Astronomy departmental seminar - Priscila Pessi (SU)

Connecting observed properties of supernovae to progenitor scenarios
Supernovae (SNe) mark the explosive death of certain groups of stars. Theoretical models that take into account stellar evolution of predefined progenitor stars propose different explosion mechanisms. However, it is still not clear how the variation of characteristics such as metallicity, mass loss rate and multiplicity – among others – impact on the observed properties of SNe. Even when some models have been supported by observations, the scarcity of direct detections of progenitor stars prevents us from understanding the exact nature of the stars that explode as different types of SNe. 
In this talk I will present the observational analysis of three different SNe samples done during my PhD. The goal of the analysis is to associate observed characteristics to progenitor properties. The first studied sample consists of the light curves of 73 type II SNe from the Carnegie Supernova Project (CSP) and 21 type IIb SNe from the literature. To compare the light curves in a consistent manner I parameterized them in terms of their time derivatives. My work is the first one implementing such analysis. We found distinct properties for the SNe II and IIb light curves. This leads to the conclusion that they most likely arise from different types of progenitors. 
For the second sample analysis, I used the novel technique of light curve time derivatives to study 54 rapid-cadence SNe Ia light curves from the CSP. Although the light curves of SNe Ia are homogeneous enough to be standardized and used as distance indicators, they present a subtle feature or “kink” soon after the i-band light curve peak that has been previously ignored. Analyzing the time derivatives, we were able to characterize the phase and strength of the kink. We could not directly link this feature to any other observed characteristic but we found that considering only the SNe with the  strongest kinks substantially reduces the Hubble residuals. 
The third sample consists of the light curves and spectral series of  six luminous SNe followed up by the Public European Southern Observatory Spectroscopic Survey of Transient Objects. The optical light curves of this sample are more luminous, exhibit bluer colors  and decline faster than other SNe type II. The spectral series are blue at early times, they show weak or nonexistent metal lines, and broad and boxy Hα emission profiles with no associated absorption component. The shared characteristics support a similar powering scenario for all of them. We propose interaction with CSM that is not dense enough to be optically thick to electron scattering on large scales, which is consistent with the lack of narrow emission lines in the spectra. I will finish the talk by presenting the project I am currently working on, that involves the study of a large sample of SLSNe II.