A5054755318- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Nuclear Physics and Applications
- Neutrino Physics Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Radio Astronomy Observations and Technology
- Superconducting Materials and Applications
- Autopsy Techniques and Outcomes
- SAS software applications and methods
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Cold Atom Physics and Bose-Einstein Condensates
- GNSS positioning and interference
- Agricultural Practices and Plant Genetics
- Agriculture and Biological Studies
- Energy Load and Power Forecasting
- Nonlinear Photonic Systems
- Agriculture, Plant Science, Crop Management
National Institute of Malaria Research
2023
Center for Astrophysics Harvard & Smithsonian
2011-2017
Harvard University Press
2013-2016
Tata Institute of Fundamental Research
2003-2013
Harvard University
2013
We present multi-wavelength observations of SN 2014C during the first 500 days. These represent solid detection a young extragalactic stripped-envelope out to high-energy X-rays ~40 keV. shows ordinary explosion parameters (Ek ~ 1.8 × 1051 erg and Mej 1.7 M⊙). However, over an ~1 year timescale, evolved from hydrogen-poor supernova into strongly interacting, hydrogen-rich supernova, violating traditional classification scheme type-I versus type-II SNe. Signatures shock interaction with dense...
We present extensive radio and millimeter observations of the unusually bright GRB 130427A at z = 0.340, spanning 0.67–12 days after burst. combine these data with detailed multi-band UV, optical, NIR, Swift X-ray find that broadband afterglow emission is composed distinct reverse shock forward contributions. The dominates in radio/millimeter ≲ 0.1 UV/optical/NIR, while X-rays ≳ UV/optical/NIR. further optical require a wind circumburst environment, pointing to massive star progenitor. Using...
We present densely sampled UBVRI/griz photometric and low-resolution (6–10 Å) optical spectroscopic observations from 4 to 270 d after explosion of a newly discovered Type II SN 2012aw in nearby (∼9.9 Mpc) galaxy M95. The light-curve characteristics apparent magnitudes, colours, bolometric luminosity the presence evolution prominent spectral features are found have striking similarity with archetypal IIP SNe 1999em, 1999gi 2004et. early time clearly detect minima light curve V, R I bands...
We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one least luminous SNe IIb or Ib observed to date. Our begin with a discovery within 1 day explosion span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly are replaced by Ib-like He-rich features on timescale week. High-cadence monitoring this transition suggests absorption attributable high velocity (>...
We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude MR = −17.3 and decaying by ∼3 mag in first 15 days post-maximum, 2005ek is among fastest I supernovae observed to date. The spectra closely resemble those normal Ic, but with an accelerated evolution. There evidence for onset nebular features at only nine post-maximum. Spectroscopic modeling reveals ejecta mass ∼0.3 M☉ that dominated oxygen...
We present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced relativistic rapidly decelerating outflow without gamma-ray burst signature. Photometry spectroscopy follow flux evolution from −13 to +272 days past B-band maximum −17.4 ± 0.5 mag. The spectra are dominated by Fe ii, O i, Ca ii absorption lines at ejecta velocities v ≈ 20,000 km s−1 change slowly over time. Other spectral consistent with...
Deep late-time X-ray observations of the relativistic, engine-driven, type Ic SN2012ap allow us to probe nearby environment explosion and reveal unique properties relativistic SNe. We find that on a local scale ~0.01 pc was shaped directly by evolution progenitor star with pre-explosion mass-loss rate <5x10^-6 Msun yr-1 in line GRBs other SN2009bb. Like sub-energetic GRBs, is characterized bright radio emission evidence for mildly ejecta. However, its late time (t~20 days) ~100 times fainter...
We present optical photometric and spectroscopic observations of SN 2013ej. It is one the brightest Type II supernovae (SNe II) exploded in a nearby (∼10 Mpc) galaxy, NGC 628. The light-curve characteristics are similar to SNe II, but with relatively shorter (∼85 days) steeper (∼1.7 mag (100 days)−1 V) plateau phase. shows large drop 2.4 V-band brightness during plateau-to-nebular transition. absolute ultraviolet (UV) light curves identical 2012aw, showing UV-plateau trend extending up 85...
ABSTRACT We present radio and X-ray observations of the nearby SN IIb 2013df in NGC 4414 from 10 to 250 days after explosion. The emission showed a peculiar steep-to-shallow spectral evolution. model which inverse Compton cooling synchrotron emitting electrons can account for observed light curve A significant mass-loss rate, <?CDATA $\dot{M}\approx 8\times {10}^{-5}\;{M}_{\odot }$?> <?MML <mml:math> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow>...
