Timothy, J. G.; Walker, Arthur B. C., Jr.;
Kirby, Helen; Morgan, Jeffrey S.; Jain, Surendra K.; Saxena, Ajay K.;
Bhattacharyya, Jagadish C.; Huber, Martin C. E.; Tondello, Giuseppe
Bibcode: 1992SPIE.1546..446B
Altcode: 1992SPIE.2011..446B
The HiRES High-Resolution EUV Spectroheliometer is a sounding rocket
instrument yielding very high spatial, spectral, and temporal resolution
images of the solar outer atmosphere, on the basis of a 45-cm Gregorian
telescope feeding a normal-incidence stigmatic EUV spectrometer with
imaging multianode microchannel-array detector system, as well as an
IR spectrometer with imaging CCD detector system. Attention is given
to the expected performance of this system, including the effects of
vibrational misalignments due to the sounding rocket flight environment.
Title: HiRES: a high-resolution stigmatic extreme ultraviolet
spectroheliometer for sudies of the fine-scale structure of the
solar chromosphere, transition region, and corona.
Authors: Timothy, J. G.; Berger, Thomas E.; Morgan, Jeffrey S.;
Walker, Arthur B. C., Jr.; Jain, Surendra K.; Saxena, Ajay K.;
Bhattacharyya, Jagadish C.; Huber, Martin C. E.; Tondello, Giuseppe;
Naletto, Giampiero
Bibcode: 1991OptEn..30.1142T
Altcode:
The authors describe the design of a high-resolution stigmatic
extreme-ultraviolet spectroheliometer, which consists of a 45 cm
Gregory telescope coupled to a spectrometer employing a single toroidal
diffraction grating in a normal-incidence Rowland circle mounting and
an imaging pulse-counting multianode microchannel array (MAMA) detector
system. The spectroheliometer will produce spatially resolved spectra
of the chromosphere, transition region, and corona with an angular
resolution of 0.4″or better, a spectral resolution λ/Δλ of about
104 in first order, and a temporal resolution of the order
of seconds. Because of the geometric fidelity of the MAMA detector
system, the spectroheliometer will be able to determine Doppler shifts
to a resolution of at least 2 mÅ at wavelengths near 600Å (≡1.0
km s-1), depending on the level of the accumulated signal.
Title: A high speed two-star photometer.
Authors: Rao, G. V.; Thomas, V. A.; Babu, V. C.; Kutty, K. R. N.;
Ashoka, B. N.; Sugumar, S.; Navada, K. C.; Seetha, S.; Marar, T. M. K.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1991BASI...19...85R
Altcode:
No abstract at ADS
Title: High-resolution stigmatic EUV spectroheliometer for studies
of the fine scale structure of the solar chromosphere, transition
region, and corona
Authors: Timothy, J. Gethyn; Berger, Thomas E.; Morgan, Jeffrey S.;
Walker, Arthur B.; Bhattacharyya, Jagadish C.; Jain, Surendra K.;
Saxena, Ajay K.; Huber, Martin C.; Tondello, Giuseppe; Naletto,
Giampiero
Bibcode: 1991SPIE.1343..350T
Altcode:
No abstract at ADS
Title: Possible good observatory sites in India.
Authors: Bhattacharyya, J. C.
Bibcode: 1991nlt..work...99B
Altcode:
No abstract at ADS
Title: Solar eclipses - A powerful tool for the study of nature
Authors: Bhattacharyya, J. C.
Bibcode: 1990IJRSP..19..525B
Altcode:
A brief review is presented concerning the phenomena of solar
eclipses. Discussions on solar eclipse durations and tracks of
totality, as well as the Saros periodic repetitions of eclipses
are included. Scientific experiments conducted during total solar
eclipses are then examined. The experiments cover the measurement of
astronomical, geophysical, and physiological phenomena. Finally, the
importance of eclipses in scientific research is briefly reviewed. It
is concluded that solar eclipses still provide the most convenient
means for studying the outer layers of the sun and the response of
the earth atmosphere to the energy flux radiated by it.
Title: A high-speed two-star photometer.
Authors: Rao, G. V.; Thomas, V. A.; Babu, V. C.; Kutty, K. R. N.;
Ashoka, B. N.; Sugumar, S.; Navada, K. C.; Seetha, S.; Marar, T. M. K.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1990BASI...18...79R
Altcode:
Design and performance of a high-speed two-star photometer are
presented. It is an ideal instrument for investigations of time
variations of variable stars.
Title: Some further characteristics of observing conditions at Leh
Authors: Singh, Jagdev; Bhattacharyya, J. C.; Babu, G. S. D.;
Appakutti, M.; Kuppuswamy, K.
Bibcode: 1990BASI...18....7S
Altcode:
The sky conditions were monitored and duration of photometric and
spectroscopic hours determined on 198 nights during the period September
1984 to October 1986. Observations were continued from May till
November 1987 and again from June to October 1988, when additionally
the temperature and relative humidity values were systematically
recorded. Several standard stars were monitored on several nights
to determine the extinction coefficients in UBV bands; in addition,
sky brightness was measured on eight nights in the months of September
and October 1988. The values of sky brightness appear to be marginally
higher than at La Palma. The average values of extinction coefficients,
determined on 27 nights during 1988 show a general agreement with the
earlier values.
Title: Book-Review - Practical Ephemeris Calculations
Authors: Montenbruck, O.; Bhattacharyya, J. C.
Bibcode: 1990BASI...18..103M
Altcode:
No abstract at ADS
Title: Atmospheric extinction measurements at Leh in near infrared
bands
Authors: Bhattacharyya, J. C.; Scaria, K. K.; Singh, Jagdev; Babu,
G. S. D.; Nair, R. Muraleedharan
Bibcode: 1990BASI...18....1B
Altcode:
Site survey observations to determine the extinction in the IR bands
were carried out at Leh. Mean extinction coefficients obtained from
'two nights' observations in J, H, and K bands are k(J) = 0.05 + or -
0.01; k(H) = 0.04 + or - 0.01; and k(K) = 0.04 + or - 0.01.
Title: Further photometric observations of AM CVn.
Authors: Seetha, S.; Ashoka, B. N.; Marar, T. M. K.; Padmini, V. N.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Bhatt, B. C.;
Paliwal, D. C.; Pandey, A. K.
Bibcode: 1990apcb.conf..139S
Altcode: 1990cvlm.proc..139S
About 18 hours of high-speed photometric data was collected during
April 1989 to determine the true nature of the 1051 s period of AM
CVn. Raw data reveals 0.05 mag amplitude variations. Results of the
period analysis are presented. Combining published data with their own,
the authors derive the rate of decrease as (3.7±0.4)×10-12s
s-1.
Title: High-speed photometry of PG 1711+336 (V795 Her).
Authors: Ashoka, B. N.; Seetha, S.; Marar, T. M. K.; Padmini, V. N.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Bhatt, B. C.;
Paliwal, D. C.; Pandey, A. K.
