B. N. Ashoka
Articles written in Journal of Astrophysics and Astronomy
Volume 8 Issue 2 June 1987 pp 195-209
The evolution of the spectrum of SN1987a is traced from 1987 February 26 to March 31. Based on the low-resolution spectroscopic data we identify the lines of H, He I, Na I, Fe II, Sc II, Ca II which are known to be present in Type II Supernovae, and also present evidence for the existence of lines of Mg I, CaI, O I, and N I. We discuss the evolution of the Hα profile, and draw attention to its complex structure around March 30. Close to the rest wavelength of Ha a double-peaked structure appeared in the profile with a peak-to-peak separation of ∼ 1400 km s−1, suggestive of an expanding shell or disc of gas.
Using the available broadband photometric information, we also trace the evolution of the photosphere of SN1987a assuming that it radiates like a supergiant.
Volume 11 Issue 4 December 1990 pp 445-460
A new radial velocity study has been made of the highly eccentric, early-type binary BD -1° 1004 using spectra from the Kavalur Observatory. All available archival material has also been reexamined. An attempt has been made to correct for line ‘dragging’ by the secondary spectrum to improve the fit of the observed data to the orbital solutions. It is found that an earlier suggestion of apsidal regression is still possible although ω is probably constant within the errors. There remain problems and inconsistencies with other orbital elements, in particular K1 and γ
Volume 22 Issue 1 March 2001 pp 131-144
The design and performance of a portable three channel photometer installed at the Uttar Pradesh State Observatory (UPSO), Naini Tal is described. The photometer is modular and the whole unit can be disassembled as individual channels such that the system can also be used as a single channel or two channel photometer. The system also has provision to monitor a guide star. The instrument was put into operation since November 1999 on the 1m Sampurnanand telescope at UPSO, Naini Tal. Since then, it is used extensively for the ‘Survey of rapidly oscillating Ap (roAp) stars in the northern sky’ from UPSO. Observational results using this new photometer in its initial phase of operation are discussed. The advantage of having continuous sky measurement is demonstrated.
Volume 26 Issue 2-3 June 2005 pp 301-309
The Indian team at ISRO has been part of the Whole Earth Telescope (WET) team since 1988 when we first participated in the campaign on V471 Tau. We have been part of many other observing campaigns over the last decade. This presentation traces the circumstances leading to our joining the WET team and how useful the coverage from the Indian longitude has been. The results of several pulsators from the WET runs during which we participated are also described. These include PG1159-035 the prototype of the GW Vir type of stars, RE J 0751+14 a cataclysmic variable, PG 1336-018 a binary with an sdB pulsator and finally HR 1217 a roAp star. The paper concludes with what the limitations are in our observations and how we can overcome them in the future.
Volume 40 | Issue 4
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