Publications (38)
Implications of aging in young supernovae
Poonam Chandra, Alak Ray
We present here the combined radio spectrum from the Giant Metrewave Radio Telescope (GMRT) and Very Large Array (VLA) of type-IIb SN 1993J (age 11 years) and a type-Ic SN 2003bg (…
Oscillation Effects On Neutrinos From The Early Phase Of a Nearby Supernova
Debasish Majumdar, Kamales Kar, Alak Ray +2
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…
Explosive and radio-selected Transients: Transient Astronomy with SKA and its Precursors
Poonam Chandra, G. C. Anupama, K. G. Arun +7
With the high sensitivity and wide-field coverage of the Square Kilometre Array (SKA), large samples of explosive transients are expected to be discovered. Radio wavelengths, espec…
The progenitor of SN 2011ja: Clues from circumstellar interaction
Sayan Chakraborti, Alak Ray, Randall Smith +7
Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until core collapse, produce Type II Plateau (IIP) supernovae. The ejecta from these explosions sh…
Ruling out Kozai resonance in highly eccentric galactic binary millisecond pulsar PSR J1903+0327
Achamveedu Gopakumar, Manjari Bagchi, Alak Ray
We investigate the observational signatures associated with one of the proposed formation scenario for the recently discovered highly eccentric binary millisecond pulsar (MSP) PSR…
Modelling type IIP/IIL supernovae interacting with recent episodic mass ejections from their presupernova stars with MESA & SNEC
Sanskriti Das, Alak Ray
We show how dense compact discrete shells of circumstellar gas immediately outside the red supergiants affect the optical light curves of type II-P/II-L SNe taking the example of S…
Detecting gravitational waves from the galactic center with Pulsar Timing
Alak Ray, Bence Kocsis, Simon Portegies Zwart
Black holes orbiting the Super Massive Black Hole (SMBH) Sgr A* in the Milky-way galaxy center (GC) generate gravitational waves. The spectrum, due to stars and black holes, is con…
Baryon Loaded Relativistic Blastwaves in Supernovae
Sayan Chakraborti, Alak Ray
We provide a new analytic blastwave solution which generalizes the Blandford-McKee solution to arbitrary ejecta masses and Lorentz factors. Until recently relativistic supernovae h…
Mapping the Galactic Center with Gravitational Wave Measurements using Pulsar Timing
Bence Kocsis, Alak Ray, Simon Portegies Zwart
We examine the nHz gravitational wave (GW) foreground of stars and black holes (BHs) orbiting SgrA* in the Galactic Center. A cusp of stars and BHs generates a continuous GW spectr…
X-rays from the explosion site: Fifteen years of light curves of SN 1993J
Poonam Chandra, Vikram V. Dwarkadas, Alak Ray +2
We present a comprehensive analysis of the X-ray light curves of SN 1993J in a nearby galaxy M81. This is the only supernova other than SN 1987A, which is so extensively followed i…
X-Ray emission from SN 2004dj: A Tale of Two Shocks
Sayan Chakraborti, Naveen Yadav, Alak Ray +2
Type IIP (Plateau) Supernovae are the most commonly observed variety of core collapse events. They have been detected in a wide range of wavelengths from radio, through optical to…
Type IIP Supernova Progenitors III: Blue to Red Supergiant Ratio in Low Metallicity Models with Convective Overshoot
Gururaj A. Wagle, Alak Ray, Adarsh Raghu
The distribution of stars in the Hertzsprung Russell diagram (HRD) for a stellar conglomeration represents a snapshot of its evolving stellar population. Some of the supergiant sta…
Gravitomagnetism and Pulsar Beam Precession near a Kerr Black Hole
Prashant Kocherlakota, Pankaj S. Joshi, Sudip Bhattacharyya +3
A rotating black hole causes the spin-axis of a nearby pulsar to precess due to geodetic and gravitomagnetic frame-dragging effects. The aim of our theoretical work here is to expl…
Orbital eccentricity of binary radio pulsars in globular clusters and interaction between stars
Manjari Bagchi, Alak Ray
We analyze the observed distribution of the orbital eccentricity and period of binary radio pulsars in globular clusters using computational tools to simulate binary-single star in…
Engine-driven Relativistic Supernovae as Sources of Ultra High Energy Cosmic Rays
Alak Ray, Sayan Chakraborti
Understanding the origin of the highest energy cosmic rays is a crucial step in probing new physics at energies unattainable by terrestrial accelerators. Their sources remain an en…
Low frequency radio observations of SN 2011dh and the evolution of its post-shock plasma properties
Naveen Yadav, Alak Ray, Sayan Chakraborti
We present late time, low frequency observations of SN 2011dh made using the Giant Metrewave Radio Telescope (GMRT). Our observations at , and $1280\ \…
An Expanding Neutral Hydrogen Supershell Evacuated by Multiple Supernovae in M101
Sayan Chakraborti, Alak Ray
Several neutral hydrogen (HI) cavities have been detected in the Milky Way and other nearby star forming galaxies. It has been suggested that at least a fraction of them may be exp…
Synchrotron aging and the radio spectrum of SN 1993J
Poonam Chandra, Alak Ray, Sanjay Bhatnagar
We combine the GMRT low frequency radio observations of SN 1993J with the VLA high frequency radio data to get a near simultaneous spectrum around day 3200 since explosion. The low…
Inferring the composition of super-Jupiter mass companions of pulsars with radio line spectroscopy
Alak Ray, Abraham Loeb
