Study of Supernovae and Massive Stars and Prospects With the 4m International Liquid Mirror Telescope

Abstract

Massive stars are the progenitors of the most energetic explosions in the Universe such as core-collapse supernovae (CCSNe) and gamma ray bursts. During their life time they follow various evolutionary phases (e.g. supergiant, luminous blue variable and Wolf-Rayet). They strongly influence their environments through their energetic ionization radiation and powerful stellar winds. Furthermore, the formation of low- and intermediate-mass stars are also being regulated by them.

The Carina nebula region, which hosts a large population of massive stars and several young star clusters, provides an ideal target for studying the feedback of massive stars. In this thesis, we investigated a wide field (32′ × 31′ ) region located in the west of the Carina nebula and centered on the massive binary WR 22. For our study, we used new optical photometry (UBVRI Hα), along with some low resolution spectroscopy, archival near infra-red (2MASS), and X-ray (Chandra, XMM-Newton) data. We estimated several parameters such as reddening, reddening law, etc. and also identified young stellar objects located in the region under study (Kumar et al., 2014b).

Among the various types of CCSNe, Type IIb are recognized with their typical observational properties. Some of them show clear indication of double peaks in their light curves. The spectral features of these SNe show a transition between Type II and Type Ib/c events at early and later epochs, respectively. It has been noticed that the occurrence of these events is not common in volume limited surveys. In this thesis we have studied the properties of the light curve and spectral evolution of the Type IIb supernova 2011fu. The observational properties of this object show resemblance to those of SN 1993J with a possible signature of the adiabatic cooling phase (Kumar et al., 2013).

When light passes through the expanding ejecta of the SNe, it retains information about the orientation of the ejected layers. In general, CCSNe exhibit a significant level of polarization during various phases of their evolution at different wavelengths. We have investigated the broad band polarimetric properties of a Type II plateau SN 2012aw and compared it with other well-studied CCSNe of similar kinds (Kumar et al., 2014a).

In the framework of the present thesis, we have also contributed to the development of the 4m International Liquid Mirror Telescope (ILMT) project which is a joint collaborative effort among different universities and research institutes in Belgium, India, Canada and Poland. We performed various experiments including the spin casting of the primary mirror, optical quality tests of the mercury surface, mylar film experiments, etc. The possible scientific capabilities and future contri- butions of this telescope are also discussed. We propose our plans to identify the transients (specially supernovae) with the ILMT and their further follow-up scheme.

The installation of the ILMT will start very soon at the Devasthal observatory, ARIES Nainital, India.