000074   Bhat C K;Kaul R K;Sapru M L;Bhat C L (Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai - 400 085) : Cosmic ray mass composition through Cerenkov technique - a feasibility study. Bull Astr Soc India 2002, 30(1), 331-4.

Detailed Monte Carlo simulations of atmospheric Cerenkov events, recorded by the 349 - pixel imaging camera of the TACTIC Imaging Cerenkov Telescope array at Mt. Abu, Rajasthan, have been carried out to study the possibility of using the Hillas image and orientation parameters for mass segregation of the primary air shower - initiating particles. Four primary species, namely, gamma rays, protons, Neon and Iron nuclei, with energies above 10 TeV have been considered for the simulations. Preliminary results indicate that, except for Width, Azwidth and Length parameters, all other image parameters may not provide a significant segregation of the primary particles in terms of their mass.

1 illus, 1 table, 3 ref

000073   Bhargavi S G (Indian Institute of Astrophysics, , Bangalore-560 034) : Multi-band observations of gamma ray bursts. J Astrophys Astr 2002, 23(1-2), 123-7.

Focuses on the various aspects learnt from multiband observations of GRBs, both before and during the afterglow era. A statistical analysis to estimate the probable redshifts of host galaxies using the luminosity function of GRBs compatible with both the afterglow redshift data as well as the overall population of GRBs is discussed. A addresses the question whether the observed fields of GRBs with precise localizations from third Inter-Planetary Network (IPN³) contain suitable candidates for their host galaxies.

1 illus, 1 table, 10 ref

000072   Bardoloi I;Barua M M (NO, Handique Girl's College, Guwahati - 781 001) : Astronomical gamma-ray lines predicting probable gamma-emitter nucleosynthesis sites as explosive events. Bull Astr Soc India 2002, 30(1), 305-11.

Astronomical gamma-ray γ lines with energy 0.5 - 15 MeV have been interpreted as due to e⁺ - e^- annihilation and decay and de-excitation of the excited nucleosynthesis yields produced in some explosive sites and then ejected into the inter steller matter (ISM). Some explosive events e.g. X-ray outbursts and novae outbursts have been considered to study, whether these possible cosmic candidates can provide enough nuclei to explain the observed highly significant 1.809 MeV, 1.275 MeV γ-lines reported by Compton Gamma-ray observatory (CGRO) and other satellite experiments. Cen X-4, Aql X-1, 1608-522, these three soft X-ray transients (SXT) during outburst can be suggested as good emitters of these two lines with emission features in observable range which may be tried with sophisticated instruments like SPI (Spectrometer INTEGRAL) on board the spacecraft INTEGRAL (International Gamma-ray Astrophysics Laboratory) to be launched by ESA (European Space Agency) in near future.

^iia5 illus, 18 ref

000071   Bandyopadhyay K;Suthar R L;Guha S;Koul R (Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai - 400 085) : Focal plane instrumentation of the MACE telescope. Bull Astr Soc India 2002, 30(1), 417-20.

The 17m MACE telescope will employ high-resolution MACE imaging camera consisting of 832 PMTs and low resolution BEST camera consisting of 108 PMTs for γ-ray astronomical experiments. To enhance the duty cycle of the telescope it is proposed to have a liquid optical filter assembly in front of the MACE imaging camera. Associated electronics and mechanical components needed for successful data capturing and processing make the design of the camera an extremely challengingg job. The basic framework for the camera design currently under progress has been described.

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000070   Ananthanarayan B;Singh R K (Centre for Theoretical Studies, Indian Institute of Science, Bangalore-560 012) : Direct observation of neutrino oscillations at the Sudbury Neutrino Observatory. Curr Sci 2002, 83(5), 553-4.

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000069   Acharya K;Chakrabarti S K;Molteni D (Centre for Space Physics, , P-61 Southend Gardens, Kolkata-700 084) : Interaction of accretion shocks with winds. J Astrophys Astr 2002, 23(1-2), 155-64.

Accretion shocks are known to oscillate in presence of cooling processes in the disk. The oscillation may also cause quasi-periodic oscillations of black holes, In the presence of strong winds, these shocks have oscillations in vertical direction as well. Shows examples of shock oscillations under the influence of both the effects. When the shocks are absent and the flow is cooler, the wind becomes weaker and the vertical oscillation becomes negligible

3 illus, 9 ref

000068   Acharya K;Chakrabarti S K;Molteni D (Centre for Space Physics, , 114/V/1A Raja S.C. Mullick Rd. Kolkata-700 047) : Wind induced instabilities in accretion flow around black holes. Bull Astr Soc India 2002, 30(1), 317-20.

A new type of instability of the accretion flow which is formed due to interaction of the outgoing winds with the incoming flow has been identified. Mainly due to shear instability, the flow oscillates around the equatorial plane. It has been shown that in the shocks that are formed in accretion flows, this new type of oscillation persists along with the usual radial oscillation.

3 illus, 8 ref

021898   Srinivasan C;Saraswathi R (Materials Science Dep, Madurai Kamaraj Univ, Madurai-625 021, Email: ceesri@yahoo.com) : 'Flash' in the synthesis of graphene. Curr Sci 2009, 97(8), 1115-16.