We propose using radio line spectroscopy to detect molecular absorption lines (such as OH at 1.6-1.7 GHz) before and after the total eclipse of black widow (BW) and other short orb…
Ultra High Energy Cosmic Ray Acceleration in Engine-driven Relativistic Supernovae
Sayan Chakraborti, Alak Ray, Alicia Soderberg +2
The origin of the highest energy cosmic rays remains an enigma. They offer a window to new physics, including tests of physical laws relevant to their propagation and interactions,…
Deep optical observations at the position of PSR1706-44 with the VLT-UT1
Peter Lundqvist, Jesper Sollerman, Alak Ray +2
We present optical data gathered by the VLT Test Camera in the V-band at the radio (interferometric) position of PSR1706-44. We find no optical counterpart to the pulsar in the VLT…
Afterglows of Mildly Relativistic Supernovae: Baryon Loaded Blastwaves
Sayan Chakraborti, Alak Ray
Relativistic supernovae have been discovered until recently only through their association with long duration Gamma Ray Bursts (GRB). As the ejecta mass is negligible in comparison…
Radio Detection of Green Peas: Implications for Magnetic Fields in Young Galaxies
Sayan Chakraborti, Naveen Yadav, Carolin Cardamone +1
Green Peas are a new class of young, emission line galaxies that were discovered by citizen volunteers in the Galaxy Zoo project. Their low stellar mass, low metallicity and very h…
Type IIP Supernova Progenitors II: Stellar Mass and Obscuration by the Dust in the Circumstellar Medium
Gururaj A. Wagle, Alak Ray
It has been well established from a variety of observations that red supergiants (RSGs) loose a lot of mass in stellar wind. Dust formed in this emitted gas over a few decades befo…
Massive stars as thermonuclear reactors and their explosions following core collapse
Alak Ray
Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are re…
Orbital parameters of binary radio pulsars in globular clusters and stellar interactions
Manjari Bagchi, Alak Ray
The observed distribution of globular cluster binary radio pulsars in the eccentricity versus orbital period plane can be explained as a result of binary-single star interactions.…
Baby supernovae through the looking glass at long wavelengths
Poonam Chandra, Alak Ray
We emphasize the importance of observations of young supernovae in wide radio band. We argue on the basis of observational results that only high or only low frequency data is not…
Radio pulsar binaries in globular clusters: their orbital eccentricities and stellar interactions
Manjari Bagchi, Alak Ray
High sensitivity searches of globular clusters (GC) for radio pulsars by improved pulsar search algorithms and sustained pulsar timing observations have so far yielded some 140 pul…
Type IIP Supernova Progenitors and their explodability I: Convective Overshoot, Blue Loops and Surface Composition
Gururaj A. Wagle, Alak Ray, Ajay Dev +1
We present the evolution of massive star progenitors of supernovae of type IIP. We take the example of the nearby and well-studied SN 2013ej. We explore how convective overshoot af…
SN 2013ej - A type IIL supernova with weak signs of interaction
Subhash Bose, Firoza Sutaria, Brijesh Kumar +11
We present optical photometric and spectroscopic observations of supernova 2013ej. It is one of the brightest type II supernovae exploded in a nearby ( Mpc) galaxy NGC 628…
Eleven years of radio monitoring of the Type IIn supernova SN 1995N
Poonam Chandra, Christopher J. Stockdale, Roger A. Chevalier +6
We present radio observations of the optically bright Type IIn supernova SN 1995N. We observed the SN at radio wavelengths with the Very Large Array (VLA) for 11 years. We also obs…
Evolution and Explosion of Massive Stars Leading to IIP-IIL SNe with MESA and SNEC
Sanskriti Das, Alak Ray
We show how the dense shells of circumstellar gas immediately outside the red supergiants (RSGs) can affect the early optical light curves of Type II-P SNe taking the example of SN…
A Missing-Link in the Supernova-GRB Connection: The Case of SN 2012ap
Sayan Chakraborti, Alicia Soderberg, Laura Chomiuk +50
Gamma Ray Bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly…
Electron Cooling in a Young Radio Supernova: SN 2012aw
Naveen Yadav, Alak Ray, Sayan Chakraborti +8
We present the radio observations and modeling of an optically bright Type II-P supernova (SN), SN 2012aw which exploded in the nearby galaxy Messier 95 (M95) at a distance of $10\…
Radio Studies of Young Core Collapse Supernovae
Poonam Chandra, Alak Ray, Sanjay Bhatnagar
Multi-frequency observations of two radio bright SNe (SN1993J, SN1979C) carried out over a year with GMRT are presented. Their radio light curves trace the evolution of the mass lo…
Probing Final Stages of Stellar Evolution with X-Ray Observations of SN 2013ej
Sayan Chakraborti, Alak Ray, Randall Smith +8
Massive stars shape their surroundings with mass loss from winds during their lifetimes. Fast ejecta from supernovae, from these massive stars, shocks this circumstellar medium. Em…
Chandra's tryst with SN 1995N
Poonam Chandra, Alak Ray, Eric M. Schlegel +2
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 fr…
SKAO and Gamma-Ray Synergies
Gianluca Castignani, Gavin Rowell, Arnau Aguasca-Cabot +26
A wide variety of Galactic and extragalactic sources are known to emitradiation across the entire electromagnetic spectrum, including both transient and steady-state phenomena. A f…