Publications (47)
Stability of strange stars (SS) derived from a realistic equation of state
Monika Sinha, Jishnu Dey, Mira Dey +3
A realistic equation of state (EOS) leads to realistic strange stars (ReSS) which are compact in the mass radius plot, close to the Schwarzchild limiting line (Dey et al 1998). Man…
Electrically charged compact stars and formation of charged black holes
Subharthi Ray, Aquino L. Espindola, Manuel Malheiro +2
We study the effect of electric charge in compact stars assuming that the charge distribution is proportional to the mass density. The pressure and the density of the matter inside…
CMB power spectrum estimation with non-circular beam and incomplete sky coverage
Sanjit Mitra, Anand S. Sengupta, Subharthi Ray +2
Over the last decade, measurements of the CMB anisotropy has spearheaded the remarkable transition of cosmology into a precision science. However, addressing the systematic effects…
Strange stars and superbursts at near-Eddington mass accretion rates
Monika Sinha, Subharthi Ray, Mira Dey +1
Careful assessment of four good superburst candidates for GX 17+2 reveals that superburst is possible at near Eddington mass accretion rates. For the other seven stars, where super…
Glimpses of a strange star
Jishnu Dey, Subharthi Ray, Xiang-Dong Li +2
There are about 2000 gamma ray burst (GRB) events known to us with data pouring in at the rate of one per day. While the afterglows of GRBs in radio, optical and X-ray bands are su…
Quark star model with charged anisotropic matter
Jefta M. Sunzu, Sunil D. Maharaj, Subharthi Ray
We find two new classes of exact solutions to the Einstein-Maxwell system of equations. The matter distribution satisfies a linear equation of state consistent with quark matter. T…
Charged polytropic compact stars
Subharthi Ray, Manuel Malheiro, Jose' P. S. Lemos +1
In this work, we analyze the effect of charge in compact stars considering the limit of the maximum amount of charge they can hold. We find that the global balance of the forces al…
Superburst: surface phenomenon of compact objects
Monika Sinha, Mira Dey, Subharthi Ray +1
We suggest that superbursts from some low mass X-ray binaries may be due to breaking and re-formation of diquark pairs, on the surface of realistic strange stars. Diquarks are expe…
Compact stars with quadratic equation of state
Sifiso A. Ngubelanga, Sunil D. Maharaj, Subharthi Ray
We provide new exact solutions to the Einstein-Maxwell system of equations for matter configurations with anisotropy and charge. The spacetime is static and spherically symmetric.…
Electrically charged compact stars
Subharthi Ray, Manuel Malheiro, Jose' P. S. Lemos +1
We review here the classical argument used to justify the electrical neutrality of stars and show that if the pressure and density of the matter and gravitational field inside the…
Density dependent strong coupling constant of QCD derived from compact star data
Subharthi Ray, Jishnu Dey, Mira Dey
The present work is an endeavour to connect the properties of tiny nearly massless objects with those of some of the most massive ones, the compact stars. Since 1996 there is major…
Charged anisotropic models for quark stars
Jefta M. Sunzu, Sunil D. Maharaj, Subharthi Ray
We perform a detailed physical analysis for a class of exact solutions for the Einstein-Maxwell equations. The linear equation of state consistent with quark stars has been incorpo…
On the nature of the compact star in 4U 1728-34
Xiang-Dong Li, Subharthi Ray, Jishnu Dey +2
The discovery of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binaries (LMXBs) with the Rossi X-ray Timing Explorer has stimulated extensive studies of these…
High Density Strange Star Matter and Observed Parity Doubling of Excited Hadrons
Taparati Gangopadhyay, Manjari Bagchi, Mira Dey +2
Parity doubling is observed in hadron states around 1.5 GeV - and the estimated energy density is found to be high. When a large excitation energy is available and the pions decoup…
Superbursts and long bursts as surface phenomenon of compact objects
Monika Sinha, Mira Dey, Subharthi Ray +1
X-ray bursts from compact stars is believed to be due to type I thermonuclear processes which are short lived, typically ~ 10 to 100 s. There are some low mass X-ray binaries (LMXB…
Charged Polytropic Stars and a Generalization of Lane-Emden Equation
Rodrigo Picanco, Manuel Malheiro, Subharthi Ray
In this paper we will discuss charged stars with polytropic equation of state, where we will try to derive an equation analogous to the Lane-Emden equation. We will assume that the…
Global structure of Black Holes via dynamical system
Apratim Ganguly, Radouane Gannouji, Rituparno Goswami +1
We recast the system of Einstein field equations for Locally Rotationally Symmetric spacetimes into an autonomous system of covariantly defined geometrical variables. The analysis…
Strange stars at finite temperature
Subharthi Ray, Manjari Bagchi, Jishnu Dey +1
We calculate strange star properties, using large N_c approximation with built-in chiral symmetry restoration (CSM). We used a relativistic Hartree Fock mean field approximation me…
Compact stars with linear equation of state in isotropic coordinates
Sifiso A. Ngubelanga, Sunil D. Maharaj, Subharthi Ray
We present a new class of spherically symmetric spacetimes for matter distributions with anisotropic pressures in the presence of an electric field. The equation of state for the m…
Have we observed the skin vibration of realistic strange stars (ReSS) ?
