arXiv subjects

Firoza K. Sutaria

Publications and source records attributed to Firoza K. Sutaria.

4 recordsLinked to original sources

arXiv2026

SN 2017hcc and SN 2023usc a comparative spectroscopic study of type IIn supernovae

We report on a spectroscopic study of the bright, nearby type-IIn supernova SN 2017hcc, and SN 2023usc using data obtained from the Himalayan Chandra Telescope (HCT). SN 2017hcc is well-studied event, and our sampling covers 7 epochs, starting from +14\,d post explosion, and continuing into the nebular stage, at +411\,d. The type-IIn event SN 2023usc was sampled over 5 epochs from +12\,d to +155\,d post explosion. The nearly featureless (except H$α$) late time (+62\,d onward) spectra of SN 2023usc, suggests a novel explosion route for this type-IIn event. Assuming a CSM model created by multi-epoch ejection of material from the pre-explosion progenitor, we present here a comparative study of both events with several other type-IIn / interacting supernovae in progenitors with persistent signatures of a CSM. We find that true narrow lines ($v \ll 1000$\,km\,s$^{-1}$) emerge in the early ($\sim$ +10\,d) spectra only in few events (SN 2017hcc, SN 2023usc and SN 2010jl) initially classified as type-IIn in our sample -- in most cases the line velocity hovers at $\sim 1000$\,km\,s$^{-1}$ even in the very early epochs. CSM line velocity being indicative of its extent and opacity, this suggests that progenitors with a highly extended CSMs, which are also optically transparent in their outer regions may be relatively rare.

astro-ph.HE↗

arXiv2016

Neutron Star Physics in the Square Kilometer Array Era : An Indian Perspective

It is an exceptionally opportune time for Astrophysics when a number of next-generation mega-instruments are poised to observe the universe across the entire electromagnetic spectrum with unprecedented data quality. The Square Kilometre Array (SKA) is undoubtedly one of the major components of this scenario. In particular, the SKA is expected to discover tens of thousands of new neutron stars giving a major fillip to a wide range of scientific investigations. India has a sizeable community of scientists working on different aspects of neutron star physics with immediate access to both the uGMRT (an SKA pathfinder) and the recently launched X-ray observatory Astrosat. The current interests of the community largely centre around studies of - a) the generation of neutron stars and the SNe connection}, b) the neutron star population and evolutionary pathways}, c) the evolution of neutron stars in binaries and the magnetic fields}, d) the neutron star equation of state}, e) the radio pulsar emission mechanism}, and, f) the radio pulsars as probes of gravitational physics}. Most of these studies are the main goals of the SKA first phase, which is likely to be operational in the next four years. This article summarises the science goals of the Indian neutron star community in the SKA era, with significant focus on coordinated efforts among the SKA and other existing/upcoming instruments.

astro-ph.HE↗

arXiv2005

Chandra's tryst with SN 1995N

We present the spectroscopic and imaging analysis of a type IIn supernova SN 1995N observed with the Chandra X-ray observatory on 2004 March 27. We compare the spectrum obtained from our Chandra observation with that of the previous observation with ASCA in 1998. We find the presence of Neon lines in the Chandra spectrum that were not reported in the ASCA observation. We see no evidence of Iron in both epochs. The observed absorption column depth indicates an extra component over and above the galactic absorption component and is possibly due to a cool dense shell between the reverse-shock and the contact discontinuity in the ejecta. The ASCA and the ROSAT observations suggested a non-linear behavior of the X-ray light curve. However, with the higher spatial resolution and sensitivity of Chandra, we separate out many nearby sources in the supernova field-of-view that had additionally contributed to the supernova flux due to the large Point Spread Function of the ASCA. Taking out the contribution of those nearby sources, we find that the light curves are consistent with a linear decline profile. We consider the light curve in the high energy band separately. We discuss our results in the context of models of nucleosynthesis and the interaction of the shock waves with the circumstellar medium in core collapse supernovae.

astro-ph↗

arXiv1998

Oscillation Effects On Neutrinos From The Early Phase Of a Nearby Supernova

Neutrinos emitted during stellar core collapse leading to a supernova are primarily of the electron neutrino type at source which may undergo oscillation between flavor eigenstates during propagation to an earth-bound detector. Although the number of neutrinos emitted during the pre-bounce collapse phase is much smaller than that emitted in the post-bounce phase (in which all flavors of neutrinos are emitted), a nearby supernova event may nevertheless register a substantial number of detections from the pre-bounce phase at SuperKamiokande (SK) and the Sudbury Neutrino Observatory (SNO). The calorimetric measurement of the supernova neutrino fluence from this stage via the charge current and neutral current detection channels in SNO and the corresponding distortion of detected spectrum in SK over the no-oscillation spectrum, can probe information about neutrino mass difference and mixing which are illustrated here in terms of two- and three-flavor oscillation models.

astro-ph↗