Harsh Kumar
A5047469533- Gamma-ray bursts and supernovae
- SAS software applications and methods
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Particle Detector Development and Performance
- Particle accelerators and beam dynamics
- Magnetic confinement fusion research
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Isotope Analysis in Ecology
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Photonic and Optical Devices
- Adaptive optics and wavefront sensing
- Atmospheric Ozone and Climate
- Solar and Space Plasma Dynamics
- Optical Network Technologies
- Nuclear Physics and Applications
- Solid State Laser Technologies
- Planetary Science and Exploration
Indian Institute of Technology Bombay
2018-2025
Center for Astrophysics Harvard & Smithsonian
2024-2025
University of Michigan
2025
The NSF AI Institute for Artificial Intelligence and Fundamental Interactions
2024
Harvard College Observatory
2024
Harvard University
2024
National Institute of Technology Rourkela
2023
Dr. D. Y. Patil Medical College, Hospital and Research Centre
2014-2022
Large Synoptic Survey Telescope Corporation
2021-2022
Guru Gobind Singh Indraprastha University
2022
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < −18), blue transients. While commonly attributed the breakout a supernova shock into dense wind, great distances transients this class found so far hampered detailed investigation their properties. We present photometry and spectroscopy from comprehensive worldwide campaign observe AT 2018cow (ATLAS 18qqn), first fast-luminous transient be in real time at low redshift. Our spectra (<2 days...
Abstract Classical gamma-ray bursts (GRBs) have two distinct emission episodes: prompt from ultrarelativistic ejecta and afterglow shocked circumstellar material. While both components are extremely luminous in known GRBs, a variety of scenarios predict the existence with little or no associated high-energy emission. We present AT 2019pim, first spectroscopically confirmed observed to be identified. Serendipitously discovered during follow-up observations gravitational-wave trigger located...
On 2019 August 14, the Advanced LIGO and Virgo interferometers detected high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that event resulted from a neutron star--black hole (NSBH) merger, or potentially low-mass binary black merger. Due to low false alarm rate precise localization (23 deg$^2$ at 90\%), S190814bv presented community with best opportunity yet directly observe an optical/near-infrared counterpart NSBH To search for potential counterparts, GROWTH...
The many unusual properties of the enigmatic AT2018cow suggested that at least some subset empirical class fast blue optical transients (FBOTs) represents a genuinely new astrophysical phenomenon. Unfortunately, intrinsic rarity and fleeting nature these events have made it difficult to identify additional examples early enough acquire observations necessary constrain theoretical models. We present here Zwicky Transient Facility discovery AT2020xnd (ZTF20acigmel, "Camel") z=0.243, first...
Abstract We present early-phase panchromatic photometric and spectroscopic coverage spanning the far-ultraviolet to near-infrared regime of nearest hydrogen-rich core-collapse supernova (SN) in last 25 yr, SN 2023ixf. observe early “flash” features optical spectra due confined dense circumstellar material (CSM). high-ionization absorption lines (Fe ii , Mg ) ultraviolet from very on. also a multipeaked emission profile H α spectrum beginning at ∼16 days, which indicates ongoing interaction...
Abstract One of the open questions following discovery GW170817 is whether neutron star (NS) mergers are only astrophysical sites capable producing r -process elements. Simulations have shown that 0.01–0.1 M ⊙ material could be generated in outflows originating from accretion disk surrounding rapidly rotating black hole forms as a remnant to both NS and collapsing massive stars associated with long-duration gamma-ray bursts (collapsars). The hallmark signature nucleosynthesis binary merger...
Abstract We present multi-wavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading (Δmr = 2.2 mag in Δt 0.74 days), luminous (Mr ∼ −30.0 mag) and red (g − r 0.50 transient at z 2.28 with accompanying radio emission. AT 2023sva does not possess a γ-ray burst (GRB) counterpart to isotropic equivalent energy limit Eγ, iso &lt; 1.6 × 1052 erg, determined through searching satellite archives between the last non-detection first detection, making it sixth example...
Abstract We report observations of the optical counterpart long gamma-ray burst GRB 221009A. Due to extreme rarity being both nearby ( z = 0.151) and highly energetic E γ ,iso ≥ 10 54 erg), 221009A offers a unique opportunity probe connection between massive star core collapse relativistic jet formation across very broad range -ray properties. Adopting phenomenological power-law model for afterglow host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian...
Abstract We report observations of the optical counterpart long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity ( z = 0.36) high energy E γ ,iso ∼ 10 53 erg) make it an important event to study as a probe connection between massive star core collapse relativistic jet formation. With phenomenological power-law model for afterglow, we find late-time flattening consistent with presence SN. 2023pel has absolute peak r -band magnitude M −19.46 ± 0.18...
