014256   Vats H O (Physical Research Labroatory, , Ahmedabad 380 009) : Coronal electron density and the gradient of coronal rotation with altitude. Bull Astr Soc India 2003, 31(3-4), 309-11.

The calculations of the gradient of coronal rotation period with altitude were performed using electron density model and the radio measurements of solar coronal rotation. The magnitude of the gradient reduces if the emission is at higher harmonics of the plasma frequency. The results seem to reduce the difference in the radio and optical measurements of coronal rotation.

2 illus, 6 ref

014255   Vani V C;Chatterjee S (Department of Instrumentation, Indian Institute of Science, Bangalore 560 012) : An extended matched filtering method to detect periodicities in a rough grating for extremely large roughness. Bull Astr Soc India 2003, 31(3-4), 457-9.

Matched filtering algorithm has been shown to be an effective method to detect hidden periodicities in a rough grating, extending detectability to regimes of higher roughness than was hiterto known. The above matched filtering is further extended to even `rougher' regimes by introducing a new filtering funcition χ_a(V_x), demonstrating improved detectability for different wavelength of light.

1 illus, 1 table, 4 ref

014254   Tripathy S C;Jain K;Hill F;Toner C G (Department of Physics, Indian Institute of Science, Bangalore 560 012) : On the p-mode asymmetry between velocity and intensity from the GONG+data. Bull Astr Soc India 2003, 31(3-4), 321-3.

Analyzes the local acoustic spectra of small regions over the solar surface at different locations from disk center to limb via the technique of ring diagrams. The analysis suggest that the frequency shifts between velocity and intensity is a function of location on the disk and is higher near the disk center than those near the limb.

1 illus, 7 ref

014253   Tripathy S C (Department of Physics, Indian Institute of Science, Bangalore 560012) : Solar cycle variation in GONG and MDI data: 1995-2002. Bull Astr Soc India 2003, 31(3-4), 153-8.

Both GONG and MDI projects have measured p-mode frequencies of the Sun for more than 7 years. Previews what has been learnt from the temporal variation of the oscillation frequencies and splitting coefficients.

3 illus, 26 ref

014252   Thomas R M C;Gangadhara R T (NO, Indian Institute of Astrophysics, Bangalore - 560034) : Radio emission by particles accelerated in pulsar magnetosphere. Bull Astr Soc India 2003, 31(3-4), 361-2.

Presents a relativistic model of pulsar radio emission by plasma accelerated along the rotating magnetic field lines projected on to a 2D plane perpendicular to the rotation axis. Derived the expression for the trajectory of a particle, and estimated the spectrum of radio emission by the plasma bunches. Use the parameters given in the paper by Peyman and Gangadhara (2002). Further, the analytical expression for the Stokes parameters are derived, and compared with the observed profiles. The one sense of circular polarization, observed in many pulsars, can be explained in the light of the model.

1 illus, 3 ref

014251   Swarup (NCRA-TIFR, , Pune 411 007) : Search for HI reionization epoch in the early universe. Bull Astr Soc India 2003, 31(3-4), 451-2.

4 ref

014250   Sujatha S;Babu G S D (NO, M.P. Birla Institute of Fundamental Research, Bangalore - 560001) : Study of old open clusters NGC 1605, Czernik 18, NGC 2509. Bull Astr Soc India 2003, 31(3-4), 379-82.

Presents the first CCD photometric UBVRI observations of three open clusters NGC 1605 (OCI 406), Czernik 18 (OCI 426) and NGC 2509 (OCI 630) obtained by using the 1.02 m telescope at Vainu Bappu Observatory, Kavalur. While the colour excess E(B-V) for the cluster OCI 426 is found to be 0.43 mag, it is estimated to be 0.14 mag for OCI 406 and 0.15 mag for OCI 630. After correcting for these colour excesses, their distances are found to be 1148pc (OCI 406), 955 pc (OCI 426), and 912 pc (OCI 630). Further, as the ages of these clusters are found to be in the range of 0.8 X 10⁹ yrs to 8 X 10 ⁹ yrs, they may be categorised as old open clusters.

1 illus, 13 ref

014249   Subramaniam A;Anupama G C (NO, Indian Institute of Astrophysics, Bangalore- 560034) : The local stellar population of slow nova regions in the SMC. Bull Astr Soc India 2003, 31(3-4), 415-416.

