004245   Dhar V K;Yadav K K;Bhattacharyya S;Kaul R K; Bhat C L;Koul R;Kaul S R;Kaul S K (NO, Bhabha Atomic Research Centre, Research Laboratory, Mumbai-400 085) : Development of a large-area, wide-angle Cerenkov radiation detector for the MYSTIQUE gamma-ray telescope. Bull Astr Soc India 1999, 27(2), 305-8.

An ultra-sensitive, multi-detector gamma-ray telescope array is being setup at Mt Abu for cosmic gamma-ray studies in the tens of TeV energy region. Presents the essential design features of the Cerenkov radiation detector, proposed to be used in the system, and described the results of some preliminary simulation studies and prototype testing.

004244   Chakraborty A (NO, IUCAA, Post Bag 4, Pune-411 007) : Dynamics of astrophysical nebulae. Bull Astr Soc India 1999, 27(2), 257-65.

39 ref

004243   Bhat P N (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Gamma ray bursts - facts and fantasies. Bull Astr Soc India 1999, 27(2), 237-41.

004242   Bhat C L;Tickoo A K;Koul R;DDhar V K;Shanthi K (NO, Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 085) : Ground-based detection of cosmic gamma-ray bursts through atmospheric scintillation technique - a feasibility study. Bull Astr Soc India 1999, 27(2), 323-6.

Ground-based experiment is proposed for detecting cosmic gamma-ray bursts. The underlying detection strategy and some salient features of the instrument are discussed.

004241   Bhat C L et al (NO, Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 085) : Simulation and experimental studies of polarization properties of atmospheric Cerenkov pulses. Bull Astr Soc India 1999, 27(2), 343-7.

004240   Banerjee D P K;Willstrop R V;Anandarao B G (Astronomy and Astrophysics Division, Physical Research Laboratory, Ahemedabad-380 009) : On the accuracy of the caustic test. Bull Astr Soc India 1999, 27(2), 339-41.

003246   Tah S;Paul S N;Chatterjee T;Basu B (Department of Mathematics, Vidyasagar College, Calcutta-700 006) : On the non-linear analysis of the propagation of density waves through the disk of the galaxy : density and velocity perturbation. Indian J Phys-Pt B 1999, 73(4), 579-92.

Density waves in the galactic disk have been considered by many authors as the real cause of generation of large scale spiral arms in the disk galaxies. Propagation of the density waves through galactic disk has been analysed by various authors over the last few decades, but so far, only linear perturbations have been considered. Analysed the problem considering the nonlinear effects. It is found that nonlinear effects are important in analysing the density wave phenomena in the outer region of the galactic disk.

21 ref

003245   Saha S K (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Speckle interferometry. Indian J Phys-Pt B 1999, 73(4), 553-77.

Auther have presented the basic mathematical treatment of interferometry in the optical domain. Its applications in astronomical observations using both the single aperture, as well as the diluted apertures are described. Also described about the shortcomings of this technique in the presence of Earth's atmosphere. A short description of the atmospheric turbulence and its effect on the flat wavefront from a stellar source is given. The formation of speckle which acts as carrier of information is defined. Laboratory experiments with phase modulation screens, as well as the resultant intensity distributions due to point source are demonstrated. The experimental method to freeze the speckles, as well as data processing techniques for both Fourier modulus and Fourier phase are described. Also discussed the technique of the aperture synthesis using non-redundant aperture masks at the pupil plane of the telescope, emphasizing set on the comparison with speckle interferometry. The various methods of image restoration and their comparisons are also discussed. Finally astrophysical problems whicha can be tackled with the newly developed speckle interferometer using the 2.34 meter Vainu Bappu Telescope (VBT), situated at the Vainu Bappu Observatory (VBO), Kavalur, India. 68 ref

^iia

000085   Yadav J S;Agrawal P C;Paul B;Rao A R;Vahia M N;Seetha S;Kasturirangan K (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : X-ray bursts from GRS 1915 + 105 observed with the IXAE. Bull Astr Soc India 1999, 27(1), 177-9.

Light curves of the galactic superluminal X-ray transient source GRS1915 + 105 observed with the pointed proportional counters (PPC) of Indian X-ray Astronomy Experiment (IXAE) on board IRS-P3 have revealed the presence of four types of intense X-ray bursts : regular persistent bursts, quasi-regular bursts and irregular bursts. Two of the four types of bursts are regular in occurrence and persist over extended durations. All the observed bursts have a slow exponential rise and a sharp linear decay. The regular bursts show two peak structure while the other type of bursts show multi-peak structure. The burst-spectrum is hardest at the end of the decay.