Bibcode: 1990apcb.conf..243A
Altcode: 1990cvlm.proc..243A
Fast photometric observations of PG 1711+336 are presented. The light
curve shows a periodic modulation of ≡2.8 hr. Although variations of
≡0.15 mag, on timescales of ≡10-12 min, are evident throughout the
light curve, a search for periodicities in the range 500-1500 s did not
reveal any coherent short period in the system. The authors also report
that the photometric phase (0.3) of the relatively large-amplitude
(0.2 mag) decrease in the light, lasting for ≡10 to 15 min, coincides
in phase with the decrease in equivalent width of a few Balmer lines
determined by Rosen et al. (1989).
Title: HDE 245770
Authors: Bhattacharyya, J. C.; Ghosh, K. K.; Rao, N. K.; Prabhu,
T. P.; Mayya, Y. D.; Kuppuswamy, K.; Muniandi, A.
Bibcode: 1989IAUC.4913....1B
Altcode: 1989IAUC.4913....0B
J. C. Bhattacharyya, Indian Institute of Astrophysics, Bangalore,
telexes: "K. K. Ghosh, N. K. Rao, T. P. Prabhu, Y. D. Mayya,
K. Kuppuswamy, and A. Muniandi obtained CCD spectra of the Be x-ray
binary HDE 245770 (= A0535+26) with the 1-m reflector of Vainu Bappu
Observatory, Kavalur, between Nov. 22 and 25. The spectra displayed
emission lines of H-alpha, C II (657.8, 658.2 nm), and He I (667.8
nm). Presence of C II emission lines suggests that either an outburst
of the Be star (Baade et al. 1988, A.Ap. 198, 211) or x-ray emission
from the compact companion (Ghosh et al. 1989, Ap.J. 344, 437) has
taken place. Ultraviolet and x-ray observations would be of interest."
Title: Nova Scuti 1989
Authors: Bhattacharyya, J. C.; Jain, S. K.
Bibcode: 1989IAUC.4881....2B
Altcode: 1989IAUC.4881....0B
J. C. Bhattacharyya, Indian Institute of Astrophysics, Bangalore,
telexes: "S. K. Jain obtained polarimetric V-band observations with
the 1-m reflector at Vainu Bappu Observatory, Kavalur. An average of
two data sets on Oct. 7.59 UT indicates a polarization of 3.68 +/-
0.22 percent at p.a. 178.4 +/- 1.7 deg. A single set on Oct. 9.56
indicates 1.47 +/- 0.19 percent at p.a. 175.7 +/- 3.6 deg."
Title: 27 Canis Majoris
Authors: Ghosh, K. K.; Kuppuswamy, K.; Bhattacharyya, J. C.
Bibcode: 1989IAUC.4881....3G
Altcode:
Bhattacharyya also reports: "K. K. Ghosh and K. Kuppuswamy obtained
echelle CCD spectra on Oct. 14 and 15 of the Be-type star 27 CMa in
the region of H-alpha, Si (634.7, 637.1 nm), and He I (587.6 nm) that
suggest this star has entered into a shell phase when compared to the
previous observations (IAUC 4777). The spectra were obtained with the
1-m telescope at Vainu Bappu Observatory, Kavalur."
Title: Observing conditions for optical astronomy at Leh
Authors: Singh, Jagdev; Bhattacharyya, J. C.; Babu, G. S. D.; Ashoka,
B. N.; Appakutty, M.
Bibcode: 1989BASI...17...83S
Altcode:
The sky and atmospheric conditions at Leh have been monitored since 1984
with a view to determining its suitability as a site for a high-altitude
observatory. During May-November, 1987, relative humidity and other
parameters were monitored giving qualitative indices viz. photometric
and spectroscopic hours, and seeing conditions throughout the nonwinter
months. Extinction coefficients in UBV bands have been measured on 30
nights in 1987. The average values of extinction coefficients are k(v)
= 0.18 + or - 0.05 (s.d.), k(b) = 0.28 + or - 0.04, and k(u) = 0.53 +
or - 0.04. These values agree well with those reported earlier for
1985-1986, and appear to represent consistent conditions.
Title: Optical telescopes in India.
Authors: Bhattacharyya, J. C.
Bibcode: 1989IJPAP..27..311B
Altcode:
Fabrication and use of optical telescopes for astronomical observations
in India have been reviewed. Evolution of telescopes, their optics,
mounting and drive system leading to large aperture instruments of
today has been described. Limitations of ground-based observations in
spectral coverage and degradation of images have been discussed. The
article describes all existing telescope installations in India and
various efforts made in the country in fabrication of telescopes for
astronomical use. A brief account of the project by which the 2.34
metre telescope was constructed is given. Some of the proposals for
future telescopes are mentioned.
Title: MU Centauri
Authors: Bhattacharyya, J. C.; Ghosh, K. K.; Kuppuswamy, K.;
Ramachandran, A.; Rajkumar, K.; Ravi, K.; Dinakaran, N.
Bibcode: 1989IAUC.4806....3B
Altcode: 1989IAUC.4806....0B
J. C. Bhattacharyya, Indian Institute of Astrophysics, Bangalore,
reports: "CCD spectroscopic observations with the echelle spectrograph
at the coude focus of the 1-m reflector at Vainu Bappu Observatory,
obtained by K. K. Ghosh, K. Kuppuswamy, A. Ramachandran, K. Rajkumar,
K. Ravi, and N. Dinakaran, revealed that the recurrent, transient
Be-type star mu Cen developed H-alpha emission between Apr. 15 (H-alpha
asymmetric absorption) and June 22 (centrally-reversed H-alpha, V/R
about 1). By June 24 the H-alpha emission strength had definitely
increased."
Title: 27 Canis Majoris
Authors: Bhattacharyya, J. C.; Ghosh, K. K.
Bibcode: 1989IAUC.4777....3B
Altcode: 1989IAUC.4777....0B
J. C. Bhattacharyya, Indian Institute of Astrophysics reports: "CCD
echelle spectra obtained by K. K. Ghosh using the 1.02-m telescope at
Vainu Bappu Observatory, Kavalur, of the Be star 27 CMa at a disperson
of 0.7 nm/mm during Apr. 16-26 show H-alpha and He I (587.6 nm) lines
with P-Cyg profiles that appear variable. Earlier observations by him
(1985-1989 Jan.) showed typical double-peaked H-alpha emission for
this star."
Title: Indian Institute of Astrophysics. Annual report 1988 - 89.
Authors: Bhattacharyya, J. C.
Bibcode: 1989iiaa.book.....B
Altcode:
No abstract at ADS
Title: Variable stars in the old galactic cluster M 67.
Authors: Rajamohan, R.; Bhattacharyya, J. C.; Kuppuswamy, K.;
Subramanian, V.