2 illus, 12 ref

021897   Sivaram C;Arun K (NO, Indian Institute of Astrophysics, Bangalore-560 034, Email: sivaram@iiap.res.in) : On internal heat production in exo-planets, fission triggered stars, etc.. Curr Sci 2009, 97(3), 296.

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021896   Scaife A M M;Grainge K J B (NO, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland, Email: ascaife@cp.dias.ie) : SZ science with an ALMA band 1 receiver system. Bull Astr Soc India 2010, 38(4), 185-93.

Presents the first full interferometric simulations of galaxy clusters containing radio plasma bubbles as observed by the proposed Q band receiver system for the ALMA telescope. Discusses the observational requirements for detecting intracluster substructure directly from the SZ signal and the advantages of these observations over those made with the current generation of SZ survey instruments.

5 illus, 1 table, 14 ref

021895   Ravindra B;Howard T A (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034, Email: ravindra@iiap.res.in) : Comparison of energies between eruptive phenomena and magnetic field in AR 10930. Bull Astr Soc India 2010, 38(4), 147-63.

Presents a study comparing the energy carried away by a coronal mass ejection (CME) and the radiative energy loss in associated flare plasma, with the decrease in magnetic free energy during a release in active region NOAA 10930 on December 13, 2006 during the declining phase of the solar cycle 23. The ejected CME was fast and directed towards the Earth with a projected speed of <126>1780 km s^-1 and a de-projected speed of <126>3060 km s^-1. We regard these as lower and upper limits for our calculations. It was accompanied by an X3.4 class flare in the active region. The CME carried (1.2-4.5)xl0³² erg (projected-deprojected) of kinetic and gravitational potential energy. The estimated radiative energy loss during the flare was found to be 9.04xlO³⁰ erg. The sum of these energies was compared with the decrease in measured free magnetic energy during the flare/CME. The free energy is ' that above the minimum energy configuration and was estimated using the magnetic virial theorem. The estimated decrease in magnetic free energy is large, 3.11 x 10³² erg after the flare/CME compared to the pre-flare energy. Given the range of possible energies we estimate that 50-100% of the CME energy arose from the active region. The rest of the free magnetic energy was distributed among the radiative energy loss, particle acceleration, plasma and magnetic field reorientation.

5 illus, 61 ref

021894   Parvathi V S;Sofia J;Murthy J;Babu B R S (Physics Dep, Calicut Univ, Kerala-673 635, Email: veena_sivaram@yahoo.co.in) : Estimation of C II and C II column densities along galactic sight-lines. Bull Astr Soc India 2010, 38(2-3), 93-101.

Presents interstellar Cu (1334.5323 A) and Cn* (1335.7077 Angstrum) column density measurements along 14 Galactic sight-lines. These sight-lines sample a variety of Galactic disk environments and include paths that range nearly two orders of magnitude in average hydrogen densities (<60>n(H)<62>) along the lines of sight. Five of the sight-lines show super-solar gas phase abundances of carbon. The results show that the excess carbon along these sight-lines may result from different mechanisms taking place in the regions associated with these stars.

3 illus, 2 tables, 27 ref

021893   Lecavelier Des Etangs A (NO, Institut d'astrophysique de Paris, CNRS/UPMC, 98bis Arago, F-75014 Paris, France, Email: lecali@iap.fr) : Evaporation of extrasolar planets. Bull Astr Soc India 2010, 38(4), 137-45.

This article presents a review on the observations and theoretical modeling of the evaporation of extrasolar planets. The observations and the resulting constraints on the upper atmosphere (thermosphere and exosphere) of the "hot-Jupiters" are described. The early observations of the first discovered transiting extrasolar planet, HD209458b, allowed the discovery that this planet has an extended atmosphere of escaping hydrogen. Subsequent observations showed the presence of oxygen and carbon at very high altitude. These observations give unique constraints on the escape rate and mechanism in the atmosphere of hot-Jupiters. The most recent Lyman-alpha HST observations of HD189733b and Mgll observations of Wasp-12b allow for the first time a comparison of the evaporation from different planets in different environments. Models to quantify the escape rate from the measured occultation depths, and an energy diagram to describe the evaporation state of hot-Jupiters are presented. Using this diagram, it is shown that few already known planets like GJ876d or CoRot-7b could be remnants of formerly giant planets.

3 illus, 41 ref

021892   Ivanov V P;Kjurkchieva D P;Srinivasa Rao M (Physics Dep, Shumen Univ, 9700 Shumen, Bulgaria, Email: viva.nov@abv.bg) : Light curve solutions of eclipsing binaries in SMC. Bull Astr Soc India 2010, 38(2-3), 83-92.

Proposed a procedure for light-curve solutions of eclipsing binary stars in the Small Magellanic Cloud (SMC) for which photometric data have been obtained in the framework of the OGLE project. Also presents a way of determining the global stellar parameters on the basis of the obtained solutions, some empirical relations as well as the distance to the SMC. Several examples illustrate this procedure.

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021891   Garn T S;Green D A;Riley J M;Alexander P (SUPA, Institute for Astronomy, Royal Observatory of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom, Email: D.A.Green@mrao.cam.ac.uk) : Further GMRT observations of the lockman hole at 610 MHz. Bull Astr Soc India 2010, 38(2-3), 103-12.

