arXiv subjects

G. C. Anupama

Publications and source records attributed to G. C. Anupama.

183 records · Page 11Linked to original sources

arXiv1998

Recurrent Novae at Quiescence: Systems with Giant Secondaries

Spectroscopic and photometric behaviour of the class of recurrent novae with giant secondaries (T Coronae Borealis, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii) at quiescence are presented in this study. The hot component in these systems is variable, with the variability manifesting as variability in the ultraviolet luminosity, the ultraviolet and optical emission line fluxes and in the UBV/visual magnitudes. The variations are uncorrelated with the binary orbital motion. The observed ultraviolet+optical spectral characteristics of the hot component in these systems can be explained by a white dwarf+accretion disc embedded in an envelope of wind from the M giant secondary. We suggest the observed variations are a result of (a) fluctuations in the mass accretion rate; (b) changes in the column density of the absorbing, optically thick, wind envelope.

astro-ph↗

arXiv1997

Short term optical variability in broad absorption line QSOs

We present the first results from a pilot programme to monitor the short term optical variability in Broad Absorption Line system QSOs. Intra-night optical variations of ~5% were detected on time scales of ~ one hour in QSOs 0846+156 and 0856+172. Further, the mean magnitude level decreased in the two objects by ~0.05 and ~0.15 magnitude respectively during the period of our observations. The observed light curves are quite similar to those previously seem in the flat spectrum radio-loud sources, especially the BL Lacertae objects, and can provide important constraints for the origin of microvariability, and also a possible evolutionary link between the radio-loud and the radio-quiet QSOs.

astro-ph↗

arXiv1996

H-alpha Imaging of the Hickson Compact Group 62

We report results of a search for optical emission line gas in the Hickson compact group 62. From narrow band (H-alpha) imaging observations we estimate 10^4 Msun of ionized hydrogen gas within the central regions of three of the galaxies in the group. There has been considerable interest in this group since ROSAT detected an extended halo of diffuse X-ray emission, possibly with a cooling flow at the center. The optical emission line luminosities from the three galaxies are comparable to each other (~10^{39} ergs/s) and resemble those seen in normal X-ray luminous early type galaxies. There is no evidence for any excess emission in the galaxy which lies at the center of the X-ray cooling flow. We find that the most likely source of excitation for the emission line nebulosities is photoionization by young stars.

astro-ph↗