Bibcode: 1988BASI...16..139R
Altcode:
Schmidt plates of the old open galactic cluster M67 were obtained on
twelve nights to find the most probable variables in the cluster. The
Sabattier technique was used to derive the magnitudes of the cluster
members. The most probable variable stars in this cluster determined
by this method are listed.
Title: Editorial
Authors: Bhattacharyya, J. C.
Bibcode: 1988JApA....9D...1B
Altcode:
No abstract at ADS
Title: Project Kalki - A sky survey with the Schmidt telescope. II
Authors: Rajamohan, R.; Shankar, P. N.; Bhattacharyya, J. C.;
Kuppuswamy, K.; Paranjpye, A.
Bibcode: 1988BASI...16...21R
Altcode:
The region of the sky photographed with the 45cm Schmidt telescope
during 1987 March-May and the position of the asteroids detected
on these plates are reported in this paper. Out of the 29 asteroids
observed four have received new temporary designations from the Minor
Planet Center : 1987 FY1, 1987 FZ1, 1987 HQ2 and 1987 HR2.
Title: Extinction measurements at Leh.
Authors: Singh, J.; Bhattacharyya, J. C.; Raveendran, A. V.; Mohin,
S.; Ashoka, B. N.; Rajamohan, R.; Jayakumar, K.; Rozario, M. J.;
Kupuswamy, K.; Paranjpye, A.; Appakutty, M.; Pukalenthi, S.; Muniandi,
A.; Murthy, V.; Selvakumar, G.
Bibcode: 1988BASI...16...15S
Altcode:
Observations were started at Leh in 1984 with a view to finding the
possibility of setting up an astronomical observatory for infrared
observations. Results of extinction measurements in UBV bands obtained
on 12 nights during 1985-86 are presented. The average values of
extinction coefficients are: k(v) = 0.20 + or - 0.13 (s.d.), k(b) =
0.29 + or - 0.04 and k(u) = 0.53 + or - 0.03.
Title: Extinction Measurements at Leh
Authors: Singh, J.; Bhattacharyya, J. C.; Raveendran, A. V.; Mohin,
S.; Ashoka, B. N.; Rajamohan, R.; Jayakumar, K.; Rozario, M. J.;
Kupuswamy, K.; Paranjpye, A.; Appakutty, M.; Pukalenthi, S.; Muniandi,
A.; Murthy, V.; Selvakumar, G.
Bibcode: 1988BASI...16...16S
Altcode:
No abstract at ADS
Title: Step towards new technology telescope - CLIMB I.
Authors: Saxena, A. K.; Bhattacharyya, J. C.
Bibcode: 1988BASI...16Q..87S
Altcode:
No abstract at ADS
Title: Solar Physics in India.
Authors: Krishan, V.; Bhattacharyya, J. C.
Bibcode: 1988sscd.conf..296K
Altcode:
No abstract at ADS
Title: New instrumentation efforts in solar studies.
Authors: Bhattacharyya, J. C.
Bibcode: 1988KodOB...9..133B
Altcode:
The techniques of solar studies aim at high magnifications and
resolutions, extremely high dispersion spectroscopy and experiments to
unveil the mysteries of a variety of weak but vital physical processes
which hold clues to our understanding the nature of cosmos.
Title: Flares on AM Canum Venaticorum.
Authors: Marar, T. M. K.; Padmini, V. N.; Seetha, S.; Narayanan Kutty,
K. R.; Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1988A&A...189..119M
Altcode:
AM CVn, an interacting binary system consisting of two helium white
dwarfs, has been classified as a nova-like object. Normally it
exhibits only small amplitude modulations of 0.05 mag with a 1051 s
periodicity. The authors report what is believed to be for the first
time, two unusually intense optical flares in AM CVn during 1985 -
87. The characteristics of the two flares in white light observed on
1985 February 24 and 1986 February 7 with Δm = 0.34 and Δm = 1.07
respectively are described. The authors estimate the maximum amount
of energy released from these flares as 2.7×1036erg and
suggest in the light of current models possible sites of origin of
the flaring activity.
Title: Project Kalki - a Sky Survey with 45-CM Schmidt Telescope -
Part One
Authors: Rajamohan, R.; Bhattacharyya, J. C.; Kuppuswamy, K.;
Paranjpye, A.
Bibcode: 1987BASI...15..174R
Altcode:
A brief description of the sky survey project taken up with the 45
cm Schmidt telescope of the Vainu Bappu Observatory at Kavalur is
given. Positions of 11 asteroids detected on plates taken during 1987
February-March are reported.
Title: Pluto-Charon Mutual Event
Authors: Vasundhara, R.; Bhattacharyya, J. C.
Bibcode: 1987BASI...15...20V
Altcode:
No abstract at ADS
Title: A Possible Explanation of the Asymmetry in the Immersion and
Emersion Light Curves at 12.5 Saturn Radii
Authors: Vasundhara, R.; Bhattacharyya, J. C.
Bibcode: 1987BeiGe..96...52V
Altcode:
No abstract at ADS
Title: A possible explanation of the asymmetry in the immersion and
emersion light curves at 12.5 Saturn radii
Authors: Vasundhara, R.; Bhattacharyya, J. C.
Bibcode: 1987oeps.proc...52V
Altcode:
The absorption features seen in the immersion and emersion light
curves at 12.5 Saturn radii have antisymmetric wings. These give rise
to dissimilarity in the two light curves. The antisymmetric wings
may arise as a reuslt of absorption by extinction lanes having large
vertical extent. From the duration of the wings an upper limit has
been set on the possible vertical thickness of these extinction zones.
Title: Plume-like structures of extinction clouds at 19 Saturn radii
Authors: Vasundhara, R.; Bhattacharyya, J. C.; Rozario, M.
Bibcode: 1986BASI...14..232V
Altcode:
Observations of the occultation of the star SAO 158763 by Saturn's
magnetospheric region around 19 RS on 1984 May 12
are compared with the observations by Mahra et al. of the same
event. Certain disparities between the Naini Tal and Kavalur data
suggest that the extinction signatures are more likely to be caused
by irregular density enhancements of ions, charged dust grains, or
gas rather than regular ring systems confined to the equatorial plane.
Title: Planetary Occultations
Authors: Brahic, A.; Grenier, I.; McLaren, R.; Grundseth, B.;
Bhattacharyya, J. C.; Vasundhara, R.; Kuppuswamy, K.; Tholen, D. J.
Bibcode: 1986IAUC.4207....2B
Altcode:
A. Brahic, I. Grenier, R. McLaren and B. Grundseth report their
observation of the Apr. 23 occultation N39 by Neptune (Mink and
Klemola 1985, A.J. 90, 1894). Continuous photometry at 2.2 micron was
obtained with the 3.6-m Canada-France-Hawaii telescope at Mauna Kea
from 11h06m to 15h00m UT with 50-ms sampling. The actual occultation
lasted from 13h01m to 13h35m (preliminary analysis), and no obvious
secondary events are visible in the raw data. J. C. Bhattacharyya,
Indian Institute of Astrophysics, telexes that R. Vasundhara and
K. Kuppuswamy photoelectrically recorded the Apr. 26 occultation of
AGK3 +23 1108 by (1) Ceres (Wasserman et al. 1985, A.J. 90, 2124)
with the 1-m telescope at Vainu Bappu Observatory, Kavalur. The event
lasted from 16h56m12s to 16h58m07s (+ 1s) UT, with a 0.24 +/- 0.05 mag
drop in light (V filter). D. J. Tholen informs us that the Pluto/Charon
occultation P4 on Apr. 30 (IAUC 4203, 4206) did not occur at Mauna Kea.