Presents further observations of the Lockman Hole field, made with the Giant Metrewave Radio Telescope at 610 MHz with a resolution of 6 x 5 arcsec². These complement our earlier observations of the central <126> 5 deg² by covering a further 8 deg², with an r.m.s. noise down to <126> 80 μJy bean T^-1. A catalogue of 4934 radio sources is presented.

3 illus, 23 ref

021890   Deb S;Singh H P;Seshadri T R;Gupta R (Physics & Astrophysics Dep, Delhi Univ, Delhi-110 007, Email: sdeb@physics.du.ac.in) : CCD photometric study of the newly discovered contact binary ASAS 134738+0410.1. Bull Astr Soc India 2010, 38(2-3), 77-82.

Presents a CCD photometric study of the star with ASAS ID 134738+0410.1 using V band observations obtained from the IUCAA Girawali Observatory (IGO) 2-metre telescope, India. The star was selected from the 6 Scuti database of All Sky Automated Survey (ASAS) (Pojmanski 2002). Our analysis reveals that the star is not a 6 Scuti variable but is in fact a W UMa type contact binary with an orbital period of 0.2853067 day. Two new times of primary and secondary minima were determined from the observed data. A preliminary solution obtained using the Wilson-Devinney light curve modelling technique indicates that the star is more likely a partially-eclipsing W UMa type contact binary. However, the determination of actual subtype of this binary is quite impossible from the photometry alone, as the observed light curve can be fitted for both A- and W-type solutions. The exact classification of this binary needs to be determined from high resolution spectroscopy.

2 illus, 17 ref

021889   Aryal B;Bachchan R K;Saurer W (Institute of Astro-and Particle Physics, Innsbruck Univ, Technikerstrasse 25 A-6020 Innsbruck, Austria, Email: binil.aryal@uibk.ac.at) : Optical search limit and preferred position angles of galaxies in 35 clusters. Bull Astr Soc India 2010, 38(4), 165-84.

Worked on POSSII and ESO films and measured the diameters and position angles of 6244 galaxies in 35 clusters using a 25-fold magnification microscope. The optical search limit has been estimated for these clusters. The position angle distributions of galaxies in the clusters have been studied. For this, chi-square, auto-correlation and the Fourier tests have been carried out. A dependence has been noticed between the optical search limit and the mean radial velocity of the cluster. The preferred position angle distribution of galaxies in the cluster has been found to be independent of the mean radial velocity of the cluster. Possible explanations of the result are discussed.

5 illus, 3 table, 36 ref

000040   Singh K P (Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005) : Peering into the hearts of galaxies. Curr Sci 2001, 81(1), 25-31.

Composed of hundreds of billions of stars and swirling masses of gas and dust bound together in different shapes, galaxies are truly majestic objects in the sky. Contained in their hearts or nuclei are perhaps the most powerful engines in the universe. In some galaxies, the central nucleus out-shines the whole surrounding galaxy. Such galaxies are known as Seyfert or active galaxies. The knowledge gained from the studies of recent images, spectra and rapid variations in the light output (X-ray, optical, etc.) from the nuclei of galaxies has led to the current paradigm for the nuclear regions of different classes of active galaxies. Briefly describes the current observational knowledge about different types of galaxies, focusing on the activity emanating from the nuclear regions or the hearts of the galaxies.

30 ref

000039   Rastogi R G;James M E (Department of Physics and Space Sciences, Gujarat University, Ahmedabad-380 009) : Geomagnetic field variations at the equatorial electrojet observatory, Etaiyapuram. Indian J Radio Space Phys 2001, 30(5), 221-32.

Extent of the effect of electromagnetic induction in sub-surface has been investigated using geomagnetic data for the period 1980-1986 from a station Etaiyapuram situated between Trivandrum and Kodaikanal and away from the sea-coast, but close to the magnetic equator. The station Etaiyapuram exhibits forenoon maximum and afternoon minimum in Z component for all seasons, similar to that for Trivandrum, contrary to the expectations from Chapman's theory of equatorial electrojet. Daily variation of Z shows characteristic features for Trivandrum during the years when sun is active, but characteristic features for Kodaikanal when sun is calm suggesting that the latitudinal extent of anomalous induction in Palk Strait decrease with decreasing solar activity. The daily variation of disturbance in geomagnetic Z field does not indicate any abnormal effect due to induction, but storm time D_st(Z) variation shows clearly the induction effects. Similarly, the amplitude of storm sudden commencement (SSC) in ΔZ at Etaiyapuram is found to be affected byelectrojet as well as by the sub-surface currents.

000038   Ghosh S;Bandyopadhyay T K;Pant C;Sen D K; Rajawat R S (NO, , 15 & B Kyd St, Calcutta-700 016) : Devri-Khera: a new L6 chondrite. Meteoritics 2001, 36(9S), A241-5.

Devri-Khera meteorite fell on 1994 October 30 in the Jhalwar district of Rajasthan, northwestern India. The texture, mineralogy and mineral and bulk compositions show that Devri-Khera is an L6 chondrite of shock facies S4.