We present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest link between subsets energetic H-poor SNe superluminous SNe. 2012au exhibited conspicuous Type-Ib-like He i lines other absorption features at velocities reaching ≈2 × 104 km s−1 in its early spectra, broad light curve peaked MB = −18.1 mag. Models these data indicate large explosion kinetic energy ∼1052 erg 56Ni mass ejection MNi ≈ 0.3 M☉ on par 1998bw. 2012au's...
We report four years of radio and X-ray monitoring the Type IIn supernova SN 2006jd at wavelengths with Very Large Array, Giant Metrewave Radio Telescope, Expanded Array; Chandra, XMM-Newton, Swift-XRT. assume that emitting particles are produced by shock interaction a dense circumstellar medium. The emission shows an initial rise can be attributed to free–free absorption cool gas mixed into nonthermal region; external is disfavored because shape rising light curves low column density...
Gamma-ray bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae generally non-relativistic ejecta. GRB afterglows decelerate rapidly, usually within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However, with heavy can be in nearly free expansion for centuries. Supernovae were thought to have outflows except few relativistic ones accompanied GRBs. This clear division was blurred SN 2009bb, the first...
ABSTRACT Massive stars shape their surroundings with mass loss from winds during lifetimes. Fast ejecta supernovae (SNe), these massive stars, shock this circumstellar medium. Emission generated by interaction provides a window into the final stages of stellar evolution, probing history progenitor. Here we use Chandra and Swift X-ray observations type II-P/L SN 2013ej to probe its We model observed X-rays as emission both heated matter ejecta. The density profile probed reveals steady 400...
We present extensive radio and X-ray observations of SN 2012au, an energetic, radio-luminous supernova Type Ib that exhibits multi-wavelength properties bridging subsets hydrogen-poor superluminous supernovae, hypernovae, normal core–collapse supernovae. The closely follow models synchrotron emission from a shock-heated circumburst medium has wind density profile (ρ∝r−2). infer sub-relativistic velocity for the shock wave v ≈ 0.2 c radius r 1.4 × 1016cm at 25 days after estimated date...
We investigate the environment of nearby (d ~ 40Mpc) broad-lined Type Ic supernova SN 2009bb. This event was observed to produce a relativistic outflow likely powered by central accreting compact object. While such phenomenon previously only in long-duration gamma-ray bursts (LGRBs), no LGRB detected association with Using an optical spectrum 2009bb explosion site, we determine variety ISM properties for host environment, including metallicity, young stellar population age, and star...
Mid-infrared (MIR) shells or bubbles around expanding H II regions have received much attention due to their ability initiate a new generation of star formation. We present multi-wavelength observations two associated with southern massive star-forming (MSF) region G8.14+0.23, investigate the triggered formation signature on edges by expansion region. found observational signatures collected molecular and cold dust material along 12CO(J=3-2) velocity map reveals that gas in is physically...
Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that thought to be associated with carbon-rich polyatomic molecules gas. However, because the central wavelengths of these do not correspond electronic transitions any known atomic or molecular species, their nature has remained uncertain since discovery almost a century ago. Here we report on unusually strong DIBs broad-lined Type Ic supernova SN 2012ap exhibit changes equivalent width...
Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until core collapse, produce Type II Plateau (IIP) supernovae. The ejecta from these explosions shock the circumstellar matter originating mass loss of progenitor during final phases its life. This interaction accelerates particles to relativistic energies then lose energy via synchrotron radiation in shock-amplified magnetic fields and inverse Compton scattering against optical photons supernova. These...
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, metallicity and very high star formation rates make nearby (z~0.2) analogs Lyman-break Galaxies (LBGs) which account for bulk early universe (z~2-5). They thus provide accessible laboratories Universe understanding formation, supernova feedback, particle acceleration magnetic field amplification galaxies. We report first direct radio...
We present the radio observations and modeling of an optically bright Type II-P supernova (SN), SN 2012aw which exploded in nearby galaxy Messier 95 (M95) at a distance 10 Mpc. The spectral index values calculated using C, X, K bands are smaller than expected for thin regime. During this time, optical bolometric light curve stays plateau phase. interpret low spectral-index to be result electron cooling. On basis comparison between Compton cooling timescale synchrotron timescale, we find that...
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as standardizable candles to measure the accelerating expansion of Universe. Yet, progenitors remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon reaching close Chandrasekhar limit, by either steadily accreting mass from companion or violently merging another star. We show that circumstellar interaction in young Galactic supernova remnants can be...
Under certain general conditions in an expanding universe, the luminosity distance (d(L)) and angular diameter (d(A)) are connected by Etherington relation as d(L)=d(A)(1+z)2. The Tolman test suggests use of objects known surface brightness, to this relation. In Letter, we propose a redshifted 21 cm signal from disk galaxies, where neutral hydrogen (HI) masses seen be almost linearly correlated with area, conduct new test. We construct simulated catalogs observed size-luminosity realistic...