Title: A Single-Channel Polarimeter
Authors: Jain, S. K.; Bhattacharyya, J. C.
Bibcode: 1986IAUS..118...95J
Altcode:
The authors have developed a single-channel photopolarimeter to measure
polarization to ≡1%, with an accuracy of 0.1%. Laboratory tests show
that the performance of the instrument matches the requirements.
Title: New Telescopes in India
Authors: Bhattacharyya, J. C.
Bibcode: 1986Ap&SS.118...45B
Altcode:
The review covers the description and present status of the two
optical/infrared telescopes designed and presently near fabrication in
India. The 234 cm aperture optical telescope expected to be installed at
Kavalur shortly has several interesting features in its control and data
acquisition systems. Design features of the 122 cm Infrared Astronomical
Telescope expected to be completed next year are described. The review
also covers the Ooty Synthesis Radio Telescope and the Gauribidanur Low
Frequency Array operating at 327 and 34 MHz, respectively, and a 10 m
aperture millimeter wave telescope being built in Bangalore. Plans and
preparations for still bigger systems for observations in different
bands of Electromagnetic spectra are also briefly described.
Title: Detection of an extremely active state of AM Canum Venaticorum.
Authors: Narayanan Kutty, K. R.; Marar, T. M. K.; Padmini, V. N.;
Seetha, S.; Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.;
Mohin, S.; Jayakumar, K.
Bibcode: 1986ASSL..128..397N
Altcode: 1986hdsr.proc..397N; 1986ASSL..128..397K; 1986IAUCo..87..397N
Fast photometric observations of AM Canum Venaticorum (AM CVn),
the ultrashort-period, hydrogen-deficient variable, are reported. An
intense flare of (Delta m) peak roughly 0.34 was detected on February
24th, 1985 in white light lasting over 200 s. Following this flare,
an enhanced double-humped structure lasting for 1051 s was observed
which is the dominant periodicity exhibited by AM CVn. The 525 s and
1051 s periods were also detected. In addition, the authors report
flickerings lasting typically 1-2 minutes that are characteristic of
cataclysmic variables.
Title: Measurement of solar magnetic fields.
Authors: Bhattacharyya, J. C.; Balasubramaniam, K. S.
Bibcode: 1986KodOB...6...30B
Altcode:
The paper reviews several methods of estimation of solar magnetic fields
so far employed. The possibility of measurement of the vector magnetic
fields by using two dimensional detector arrays is discussed. A program
for vector measurements of strong fields around solar active regions
is described and an experiment for determining the errors in these
measurements is discussed.
Title: Identification of emission bands in P/Halley.
Authors: Bhattacharyya, J. C.; Babu, G. S. D.; Ghosh, K. K.; Jayakumar,
K.; Appakutty, M.
Bibcode: 1986CSci...55..761B
Altcode:
No abstract at ADS
Title: Proceedings of the national workshop on solar physics, held
at Kodaikanal, India, 4 - 6 September 1985.
Authors: Sastry, C. V.; Krishan, V.; Bhattacharyya, J. C.
Bibcode: 1986pnwo.book.....S
Altcode:
No abstract at ADS
Title: Photometry of Intermediate Polars Ao-Piscium and
V1223-SAGITTARII
Authors: Padmini, V. N.; Marar, T. M. K.; Seetha, S.; Padmanabhan,
P.; Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Kuppuswamy,
K.; Rozario, M. J.
Bibcode: 1985Ap&SS.117..287P
Altcode:
We present optical photometric observations of the cataclysmic
variables AO Psc and V 1223 Sgr, both of which are believed to contain
slowly-rotating white-dwarf pulsars. These objectes belong to the
new class of intermediate polars in which the magnetized-white-dwarf
rotation period lies in between synchrous and extremely fast rotation
periods. The observations reported here were carried out from the
Kavalur Observatory using a 1 m reflector. High-time resolution
light curves depicting a rich variety of flicker phenomena are
presented. Results of a periodic analysis to search for coherent
periodic modulations in the light curves are also presented. We have
also derived the optical pulse profile of AO Psc and point out its
similarities to the X-ray pulse profile.
Title: Gravitational Instability of Interstellar Magnetic Clouds
Authors: Ghosh, K. K.; Bhattacharyya, J. C.
Bibcode: 1985Ap&SS.117...89G
Altcode:
The gravitational instability of a nonrotating isothermal gaseous disk
permeated by a uniform frozen-in magnetic field is investigated using
a fourth-order perturbation technique. From the results it is found
that the disk is stable whenn/B 0 < (4/3π3
G)-1/2, wheren andB are the column density of the disk and
unperturbed magnetic field, respectively, andG is the gravitational
constant. The disk is gravitationally unstable only whenn/B 0
> (4/3π3 G)-1/2.
Title: High Speed Photometry of SS Cygni after an Outburst
Authors: Seetha, S.; Padmini, V. N.; Marar, T. M. K.; Kasturirangan,
K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1985IBVS.2839....1S
Altcode:
No abstract at ADS
Title: Measurement of Vector Magnetic Fields - Part One - Theoretical
Approach to the Instrumental Polarization of the Kodaikanal Solar
Tower
Authors: Balasubramaniam, K. S.; Venkatakrishnan, P.; Bhattacharyya,
J. C.
Bibcode: 1985SoPh...99..333B
Altcode:
The observations of Stokes line profiles require an accurate knowledge
of the instrumental polarisation caused by optical components in the
path of the light beam. In this context we present a theoretical
approach to the instrumental polarisation caused by the 3-mirror
coelostat system of the Kodaikanal Solar Tower.
Title: Search for Optical Bursts from the Gamma Ray Source GBS 0526-66
Authors: Seetha, S.; Sreenivasaiah, K. V.; Marar, T. M. K.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1985ICRC....1...23S
Altcode: 1985ICRC...19a..23S
Attempts were made to detect optical bursts from the gamma-ray
burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985
and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the
Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the
predicted 164 day period of burst activity from the source (Rothschild
and Lingenfelter, 1984). A new optical burst photon counting system
with adjustable trigger threshold was used in parallel with a high
speed photometer for the observations. The best time resolution was 1
ms and maximum count rate capability was 255,000 counts s(-1). Details
of the instrumentation and observational results are presented.
Title: The microprocessor control of the Kavalur 234-cm optical
telescope
Authors: Chinnappan, V.; Bhattacharyya, J. C.