Monika Sinha, Jishnu Dey, Mira Dey +2
Skin vibration of ReSS and consequent resonance absorption can account for the absorption lines in the spectrum of X-ray emission from many compact stellar objects and in particula…
`Strange Stars' - have they been discovered ?
A. R. Prasanna, Subharthi Ray
Recently there is a suggestion about the star RXJ1856.53754, being a possible candidate for quark star. While from the estimates of the radiation radius, given by the authors, i…
Chromo-thermal oscillations and collapse of strange stars to black holes : Astrophysical Implications
Manjari Bagchi, Rachid Ouyed, Jan Staff +3
The effects of temperature on strange stars are studied and it is found that the maximum mass of the star decreases with the increase of temperature since at high temperatures the…
CMB polarization TE power spectrum estimation with non-circular beam
Fidy A. Ramamonjisoa, Subharthi Ray, Sanjit Mitra +1
Precise measurements of the Cosmic Microwave Background (CMB) anisotropy have been one of the foremost concerns in modern cosmology as it provides valuable information on the cosmo…
Entropy & viscosity bound of strange stars
Sibasish Laha, Taparati Gangopadhyay, Manjari Bagchi +4
At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (η/s). We find…
Theoretical Description of kHz QPOs in accreting LMXB systems
Banibrata Mukhopadhyay, Subharthi Ray, Jishnu Dey +1
We describe kHz QPOs from the hydrodynamical model of accretion disks for LMXB systems. Out of the pair, the higher frequency originates due to the viscous effects of an accretion…
Non-Circular beam correction to the CMB power spectrum
Tarun Souradeep, Sanjit Mitra, Anand Sengupta +2
In the era of high precision CMB measurements, systematic effects are beginning to limit the ability to extract subtler cosmological information. The non-circularity of the experim…
Stability of realistic strange stars (RSS)
Siddhartha Bhowmick, Jishnu Dey, Mira Dey +2
A modified version of this paper is under process and with a new title and abstract. Hence, this version of the article is completely withdrawn.
Evidence for strange stars from joint observation of harmonic absorption bands and of redshift
Manjari Bagchi, Subharthi Ray, Mira Dey +1
From recent reports on terrestrial heavy ion collision experiments it appears that one may not obtain information about the existence of asymptotic freedom (AF) and chiral symmetry…
Stability of strange stars (SS) under radial oscillation
Monika Sinha, Jishnu Dey, Mira Dey +2
A realistic Equation of State (EOS) leads to strange stars (ReSS) which are compact in the mass radius plot, close to the Schwarzchild limiting line (Dey et al. 1998). We carry out…
Strange Stars with Realistic Quark Vector Interaction and Phenomenological Density-dependent Scalar Potential
Mira Dey, Ignazio Bombaci, Jishnu Dey +2
We derive an equation of state (EOS) for strange matter, starting from an interquark potential which (i) has asymptotic freedom built into it, (ii) shows confinement at zero baryon…
Self lensing effects for compact stars and their mass-radius relation
A. R. Prasanna, Subharthi Ray
During the last couple of years astronomers and astrophysicists have been debating on the fact whether the so called `strange stars' - stars made up of strange quark matter, have b…
Stellar objects in the quadratic regime
P. Mafa Takisa, S. D. Maharaj, Subharthi Ray
We model a charged anisotropic relativistic star with a quadratic equation of state. Physical features of an exact solution of the Einstein-Maxwell system are studied by incorporat…
Limiting temperature of hadrons using states predicted from kappa-deformed Poincaré algebra
Jishnu Dey, Siddhartha Bhowmik, Kanad Ray +1
The experimental hadronic density of states dN/dm, assumed to be a sum of normalized Breit- Wigner distributions and plotted as a function of the hadron mass m, fails to show a Hag…
Effect of variable crustal density on the surface magnetic field of Radio Pulsars
Kathleen Sellick, Subharthi Ray