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000037   Chakrabarti S K;Nandi A (S N Bose National Centre for Basic Sciences, , JD Block, Salt Lake, Sector-III, Calcutta-700 098) : Fundamental states of accretion/jet configuration and the black hole candidate GRS1915+105. Indian J Phys-Pt B 2000, 75(1), 1-4.

Advective disk paradign of black hole accretion includes self-consistent formation of shocks and outflows from post-shock region. Applies this paradign to understand rich variation of the light curve of the black hole candidate GRS1915+105. Author propose that out of five possible fundamental states the black hole candidate GRS1915+105 moves around among three of them creating all possible observed light curves.

17 ref

000036   Bose S K;Bhattacharya A B (Department of Physics, Kalyani University, Kalyani-741 235) : Local time dependence of decametric radio emission from Jupiter observed from earth stations at different solar activity. Indian J Radio Space Phys 2001, 30(5), 233-42.

Investigates the local time dependence of decametric radio emission from Jupiter observed from earth stations and examines the phenomenon at different solar activity conditions. The results exhibit that, at different solar activity periods, all non-Io sources show high occurrence probability of decametric radio emission corresponding to high polar coronal hole size, and at the time of crossing of interplanetary magnetic field sector boundary to the Jovian magnetosphere, occurrence probability shows high intensity. The results have been critically interpreted by considering the interaction of solar wind with the Jovian magnetosphere.

022096   Vaitheeswaran V;Kamath U S;Rangaswamy V (Indian Institute of Astrophysics, , Bangalore 560 034) : IR-IMAC - a development approach. Bull Astr Soc India 2004, 32(1), 75-9.

IR-IMAC is a multi-utility software package developed to remotely control the Near-Infrared imager installed on the 2-metre Himalayan Chandra Telescope at Mt. Saraswati, Hanle. The core idea in the development of IR-IMAC was to effectively use the existing Open Source Code (OSC), Features of IR-IMAC and its component-based development using Open Source Code approach are presented.

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022095   Sanwal B B;Kumar B;Mahendra Singh (State Observatory, , Manora Peak, Nainital 263 129) : Spectrophotometry of the comet C/2002 V1 NEAT. Bull Astr Soc India 2004, 32(1), 25-31.

Spectrophotometric observations of the coma of the comet C/2002 V1 (NEAT) on January 24, 25 and February 4, 2003, with 104-cm telescope of the State Observatory, Nainital. CN (3883 A) and C2 swan bands (4695, 5165 and 5538 A) were identified. An estimate of CN and C2 abundances and their production rates were made. Dust production rates have also been determined.

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022094   Peraiah A (NO, , 57, 4th Cross 36th Main, B T M 1st Stage, Madiwala-Dollar Scheme, Bangalore 560 068) : Transfer of resonance line radiation in advected atmospheres with partial frequency redistribution of photons. Bull Astr Soc India 2004, 32(1), 33-57.

Influence of high velocities of expansion on resonance line radiation by taking into account of aberration and advection were studied. An angle averaged redistribution function R<11> was used in spherically symmetric media. Three types of media are considered. These are:(1) purely scattering medium (2) partly scattering and emission from continuum medium and (3) partly scattering and continuum and line emission medium. The spherical schells that are being used have thicknesses equal to 2,10 and 100 times the stellar radii. The radiation field is shown in terms of the source functions. Computations are performed in the comoving frame of the gas and the line profiles are calculated at the observer's point at infinity. The line profiles computed in the first type of medium show P Cygni characteristics and those computed in the second and third type of media show central emission and self absorption.

19 illus, 6 ref

022093   Lata S;Mohan V;Pandey A K;Ram Sagar (State Observatory, , Manora Peak, Naini Tal 263 129) : CCD photometry of the unstudied galactic star clusters Be 10, Be 67 and To 5. Bull Astr Soc India 2004, 32(1), 59-74.

Broad band Johnson UBV and Cousins RI CCD photometric observations for open clusters Be 10, Be 67 and To 5 were presented. So far no photometric study of these clusters is published. The colour-magnitude diagrams indicate that all the three clusters are of intermediate age. The reddening E(B-V), estimated from colour-colour diagrams/colour-magnitude diagrams, is 0.87±0.05 mag for Be 10, 0.79±0.05 mag for Be 67 and 0.80±0.05 mag for To 5. The comparison of colour magnitude diagrams with the stellar models with convective overshoot by Girardi et al. (2002) produces a good fit for a metallicity Z = 0.0008 for cluster Be 10 and Z = 0.02 for clusters Be 67 and To 5. Ages for Be 10, Be 67 and To 5 are log (age) = 8.8±0.1, 9.0±0.1 and 8.3±0.2 respectively. The corresponding distances for these clusters are 2.29±0.21,2.45±0.23and 1.75±0.16 kpc respectively. Analysis of the radial distribution of stellar surface density indicates that radius values for Be 10, Be 67 and To 5 are 6.0, 3.5 and 6.0 arcmin respectively.

7 illus, 23 ref

022092   Das T K;De B K;Bhattacharyya J (Institute of Radio Physics & Electronics, Calcutta University, 92, A P C Road, Kolkata 700 009) : Different distribution functions of solar X-ray flares. Bull Astr Soc India 2004, 32(1), 15-23.