Bibcode: 1985BASI...13..153C
Altcode:
This paper gives an introduction to the control system of the 234-cm
optical telescope. The computer used in control is based on an
INTEL 16 bit microprocessor. The VAX 11/780 system has a supervisory
role in the control system and is used primarily to calculate the
pointing errors due to mechanical imperfections of the telescope,
atmospheric refraction, and other similar errors. The microcomputer
and the VAX system are coupled with bidirectional drivers and exchange
data at predetermined sidereal intervals. The various tasks involved
in the control of the telescope are explained. The interface circuits
developed at the electronics laboratory are briefly mentioned. Circuits
necessary for the display to telescope position, celestial coordinates,
and sidereal time are included.
Title: Photometry of intermediate polars V1223 Sgr and H 2252-035.
Authors: Marar, T. M. K.; Seetha, S.; Padmanabhan, P.; Padmini, V. N.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Kuppuswamy, K.;
Rozario, M. J.
Bibcode: 1985BASI...13...83M
Altcode:
No abstract at ADS
Title: Astronomy in India in the 20th century.
Authors: Bhattacharyya, J. C.; Vagiswari, A.
Bibcode: 1985InJHS..20..403B
Altcode:
No abstract at ADS
Title: A fast optical pulse counting system for Crab pulsar.
Authors: Santhanam, P.; Bhattacharyya, J. C.
Bibcode: 1985KodOB...5...27S
Altcode:
A sub-millisecond resolution counting system for recording shapes of
short periodic pulses is described. Results obtained in recording the
shape of optical pulses from Crab pulsar are given. The flexibility
of the system for multi-channel photoelectric photometry application
is explained.
Title: Outer rings of Saturn.
Authors: Bhattacharyya, J. C.; Vasundhara, R.
Bibcode: 1985CSci...54...60B
Altcode:
No abstract at ADS
Title: Possible detection of a ring system in Saturn's magnetosphere
Authors: Vasundhara, R.; Bhattacharyya, J. C.; Santhanam, P.; Pande,
A. K.; Mohan, Vijay; Mahra, H. S.
Bibcode: 1984Natur.312..621V
Altcode:
The region of the magnetosphere of Saturn around 14 radii and 19 radii
has been of special interest since the detection of anamolous dips in
the low-energy plasma ion-density in these regions by the Voyager 1,
Voyager 2 and Pioneer 11 spacecrafts. Lazarus et al. suggested that
these density dips may be due to long-lived particulate or gaseous
structures in the equatorial plane of Saturn1. Baron and
Elliot, using the charge-coupled device (CCD) imaging technique,
found no evidence of any material existing between 10 and 36 Saturn
radii2. Their negative results, however, have set an
upper limit on the extent of a possible material cloud with several
assumptions regarding its nature and density. We have observed the
occultation of the star SAO158913 from two stations in India following
predictions by Mink3. This star showed symmetric dips in
the light curves on 24 March 1984 (immersion event) and on 25 March
1984 (emersion event), suggesting the possible presence of particulate
matter.
Title: Possible Occultation by Saturnian Magnetospheric Ring
Authors: Bhattacharyya, J. C.; Santhanam, P.; Rozario, M. J.
Bibcode: 1984IAUC.3941....2B
Altcode: 1984IAUC.3941....0B
J. C. Bhattacharyya, Indian Institute of Astrophysics, Bangalore,
reports that observations by Santhanam and Rozario with the 1-m
telescope at Kavalur indicate systematic extinction of SAO 158913
on March 24 and 25, apparently in accordance with the prediction by
Mink (1983, A.J. 88, 559) of occultations of the star by the supposed
magnetospheric ring at 14 radii from the center of Saturn. Observations
on Mar. 24 in integrated light showed two prominent and several
smaller and narrow absorbing features beween 20h14m and 20h20m UT,
the maximum extinction being 0.58 mag. Observations on Mar. 25 using
a B filter showed similar structures between 20h18m and 20h24m with
a maximum extinction of 0.28 mag.
Title: Minor planets and planetary rings.
Authors: Bhattacharyya, J. C.
Bibcode: 1984bims.symp...95B
Altcode:
Circumstances of the discovery of the first asteroid and the
characteristics of various orbits followed by them have been
discussed. Their shapes, compositions and evolutionary histories so
far known have also been described. The review also covers the present
status of knowledge about the rings surrounding 3 giant planets.
Title: Das Ringsystem des Planeten Uranus - eine bemerkenswerte
Entdeckung im Sonnensystem.
Authors: Bhattacharyya, J. C.
Bibcode: 1984JenRu..29..114B
Altcode:
No abstract at ADS
Title: Evidence for interpulses between photometric maxima of EX Hya.
Authors: Sharma, D. P.; Marar, T. M. K.; Seetha, S.; Padmini, V. N.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Rajamohan, R.
Bibcode: 1984BASI...12S..63S
Altcode:
No abstract at ADS
Title: Thrust areas in astronomy and astrophysics
Authors: Bhattacharyya, J. C.; Venugopal, V. R.
Bibcode: 1984taaa.book.....B
Altcode: 1984QB43.2.B48.....
No abstract at ADS
Title: Magnetic field - plasma interaction on the Sun. Proceedings of
a colloquium held at Kodaikanal on January 23, 1984 in commemoration
of the 75th anniversary of the discovery of the Evershed effect.
Authors: Sivaraman, K. R.; Raju, P. K.; Bhattacharyya, J. C.;
Howard, R.
Bibcode: 1984mafi.book.....S
Altcode:
No abstract at ADS
Title: Indications of Twist in the Epsilon Ring of Uranus
Authors: Vasundhara, R.; Bhattacharyya, J. C.
Bibcode: 1984plri.coll..193V
Altcode: 1984IAUCo..75..193V; 1984prin.conf..193V
A comparison of light curves during stellar occultations by the ɛ
ring of Uranus indicates that this ring assembly possesses stable fine
structures. The authors discuss the possibility that the ring contains
a twisted bundle of narrow lanes of condensed material similar to that
of Saturn's F ring.
Title: Observations of X-Persei in Optical Domain
Authors: Sharma, D. P.; Nagaraja, B. V.; Bhattacharyya, J. C.; Mohin,
S.; Raveendran, A. V.
Bibcode: 1983Ap&SS..95...65S
Altcode:
We have monitored the X-ray source X-Per (4U 0352+30) on 31 August, 1979
through aU filter for about 1.5 hr using 102-cm telescope of Kavalur
observatory. During this period intensity of X-Per fluctuated for
some time, on time scales of few minutes but recovered in the end. It
was again monitored from 27 December, 1979 to January 1980 through a
standardU, B, V photometer attached to a 34-cm telescope. In this paper
we present the data on the fast flickerings observed on 31 August,
1979 and on the long term monitoring from December 1979 to January 1980.
