Abstract Details
| Name: Shubham Srivastav Affiliation: Indian Institute of Astrophysics Conference ID: ASI2018_807 Title : Observational Studies of Low Redshift Supernovae Authors and Co-Authors : G. C. Anupama (Indian Institute of Astrophysics) Abstract Type : Thesis Abstract Category : Thesis Abstract : Supernovae (SNe) are explosive transient events that mark the end stages of stellar evolution. This work presents a study of low redshift, hydrogen deficient (Type I) SNe, with emphasis on SNe of type Ia. The data were primarily obtained from the 2-m Himalayan Chandra Telescope (HCT). SNe Ia are caused by thermonuclear disruption of accreting White Dwarfs (WDs). In general, SNe Ia follow the width-luminosity relation, making them valuable cosmic standard candles. However, the nature of the WD companion and the details of the explosion physics remain poorly understood. The homogeneous nature of SNe Ia as a class of events notwithstanding, a substantial diversity is undeniably present. This diversity can be traced ultimately to different progenitor scenarios and explosion mechanisms. `Normal' Ia events constitute $\sim 70 \%$ of all SNe Ia and show minimal scatter in their properties, making them most useful for cosmology. A fraction of SNe Ia, termed as SN 1991T-like events, show slow declining light curves relative to normal events, and are generally overluminous. Another fraction of SNe Ia, the SN 1991bg subclass occupy the other end of the luminosity distribution, with fast declining, narrow light curves, low luminosities and very red intrinsic colours. The diversity in SNe Ia, and in particular the subclass of peculiar events, poses a challenge to theoretical progenitor and explosion models. The normal SNe Ia 2014J, 2014dg and 2011ao are studied in this work. Analytical modelling of their bolometric light curves suggests a total ejected mass of $\sim 1.4$ M$_{\odot}$, consistent with the Chandrasekhar limit. This is consistent with the notion that normal SNe Ia originate from Chandrasekhar mass WDs, that explains the low scatter in their observed properties. `Transitional' SNe Ia have properties intermediate to normal and extremely fast declining, subluminous 1991bg-like events. Transitional events thus signify a link between normal and subluminous SNe Ia and hold the key to understand the progenitor scenario. Transitional SNe 2015bp, iPTF13ebh and 2003gs are studied in this work. Modelling the bolometric light curves of SNe 2015bp and 2003gs suggests a total ejected mass of $\leq 1$ M$_{\odot}$, indicating a sub-Chandrasekhar mass WD progenitor. Stripped envelope core collapse SNe (types Ib and Ic) form a relatively rare subclass of SNe. A study of the type Ib event iPTF13bvn is presented in this work. Fitting analytic models to the bolometric light curve of iPTF13bvn indicates a small ejecta mass, thus ruling out a single, massive Wolf Rayet star as the progenitor. Finally, future prospects in supernova astronomy are discussed in the context of upcoming wide-field, high sensitivity and high cadence surveys, and advanced observational facilities. |