Population synthesis models of the statistics and properties of Galactic cataclysmic variables (CVs) and extragalactic novae indicate that the rate of formation of CVs, the nova rate and the distribution of novae over speed classes depend on the star formation history of the Galaxy. It was also suggested that the fast novae belong to the disk population, whereas the slow novae belong to the bulge population. Pervious study on the stellar population of the nova regions in the LMC (Subramaniam & Anupama 2002) indicated that the parent population of fast and moderately fast novae is likely to be in the age range 1.0-3.2 Gyr. The single slow nova in the LMC indicated that the parent poulation of slow novae could be older than that of the tast hovas. The identification of the parent population of the two slow nova in the SMC would thus help in understanding the progenitors of novae of different speed classes.

1 illus, 13 ref

014248   Subramaniam A (NO, Indian Institute of Astrophysics, Bangalore - 560034) : A warp in the LMC bar?. Bull Astr Soc India 2003, 31(3-4), 413-14.

LMC, SMC Milky Way are known to have experienced close encounters. The interaction of the Milky Way with the Magellanic Clouds could result in tidal forces which could alter the structure of the Clouds. Evidence of the interaction, like the presence of a warp has been looked into by studying the geometrical structure of the LMC bar. The brightness of core helium-burning red clump stars in the central regions of the LMC has been used. The difference in the mean magnitudes of the de-reddened red clump stars is used as differential distance indicator. The analysis is similar to that of Olsen & Salyk (2002), but the central region of LMC near the bar, is studied.

1 illus, 5 ref

014247   Stalin C S (NO, State Observatory, Manor Peak, Naini Tal - 263129 and NCRA-TIFR, Pune-411007) : A comparative study of intra-night optical micro-variability of high luminosity AGN classes. Bull Astr Soc India 2003, 31(3-4), 265-72.

Reports that the substantial differences in INOV properties of RQQs and LDQs as compared to BL Lacs can be explained in terms of special relativistic effects arising from viewing the latter at small angles to the jet direction. Thus the mechanism producing the optical variation in radio-loud and radio-quiet AGNs can be very similar, and subparsec scale jets may well be present in all types of AGNs, obviating the need for any fundamental difference between the central engines of RQQs and radio-loud quasars.

2 illus, table, 27 ref

014246   Srinivasan G (NO, Raman Research Institute, Bangalore-560 080) : Realm of the supermassive black holes. Bull Astr Soc India 2003, 31(3-4), 121-39.

One of the pardigms of astronomy at the dawn of the new millennium is that most galaxies, if not all, have massive black holes at their centres. Highlights the arguments that led one to this conclusion, the current observational evidence in support of this pardigm and also the possible formation mechanisms of such supermassive black holes.

10 illus, 34 ref

014245   Sridharan R;Raja Bayanna A;Srivastavan B K; Ravindra B;Gupta S K;Jain N;Ambastha A;Venkatakrishnan P (Udaipur Solar Observatory, , Udaipur 313 004) : Performance evaluation of adaptive optics systems. Bull Astr Soc India 2003, 31(3-4), 455-6.

Adaptive Optics (AO) systems improve the resolution of ground based telescopes and allow for long exposure images. Their performance depends on the seeing conditions at the time of observations. Evaluates the performance of AO system under various seeing condition through simulation. Presents the wave-front sensing and correction schemes that would be used in the first phase of the AO system to be developed at the Udaipur Solar Observatory.

3 ref

014244   Sinha S (Space Astronomy and Instrumentation Division, ISRO Satellite Centre, Bangalore 560 017) : Gamma ray burst data analysis: algorithms and procedures. Bull Astr Soc India 2003, 31(3-4), 501-2.

In Gamma Ray Burst experiments it is very important to obtain realistic and accurate estimates of the Burst parmeters, viz.the event trigger time, the duration, peak hardness ratio, peak fluxes and fluences in different energy bands. Several algorithms and procedures have been developed independently from first principles. One of these is described.

2 ref

014243   Sinha S (Space Astronomy and Instrumentation Division, ISRO Satellite Center, Bangalore-560 017) : A high energy photon detector simulation system. Bull Astr Soc India 2003, 31(3-4), 493-4.