Title: Some Further Measurements of Uranian Ring Condensations
Authors: Vasundhara, R.; Bhattacharyya, J. C.; Rajamohan, R.; Mahra,
H. S.
Bibcode: 1983M&P....29...79V
Altcode:
The results of photometric observations of the occultation of BD-19°
4222 by Uranus on April 26, 1981 from two stations in India conform
with the model proposed by Elliotet al. (1981).
Title: Photometric Observations of the X-Ray Dwarf Nova HL Canis
Majoris
Authors: Seetha, S.; Marar, T. M. K.; Sharma, D. P.; Kasturirangan,
K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1983ICRC....9....5S
Altcode: 1983ICRC...18i...5S
High speed optical photometric observations of the X-ray dwarf nova HL
Canis Majoris (1E 0643-1648), discovered with the Einstein Observatory,
are presented. Results of long term monitoring and attempts to detect
photometric eclipses at the reported orbital periods of 0.22 d or 0.18
d of the binary system are presented.
Title: High speed photometry of dwarf nova EX Hydrae.
Authors: Sharma, D. P.; Marar, T. M. K.; Seetha, S.; Kasturirangan,
K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1983ICRC....9..330S
Altcode: 1983ICRC...18i.330S
High speed optical photometric observations of the hard X-ray source
EX Hya, carried out with the reflector of the Kevalur Observatory, are
presented. The observations with time resolutions of 1 s or 2 s were
made on four nights in March 1982 for a total duration of 6.8 h. Light
curves that reveal fast flickerings and the 67 min oscillations are
presented. A new ephemeris for the photometric period confirms the trend
towards decreasing period on a time scale of 10-million years. Evidence
for the presence of interpulses in the light curves between successive
photometric maxima is also shown.
Title: Photometric Observations of the X-Ray Dwarf Nova HL Canis
Majoris
Authors: Seetha, S.; Marar, T. M. K.; Sharma, D. P.; Kasturirangan,
K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1983ICRC....1...11S
Altcode: 1983ICRC...18a..11S
No abstract at ADS
Title: Discovery of a Flare Star Near Sirius
Authors: Sharma, D. P.; Marar, T. M. K.; Seetha, S.; Shyla, K. S.;
Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.; Rozario, M. J.
Bibcode: 1983Ap&SS..91..467S
Altcode:
The discovery of a flare star
(R.A. (1950)=6h43m6s.07,
Decl.(1950)=-16°45'24″) located about 6 arc min south of Sirius is
reported. During photometric observations on the night of 13 January,
1982, using the 102 cm telescope at Kavalur, India, the star was
seen to brighten by 2.55 mag. inV band over a duration of about 200
s. Observations on this object for a duration of about 10.5 hr spread
over seven more nights indicate the star to be variable. The results
of these observations are presented.
Title: Obituary - Bappu, M.K.
Authors: Bhattacharyya, J. C.
Bibcode: 1983QJRAS..24..360B
Altcode: 1983QJRAS..24..360.
No abstract at ADS
Title: Tribute to the memory of Professor M. K. V. Bappu (August 10,
1927 - August 19, 1982), given at the XVIIIth General Assembly of
the IAU.
Authors: Kharadze, E. K.; Bhattacharyya, J. C.; Xanthakis, J.; Goudas,
C. L.; Blaauw, A.; Smith, H. G.
Bibcode: 1983IAUTB..18....1K
Altcode:
No abstract at ADS
Title: In memoriam: M. K. V. Bappu (1927-1982).
Authors: Bhattacharyya, J. C.
Bibcode: 1983Ap&SS..89....3B
Altcode:
No abstract at ADS
Title: In memoriam
Authors: Bhattacharyya, J. C.
Bibcode: 1983Ap&SS..89D...2B
Altcode:
No abstract at ADS
Title: High Speed Photometry of Dwarf Nova Ex-Hydrae
Authors: Sharma, D. P.; Marar, T. M. K.; Seetha, S.; Kasturirangan,
K.; Rao, U. R.; Bhattacharyya, J. C.
Bibcode: 1983ICRC....2..406S
Altcode: 1983ICRC...18b.406S
No abstract at ADS
Title: Asia's biggest telescope.
Authors: Bhattacharyya, J. G.
Bibcode: 1983InEE..125..274B
Altcode:
No abstract at ADS
Title: Scientific Objectives of the Observations
Authors: Bhattacharyya, J. C.
Bibcode: 1982tsef.conf....1B
Altcode:
No abstract at ADS
Title: Notes and News
Authors: Kapahi, V. K.; Sarma, N. V. G.; Bhattacharyya, J. C.
Bibcode: 1981BASI....9..323K
Altcode:
No abstract at ADS
Title: The second Asian-Pacific regional meeting of astronomy.
Authors: Bhattacharyya, J. C.
Bibcode: 1981BASI....9..328B
Altcode:
No abstract at ADS
Title: Observations of the total solar eclipse of 16 February
1980. (Preliminary results).
Authors: Trehan, S. K.; Bhattacharyya, J. C.
Bibcode: 1981otse.conf.....T
Altcode:
No abstract at ADS
Title: Observations of optical emission from X-Per and SCO X-1
Authors: Sharma, D. P.; Nagaraja, B. V.; Marar, T. M. K.;
Bhattacharyya, J. C.; Mohin, S.
Bibcode: 1981ICRC....9...13S
Altcode: 1982ICRC....9...13S; 1981ICRC...17i..13S
High speed photometric observations of X-Per, and Sco X-1 have been
carried out during 1979-80 with the 102 cm and 33 cm telescopes at
the Kavalur observatory. Results from some of these observations are
presented in this paper. Data on long term intensity variations at a
differential magnitude level of plus or minus 0.1 and fast flickering
in X-Per are presented and discussed.
Title: Application aspects of time and frequency to astronomy.
Authors: Bhattacharyya, J. C.
Bibcode: 1981JIETE..27..593B
Altcode:
No abstract at ADS
Title: Determination of the limb darkening of the solar disc in the
visible and near ultraviolet.
Authors: Bhattacharyya, J. C.; Chandramohan, R.; Sundareswaran, A.;
Charles, A.
Bibcode: 1981otse.conf....4B
Altcode:
No abstract at ADS
Title: Total solar eclipse of February 16, 1980.
Authors: Bhattacharyya, J. C.
Bibcode: 1980PINSA..46..191B
Altcode:
No abstract at ADS
Title: A simple digital system drive for small telescopes.
Authors: Bhattacharyya, J. C.; Ramamoorthy, K. S.; Chandramohan, R.
Bibcode: 1980KodOB...3...26B
Altcode:
A variable stable frequency source employing a crystal oscillator and a
programmable digital divider chain is described. The system offers an
ideal arrangement for controlling tracking rates of small and medium
size telescopes by which limitations due to mechanical imperfections
can almost be completely eliminated.