10 ref

000084   Verma R P;Ghosh S K;Karnik A D;Mookerjea B; Rengarajan T N (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Mid-infrared observations of three compact HII regions and PAH emission. Bull Astr Soc India 1999, 27(1), 159-61.

000083   Vats H O;Deshpande M R;Mehta M;Shah C R;Shah K J (NO, Physical Research Laboratory, Ahmedabad-380 009) : Radio emission as a diagnostic for solar coronal rotation. Bull Astr Soc India 1999, 27(1), 61-3.

Time series of solar radio emission at 2.8 GHz is analysed using correlation methods. The analysis showed that this type of time series can be used to infer the rotation period of the source (in this case solar corona). It is found that the correlograms have a very strong persistence of rotational modulation. These values are significantly lower than those reported earlier by other methods. The reasons for this difference are unknown.

000082   Vaidya D B;Anandarao B G;Desai J N (NO, Physical Research Laboratory, Ahmedabad-380 009) : Interstellar grains towards orion. Bull Astr Soc India 1999, 27(1), 141-4.

Using discrete dipole approximation (DDA) calculate the extinction efficiencies of the porous silicate grains. Use these efficiencies to reproduce the observed extinction in the region of star formation in Orion and find that the grain models with about 40 per cent porosity fit the observed extinction reasonably well.

13 ref

000081   Sreedhar Rao S;Raghavender Rao C;Kilambi G C (NO, Centre of Advanced Study in Astronomy, Osmania University, Hyderabad-500 007) : HR 3040 - on the Am track. Bull Astr Soc India 1999, 27(1), 123-7.

HR 3040 (HD 63589) exhibits pseudo-luminosity effects similar to many a main-sequence Am star, especially a strong Sr II 4077 line indicating a higher luminosity class. Its K-line matches that of A3 V, violet and blue metallic line spectrum resembles F2 III-IV, whereas its Sr II 4077 is as strong as that in an F5 III standard. With respect to its observed spectral characteristics and estimated orbital parameters, the position of HR 3040 vis-a-vis similar Am systems on the HR diagram is discussed.

19 ref

000080   Shanthi K;Rao A R;Bhat C L;Vahia M N (NO, Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 005) : Hint of a galactic origin for a sub-population of extremely short and hard cosmic gamma-ray bursts. Bull Astr Soc India 1999, 27(1), 195-8.

Gamma ray bursts (GRBs) belong to an exotic class of astronomical phenomena whose origin and nature continues to puzzle the astrophysical community. These enigmatic events are seen as intense outbursts of high-energy photon radiation (10's of keV to 10's of MeV), lasting from a few milliseconds to as long as several minutes. The understanding of gamma-ray bursts has to rely heavily on the statistical study of their properties. Authors have taken the BATSE 3B burst catalog for analysis and have found a clear signature of a bimodality when bursts are classified on the basis of their time-duration and hardness-ratio. Two populations of events are suggested, one characterized by shorter bursts with harder spectra and the other by longer bursts with softer spectra. A subclass within the first group, comprising the hardest and the shortest bursts, indicate an association with some galactic feature/population.

000079   Sanwal B B;Mahendra Singh (NO, Uttar Pradesh State Observatory, Manora Peak, Nainital-263 129) : CN and C₂ molecules in the coma of comet C/1995 01 Hale-Bopp. Bull Astr Soc India 1999, 27(1), 79-80.

Spectrophotometric observations of the Comet C/1995 01 Hale-Bopp were taken through 104 cm telescope of the U.P. State Observatory, Nainital using EG and G spectrograph coupled with an Optical Multi Channel Analyser and Reticon Array Detector in the optical region of the spectrum, during its closest approach (19-24 April 1997) for four nights. The molecular emission bands of CN at 3888 A^°, and C₂ (Δ v=+1, 0, -1) at 4690 A^°, 5160 A^°, 5530 A^° respectively, were detected. Column densities and production rates at different heliocentric and geocentric distances were also determined.

000078   Sagar R;Pandey A K;Mohan V;Yadav R K S; Nilakshi;Bhattacharya D;Castro-Tirado A J (NO, U.P. State Observatory, Manora Peak, Nainital-263 129) : Optical follow up of the GRB 990123 source from UPSO, Nainital. Bull Astr Soc India 1999, 27(1), 3-7.