A high energy photon detector simulation software based on detailed Monte Carlo method starting from first principles is under development. The current status of this endeavour and some of the results obtained recently from this program are presented.

1 illus, 1 ref

014242   Singh Jagde (NO, Indian Institute of Asrophysics, Bangalore 560034) : Spectroscopic studies of solar corona during eclipse and with coronagraph. Bull Astr Soc India 2003, 31(3-4), 141-51.

Reports that it may not always be possible to interpret the observed increase in FWHM with height in terms of an increase in non-thermal velocity, and hence rules out the existence of waves in steady coronal structures.

4 illus 22 ref

014241   Shastri P;Murthy J;Hutchings J;Wills B J (NO, Indian Institute of Astrophysics, Bangalore 560 034) : Spectroscopy of Seyferts in the far-UV. Bull Astr Soc India 2003, 31(3-4), 429-31.

Presents preliminary far-ultraviolet spectra of the Seyfert Mrk 533 obtained with FUSE. These are among the first FUV spectra of a purportedly edge-on Seyfert, and show narrow OVI emission as well as some evidence for intrinsic absorption.

1 illus, 5 ref

014240   Sharma M;Kaul R K (Nuclear Research Laboratory, Bhabha Atomic Research Centre, Mumbai - 400085) : A statistical study of 3EG source characteristics. Bull Astr Soc India 2003, 31(3-4), 443-5.

A detailed statistical study of 3EG source characteristics and their variation as a function of galactic latitude shows that a majority of unidentified sources at mid galactic latitudes are so-far undetected AGN.

1 illus, 2 ref

014239   Sengupta C;Balasubramanyam R;Bekki K (NO, Raman Research Institute, Bangalore-560080) : GMRT neutral hydrogen observations of the Sombrero galaxy. Bull Astr Soc India 2003, 31(3-4), 419-20.

1 illus, 1 table, 3 ref

014238   Seetha S (ISRO Satellite Center, , Airport Road, Bangalore 560 017) : Scanning sky monitor (SSM) on ASTROSAT- a status report. Bull Astr Soc India 2003, 31(3-4), 485-6.

6 ref

014237   Sarala S (Physics Department, , IIT Kanpur 208016) : Study of radio and optical polarization anisotropies in the electromagnetic waves from extragalactic sources. Bull Astr Soc India 2003, 31(3-4), 273-9.

Polarizations of electromagnetic radiation from active galactic nuclei (AGN) show some intersting effects such as the existence of a global anisotropy in the orientations of the radio wave polarizations from distant radio galaxies and quasars and a very large scale alignment of optical polarizations of quasars. Studies in detail whether the observational bias in the data would have led to these effects. Proposes that existence of a hypothetical pseudoscalar explains these effects.

3 illus, 11 ref

014236   Saikia D J;Gupta N (National Centre for Radio Astrophysics, TIFR, Pune 411 007) : Polarization asymmetry in CSS sources. Bull Astr Soc India 2003, 31(3-4), 441-2.

Shows that the compact steep spectrum sources are more asymmetric in the polarization of the outer lobes compared with the more extended ones. This could be due to interaction of the jets with infalling material, which fuels the radio source. The CSS sources show no dependence of the polarization asymmetry on redshift, suggesting that the environments on the CSS scales are similar at different redshifts. However, the polarization asymmetry of the oppositely-directed lobes is larger at higher redshifts for the more extended sources, possibly reflecting the higher incidence of interactions in the past.

2 illus, 2 ref

014235   Sahayanathan S;Misra R;Kembhavi A K;Kaul C L (Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai-400 085) : An expanding plasma model for the X-ray radio knots in KPC-scale jets of active galactic nuclei. Bull Astr Soc India 2003, 31(3-4), 439-40.

Models the observed X-ray/radio knots in Active Galactic Nuclei (AGN) as isotropically expanding spherical plasma clouds fed continously by non-thermal electrons. The time-dependent electron distribution and the emitted photon spectrum are computed using the standard kinetic equation considering synchrotron, adiabatic and inverse Compton cooling processes. This model is used to study the knots of 1136-135 and 1150+497, recenly observed by Chandra.

1 illus, 5 ref

014234   Roy Choudhury T (NO, Inter University Centre for Astronomy and Astrophysics, Pune - 411007) : Physics of structure formation in the universe. Bull Astr Soc India 2003, 31(3-4), 281-8.