Title: A High Time Resolution Photometer for Optical Monitoring of
X-Ray Sources
Authors: Sharma, D. P.; Sharma, M. R.; Hathwar, G. R.; Bhattacharyya,
J. C.
Bibcode: 1979BASI....7..123S
Altcode:
No abstract at ADS
Title: Extended Ring System of Uranus
Authors: Bhattacharyya, J. C.; Bappu, M. K. V.; Mohin, S.; Mahra,
H. S.; Gupta, S. K.
Bibcode: 1979M&P....21..393B
Altcode:
Two photoelectric records of the occultation event on 10 March, 1977,
obtained by two 102-cm-aperture telescopes, spaced 1500 km apart,
are critically analysed and indications of a complex structure
of distribution of occulting material surrounding the planet are
obtained. The results confirm the existence of a very shallow broad
ring system with local condensation lanes of narrow and intermediate
widths. A system of numerous thin rings are also present around the
planet in the equatorial plane.
Title: Automatic Photon Counting and Printing Device for Small
Telescopes
Authors: Chandramohan, R.; Bhattacharyya, J. C.
Bibcode: 1979BASI....7..124C
Altcode:
No abstract at ADS
Title: Total Solar Eclipse of 1980
Authors: Bhattacharyya, J. C.
Bibcode: 1978BASI....6...17B
Altcode:
No abstract at ADS
Title: Saturn-like ring system around Uranus
Authors: Bhattacharyya, J. C.; Bappu, M. K. V.
Bibcode: 1977Natur.270..503B
Altcode:
OBSERVATIONS made at Kavalur1,2 of the occultation of
SAO158687 by Uranus on 10 March 1977 showed, in addition to the
occultation by a satellite system termed the ɛ ring, a dimming of the
light of the star close to the time when the atmosphere of the planet
could have caused the phenomenon. Since then, the identities of the α,
β, γ, δ rings have also become well established, and a theoretical
interpretation of their origin3 has been proposed. We have
closely examined the Kavalur photoelectric record and describe here
several new features of the satellite ring system of Uranus.
Title: A new satellite of Uranus
Authors: Bhattacharyya, J. C.; Kuppuswamy, K.
Bibcode: 1977Natur.267..331B
Altcode:
WHILE observing the occultation of the star SAO 158687 by Uranus on 10
March 1977 we came across an unexpected event suggesting the existence
of a hitherto unknown satellite of the planet. The observations
were carried out at the Kavalur Observatory (lat. 12° 34' 32'' N:
long 78° 49' 54'' E) using a near infrared photometer consisting
of a refrigerated EMI 9558B phototube and Kodak Wratten 89B filter
attached to the Cassegrain focus of the 102-cm telescope. The individual
deflections due to the star and the planet were measured during the
previous night, as well as a few hours before the predicted instant of
occultation. A 16-arc s diaphragm was used during occultation, whereby
the planet and the star could be conveniently contained for several
hours around the epoch of occultation. Guiding and monitoring of the
objects were done through the 20-cm guide telescope, with periodic
checking of the centering in the main telescope. As indicated by the
prediction1, we expected only a grazing occultation to be
visible at Kavalur, resulting in a slight diminution in the intensity
of starlight owing to the extinction effect by differential refraction
in the outer layers of the planet's atmosphere2. A very
shallow depression of 0.046 magnitudes in the light of SAO 158687 was
indeed observed.
Title: Occultation of SAO 158687 by Uranian Rings
Authors: Hubbard, W. B.; Zellner, B.; Wasserman, L. H.; Elliot, J. L.;
Bhattacharyya, J. C.; Kupppswamy, K.
Bibcode: 1977IAUC.3058....1H
Altcode:
W. B. Hubbard, Lunar and Planetary Laboratory, reports that analysis
of photometric traces obtained by B. Zellner at the Perth Observatory
shows the following occultations. These events can be identified with
occultations observed by Elliot et al., so their notation (cf. IAUC
3051) is utilized: Event UT Event UT alpha1 20h20m06s alpha2 21h42m21s
beta2 21 43 38 These timings are preliminary (uncertainty +/- 5s for
alpha2 and beta2). Nothing of statistical significance appears at the
times of the events alpha3 and beta3 reported by Millis et al. (IAUC
3051). Observations were not made around the times of the other reported
events. L. H. Wasserman, Lowell Observatory, reports that Millis et
al. could not have observed the alpha1 and delta1 events, for these
would have taken place at Perth at a few seconds after 20h20m and 20h15m
UT, respectively, and observations were interrupted for recentering for
some 5-10 seconds beginning at these exact times. The events alpha3 and
beta3 were noticeably shallower than the others J. L. Elliot, Cornell
University, remarks that the events alpha3 and beta3 are probably
present in the Kuiper Airborne Observatory data but are not at all
conspicuous. J. C. Bhattacharyya, Indian Institute of Astrophysics,
reports that the event observed by K. Kupppswamy and himself at Kavalur
began at 20h19m38s UT (i.e., epsilon5 = 20h19m42s; cf. IAUC 3048,
3051). The shorter occultations were not noted, and observations had
ceased by the time of any corresponding events after the Uranus appulse.
Title: Discovery of a New Satellite of Uranus
Authors: Bhattacharyya, J. C.; Kuppuswamy, K.
Bibcode: 1977BASI....5...19B
Altcode:
No abstract at ADS
Title: Occultation of SAO 158687 by Uranus and Satellite Belt
Authors: Elliot, J. L.; Dunham, E.; Mink, D.; Millis, R. L.; Birch,
P.; Trout, D.; Bappu, M. K. V.; Bhattacharyya, J. C.; Kuppuswamy;
Marsden, B. G.
Bibcode: 1977IAUC.3048....1E
Altcode:
Amplifying the brief announcement on IAUC 3047, J. L. Elliot reports
that several secondary occultations of SAO 158687 on Mar. 10 were
observed by E. Dunham, D. Mink and himself from the Kuiper Airborne
Observatory and also by R. L. Millis, P. Birch and D. Trout at the Perth
Observatory. Both groups independently concluded that these occultations
were caused by bodies that are apparently part of a satellite belt
about 40 000 km distant from the center of Uranus. The diameters of the
satellites range from 100 km to much smaller values. The occultation by
Uranus itself was successfully observed from the Airborne Observatory
(located at Long. = -90o, Lat. = -50o) and lasted ~ 25 min centered
on 21h06m UT. The Uranus occultation did not occur at the Perth
Observatory. The secondary occultations took place during an 8-9
min interval around 20h16m UT and during a similar interval around
21h50m UT (although dawn prevented observations of the latter events
in Perth). M. K. V. Bappu, Indian Institute of Astrophysics, cables:
"Using the 102-cm reflector at Kavalur (Long. = -5h15m19s.6, Lat. =
+12o34'32"), Bhattacharyya and Kuppuswamy found the diminution of
SAO 158687 during the occultation by the atmosphere of Uranus to be
0.046 magnitude at an effective wavelength of 7500 A. Visually and
photoelectrically they observed the complete disappearance of the star
for 8s.9 beginning at 20h19m15s UT and ascribe this to obscuration
by a hitherto unknown satellite of the planet." Computations by the
undersigned show that the asymmetry in the times of the satellite
occultations about the main occultation (as observed at the Airborne
Observatory) is consistent with the existence of a circular belt in
the plane of Uranus' equator. Allowance for foreshortening yields the
radii of the inner and outer edges of the belt as 44 000 and 51 000
km, respectively. The Kavalur observation suggests occultation by a
100-km-sized body near the outer edge of the belt. Other observers are
urged to examine their records for further evidence of this belt. At
Sutherland, times of mid-occultation by the belt would have been
20h22m and 21h59m UT; at Mauritius, 20h23m and 21h54m; at Lembang,
20h20m and 21h46m; at Kyoto, 20h22m; at Helwan, 21h56m. Those wishing
to attempt to detect the satellite belt directly are advised that at
the present opposition it should be located from 3".5 to 4".0 to the
north and south of the center of Uranus and from 2".7 to 3".1 to the
east and west; the brightest bodies in it are expected to have mv ~ 19.