CCD magnitudes in Johnson BV and Cousins R photometric passbands are determined for the optical transient of GRB 990123. These observations have been taken approximately 12 hours after trigger of the gamma-ray burst. BVR photometric light curves are obtained by combining the published data with the present measurements. They indicate that the flux decay constants in BV and R passbands are almost the same. Its value is 1.1 ± 0.06. Such decay is quite consistent with the fireball models for the optical transient.

11 ref

000077   Rastogi S (Physics Department, Lucknow University, Lucknow-226 007) : Interstellar biomolecules and infrared astronomy. Bull Astr Soc India 1999, 27(1), 221-5.

Ubiquitous presence of organic molecules in the interstellar clouds, comets and asteroids, and the evidence of extraterrestrial amino acids in carbonaceous meteorites strongly support a cosmic perspective on the origin of life. Hoyle and Wickramasinghe in a series of publications have argued that dust grains in the interstellar clouds contain bacteria and that the disruption of bio-grains in the presence of a UV flux is responsible for the large scale presence of Polycyclic Aromatic Hydrocarbons and other organic polymers. It is proposed that proteins and polypeptides will also result in the disruptions of bacteria in the interstellar clouds. These polypeptides have characteristic vibrational modes of the amide group in the polymer chain. The observational regions in the infrared for the amide modes of α helical polypeptides is suggested. Since amino acids appearing on disruptions of biotic matter may be predominantly in polymeric form and rotational transitions would not occur, their vibrational transitions are of significant importance. Thus infrared spectroscopy of circumstellar shells and dense clouds in the star forming regions for the amide bands in the 2.5 to 18 μm IR range would play a decisive role in the theories of interstellar biomolecules.

20 ref

000076   Ramesh B (NO, Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore-560 080) : Detection of 6 new 107 GHz methanol masers. Bull Astr Soc India 1999, 27(1), 199-202.

000075   Raju K P;Srikanth R;Jagdev Singh (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Lifetimes and sizes of supergranular cells. Bull Astr Soc India 1999, 27(1), 65-8.

Supergranulation is the surface manifestation of large scale solar convection. Since there is a strong correspondence between supergranulation pattern and Ca K chromospheric network, lifetimes and sizes may be obtained from the temporal and spatial autocorrelation functions (ACF), calculated from Ca K filtergrams of the Sun. Study the lifetimes and spatial scales of supergranulation through an extensive digital analysis. The temporal ACF was calculated from a 106 hour time-sequence of the data obtained from Antarctica. The lifetimes of quiet cells were found to be about 24-34 hours while that of active cells were about 58-61 hours. The temporal autocorrelation function sometimes showed an oscillatory pattern which may be due to long-term intensity variations or length scale changes associated with the network. The cell sizes were obtained from Ca K spectroheliograms belonging to the solar minimum phases of 1913-1974 from Kodaikanal Solar Observatory. The average cell size was found to show a curious dependence on solar latitude.

11 ref

000074   Paul B (NO, Tata Institute of Fundamental Research, Mumbai-400 005) : Timing study of some x-ray binaries. Bull Astr Soc India 1999, 27(1), 109-15.

000073   Paul B (NO, Tata Institute of Fundamental Research, Mumbai-400 005) : First results from the Indian x-ray astronomy satellite. Bull Astr Soc India 1999, 27(1), 103-8.

000072   Padmakar;Pandey S K (NO, School of Studies in Physics, Pt. Ravishankar Shukla University, Raipur-492 010) : Stellar activity in the RS CVn binary star UX arietis. Bull Astr Soc India 1999, 27(1), 117-21.

12 ref

000071   Muthu C;Anandarao B G (NO, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009) : Spatio-kinematic study of the planetary nebula NGC 246 in the [0III) 5007 A<. Bull Astr Soc India 1999, 27(1), 175-6.

000070   Muthu C;Anandarao B G (NO, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009) : Possible trends in expansion velocities of planetary nebulae evolved from common envelope binary systems. Bull Astr Soc India 1999, 27(1), 171-3.

000069   Mukerjee K;Agrawal P C;Paul B;Rao A R;Vahia M N;Yadav J S;Seetha S;Kasturirangan K (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Energy dependence of x-ray pulse profile of the crab pulsar. Bull Astr Soc India 1999, 27(1), 181-4.