Reports that the redshift distribution of gamma ray bursts can, in principle, be used for studying the physical conditions of the universe before reionization epoch (which is otherwise a difficult task). It might be possible that the dark matter and dark energy arise from the same scalar field, provided the equation of state has a dependence on the length scale. The possibility of using the kinematical and geometrical measurements (such as supernova observations) for determining the nature and evolution of the dark energy is discussed.

7 illus, 13 ref

014233   Resmi L;Bhattacharya D (NO, Roman Research Institute, Bangalore -560 080) : Energy and radiation spectrum of electrons in ultra-relativistic shocks of GRB afterglows. Bull Astr Soc India 2003, 31(3-4), 353-5.

Considers particle acceleration near ultra relativistic shocks(Γ_shock<62><62>1) and the distribution of accelerated particles in the shock downstream. Suggests that the electron energy spectrum will settle into an "Universal" power law with index p <55>2.2 above an "injection break" at γ_e =γ_i ≡ m_p/m_{e(D>Γshock, and will be flatter at lower energies. The synchrotron radiation spectrum arising from these electrons is computed for a decelarating relativistic fireball. Shows that this model can account well for the observed spectra and lightcurves of Gamma Ray Burst Afterglows}

10 ref

014232   Ravindra B (Udaipur Solar Observatory, , Udaipur 313001) : Quiet sun chromospheric network magnetic field. Bull Astr Soc India 2003, 31(3-4), 297-8.

The 3-D structure of quiet Sun chromospheric network magnetic field is studied by comparing the observed and computed chromospheric magnetograms. The comparison shows that the best correlation occurs at≈ 1800 km above the photophere at which the Fe 8688 line forms.

1 illus, 3 ref

014231   Ravi Shankar B T;Bhattacharya D (NO, Raman Research Institute, Bangalore 560 080) : Image reconstruction for a continuously rotating coded mask camera. Bull Astr Soc India 2003, 31(3-4), 491-2.

Discusses a method for reconstructing the image for Scanning Sky Monitor which is a continously rotating X-ray coded mask camera aboard the Indian astronomical satellite, ASTROSAT.

3 ref

014230   Rannot R C et al (Bhabha Atomic Research Centre, Nuclear Research Laboratory, Mumbai - 400 085) : Energy sensitive search for pulsed photons from crab pulsar using the TACTIC imaging element. Bull Astr Soc India 2003, 31(3-4), 357-60.

The Imaging Element (IE) of the 4-element TACTIC array of atmospheric Cherenkov telescopes is in operation at Mt. Abu, Rajasthan, in Western India. Successfully detected a steady signal from the Crab nebula at a sensitivity level of<126> 6.3 σin 40 hours at E _γ <147>1 TeV, during the period Jan.-March 2001. This database has been used to carry out a search for the presence of pulsed photons at two higher thresholdenergies (E_γ≥2 Te V and E_<103><147>3 TeV) by applying energy-sensitive size cuts. No evidence has been found for the presence of an energy-dependent pulsed photon signal from the Crab pulsar direction. However, places the upper limits of 1.08 X 10^-12and 8.88 X 10^-13 photons cm^-2 sec^-1 for the 2 TeV and 3TeV light curves respectively. Results presented, are however preliminary and more data on the source are being collected so as to be able to arrive at a more definite conclusion about the TeV γ-ray pulsed emission from the Crab pulsar

1 illus, 1 table, 17 ref

014229   Rangarajan K E;Varghese B A (NO, Indian Institute of Astrophysics, Bangalore-560034) : Ground based microwave radiometric technique in remote sensing. Bull Astr Soc India 2003, 31(3-4), 223-30.

As an important tool of atmospheric remote sensing, microwave radiometers are used for temperature profiling and vapor and liquid column measurements. In addition, ice water path can be retrieved usin radiometer observations. The potential of radiometers is demonstrated by comparison with radiosonde data and observations using Global Positioning Systems (GPS). Performance of various mathematical retrieval methods for water vapor and cloud liquid water profiles using microwave radiometer measurements are compared. These include regression methods, Newton iteration and neural networking. A specific case of temperature inversion near the ground and its retrieval by Philips-Twomay method is discussed.