A statistical study has been done on soft x-ray (SXR) flares, the date of which were collected by Geostationary Operational Environmental Satellites (GOES) during the period July 1993-June 1994.From the analysis different distribution functions were obtained empirically which give the number of SXR flares per unit interval of intensity and asymmetry in duration and angular interval of longitude. These distribution functions have been used for evaluating the center to limb variation of optical thickness for SXR flares.

4 illus, 6 tables, 8 ref

022091   Bardoloi I;Baruah M M (Handique Girls' College, , Guwahati 781 001) : Binary accreting neutron star as a source of X-ray transients-Aql X-1, Cen X-4, 1608-522. Bull Astr Soc India 2004, 32(1), 3-13.

A thermonuclear model for X-ray transients has been considered to explain the observed characteristics of X-ray transient outbursts in Aql X-1, Cen X-4, 1608-522. The model is of a compact primary neutron star (NS) in a close binary system. When the secondary companion fills up the Roche-lobe, sometimes sudden rise of mass accretion is there onto the NS. When the accretion rate is quite high (~10^-10M_ω Yr^-1), temperature and density increase up to ~ 10⁸ and ~ 10⁶ g cm^-3 respectively leading to thermonuclear flash. Using most recent proton capturing nuclear reaction rates and beta-decay rates, hydrogen burning cyclic reactions proceeding with seed nuclei C, O, Ne, Mg, have been studied and examined about energy generation during transient x-ray outburst time scale. Presently calculated valued of energy production, luminosity etc. are found to tally well with the observed parameters. During x-ray outbursts, mass is ejected from the source. Abundances of the nuclei (Z= 6-13) in the ejected mass have been calculated and compared with the recently observed cosmic ray source composition. Moreover,probable gamma-ray (Y) line spectra radiated by the excited product nuclei have been studies.

4 illus, 3 tables, 24 ref

000041   Mohan A;Dwivedi B N (Applied Phys Dep, Inst of Technol, BHU, Varanasi-221 005) : Composition of the solar atmosphere. Curr Sci 2004, 86(7), 921-9.

Unlike the uniform composition of the Sun's photosphere, the composition of the Sun's atmosphere is not well defined. Systematic differences do exist between the composition of the solar corona and the photosphere. Spatial and time variability in the composition of various coronal features have also been reported. The spectroscopic techniques used and the progress made in recent years to derive the plasma compositions of various structures in the solar atmosphare have been reviewed.

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020000   Agarwal S;Bhatnagar M C;Sharma G L (Thin film Laboratory, Dep of Physics, Indian Institute of TechnologyDelhi, Hauz Khas, New Delhi-110016) : Electrical characterization of Ba Sr TiO₃ thin films grown by sol-gel technique for humdity sensor applications. Asian J Phys 2003, 12(2-3), 299-302.

(Ba.Sr)TiO₃ (BST) thin films made by sol-gel technique are polyerystaline and porous in nature. It was found that the electrical properties such as flat band voltage, dielectric constant, and interface charge density are affected by relative humidity. The values of flat band voltage V_FB corresponding to 0% RH and 45% RH are found to be -0.1 volt and -1.1 respectively. The total interface trap charges density (Q_t is calculated to be 87.6pC/cm² at 0% RH and 12.95nC/cm² at 45% RH. These films were also studied at different pH varying from 7.4 to 9.5 for a solution of 0.3M molarity. As the pH of solution increase, the grain size decreases.

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018981   Trimble V (Physics and Astronomy Dep, University of California, Irvine, CA 92697-4575, USA, ) : Extra-solar system planets: searches, discoveries and characteristics. Bull Astr Soc India 2004, 32(2), 87-98.

The study of planets outside the solar system constitutes a new branch of astronomy that literally did not exist a decade ago. This discussion begins with How people have thought about other worlds in the past and some of the reported detections that turned out to be take have been discussed. A brief description of several successful ways of finding exoplanets and the properties of the planets found and their host stars have been discussed and an attempt has been made to look ahead. Most of the planets now known revealed themselves because their mutual orbits with their parent stars impose small, periodic radial velocity shifts in the stellar spectra, and most of the host stars are rich in heavy elements by the standards of the solar neighbourhood. The inventory of actual and potential detection methods has reached about two dozen.

117 ref

018980   Sriraghavan S M;Jayakumar K;Babu G S D; Sujatha S (M.P. Birla Institute of Fundamental Research, , Bangalore-560 001) : Variation of the Si II features in the chemically peculiar star -HD 115735. Bull Astr Soc India 2004, 32(2), 113-9.

The chemically peculiar star HD 115735 ( = HR 5023 + 21 CVn) was observed with the 2.34 meter Vainu Bapu Telescope at Kavalur during the period of January 1999 to April 2000. A total of 47 spectrograms were obtained in the wavelength region of 3900 Angstrom to 4400 Angstrom to 4400 Angstrom at a resolutio of 0.65 Angstrom per pixel. The equivalent widths of Si II features at 4077, 2128, 4131 Angstrom have been found to be varying with a period of 0.8±0.02 day, the amplitudes being about 0.1 Angstrom. This is the first report of spectroscopic variations of these features in this star.