Obtained pulse profiles of Crab pulsar in 4 different X-ray energy bands between 2 and 30 keV. Authors found that all the profiles in these energy ranges show two peaks occurring at the same phase joined by a lower but non zero flux region named as the bridge. Integrated flux or fluence of peak-2 and bridge show energy dependent variation with respect to peak-1. These fluence ratios increase with energy in a similar pattern indicating common origin for these changes. These increasing trends of the fluence ratios have different implications on current pulsar emission models and offer new challenges for refinement of existing models.

000068   Mookerjea B;Ghosh S K;Karnik A D;Rengarajan T N;Tandon S N;Verma R P (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Infrared emission from IRAS 00338 + 6312. Bull Astr Soc India 1999, 27(1), 155-8.

Galactic star forming region associated with IRAS 00338 + 6312 has been mapped in 2 Far Infrared (FIR) bands centered around 140 and 185 μm, using the TIFR 100 cm balloon-borne telescope with liquid ³He cooled bolometer arrays. The results from these observations and the physical parameters derived from radiation transfer modelling of the source are presented.

000067   Mitra D;Deshpande A A (NO, Raman Research Institute, Bangalore-560 080) : Shape of pulsar beams revisited. Bull Astr Soc India 1999, 27(1), 203-5.

Using a carefully selected subset of the recently published multifrequency polarimetric observations of 301 radio pulsars (Gould and Lyne 1997), authors have attempted modelling the shape of pulsar beams. From the 6-frequency data selected on conal triple and multiple component profiles, find that there are three distinct cones of emission and that the pulsar beam shape changes from circular (for an aligned rotator) to latitudinally compressed form (for an orthogonal rotator). No evidence in support of the evolution of the pulsar beam shape as a function of period, while as expected the overall size scales as P^-0.5, where P is the pulsar period.

10 ref

000066   Krishna Swamy K S (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Emission band ratios of CO in comets. Bull Astr Soc India 1999, 27(1), 75-7.

10 ref

000065   Kaul R K;Kaul C L;Bhat C L (NO, Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 085) : Millisecond pulsars as VHE gamma-ray sources. Bull Astr Soc India 1999, 27(1), 191-4.

Detectability of millisecond pulsars in VHE gamma-ray bracket (<62> 5 x 10¹¹ eV), with the recently-commissioned TACTIC array, has been investigated on the basis of system energetics and the pulsar polar gap model. It is shown that, out of the 24 millisecond pulsars with known values of period, period derivative and distance, at least two millisecond pulsars qualify as potentially detectable by the TACTIC array above 0.5 TeV photon energy.

000064   Karnik A D;Ghosh S K;Rengarajan T N;Tandon S N;Verma R P (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Infrared spectral energy distribution of four star forming regions. Bull Astr Soc India 1999, 27(1), 167-70.

Star forming regions associated with IRAS 19181 + 1349, 20255 + 3712, 20178 + 4046 and 10049 + 5657 have been mapped simultaneously in two far infrared bands (λ_eff ″ 130 and 210 μm), using TIFR 1m balloon borne telescope with liquid ³He cooled bolometer arrays. HIRES processed IRAS maps at 12, 25, 60 and 100 μm have been compared with ours. The TIFR maps show much more structural details due to their superior angular resolution. Detail radiation transfer modelling has been carried out for each of these sources and compared with observed spectral energy distributions.

000063   Kapoor R C;Shukre C S (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034) : Geometrical constraints on pulsar emission II. Bull Astr Soc India 1999, 27(1), 207-8.

000062   Javaraiah J (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Comparison of periodicities of the sun's `mean' and differential rotations determined from sunspot group and from Mt. Wilson velocity data. Bull Astr Soc India 1999, 27(1), 73-4.

There seem to be considerable differences in the periodicities (in the range 2-11 years) of the differential rotation coefficients A and B determined from the spot group data and the velocity data. These differences may be because the rotation rate determined from the velocity data represents the rotation rate of shallower layers (″ 1.0 R_o), whereas the average rotation rate determined from combined data of all types of sunspot groups represents the rotation rate of the deeper layers (″ 0.9 R_o).

000061   Goswami A;Kameswara Rao N;Lambert D L (NO, Indian Institute of Astrophysics, Bangalore-560 034) : DZ andromedae : a search for the spectral evidence of its possible RCB nature. Bull Astr Soc India 1999, 27(1), 129-31.

Analysis of high-resolution spectra of DZ Andromedae, a suspected R Coronae Borealis variable, is presented. The spectra of DZ and show the characteristics of a normal K2 III star, indicating that the star was earlier misclassified. A detailed abundance analysis also indicates that the star's composition is not consistent with its membership in the RCB class.