3 illus, 13 ref

014228   Rana V R;Singh K P (NO, Tata Institute of Fundamental Research, Mumbai-400005) : RXTE observations of magnetic cataclysmic variables. Bull Astr Soc India 2003, 31(3-4), 347-9.

Results from hard X-ray observations with RXTE of 5 Polar systems-V2301 Oph, V1432 Aql, EP Dra, GG Leo and V834 Cen, and an Intermediate Polar TV Col are presented. An improved ephemeris for V2301 Oph using mid-eclipse timings has been derived. V1432 Aql shows structured lightcurve containing several prominet peaks and dips. A likely eclipse of X-ray source in EP Dra is observed for the first time. The X-ray emission in EP Dra and GG Leo is found to be consistent with a single pole accretion. V834 Cen was observed to be bright during 1996-1998, but was≥16 times fainter during 2002 observations. The power spectrum of TV Col shows a significant power at frequencies corresponding to the spin period (1910s) and the binary period (5.5hr) and their side-bands, thereby suggesting that both the streamfed and disk-fed accretion components are present in TV Col.

1 illus, 9 ref

014227   Rai Choudhuri A ;Konar S (Dep Phys, Indian Inst of Sci, Bangalore 560 012) : Why do millisecond pulsars have weaker magnetic fields compared to ordinary pulsars?. Curr Sci 2004, 86(3), 444-6.

Millisecond pulsars, with magenitic fields weaker by three to four orders compared to those of ordinary pulsars, are presumed to be neutron stars spun up by binary accretion. The magnetic field is expected to get secreened by the accereted material. Simulation of this screening mechanism shows that the field deceases by a purely geometric factor sin(^>-7/2 θp,i before freezing to an asymptotic value, where θp,i is the intiial angular width of the polar cap. If θp,i lies in the range 5-10°p,i, then the magnetic field diminution factor turns out to be <95>10³-10⁴, in conformity with observational data.

3 illus, 22 ref

014226   Pati A K;Mahesh P K;Nagabhushana S; Subramanian V K (NO, Indian Institute of Asrophysics, Bangalore) : The ultra violet imaging telescope: mechanical design. Bull Astr Soc India 2003, 31(3-4), 479-82.

The Ultra Violet Imaging Telescope (UVIT) is one of the major scientific instruments on the proposed ASTROSAT mission of the Indian Space Research Organisation. The design of a telescope to meet the scientific requirements within the weight and volume constraints of the satellite bus has been a major challenge. The design has also to meet the qualification levels for launch into orbit as well as the thermal environment in orbit. Presents the overall design of the UVIT mechanical structure with details of some critical aspects.

2 illus, 2 ref

014225   Parihar P S;Sahu D K;Bhatt B C;Subramaniam A ;Anupama G C;Prabhu T P (Centre for Research in Science & Technology, Indian Institute of Astrophysics, Bangalore 560034) : Night sky extinction measurements at the Indian astronomical observatory, Hanle. Bull Astr Soc India 2003, 31(3-4), (NULL).

Presents the estimates of the night sky extinction at the Indian Astronomical Observatory. Also presented are the estimates of the night sky brightness. The extinction in the U band at IAO is found to be lower than the value expected theoretically for an altitude of 4500 m.

1 illus, 1 table, 2 ref

014224   Pandey S B;Sahu D K;Anupama G C;Bhattacharya D;Sagar R (State Observatory, , Manora Peak, Naini Tal - 263 129) : SN 2002ap, the hypernova of class Ic. Bull Astr Soc India 2003, 31(3-4), 351-2.

The supernova SN 2002ap was discovered in the outer regions of the nearby spiral M74 on January 29.4 UT. Early photometric and spectroscopic observations indicate the supernova belongs to the class of Ic hypernova. Late time (After JD 2452500) light curve decay slopes are similar to that of the hypernovae SN 1997ef and SN 1998bw. Presents the BVRI photometric light curves and colour evolutions of SN 2002ap to investigate the late time nature of the light curve.

1 illus, 4 ref

014223   Pandey J C (State Observatory, , Manora Peak, Naini Tal 263 129) : FR Cnc-a young spotted star. Bull Astr Soc India 2003, 31(3-4), 329-31.