The third observing run by LVC has brought the discovery of many compact binary coalescences. Following detection first neutron star merger in this (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. initial skymap single-detector gravitational wave (GW) trigger spanned most sky observable from Observatory. Covering 8000 deg$^2$ over next two nights, corresponding to 46\% integrated probability, ZTF system...
Abstract Dirty fireballs are a hypothesized class of relativistic massive-star explosions with an initial Lorentz factor Γ init below the ∼ 100 required to produce long-duration gamma-ray burst (LGRB), but which could still optical emission resembling LGRB afterglows. Here we present results search for on-axis afterglows using Zwicky Transient Facility (ZTF). Our yielded seven transients that resemble in terms their red colors ( g − r > 0 mag), faint host galaxies 23 rapid fading dr / dt...
We present radio and optical afterglow observations of the TeV-bright long Gamma Ray Burst (GRB) 190114C at a redshift $z=0.425$, which was detected by MAGIC telescope. Our with ALMA, ATCA, uGMRT were obtained our low frequency observing campaign range from $\sim1$ to $\sim140$ days after burst done three telescopes spanning up $\sim25$ burst. Long term radio/mm reveal complex nature afterglow, does not follow spectral temporal closure relations expected standard model. find that...
Abstract We present the design and performance of GROWTH-India telescope, a 0.7 m robotic telescope dedicated to time-domain astronomy. The is equipped with 4k back-illuminated camera that gives 0.°82 field view sensitivity g′ ∼ 20.5 in 5 minute exposures. Custom software handles observatory operations: attaining high on-sky observing efficiencies (≳80%) allowing rapid response targets opportunity. data processing pipelines are capable performing point-spread function photometry as well...
We present a detailed study of SN 2024ahr, hydrogen-poor superluminous supernova (SLSN-I), for which we determine redshift $z=0.0861$. 2024ahr has peak absolute magnitude $M_g\approx M_r\approx -21$ mag, rest-frame rise and decline times (50$\%$ peak) about 40 80 days, respectively, typical spectroscopic evolution in the optical band. Similarly, modeling UV/optical light curves with magnetar spin-down engine leads to parameters: an initial spin period $\approx 3.3$ ms, magnetic field...
<b>Background:</b> Autoimmune blistering diseases are a group of bullous disorders characterized by pathogenic antibodies directed at the target antigens, which components desmosomes or adhesion complex dermoepidermal junction. Direct immunofluorescence (DIF) is invaluable in diagnosis these lesions. <b>Aim:</b> The aim this study was to evaluate sensitivity DIF immunobullous dermatoses and pattern DIF. also aims correlate with clinical histologic findings analyze discrepancies. <b>Materials...
Classical gamma-ray bursts (GRBs) have two distinct emission episodes: prompt from ultra-relativistic ejecta and afterglow shocked circumstellar material. While both components are extremely luminous in known GRBs, a variety of scenarios predict the existence with little or no associated high-energy emission. We present AT 2019pim, first secure example this phenomenon to be identified. Serendipitously discovered during follow-up observations gravitational-wave trigger located contemporaneous...
Context. In about 2000, the south pole of Triton experienced an extreme summer solstice that occurs every ∼650 years, when subsolar latitude reached 50°S. Bracketing this epoch, a few occultations probed atmosphere in 1989, 1995, 1997, 2008, and 2017. A recent ground-based stellar occultation observed on 6 October 2022 provides new measurement atmospheric pressure Triton. This is presented here. Aims. The goal to constrain volatile transport models (VTMs) atmosphere. basically vapor...
During the first half of fourth observing run (O4a) International Gravitational Wave Network (IGWN), Zwicky Transient Facility (ZTF) conducted a systematic search for kilonova (KN) counterparts to binary neutron star (BNS) and star-black hole (NSBH) merger candidates. Here, we present comprehensive study five high-significance (FAR < 1 per year) BNS NSBH candidates in O4a. Our follow-up campaigns relied on both target-of-opportunity observations (ToO) re-weighting nominal survey schedule...
Abstract We present the most comprehensive catalog to date of Type I Superluminous Supernovae (SLSNe), a class stripped envelope supernovae (SNe) characterized by exceptionally high luminosities. have compiled sample 262 SLSNe reported through 2022 December 31. verified spectroscopic classification each SLSN and collated an exhaustive data set UV, optical IR photometry totaling over 30,000 photometric detections. Using these we derive observational parameters such as peak absolute...