000060   Giridhar S (NO, Indian Institute of Astrophysics, Bangalore-500 034) : Surface compositional changes observed during last stages of stellar evolution. Bull Astr Soc India 1999, 27(1), 99-102.

18 ref

000059   Ghosh S K;Verma R P (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Modelling infrared spectra of a few compact HII regions. Bull Astr Soc India 1999, 27(1), 163-6.

Observed near infrared to sub-mm spectra of five compact HII regions, viz., IRAS 18116-1646, 18162-2048, 19422 + 2427, 22308 + 5812 and 18434-0242, consisting of the continuum as well as several features, have been explained well by radiative transfer through a spherical dust cloud. In addition to the equilibrium thermal emission from the normal dust grains (BG), the non-equilibrium processes, e.g. transient heating of the very small grains (VSG) as well as the Polycyclic Aromatic Hydrocarbon (PAH) are also taken into account by a novel scheme of segmenting the main cloud into individual "onion skin" cloud shells. The following have been concluded about these compact HII regions : the uniform radial density distribution gives an excellent fit to the entire body of the data (other cases e.g. r^-1, r^-1.5 or r^-2 etc can be ruled out); the PAH features are predicted very well only if these molecules exist exclusively in the central region (a few % of radius) of the cloud; and the silicate grains constitute only 5-25% of the BG component (rest being graphite).

11 ref

000058   Ghosh S K;Mookerjea B (NO, Tata Institute of Fundamental Research, Mumbai-400 005) : Infrared spectroscopic diagnostics for initial mass function. Bull Astr Soc India 1999, 27(1), 151-4.

Diagnostic values of various atomic/nebular infrared spectral lines of relatively abundant elements (in different ionization states) in Galactic star forming regions, have been studied quantitatively. The code cloudy (Ferland 1996) has been used to model spherically symmetric interstellar clouds with embedded ZAMS stars/young star clusters. In particular, the question of deciphering the upper mass limit of initial mass function has been addressed, in the light of the capabilities of the two spectrometers onboard Infrared Space Observatory (ISO-SWS covering 2.5-4.5 ,109>m; and ISO-LWS covering 45-200 μm).

000057   Gauri Shankar (School of Studies in Statistics, Pt. R.S. University, Raipur-492 010) : Gert analysis of corrective action plan for the production processes. Opsearch 1999, 36(2), 85-94.

Presents a corrective action plan to maintain high quality level of the production process. Graphical Evaluation and Review Technique (GERT) has been applied to model and analyse the dynamic characteristics of the plan. The expression for OC and other performance characteristics of the plan have been derived and illustrated numerically.

12 ref

000056   Chitnis V R;Bhat P N (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Fluctuations in cerenkov photon density in extensive air showers. Bull Astr Soc India 1999, 27(1), 213-6.

In the absence of a standard source of γ-rays or hadrons of known energy one has to study the details of production of Cerenkov light at the observation level only through detailed simulation studies. Recently such studies have become all the more important in view of the various techniques resulting from such studies, to distinguish between γ-ray initiated events from those generated by much more abundant hadronic component of cosmic rays. Detailed simulation studies using the CORSIKA package in order to study the Cerenkov photon density fluctuations for 5 different energies in the range 50 GeV to 1000 GeV, at various core distances, both for γ-ray and proton primaries incident vertically at the top of the atmosphere. The density fluctuations are found to be significantly non-statistical. Also proton showers are found to show more fluctuations in shower size as well as density compared to γ-ray showers, at the energies. Also studied the contributions to fluctuations from various known processes, including Coulomb scattering of electrons, fluctuations in the height of first point of interaction and fluctuations in electron energy spectra. In principle, the differences in density fluctuations could be used to identify the nature of primary.

000055   Chandrasekhar T (NO, Physical Research Laboratory, Ahmedabad-380 009) : Near IR lunar occultation observations and results from Gurushikhar observatory. Bull Astr Soc India 1999, 27(1), 43-50.

Lunar occultation in the near infrared is an elegant and effective technique of achieving high angular resolution in the range of milliarcseconds. Apart from determining with good accuracy the angular diameter and effective temperature of many late type giants and supergiants, the method has also been used to probe the circumstellar regions of many of these stars. A program of high angular resolution studies by the method of lunar occultations in the infrared is being pursued at the 1.2 m Gurushikhar telescope. The method is outlined and highlighted with interesting results from the Gurushikhar telescope.