Optical photometric and spectroscopic studies of the star FR Cnc=BD +16 1753 have been carried out during the years 2001-2002. The star is photometrically variable with a mean period of 0^d.8271±0.0002. The rapid changes in the shape of light curve can be attributed to the formation and distribution of two groups of spots on the surface of the star. The presence of strong CaII H, K and H_α emission lines in the spectra indicates high chromospheric activity in the star. The kinematics of the star suggest that it belongs young population of disk stars

1 illus, 4 ref

014222   Pandey A K;Upadhyay K;Ogura K;Sagar R (State Observatory, , Manora Peak, Naini Tal-263 129) : Wide field CCD photometry of the young open cluster NGC 663. Bull Astr Soc India 2003, 31(3-4), 377-8.

A deep and wide field CCD photometry of the young open cluster NGC 663 has been carried out. Reports preliminary results of the investigations, specifically the determination of the cluster mass function which is found variable within the cluster region.

1 illus, 4 ref

014221   Pandey A K (NO, State Observatory, Manora Peak, Naini Tal -263 129) : Open star clusters: star formation and structure. Bull Astr Soc India 2003, 31(3-4), 175-80.

Observational evidences indicate that the formation of open star clusters has been efficient throughout the life of Earth, galaxy. As a consequence, one finds open clusters with ages ranging from a few Myr to few Gyr. This makes open clusters natural laboratories where the theory of star formation and stellar evolution can be tested. Study of young open clusters indicates that the star formation in a few clusters is non-coeval and the star information efficiency depends on the IMF. The work supports the existence of corona a round open clusters. The coronal regions in bound open clusters are dynamically stabel in the tidal forces of the Galaxy.

31 ref

014220   Panchapakesan N (Department of Physics and Astrophysics, University of Delhi, Delhi-110007) : Magnetars-A Review. Bull Astr Soc India 2003, 31(3-4), 195-9.

Magnetars are neutron stars in which a decaying high magnetic field is the source of energy production. The suggestion that magnetars are the dominant source of energy for soft gamma repeaters and anomalous x-ray pulsars is examined. Some questions that arise, because of the very high magnetic fields, are considered.

9 ref

014219   Ojha D K;Ghosh S K;Verma R P;Anandarao B G (NO, Tata Institute of Fundamental Research, Mumbai - 400 005) : Infrared L' band λ_cen<126>3.9 μm) observations with TIFR near-infrared camera (TIRCAM). Bull Astr Soc India 2003, 31(3-4), 467-70.

TIRCAM is based on the SBRC InSb Focal Plane Array (58 62 pixels) sensitive between 1-5μm. TIRCAM system is described in Ojha et al. (2002). TIRCAM had its first light observations during March-April 2001 from Gurusikhar 1.2m PRL telescope at Mt. Abu. After having the successful first run in 2001, the TIRCAM was used for the L' band observations of a few scientific targets in combination with fresh telescope mirrors in Nov. 2002 & Jan. 2003 (the alumnising operation of the primary & secondary mirrors of 1.2m telescope was carried out in mid 2002). Several infrared standard stars and the Trapezium cluster were observed in L'band centred at 3.9μm. Stars upto<126> 7 mag in L'band could be detected from the Gurusikhar site. The TIRCAM L'mag of detected stars in Trapezium cluster were compared with the L band (3.5μm) data of Muench et al. (2002). These measurements are in good agreement with each other considering the two different centre wavelengths. Plans to explore TIRCAM's performance in the broad L (3.5 μm)& M (4.5μm) bands from Hanle site in near future.

2 illus, 2 tables, 2 ref

014218   Ojha D K;Ghosh S K;Kulkarni V K;Testi L;Verma R P;Vig S (NO, Tata Institute of Fundamental Research, Mumbai-400 005) : A study of the Galactic star forming region IRAS 02593+6016/S 201 in Infrared and radio wavelengths. Bull Astr Soc India 2003, 31(3-4), 387-90.

Presents infrared and radio observations of IRAS 02593+6016/S 201 star forming region. A young star cluster is observed in this region, which contains different classes of young stellar objects. The near-infrared (NIR) colour-colour and colour-magnitude diagrams are studied to discuss the nature of these sources. The clumps of molecular hydrogen emission have been discovered at 2.122μm in the central region of S 201. These clumps are clearly seen along the diffuse emission in north west direction from the main IRAS source, which are probably the obscured Herbig-Haro objects. High sensitivity and high resolution radio continuum images made with GMRT at 610 and 1280 MHz show an interesting arc-shaped structure due to the interaction between the HII region and the adjacent molecular cloud. The ionization front at the interface between the HII region and the molecular cloud is clearly seen by comparing the radio, molecular hydrogen and Brγ images.