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018979   Singh R N (Mitra Niketan, Banaras Hindu Univ, Varanasi-221005) : Awaited unfolding of Saturn-the ringed world. Curr Sci 2004, 86(8), 1071-5.

Saturn is second largest planet in our solour system. With a colourful ring system surrounding the plantet, it is highly attractive. Only brief observations, using telescopes, Pioneer-11, Voyager-1, and Voyager-2 in situ recorders have been made. Comparatively impressive detailed of Saturn have already been obtained. A space mission named Cassini-Huygens is on its way to explore Saturn's biggest moon, Tital, which is slightly smaller than our earth. This mission is well planned to study Saturn and explore various details of its atmosphere. It is also expected to spend four out of fifteen years to go round Titan. With the on-board payloads, it is hoped that we will be able to get valuable details for updating current knowledge of Saturn and Titan. Cassini has already sent the first colour picture postcards of Saturn taken from a distance of 285 million kilometers.

4 illus, 2 tables, 22 ref

018978   Shinde G N;Patil P B;Mirkute P R (Dep of Electronics, Yeshwant College, Nanded-431602) : A third-order active-R filter with feed ward input signal. Sadhana 2003, 28(6), 1019-26.

A realizatoin of voltage-mode transfer functions with feedforward input signal for third-order active-R filter using an oprational amplifier has been presented. This filter is useful for high frequency operation, monolithic IC implementation and is easy to design. The single circuit gives three filter functions, how pass, high pass and band pass. This filter circuit can be used for different Q an fo with high passband gain. This gives better stop band attenuation and sharper cut-off at the edge of the passband.

7 illus, 1 table, 9 ref

018977   Saikia D J (NO, , ) : Highlights from the observatories. Bull Astr Soc India 2004, 32(2), 133-8.

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018976   Rudraiah N;Ng C (Dep of Mechanical Engineering, The Univ of Hong Kong, Pokfulam Road, Hong Kong, Peoples Republic of China) : A model of manufacture of nanosized smart materials free from impuities. Curr Sci 2004, 86(8), 1076-91.

The importance of nano-sized smart materials in structural engineering, biomedical engineering, and in military applications is discussed. It is shown that the solidification of poorly conducting alloys involved in the manufacture of these materials gives rise to surface and convective instabilities. Different types of surface and convective instabliities are briefly discussed. These instabilities produce a mushy zone regarded as dendrites of nano-sized crystals. These dendrites arising from instabilities are regarded as impurities. To manufacture nano-sized smart materials free from impurities it is essential to control both surface and convective instabilities. Different types of convective and surface instabilities in a poorly conducting fluid. Also have been discussed briefly different mechanisms of control of these instabilities. Different analytical and numerical techniques used different boundary conditions have been discussed. The moment method is explained to find the condition for the onset of convection, and porous lining is used to suppress the growth rate of surface instability. This is useful in the manufacture of nano-sized smart materials free from impurities. Different methods to obtain the required basic equations and the corresponding boundry conditions are briefly discussed.

51 ref

018975   Padmanbhan N;Ramkrishnan R;Gurjar S B (Space Applications Centre, Indian Space Research Organization, Jodhpur Tekra, Ahmedabad-380015) : Geometric modelling of INSAT-2E CCD payload and multistrip mosaicking for geocoding large areas. Curr Sci 2004, 86(8), 1113-21.

The Indian National Satelllite (INSAT-2E), a gestationary satellite, carries a Charged Coupled Device camera. This camera is of scanning-mirror-type with a large field-of view of 10° X 10°. It generates three band image data in strips of about 300 km in the North-south direction. A method of removing the distrotions due to the scan imaging, and mosaicking the corrected strips to generate geocoded images of India and its environs have been described. The method can be used to generate geocoded images of any area imaged by any satellite of the same type. The accuracy of the absolute earth location calculated by considering some ground control points, is found to be about 5 pixels, both in the N-S and E-W directions.

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018974   Natesan U (Centre for Environmental Studies, Anna Univ, Chennai-600025) : Role of Satllites in monitoring sediment dynamics. Curr Sci 2004, 86(8), 1068-9.

2 illus, 1 table, 5 ref

018973   Murthy B S;Parasnis S S;Ek M (Indian Institute of Tropical Meterology, Dro Homi Bhabha Road, Pune 411 008) : Interactions of the land-surface with the atmospheric boundary layer: case studies from LASPEX. Curr Sci 2004, 86(8), 1128-30.

The daytime interaction of the land-surface with the Atomospheric Boundary Layer (ABL) is studied for two case study days representing pre-monsoon and monsoon conditions during the Land Surface Process Experiment (LASPES) field program which was carried out in the tropical semi-arid region in the northwest Indian state of Gujarat. In this study, a one-dimensional (column)ABL model which has a land-surface scheme that interacts with the ABL is used. Results indicate that in coupled land-atmosphere simulations realistic daytime surface fluxes and atmospheric profiles are produced, through improvement is needed, particularly in the transpiration and soil heat flux formulation.

8 illus, 2 tables, 21 ref

018972   Das H K;Kohok A;Tandon S N (NO, Inter University Center for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, Pune-411 007) : An implementation of transfer-pupil in a spectrograph on optical telescopes. Bull Astr Soc India 2004, 32(2), 121-31.

