arXiv subjects

Mridweeka Singh

Publications and source records attributed to Mridweeka Singh.

40 records · Page 3Linked to original sources

arXiv2018

SN 2015as: A low luminosity Type IIb supernova without an early light curve peak

We present results of the photometric (from 3 to 509 days past explosion) and spectroscopic (up to 230 days past explosion) monitoring campaign of the He-rich Type IIb supernova (SN) 2015as. The {\it (B-V)} colour evolution of SN 2015as closely resemble those of SN 2008ax, suggesting that SN 2015as belongs to the SN IIb subgroup that does not show the early, short-duration photometric peak. The light curve of SN 2015as reaches the $B$-band maximum about 22 days after the explosion, at an absolute magnitude of -16.82 $\pm$ 0.18 mag. At $\sim$ 75 days after the explosion, its spectrum transitions from that of a SN II to a SN Ib. P~Cygni features due to He I lines appear at around 30 days after explosion, indicating that the progenitor of SN 2015as was partially stripped. For SN~2015as, we estimate a $^{56}$Ni mass of $\sim$ 0.08 M$_{\odot}$ and ejecta mass of 1.1--2.2 M$_{\odot}$, which are similar to the values inferred for SN 2008ax. The quasi bolometric analytical light curve modelling suggests that the progenitor of SN 2015as has a modest mass ($\sim$ 0.1 M$_{\odot}$), a nearly-compact ($\sim$ 0.05$\times$10$^{13}$ cm) H envelope on top of a dense, compact ($\sim$ 2$\times$10$^{11}$ cm) and a more massive ($\sim$ 1.2 M$_{\odot}$) He core. The analysis of the nebular phase spectra indicates that $\sim$ 0.44 M$_{\odot}$ of O is ejected in the explosion. The intensity ratio of the [Ca II]/[O I] nebular lines favours either a main sequence progenitor mass of $\sim$ 15 M$_{\odot}$ or a Wolf Rayet star of 20 M$_{\odot}$.

astro-ph.HE↗

arXiv2017

Exploring the optical behaviour of a type Iax supernova SN 2014dt

We present optical photometric (upto $\sim$410 days since $B$$_{max}$) and spectroscopic (upto $\sim$157 days since $B$$_{max}$) observations of a Type Iax supernova (SN) 2014dt located in M61. SN 2014dt is one of the brightest and closest (D $\sim$ 20 Mpc) discovered Type Iax SN. SN 2014dt best matches the light curve evolution of SN 2005hk and reaches a peak magnitude of $M$$_B$ $\sim$-18.13$\pm$0.04 mag with $Δm_{15}$ $\sim$1.35$\pm 0.06$ mag. The early spectra of SN 2014dt are similar to other Type Iax SNe, whereas the nebular spectrum at 157 days is dominated by narrow emission features with less blending as compared to SNe 2008ge and 2012Z. The ejecta velocities are between 5000 to 1000 km sec$^{-1}$ which also confirms the low energy budget of Type Iax SN 2014dt as compared to normal Type Ia SNe. Using the peak bolometric luminosity of SN 2005hk we estimate $^{56}$Ni mass of $\sim$0.14 M$_{\odot}$ and the striking similarity between SN 2014dt and SN 2005hk implies that a comparable amount of $^{56}$Ni would have been synthesized in the explosion of SN 2014dt.

astro-ph.HE↗

arXiv2015

Photometric and polarimetric observations of fast declining Type II supernovae 2013hj and 2014G

We present broadband photometric and polarimetric observations of two type II supernovae (SNe) 2013hj and 2014G. SN 2014G is a spectroscopically classified type IIL event, which we also confirm photometrically as its light curve show characteristic features (plateau slope of 2.55 mag (100 d)$ ^{-1} $ in V-band and duration of $ \sim77 $d) of a generic IIL SN. On the other hand SN 2013hj also shows high plateau decline rate of $ 1.5 $ mag (100 d)$ ^{-1} $ in V-band, similar to SNe IIL, but marginally lower than SNe IIL template light curves. Our high cadence photometric observations of SNe 2013hj and 2014G enables us to cover all characteristic phases up to radioactive tail of optical light curves. Broadband polarimetric observations reveal some polarization in SN 2013hj with subtle enhancement as SN evolves towards plateau end, however the polarization angle remains constant throughout the evolution. This characteristic is consistent with the idea that the evolving SN with recombining hydrogen envelope is slowly revealing more asymmetric central region of explosion. Modelling of bolometric light curve yields a progenitor mass of $ \sim11 $M$_{\odot}$ with a radius of $ \sim700 $R$_{\odot}$ for SN 2013hj, while for SN 2014G model estimated progenitor mass is $ \sim9 $M$_{\odot}$ with a radius of $ \sim630 $R$_{\odot}$, both having a typical energy budget of $ \sim2\times10^{51} $ erg.

astro-ph.HE↗

arXiv2015

SN 2013ej - A type IIL supernova with weak signs of interaction

We present optical photometric and spectroscopic observations of supernova 2013ej. It is one of the brightest type II supernovae exploded in a nearby ($\sim 10$ Mpc) galaxy NGC 628. The light curve characteristics are similar to type II SNe, but with a relatively shorter ($ \sim85 $ day) and steeper ($ \sim1.7 $ mag (100 d)$^{-1} $ in V) plateau phase. The SN shows a large drop of 2.4 mag in V band brightness during plateau to nebular transition. The absolute ultraviolet (UV) light curves are identical to SN 2012aw, showing a similar UV plateau trend extending up to 85 days. The radioactive $^{56}$Ni mass estimated from the tail luminosity is $ 0.02 $M$_{\odot}$ which is significantly lower than typical type IIP SNe. The characteristics of spectral features and evolution of line velocities indicate that SN 2013ej is a type II event. However, light curve characteristics and some spectroscopic features provide strong support in classifying it as a type IIL event. A detailed SYNOW modelling of spectra indicates the presence of some high velocity components in H$α$ and H$β$ profiles, implying possible ejecta-CSM interaction. The nebular phase spectrum shows an unusual notch in the H$α$ emission which may indicate bipolar distribution of $^{56}$Ni. Modelling of the bolometric light curve yields a progenitor mass of $ \sim14 $M$_{\odot}$ and a radius of $ \sim450 $R$_{\odot}$, with a total explosion energy of $ \sim2.3\times10^{51} $ erg.

astro-ph.HE↗