A5088722322- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Cosmology and Gravitation Theories
- Astro and Planetary Science
- Fluid Dynamics and Turbulent Flows
- Astrophysics and Star Formation Studies
- Radiative Heat Transfer Studies
- Calibration and Measurement Techniques
- Physics of Superconductivity and Magnetism
- Ionosphere and magnetosphere dynamics
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- Magnetic and transport properties of perovskites and related materials
- Fungal Infections and Studies
- Analytical Chemistry and Sensors
- Magnetic Properties of Alloys
- Atomic and Molecular Physics
- Autopsy Techniques and Outcomes
- Advanced Differential Geometry Research
- History and Developments in Astronomy
National Institute of Science Education and Research
2024
University of Colorado Boulder
2019-2022
Stockholm University
2019-2021
KTH Royal Institute of Technology
2019-2021
Carnegie Mellon University
2021
Ilia State University
2021
Nordic Institute for Theoretical Physics
2020
Joint Institute for Laboratory Astrophysics
2016-2019
National Institute of Standards and Technology
2017-2018
Indian Institute of Science Bangalore
2012-2015
Type Ia supernovae, sparked off by exploding white dwarfs of mass close to the Chandrasekhar limit, play key role in understanding expansion rate Universe. However, recent observations several peculiar type supernovae argue for its progenitor be significantly super-Chandrasekhar. We show that strongly magnetized not only can violate limit significantly, but exhibit a different limit. establish from foundational level generic is 2.58 solar mass. This explains origin overluminous supernovae....
We consider a relativistic, degenerate electron gas at zero temperature under the influence of strong, uniform, static magnetic field, neglecting any form interactions. Since density states for electrons changes due to presence field (which gives rise Landau quantization), corresponding equation state also gets modified. In order investigate effect very strong we focus only on systems in which maximum either one, two, or three level(s) is/are occupied. This is important since, if large...
ABSTRACT We present the largest optical photometry compilation of gamma-ray bursts (GRBs) with redshifts (z). include 64813 observations 535 events (including upper limits) from 28 February 1997 to 18 August 2023. also a user-friendly web tool grbLC which allows users visualize photometry, coordinates, redshift, host galaxy extinction, and spectral indices for each event in our database. Furthermore, we have added Gamma-ray Coordinate Network (GCN) scraper that can be used collect data by...
We explore the effect of modification to Einstein's gravity in white dwarfs for first time literature, best our knowledge. This leads significantly sub- and super-Chandrasekhar limiting masses dwarfs, determined by a single model parameter. On other hand, type Ia supernovae (SNeIa), key unravel evolutionary history universe, are believed be triggered having mass close Chandrasekhar limit. However, observations several peculiar, under- over-luminous SNeIa argue exploding widely different from...
We consider a relativistic, degenerate, electron gas under the influence of strong magnetic field, which describes magnetized white dwarfs. Landau quantization changes density states available to electrons, thus modifying underlying equation state. In presence very fields maximum either one, two or three level(s) is/are occupied. obtain mass–radius relations for such dwarfs and their detailed investigation leads us propose existence having mass ~2.3M ⊙ , overwhelmingly exceeds Chandrasekhar limit.
We address the issue of stability recently proposed significantly super-Chandrasekhar white dwarfs. present stable solutions magnetostatic equilibrium models for dwarfs pertaining to various magnetic field profiles. This has been obtained by self-consistently including effects pressure gradient and total density in a general relativistic framework. estimate that maximum mass magnetized could be more than 3 solar mass. is very useful explain peculiar, overluminous type Ia supernovae which do...
The topic of magnetized super-Chandrasekhar white dwarfs is in the limelight, particularly last few years, since our proposal their existence. By full-scale general relativistic magnetohydrodynamic (GRMHD) numerical analysis, we confirm this work existence stable, highly magnetized, significantly with mass more than 3 solar mass. While a poloidal field geometry renders oblate, toroidal makes them prolate retaining an overall quasi-spherical shape, as speculated earlier work. These are...
We examine the properties of strongly magnetized accretion discs in a global framework, with particular focus on evolution magnetohydrodynamic instabilities such as magnetorotational instability (MRI). Work by Pessah & Psaltis showed that MRI is stabilized beyond critical toroidal field compressible, differentially rotating flows and, also, reported appearance two new this field. Their results stemmed from considering geometric curvature effects due to suprathermal background field, which...
Several recently discovered peculiar type Ia supernovae seem to demand an altogether new formation theory that might help explain the puzzling dissimilarities between them and standard supernovae. The most striking aspect of observational analysis is necessity invoking super-Chandrasekhar white dwarfs having masses ~ 2.1-2.8M_sun, M_sun being mass Sun, as their probable progenitors. Strongly magnetized were already established be potential candidates for progenitors Owing Landau quantization...
