Research Interests

Accreting magnetized neutron stars

Magnetized neutron stars in X-ray binaries show a variety of spectacular timing and spectral properties. The strong NS magnetosphere dominates the accretion flow beyond the magnetospheric radius and channels matter to flow along the field lines on to the magnetic poles of the NS. X-ray emission from this region of the NS is modulated at the NS spin frequency and is observed as periodic X-ray pulsations.As part of my study of such accretion powered X-ray pulsars, I am interested in understanding the accretion flow-induced variability signatures like Quasi Periodic Oscillations (QPOs), Cyclotron Resonant Scattering Features (CRSF), flares and outbursts. Characterizing such properties in various samples of low mass and high mass X-ray binary systems will not only enable constraining the various theoretical emission models and flow instability models, but also allow for understanding the various possible evolutionary pathways for Pulsars in general.

Thermonuclear X-ray bursts

In weakly magnetized NS systems, the disk can extend all the way close to the NS surface. The accreted material dumps layers and layers of fuel on top the NS. Compression and ignition of this fuel leads to a rapid unstable thermonuclear runaway process. This gives rise to X-ray features called thermonuclear X-rays bursts. These bursts light up the entire binary system like a flashlight and enables one to study the different binary parameters and accretion effects in great detail.
I work on understanding the different aspects of type 1 X-ray burst properties in photos[heric in NS binary systems and I am seeking to understand the entire class of type-1 bursts that also exhibit Burst Oscillations (BO).

Gamma Ray Bursts

Gamma ray bursts are some of the most energetic explosions that occur in the keV-MeV energy range. Progenitor scenarios for such events are still debated however some observational properties are well in place and hence well categorized. The main two classes widely talked about are the short duration (<2s) and the long duration ( 10 - 1000s s) GRBs. At least a sub population of the sGRB variety is understood to arise from compact binary mergers. This was established in 2017 when a sGRB was detected right after the NS-NS merger event took place. Long GRBs are thought to arise out of massive stellar collapse. My recent studies of GRBs include the exploration of their timing properties. I am working on understanding if we can distinguish between various formation channels and understand their progenitors purely using X-ray timing methods.

Electromagnetic follow up of Gravitational Waves

The detection of the EM counterpart of the neutron star merger event GW170817 has opened an entirely new window to the universe. Compact mergers involving neutron stars are expected to be EM bright. Prompt localization of the GW trigger in the sky would require enormous follow-up efforts from teams across the electromagnetic spectrum. I am currently involved with the Swift BAT GUANO-NITRATES infrastructure that uses an external trigger to carry out a maximum likelihood analysis that helps detection and possibly arc-minute localization of weak Gamma Ray transients. Triggers ingested include Gamm Ray Bursts (GRBs), Fast Radio Bursts (FRBs), LIGO-Virgo triggers (currently in O4) and ice-cube neutrino events. We regularly publish GCN circulars with detection details and flux upper limits.

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