Based on the transfer pupil technique a method to measure the lower order aberration coefficients for optical telescopes has been developed; the method makes use of a Hartmann mask in a spectrograph for sampling the wavefront at different locations.

5 illus, 7 ref

018971   Balasubramaniam R;Dass M I (Dep of Materials and Matallurgical Engineering, Indian Institute of Technology, Kanpur-208016, 154, Area colony Bhopal -426016) : On the astronomical Significance of the Delhi iron pillar. Curr Sci 2004, 86(8), 1134-42.

The astronomical significance of the Delhi iron pillar has been highlighted by addressing its probably original erection site at Udayagiri and the probably image that was atop the pillar's capital. Based on the astronomical significance of Udayagir's location on the Tropic of Cancer, and earlier solar observations at Udayagiri, it has been shown that the iron pillar may have been aligned with the cardinal directions such that, on summer solstice day, the early-morning shadow of the pillar fell along a specially cut passageway in the direction of one of the important as reliefs (in cave temple 15) at Udayagiri site. Evidence have been provided to corroborate the identification of a circular disc-shaped object (20" diameter and 2" thick) that was probably atop the Delhi iron pillar capital.

9 illus, tables, 20 ref

018970   Ananthasubramanian P G;Yamamoto S;Prabhu T P; Angchuk D (Astrophysics Group, Cavendish Lab., University of Cambridge, Combridge CB3 OHE, UK) : Measurements of 220 GHz atmospheric transparency at IAO, Hanle, during 2000-2003. Bull Astr Soc India 2004, 32(2), 99-111.

A 220 GHz tipping radiometer was installed at the Indian Astronimcal Observatory (IAO), Hanle (Latitude 32°46'47" N; Longitude 78°57'51" E; Altitude 4500 m, above msl) towards the end of December 1999. The system is in continuous operation since early October 2000. A sky scan, i.e., a forward and a reverse scan is taken once every 10 minutes and these data are averaged to fit for zenith opacity. Detailed results of zenith opacity measuements for a continuous 3-year period have been reported. The system was up and running to make these measurements for nearly 90% of the time during this period. In particular the opacity trends in three consecutive 6-month periods of `winter' months (October to March, 2000-01, 2001-02 & 2002-03) and three 6-month periods of `summer' months (April to September, 2001, 2002 & 2003) were covered. The fractional time for opacities less than 0.06 in the three winter periods mentioned are above 30% and the corresponding fractional time for opacities less than 0.1 are above 70%. The opacities show seasonal variations as normally expected and in general one month in summer (July or August) peaks in opacity values. Diurnal variations are not easily noticeable. These results indicate that Hanle is a very promising site for sub-mm and infrared astronomy during most of the year excluding the months of July-August.

7 illus, 2 tables, 13 ref

014264   Yadav R K S (NO, State Observatory, Manora Peak, Naini Tal 263 129) : Studies of young stellar objects. Bull Astr Soc India 2003, 31(3-4), 257-64.

Presents a detailed study of four young open star clusters and two OB associations using deep CCD UBVRI and 2 MASS JHK_s measurements. Physical parameters of the clusters have been estimated using optical as well as near-IR data. Ages of objects under study range 10-100 Myr. Mass function slope of the sample of clusters are in agreement with the Salpeter (1955) value. From a comparison of mass function slope of clusters and OB association in the Galaxy of the Sun with those in external galaxies, it has been argned that the star formation processes are such that they yield almost similar stellar mass distribution in vastly different star forming environments. Mass segregation suggests theat the cluters under study are dynamically relaged and have may segragation may be due to dynamical evolution or imprint of star formation or both. The extinction properties of a sample of 18 young star clusters have been investigated utilizing recent data avilable in literature. The study suggests that there is no uniformity in extinction properties amongst these clusters. A non-uniform extinction has been noticed for the first time in NGC 1502 and Tr 37 along with the existence of circumstellar shell around some early type stars in NGC884, NGC2264, Tr 14 and Tr 16.

4 tables, 9 ref

014263   Wahab Uddin;Joshi B;Ramesh Chandra;Joshi A (State Observatory, , Manora Peak, Naini Tal 263 129) : Dynamics of limb flare and associated primary and secondary Post flare loops. Bull Astr Soc India 2003, 31(3-4), 303-8.

Presents the analysis of M 1.8 class (GOES SXR) limb flare and associated post flare loops of 2 May, 2001 which erupted on the west limb in NOAA 9433 (N15, W88). The flare started at around 00.32 UT from a small mound of twisted loops. When Hα observations were started at 00.52 UT the flare was in decay phase enveloped by highly sheared/twisted post flare loops which are called primary post flare loops. The unique teatime of this flare was that a new system of loops were developed when the primary loops were almost decaying. These newly formed loops have been named as secondary loops. The main aim is to study the dynamics of the Hαflare/post flare loops and to understand how the magnetic fields gets relaxed from highly sheared/twisted stage to a simplified potential field. The nature of temporal behaviour of the temperature and emission measure of the flare has been discused. The post flare condensation and formation of secondary loops has also been studied. The flare was also associated with SXR, HXR and MW emissions.