We study the effects of optically thin radiative cooling on structure radiatively inefficient accretion flows (RIAFs). The flow is geometrically thick, and independent gas density cooling, if time longer than viscous time-scale (i.e. tcool ≳ tvisc). For higher densities, can cool before it accrete forms standard thin, thick Shakura–Sunyaev disc. usual processes (such as bremsstrahlung), we expect an inner hot outer a short separates into two phases: coronal phase cold argue that there upper...
We calculate the energy distribution associated with a static spherically symmetric non-singular phantom black hole metric in Einstein's prescription general relativity. As required for Einstein energy-momentum complex, we perform calculations quasi-Cartesian coordinates. also momentum components and obtain zero value, as expected from geometry of metric.
We carry out an extensive linear stability analysis of magnetized cylindrical jets in a global framework. Foregoing the commonly invoked force-free limit, we focus on small-scale, internal instabilities triggered regions jet dominated by toroidal magnetic field, with weak vertical field and finite thermal pressure gradient. Such are likely to occur far from source boundaries, potential sites energy dissipation that is essential explain particle acceleration radiation observed astrophysical...
We clarify important physics issues related to the recently established new mass limit for magnetized white dwarfs which is significantly super-Chandrasekhar. The include, justification of high magnetic field and corresponding formation stable dwarfs, contribution total density pressure, flux freezing, variation currents therein. also attempt address observational connection such highly dwarfs.
We establish the importance of modified Einstein's gravity (MG) in white dwarfs (WDs) for first time literature. show that MG leads to significantly sub- and super-Chandrasekhar limiting mass WDs, depending on a single model parameter. However, conventional WDs approaching Chandrasekhar's limit are expected trigger type Ia supernovae (SNeIa), key unravel evolutionary history universe. Nevertheless, observations several peculiar, under- over-luminous SNeIa argue widely different from limit....
Is the Chandrasekhar mass limit for white dwarfs (WDs) set in stone? Not anymore, recent observations of over-luminous, peculiar type Ia supernovae can be explained if significantly super-Chandrasekhar WDs exist as their progenitors, thus barring them to used cosmic distance indicators. However, there is no estimate a these WD candidates yet. Can they arbitrarily large? In fact, answer no! We arrive at this revelation by exploiting flux freezing theorem observed, accreting, magnetized WDs,...
Since 2012, we have initiated a new idea showing that the mass of highly magnetized or modified Einstein's gravity induced white dwarfs could be significantly super-Chandrasekhar with different mass-limit. This discovery has several important consequences, including explanation peculiar, over-luminous type Ia supernovae, soft gamma-ray repeaters and anomalous X-ray pulsars without invoking extraordinarily strong, yet unobserved, magnetic fields. It further argues for possible second standard...
Radiation transport plays an important role in stellar atmospheres, but the effects of turbulence are being obscured by other such as stratification. Using radiative hydrodynamic simulations forced turbulence, we determine decay rates sinusoidal large-scale temperature perturbations different wavenumbers optically thick and thin regimes. Increasing wavenumber increases rate both regimes, this effect is much weaker than for usual turbulent diffusion passive scalars, where increase quadratic...
We present the largest optical photometry compilation of Gamma-Ray Bursts (GRBs) with redshifts ($z$). include 64813 observations 535 events (including upper limits) from 28 February 1997 up to 18 August 2023. also a user-friendly web tool \textit{grbLC} which allows users visualization photometry, coordinates, redshift, host galaxy extinction, and spectral indices for each event in our database. Furthermore, we have added Gamma Ray Coordinate Network (GCN) scraper that can be used collect...
Introduction: Kidney diseases have shown a rising upward trend in the last few decades due to increase incidence of associated chronic like diabetes, hypertension. However frequency and spectrum renal pathology autopsy specimens is not well documented or overlooked by physicians as pathologists. Aim: To analyse various types pathologies, based on histopathological analysis tissue where autopsies were performed routinely with no history diseases. Materials Methods: This cross-sectional study...
Introduction: Infection with tuberculosis is a worldwide health concern. Nearly every organ in the body can be affected by Extrapulmonary Tuberculosis (EPTB). A simple diagnosis of Pulmonary (PTB) made using radiography and positive sputum test. On other hand, diagnosing EPTB difficult due to peculiar presentation lesions, which are paucibacillary exhibit varied sensitivity specificity different diagnostic tests across infected tissues. Aim: To analyse clinical presentations infection assess...
Explicit radiation hydrodynamic simulations of the atmospheres massive stars and convection in accretion discs around white dwarfs suffer from prohibitively short time steps due to radiation. This constraint is related cooling rather than radiative pressure, which also becomes important hot discs. We show that step governed by minimum sum optically thick thin contributions smaller one two. In with Pencil Code, their weighting fractions are found empirically. three-dimensional convective disc...
We show that the upper bound for central magnetic field of a super-Chandrasekhar white dwarf calculated by Nityananda and Konar [Phys. Rev. D 89, 103017 (2014)] is completely erroneous. This in turn strengthens argument favor stability recently proposed magnetized dwarfs. also point out several other numerical errors their work. Overall we conclude, based on our calculations, arguments put forth are fallacious misleading.