2 illus, 6 ref

014217   Murthy J (NO, Indian Institute for Astronomy, Koramangala, Bangalore 560034) : TAUVEX-an ultraviolet imager on the Indian GSAT-4 satallite. Bull Astr Soc India 2003, 31(3-4), 243-8.

The TAUVEX instrument consists of three imagers operating in several bands in the mid to near UV. It has been proposed to fly TAUVEX as a secondary payload on the GSAT-4 mission to be launched in late 2004 and this proposal is currently under consideration by ISRO. The TAUVEX mission will consist of a series of scans over 1 degree wide bands in the sky which will be built up into a survey of the ultraviolet sky. The limiting magnitude in each of the three colours will be on the order of 19. It is hoped to make the data available to the Indian astronomical community soon after launch.

3 illus, 5 ref

014216   Muneer S;Singh J (Vainu Bappu Observatory, Indian Institute of Astrophysics, Kavalur - 635 701) : Daily variation of tilt angles of sunspot groups. Bull Astr Soc India 2003, 31(3-4), 313-14.

The influence of polarity separation on the daily tilt angle variation of sunspot groups has been studied from a selected number of observations of the Sun spanning the entire 22nd solar cycle. Daily white-light images of the Sun from Kodaikanal Observatory have been utilized to obtain both polarity separation and axial tilt of sunspot groups. Over 100 long-lived spot groups that had well distinct leading and following parts are chosen from different latitude belts for this purpose. Variation of tilt angle with polarity separation has been studied after classifying the spot groups according to its age and area. Preliminary results of this analysis have been discussed.

2 illus, 8 ref

014215   Mukherjee U;Paul B (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005) : X-ray spectroscopy of the HMXB pulsar GX 301-2 with Chandra. Bull Astr Soc India 2003, 31(3-4), 369-70.

Presents analysis of X-ray spectra of the accreting pulsar GX 301-2, from two observations with the Chandra X-ray observatory made during different phases of its orbital period. Analysis of the zeroth order ACIS spectra and the high energy resolution grating spectra show that the spectra obtained in both the orbital phases can be fitted with a partial covering power-law model. Strong K_α and K_β iron emission lines with finite width and iron absorption edges are present in both the spectra. In one of the observations another broad emission component was found probably formed by Compton scattering.

1 illus, 3 ref

014214   Morel T;Marchenko S V;Pati A K;Kuppuswamy K; Carini M T;Wood E;Zimmerman R (Osservatorio Astronomico di Palemo, , Italy) : Large-scale wind structures in OB supergiants: a search for rotationally modulated Hα variability. Bull Astr Soc India 2003, 31(3-4), 333-5.

Presents preliminary results of a long-term spectroscopic monitoring of a sample of bright OB-supergiants aimed at establishing the incidence of corotating, large-scale wind structures by detecting rotationally modulated variability in Hα. Dramatic line-profile variations operating on a daily (and in some cases on a hourly) timescale are observed. A detailed period analysis has been so far carried out for 2 stars, and revealed in both cases the existence of cyclical Hα variations consistent with rotational modulation. In the case of HD 14134, the same periodicity is found in the contemporaneous light curve.

2 illus, 17 ref

014213   Mishra S D;Bhattacharya D (NO, Raman Research Institute, Bangalore) : A Dynamic sky simulation for the scanning sky monitor on ASTROSAT. Bull Astr Soc India 2003, 31(3-4), 487-9.

Developes a daynamic sky simulation software for the visualization of the operation of the Scanning Sky Monitor cameras. This software can be used for the background modelling of the cameras and the refinement of source location using multiple cameras with corssed fields of view.

1 illus, 2 ref

014212   Mangalam A (NO, Indian Institute of Astrophysics, Koramangala Bangalore-560 034) : Physics of supermassive disks: formation and collapse. Bull Astr Soc India 2003, 31(3-4), 207-13.