We study the surface magnetic field fluctuations due to radial oscillations as a viable cause for the micro structures of the radio pulsar pulse patterns. The electrical conductivi…
Incompressibility of strange matter
Monika Sinha, Manjari Bagchi, Jishnu Dey +3
Strange stars calculated from a realistic equation of state (EOS), that incorporate chiral symmetry restoration as well as deconfinement at high density show compact objects in the…
Strange star equation of state fits the refined mass measurement of 12 pulsars and predicts their radii
Taparati Gangopadhyay, Subharthi Ray, Xiang-Dong Li +2
There are three categories of stars whose masses have been found accurately in recent times: (1) two for which Shapiro delay is used which is possible due to GR light bending as th…
Compact strange stars with a medium dependence in gluons at finite temperature
Manjari Bagchi, Subharthi Ray, Mira Dey +1
The possible existence of strange stars in the universe will help in the understanding of various properties of quantum chromodynamics, like asymptotic freedom and chiral symmetry…
Possible evidence of surface vibration of strange stars from stellar observations
Subharthi Ray, Jishnu Dey, Mira Dey +1
Emission lines in the eV and keV range by certain stellar candidates from their recent analysis invoke the question of their possible origin. These stars under consideration, are t…
General relativistic effects of strong magnetic fields on the gravitational force: a driving engine for bursts of gamma rays in SGRs?
Manuel Malheiro, Subharthi Ray, Herman J. M. Cuesta +1
In general relativity all forms of energy contribute to gravity and not only just ordinary matter as in Newtonian Physics. This fact can be seen in the modified hydrostatic equilib…
KHz QPOs in LMXBs, relations between different frequencies and compactness of stars
Taparati Gangopadhyay, Xiang-Dong Li, Subharthi Ray +2
We suggest that the mass of four compact stars SAX J1808.43658, KS 1731260, SAX J1750.82900 and IGR J171912821 can be determined from the difference in the observed kil…
Strange Star Equation of State With a Modified Richardson Potential
Manjari Bagchi, Subharthi Ray, Mira Dey +1
Richardson potential is an phenomenological interquark interaction taking care of two aspects of QCD, namely the asymptotic freedom and the confinement. The original potential has…
Physical properties of Tolman-Bayin solutions: some cases of static charged fluid spheres in general relativity
Saibal Ray, Basanti Das, Farook Rahaman +1
In this article, Einstein-Maxwell space-time has been considered in connection to some of the astrophysical solutions as previously obtained by Tolman (1939) and Bayin (1978). The…
Origin and interpretation of kilohertz QPOs from strange stars in X-ray binary system: theoretical hydrodynamical description
Banibrata Mukhopadhyay, Subharthi Ray, Jishnu Dey +1
We model and interpret the Kilohertz QPOs from the hydrodynamical description of accretion disk around a rapidly rotating compact strange star. The higher QPO frequency is describe…
Bound for entropy and viscosity ratio for strange quark matter
Manjari Bagchi, Jishnu Dey, Mira Dey +4
High energy density ($\eps$) and temperature (T) links general relativity and hydrodynamics leading to a lower bound for the ratio of shear viscosity () and entropy density ($s…
Neutron stars in Starobinsky model
Apratim Ganguly, Radouane Gannouji, Rituparno Goswami +1
We study the structure of neutron stars in theory of gravity (Starobinsky model), in an exact and non-perturbative approach. In this model, apart from the standard…
Strange Stars : An interesting member of the compact object family
Manjari Bagchi, Subharthi Ray, Jishnu Dey +1
We have studied strange star properties both at zero temperature and at finite temperatures and searched signatures of strange stars in gamma-ray, x-ray and radio astronomy. We hav…
Observing the Evolution of the Universe
James Aguirre, Alexandre Amblard, Amjad Ashoorioon +172
How did the universe evolve? The fine angular scale (l>1000) temperature and polarization anisotropies in the CMB are a Rosetta stone for understanding the evolution of the univers…