Title: An analog system for fast light curve registration.
Authors: Bhattacharyya, J. C.; Sundareswaran, A.
Bibcode: 1977KodOB...2...69B
Altcode:
No abstract at ADS
Title: Preliminary results of the structure of Alpha Vir from lunar
occultation measurements.
Authors: Bhattacharyya, J. C.; Sundareswarn, A.
Bibcode: 1976BASI....4...83B
Altcode:
No abstract at ADS
Title: Ionospheric electron content and equivalent slab thickness
in the equatorial region
Authors: Das Gupta, A.; Basu, S.; Bhar, J. N.; Bhattacharyya, J. C.
Bibcode: 1975JGR....80..699D
Altcode:
No abstract at ADS
Title: Fine structure of photospheric magnetic field and
Ca+K3 network.
Authors: Bhattacharyya, J. C.; Saxena, A. K.; Singh, J.
Bibcode: 1975BASI....3R..28B
Altcode:
No abstract at ADS
Title: A system for recording fast varying light curves.
Authors: Bhattacharyya, J. C.; Sundareswaran, A.
Bibcode: 1975BASI....3Q..28B
Altcode:
No abstract at ADS
Title: Velocity oscillations of the solar atmosphere at chromospheric
heights.
Authors: Bhattacharyya, J. C.
Bibcode: 1974BASI....2...40B
Altcode:
No abstract at ADS
Title: An Atmosphere on Ganymede from Its Occultation of SAO 186800
on 7 June 1972
Authors: Carlson, R. W.; Bhattacharyya, J. C.; Smith, B. A.;
Johnson, T. V.; Hidayat, B.; Smith, S. A.; Taylor, G. E.; O'Leary,
B.; Brinkmann, R. T.
Bibcode: 1973Sci...182...53C
Altcode:
On 7 June 1972 the third Jovian satellite Ganymede occulted the
eighth-magnitude star SAO 186800. Successful photoelectric observations
obtained at Lembang, Java (Indonesia), and Kavalur, India, show
nonabrupt immersions and emersions, indicating the presence of an
atmosphere whose surface pressure is greater than about 10-3
millibar. By fitting the two occultation durations as chords to a
model disk, the diameter is found to be 5270 (+30, -~ 200) kilometers,
the major error contribution arising from the uncertain atmospheric
thickness below the occultation layer. The derived mean density is 2.0
(-0.03, + ~ 0.2) grams per cubic centimeter.
Title: Photometry of the solar corona of March 7, 1970.
Authors: Bappu, M. K. V.; Bhattacharyya, J. C.; Sivaraman, K. R.
Bibcode: 1973Prama...1..117B
Altcode:
No abstract at ADS
Title: On Emission Lines of Hydrogen, Helium and Ionized Calcium
Seen on a Coronal Spectrogram of the March 7, 1970 Eclipse
Authors: Bappu, M. K. V.; Bhattacharyya, J. C.; Sivaraman, K. R.
Bibcode: 1972SoPh...26..366B
Altcode:
Emission lines of the Balmer series, D3 and H and K are
reported present on a coronal spectrogram obtained at the March 7,
1970 eclipse. Arguments are presented to show that these could not
have originated from scattering in the Earth's atmosphere and hence
possibly have a coronal origin.
Title: Occultation of Beta Scorpii by Jupiter on May 13, 1971
Authors: Bhattacharyya, J. C.
Bibcode: 1972NPhS..238...55B
Altcode: 1972Natur.238...55B
PHOTOELECTRIC observations of the occultation of the star β Scorpii by
Jupiter were carried out at our field station at Kavalur on the night
of May 13-14, 1971, at the cassegrain focus of the 38 cm reflecting
telescope. Our photometric record was made by photographing a CRO trace
in order to record the true light emission curve during the immersion
and emersion phases of the occultation. The record was calibrated by
photographing seconds pulses from a quartz clock simultaneously. A
thin glass plate behind the focal plane diaphragm allowed continuous
visual monitoring of the Jovian limb and the occultation phenomenon.
Title: Velocity Oscillations in the Solar Atmosphere
Authors: Bhattacharyya, J. C.
Bibcode: 1972SoPh...24..274B
Altcode:
From a series of long duration continuous Doppler records of selected
spectral lines, characteristics of solar velocity oscillations have
been studied. Statistical distribution of the durations of the bursts
of oscillations has been estimated. From the nature of distortion of
the waveforms of the oscillation, the presence of disturbing impulses
has been speculated. Constancy and homogeneity of the oscillations have
been examined from detailed spectral density plots. Duration indices
for the oscillations at different heights in the solar atmosphere have
been derived by estimating mean spectral densities of characteristic
oscillation amplitudes during several individual bursts and comparing
them with corresponding spectral densities from long records. The
variation among experimental results has been explained as due to the
limitations of the power spectral analysis method on short records.
Title: Occultation of SAO 186800 by Jupiter III.
Authors: Bhattacharyya, J. C.
Bibcode: 1972IAUC.2412Q...1B
Altcode:
No abstract at ADS
Title: Ionospheric indication of short-time solar activity variations.
Authors: Bhattacharyya, J. C.; Sunder, R. S.
Bibcode: 1970IJPAP...8..544B
Altcode:
No abstract at ADS
Title: The solar magnetometer of Kodaikanal Observatory.
Authors: Bhattacharyya, J. C.
Bibcode: 1970KodOB.205..203B
Altcode:
No abstract at ADS
Title: Spectral characteristics of a solar flare from ionospheric data
Authors: Bhattacharyya, J. C.; Balakeishnan, T. K.
Bibcode: 1967JATP...29.1573B
Altcode:
From the height variation of electron densities during a solar flare,
ultra violet and X-ray contribution of ionization process has been
estimated. The results thus obtained are in conformity with direct
measurements of solar ultraviolet and X-ray spectra by rocket
techniques.