Supermassive disks are thought to be precursors of supermassive black holes that are believed to power quasars and exist at centres of galaxies. Formation scenarios of such disks are reviewed and it is argued that gas dynamical schemes are favourable compared to stellar dynamical schemes which could however be important feeding mechanisms for the growth of the black hole. A new self-similar model of a collapse of a self-gravitating disk due to radiation induced stresses applicable to two different situations of radiative viscosity and Compton drag is presented. The collapse timescale purely due to radiative viscosity is found to be fraction of Hubble time,τ_γ<126><1 15>_Tc(m_pG)(L_edd/L)≈6x10⁹ yrs is slow and probably magnetic fields play an important role before general relativistic effects take over. A model of self-gravitating disk collapsing due to Compton drag by the Cosmic Microware Background is also presented which is found to be effective at redshifts 1400<62> z<62><126>300. It is proposed that the small <60><126>10⁵M. objects that form the high redshift quasars seen. Supermassive stars which are systems (and could be end products of a supermassive disk phase)en route to the final collapse are also briefly reviewed.

24 ref

014211   Mallik S V (NO, Indian Institute of Asrophysics, Bangalore 560034) : Lithium in stars on the main sequence and beyond. Bull Astr Soc India 2003, 31(3-4), 167-74.

Li provides a rare constraint on the baryonic density of the Universe and because of its fragile nature, it is also an excellent diagnostic of the physical processes occurring inside stars. The study of Li in Pop.I stars is crucial to understanding its primordial abundance. Observations suggest that a vast majority of them deplete their Li severely, in contrast to the predictions of the standard steller models. A fresh study of 130 stars supports the idea that the large spread in Li is driven by the rotational history of the star. Open clusters reveal much more because each represents a sample with the same age and metallicity. Discusses briefly what has been learnt from these studies.

5 illus 25 ref

014210   Lal D V;Pramesh Rao A (National Centre for Radio Astrophysics (TIFR), Pune Univ Campus, Ganeshkhind, Pune 411 007) : Low frequency observations of a head-tail radio source. Bull Astr Soc India 2003, 31(3-4), 427-8.

Maps the head-tail radio galaxy, 3C 129 at 240 and 610 MHz using the GMRT and studies the detailed morphology and spectral index variations in this object. This is the first attempt to observe a sample of head-tail sources at low frequencies. Finds weak spectral steepening as one goes away from the head along the jet. The Crosspiece has a spectral index of 0.7 (S_<110>∝ν_{-< 97>}) and is flatter than the spectral index estimated by Lane et al. (2002). Also a low surface brightness, diffuse feature at 240 MHz and could be a possible radio relic candidate is seen.

2 illus

014209   Kulkarni V P (Dep of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 U.S.A.) : Evolution of stars and metals in damped Lyman-alpha galaxies. Bull Astr Soc India 2003, 31(3-4), 201-6.

A unique tool to investigate distant young galaxies is to study the absorption lines they produce in the spectra of background quasars. The damped Lyman-alpha (DLA) quasar absorption line systems allows empirical tracing of galaxy evolution. Results of abundance surveys of DLAs and their implications for the evolution of the global matallicity in galaxies have been discussed. Deep imaging studies with the Hubble Space Telescope (HST) and ground-based facilities, directed at investigating the luminosities and star formation rates of the absorbers have also been described. These observations are helping to clarify the absorber-galaxy connection, and shedding light on the evolution of stars and metals in normal galaxies over the past 80% of the cosmic history.

2 illus, 37 ref

014208   Koul M K;Sapru M L (Nuclear Research Laboratory, Bhabha Atomic Research Centre, Mumbai - 400085) : Simulation studies for optimizing the trigger field of view of the TACTIC imaging element. Bull Astr Soc India 2003, 31(3-4), 497-8.

Simulation studies, for the imaging camera of the TACTIC <103>-ray telescope have been carried out to optimize its trigger field of view for a point <103>-ray source. The results indicate that a trigger field of 9x9 pixels should improve the sensitivity of the telescope.

1 illus, 3 ref

014207   Konar S (Department of Physics & Meterology, Centre for Theoretical Studies, Indian Institute of Technology, Kharag, ) : Of neutrinos and magnetars. Bull Astr Soc India 2003, 31(3-4), 365-6.

Discusses the nature of neutrino propagation in presence of the strong magnetic field of magnetars.

1 illus, 6 ref