My research interests are in the field of evolution of massive stars and explaosive transients. I am part of UVA's Exploding Stars and Time Domain Astronomy research group. My research logo CHASERS stands for Chandra's Hub for Astrophysical Studies of Transients and Related Science. This encompasses most of my research interests.
Spectropolarimetric surveys show that around 10 percent of all massive stars are magnetic with kG dipolar magnetic fields.
Our group aims to understand the evolution of such stars and various ways in which magnetic fields manifest themselves. Towards this goal our group carried out a systematic study of magnetic massive stars in radio bands and discovered a rare Cyclotron Maser Emission (ECME) in a fraction of magnetic stars.
Currently more than 2/3rd of all known magnetic stars exhibiting ECME have been discovered by our group with the Indian upgraded Giant Metrewave Radio Telescope (GMRT) and this has put the GMRT on the world map. The discovery of ECME has allowed us
to unravel the 3D magnetic topology of the stars and plasma very close to stars, inaccessible by any other means. This has important implications of Stellar demise and end products, which we aim to unravel.
Hence they hold the key to the Universe, yet remain poorly understood and the very last
moments of stellar deaths leading to supernovae are not well understood. Studying the
supersonically moving supernova ejecta’s interaction with the surrounding slow winds, which reveals
itself in radio and X-ray emission, enables one to study the stellar evolution just before the explosion.
This is because the winds are formed by the mass-lost from the star and their evolution
carry the unique footprints of the progenitor star’s history, hence work as a “Time Machine”. We are
using this novel technique and has several highly significant findings in this field. Our most notable
contributions came in supernovae exploding in dense environments, where we unravelled the presence of
rare internal absorption, previously only speculative in one case, confirming the asymmetry in the explosion,
and non-smooth mass-loss history. We also found the mass-loss rates in these stars to be 3-4 orders of
magnitude higher than the ones predicted from stellar evolution models, an open problem in the field.
Our X-ray observations of SN 2010jl have revealed the direct presence of the circumstellar medium due to
mass loss by measuring 1000 times higher column density in SN medium than the Galactic one.
Recently we have proposed a realistic inhomogeneous radio emission caused by varying magnetic fields in
stripped supernovae.
We also collected 15 years of data on a special stripped envelope supernova (supernovae arising from stars which have lost their Hydrogen and Helium envelope at the time of explosion) in radio, optical and X-ray bands and have shown that such explosions occur via common envelope scenario in a binary system.
The focus of our group is to explore the landscape of interactions in core collapse supernovae.
Another most important finding by us is in the field of electromagnetic (EM) counterparts of gravitational waves (GWs),
discovered first in Sep 2015, nearly 100 years after the prediction of their existence by Einstein. We
studied the the GW event of 2017 Aug 17 (GW170817; the only GW event from neutron stars’ merger)
with the upgraded GMRT and several other radio telescopes across the world.
This research has made fundamental contributions in our understanding of merger environments producing GWs, implications for short GRBs,
and the evolution of the jet. Our work has defied previous jet models in favour of a wide cocoon breaking out of polar region and emitting across the EM bands. The upgraded GMRT observations provided the lowest frequency observations till date, putting the best constraints on the density.