000054   Biswas S N (NO, Mahatma Aswini K.R. Road, P.O. Nabapalli-743 203, North 24-Parganas, ) : Some statistical aspects of comet orbits and their discoveries. Bull Astr Soc India 1999, 27(1), 91-4.

000053   Bhattacharya S;Kaul R K;Kaul C L;Bhat C L (NO, Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 085) : Gamma ray production in SNR's - contribution from photomeson process. Bull Astr Soc India 1999, 27(1), 185-9.

Estimates the integral γ-ray fluxes above 10 MeV photon energy, likely to result from neutral pion decay, following photomeson interactions between ultra-high energy protons accelerated in Supernova Remnants (SNR) and the background non-thermal X-ray photon field. Taking SN1006 as a test case, finds that the integral fluxes in the TeV range are significantly lower than the experimentally reported values, indicating the ineffectiveness of the photo-meson interaction as a source of the reported TeV γ-ray signal from SNR.

12 ref

000052   Bhatt H C (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Star formation in molecular clouds and the initial mass function. Bull Astr Soc India 1999, 27(1), 145-9.

Observed mass spectra for stars and interstellar clouds are discussed. Stars are both from clouds, but their mass spectra are fundamentally different. A new model is proposed in which the Salpeter function representing the stellar mass spectrum is shown to result from the parent cloud mass spectrum. Stars form in the cores of the clumps in a cloud and grow by accretion. The accretion energy is deposited into the clump and disrupts it when the star has grown to a limiting mass. The limiting mass is derived. Combined with the observed clump mass spectrum, this leads to the Salpeter function for the stellar mass spectrum. Several other observed features of clouds and stars also follow.

13 ref

000051   Bhatt H C (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Planet formation in sun-like systems. Bull Astr Soc India 1999, 27(1), 51-9.

Recent discoveries of substellar and planetary-mass objects in orbit around other stars represent the most remarkable progress achieved in the search for extrasolar planetary systems. The evidence for their existence is summarised. The physical properties and orbital characteristics of these systems are discussed and compared with those of the solar system. The new discoveries raise new questions for the theories of planet formation as part of the star formation process.

42 ref

000050   Barman S K (NO, Milki H.S. School and IGNOU, Malda, AT/Puratuli, Malda-732 101) : Linear polarization in binaries with grey atmosphere I conservative Rayleigh scattering. Bull Astr Soc India 1999, 27(1), 217-20.

Presents a method of calculating linear polarization from binaries whose surface are distorted due to tidal and rotational forces. The atmospheres in stars are grey, plane-parallel and pure scattering. The polarization as high as 3.51% is calculated for a single star and 2.89% for a binary with a mass ratio q=0.3. The method has been applied to some early type binaries to calculate polarizations in them.

000049   Asgekar A;Deshpande A A (NO, Joint Astronomy Program, Indian Institute of Science, Bangalore-560 012) : New pulsar observations using the Gauribidanur radio telescope. Bull Astr Soc India 1999, 27(1), 209-11.

Pulsar observations with improved sensitivity have been initiated at 34.5 MHz and a 1-MHz bandwidth using the Gauribidanur Radio Telescope. Describes new procedure where the raw (2-bit) signal voltages are recorded and the data are processed optimally off-line. A few preliminary results from these observations are presented.

000048   Apparao K M V (Department of Physics, University of Bombay, Santa Cruz East, Bombay-400 098) : Be star binary systems with non-compact secondaries. Bull Astr Soc India 1999, 27(1), 137-9.

000047   Apparao K M V (NO, University of Bombay, Bombay-400 098) : Shocks in binary systems with high density winds or envelopes. Bull Astr Soc India 1999, 27(1), 133-5.

000046   Antia H M;Chitre S M (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Can <. Bull Astr Soc India 1999, 27(1), 69-71.

000045   Anandarao B G (NO, Physical Research Laboratory, Ahmedabad-380 009) : Infrared studies of circumstellar matter of evolved stars. Bull Astr Soc India 1999, 27(1), 95-8.

27 ref

024435   Tripathi M M (Department of Mathematics and Astronomy, Lucknow University, Lucknow-226 007) : On CR submanifolds of nearly and closely cosymplectic manifolds. Ganita 2000, 51(1), 45-56.

CR submanifolds of nearly cosymplectic and closely cosymplectic manifolds are studied. Properties such as integrability, autoparallelness and nearly autoparallelness of certain distributions on the submanifold are studied. Totally imbilical, totally contact umbilical, totally geodesic and totally contact geodesic submanifolds are also studied.

12 ref