4 illus, 9 ref

014262   Vinay Kumar;Dave H (Physical Research Laboratory, , Ahmedabad - 380 009) : High resolution spectroscopy with submillimeter-wave. Bull Astr Soc India 2003, 31(3-4), 475-7.

In order to explain the characteristic features of planetary atmosphere, detection and precise measurements of environmentally important gases such as CO, CIO, NO becomes necessary. Since most of the polyatomic molecules have (ro-vibrational) transitions in submillimeter region (100μ-1000-μ), probing in this wavelength region is vital. The specific rotational and vibrational states are the result of interactions between different atoms in the molecule. Since each molecule has a unique arrangement of atoms, it has an exclusive submillimeter signature. A portable heterodyne receiver system at Physical Research Laboratory, Ahmedabad to perform high-resolution spectroscopy in this wavelength region.

1 illus, 4 ref

014261   Vig S;Ghosh S K;Ojha D K (NO, Tata Institute of Fundamental Research, Mumbai - 400 005) : Warp of the galactic disk as seen in mid infrared from Midcourse Space Experiment. Bull Astr Soc India 2003, 31(3-4), 407-10.

The nature of the warp structure in the distribution of stellar as well as warm interstellar dust (WISD) components in the Galactic disk has been investigated using respective mid infrared emissions. Such a study with high angular resolution has only recently become possible with the advent of Galactic plane survey in four major bands (8, 12, 14 & 21<128><109>m) by the Midcourse Space Experiment (MSX). The MSK Point Source Catalog as well as the panoramic images have been used here. Various measures represneting the location of the mid-plane for the stellar and WISD components have been extracted. The resulting mid-plane latitude versus longitude data have been fitted well with a simple sinusoidal function to look for a warp signature (WS). The WS has been clearly detected in all the four bands for both the stellar as well as the WISD components with similar phases but amplitudes ranging from 0.2<128><144> - 0.5<128><144> in latitude. Results have been compared with those from other studies of similiar measures of WS.

2 illus, 1 table, 7 ref

014260   Vig S;Ghosh S K;Kulkarni V K;Ojha D K;Verma R P (NO, Tata Institute of Fundamental Research, Mumbai-400005) : Infrared and radio observations towards the ultracompact HII region IRAS 19111+1048. Bull Astr Soc India 2003, 31(3-4), 395-7.

The ultracompact HII region IRAS 19111+1048 (G45.12+0.13) has been studied at mid & far infrared bands and at radio wavelengths. The far infrared maps of this region have been obtained using TIFR 1 metre telescope at 130 & 200 <128><109>m. The ionized gas component has been studied in the radio region using GMRT at 1280 and 610 MHz. Maps at both these frequencies for IRAS 19111+1048 show a strong compact source near the infrared peak and a weaker but extended diffuse emission due north-west. The mid-infrared images form Midcourse Space Experiment are used to quantify the distribution of hotter dust and carriers of Unidentified Infrared Bands.

1 illus, 4 ref

014259   Verma V K;Vats H O (NO, State observatory, Manora Peak, Naini Tal - 263129) : Study of three hamologous solar flares observed from active region NOAA 9033 on 12th June 2000. Bull Astr Soc India 2003, 31(3-4), 289-93.

Presents a study of three homologous Hα flares observed on 12th June 2000 in active region (AR) NOAA 9033. During the observation of AR NOAA 9033 on 12th June 2000, Ist solar flares between 0135-0155 UT, 2nd flare between 0236-0253 UT and 3rd flare between 0259-0323 UT. The study supports the quadrapolar reconnection scenario presented by Machado et al. (1983) and also shows the presence of 26.7 min periodicity in intensity data estimated from the site of the homologous flares.

4 illus, 1 table, 9 ref

014258   Verma R P;Ghosh S K;Kulkarni V K;Ojha D K (NO, Tata Institute of Fundamental Research, Mumbai 400 005) : Infrared and radio observations of IRAS 16571-4029 (RCW 116B). Bull Astr Soc India 2003, 31(3-4), 399-401.

Southern HII region RCW 116B (IRAS 16571-4029) has been mapped simultaneously at two far infrared wavelength (at 150 and 210 <128><109>m) with a resolution of <128><126>1' using the TIFR 1 m ballon-borne telescope. High angular resolution radio continuum observations at 325,610 and 1280 MHz have been carried out using GMRT. In addion, IRAS survey data for this region in the four IRAS bands (processed using the HIRES routine) have been used. In the far infrared maps, as well as mid infrared maps, multiple embeded sources have been resolved. IRAS 16571-4029 has also been resolved in radio.

2 illus, 1 table, 4 ref

014257   Venkatakrishnan P;Brajesh Kumar;Ravindra B (Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Udaipur 313 004) : On the rapid variations of solar magnetic fields. Bull Astr Soc India 2003, 31(3-4), 299-301.

Reports on the rapid variations of solar magnetic fields that appear to be enhanced significantly above the background variability, at a few locations within the solar active regions, as observed with the Michelson Doppler Image (MDI) on board the SOHO spacecraft. The pressure fluctuations estimated to arise from this variability far exceed the general level of acoustic pressure fluctuations. The equivalent mechanical flux that could be generated from these rapid magnetic variations is more than adequate for the heating of the active region chromosphere and corona.

1 illus, 3 ref