About
29
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Introduction
I am an Assistant Professor of Physics (Academic Level-11) in Department of Applied Sciences, Tezpur University. I am working on the theoretical and observational aspects of accretion process around compact objects. My research interests include the theoretical modeling of astrophysical flows, study of X-ray binaries, X-ray data analysis and interpretation.
Skills and Expertise
Current institution
Additional affiliations
July 2018 - January 2020
Position
- Assistant Professor
Description
- Teaching, Research & University Activities
July 2011 - August 2018
Position
- Research Assistant
Description
- M.Sc. 2nd and 3rd Sem Physics Lab, B. Tech First Year General Physics Lab
July 2011 - August 2018
Position
- Astrophysical Flows around Compact Objects
Description
- PhD Scholar
Education
August 2009 - May 2011
August 2006 - June 2009
Publications
Publications (29)
This book, titled Physics Frontier (Volume-I), serves as a comprehensive compilation of research articles presented at the national conferenece "Physics Frontiers-2024: Bridging Theories and Experiment",held on 2-4 July 2024 hosted by Bhawanipur Anchalik College.
This paper investigates the effects of saturated thermal conduction (TC) and thermal-driven winds (TDWs) on magnetized advection-dominated accretion onto a rotating black hole (BH). We incorporate dissipative processes in the magnetized accretion flow and expect the accretion disk to be threaded by predominantly toroidal and turbulent magnetic fiel...
In this work, we performed a spectro-temporal investigation of the low-mass X-ray binary GX 9+9 using the Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT) observation on board AstroSat. The source was detected in the soft state during the observation, which results in a disk dominating energy spectrum within the energy r...
Accretion disc outbursts are re-occurring events observed in various astrophysical systems, including X-ray binaries and cataclysmic variables. These outbursts are characterized by a sudden increase in luminosity due to various instabilities in the accretion disc. We need to investigate the time-dependent accretion flow models to understand the mec...
Relativistic accretors are cosmic objects that pull matter from their surroundings at speeds almost equal to the light's speed. Because of the tremendous gravitational force from the accretors and the angular momentum of infalling material, which often result in discs of gas and dust that are heated to extremely high temperatures. We encounter stro...
Accretion physics studies the process of gravitational capture of ambient matter by massive stars. The background processes are very challenging to observe and measure due to the extreme conditions in these systems. Numerical simulations play a crucial role in accretion physics because they provide the only practical method to model the complex pro...
We report results from a detailed study of the neutron star X-ray binary, 4U 1608-52, using observations with AstroSat (Large Area X-ray Proportional Counter/Soft X-ray Telescope) and the Neutron Star Interior Composition Explorer during its 2016 and 2020 outbursts. The 0.7–20.0 keV spectra could be well described with the disk blackbody and therma...
Plasma naturally exists throughout the universe, and recently, mankind has realized its vast technological applications. The scope of current plasma physics experiments has produced several well-established industrial applications in addition to several exciting new ones. This review aims to give a basic overview of the area of plasmas and the role...
In astronomy, gamma-ray bursts (GRBs) are some of the most intriguing and enigmatic phenomena. GRBs are the most luminous events in the cosmos, and they are bursts of strong but brief gamma-ray (GR) flashes. GRBs have a highly interesting nature and can last anywhere from a few hundred seconds to a tiny fraction of a second. A GRB produces an after...
Active Galaxies Nuclei (AGNs) are some of the most violent sources in the universe. Several ongoing studies are trying to explain the underlying physical processes of enormous energy emission and the particle acceleration to very high energies in the jet. However, ongoing debates remain regarding its unification scheme based on the properties of ra...
This chapter gives an idea of how Science and Technology (S&T) are interconnected though they are distinct in their way. Science is a systematic study through observation and experiment that provides a basis for Technology; without Technology, Science is worthless, and similarly, Technology is impossible without Science. However, there are some ins...
We report the results of an observation of low-mass X-ray binary GX 3+1 with AstroSat’s large area X-ray proportional counter (LAXPC) and soft X-ray telescope (SXT) instruments on-board for the first time. We have detected type-I thermonuclear burst (∼15 s) present in the LAXPC 20 light curve with a double peak feature at higher energies and our st...
4U 1608−52 is a transient neutron star low mass X-ray binary (LMXB) which shows occasional outbursts.
In this poster, we present the broadband X-ray data analysis of LMXB 4U 1608-52 using AstroSat, India's first multi-wavelength mission.
We aim at performing a detailed timing and spectral study of the source using the
observations made with Astro...
This poster discusses the X-ray transient universe very straightforwardly, starting from discovering the transient X-ray sources and explaining the various types and behavior.
This paper describes the general term `curriculum' and provides an overview of college education. Here we discuss the various elements of an effective college education curriculum. Again, in recent years, activity based teaching-learning (ABTL) has proven to be an effective pedagogy for students to become actively involved in the learning process....
Abstract: X-ray astronomy started in the early 1960s and since then, the X-ray range of electromagnetic radiation has produced a great deal of astronomical information about the high-energy universe. We begin this article by giving a brief introduction to X-ray astronomy. We then provide a concise explanation of the emission and detection of X-rays...
We investigate the dynamical behavior of a magnetized, dissipative accretion flow around a rapidly rotating black hole. We solve the magnetohydrodynamic equations and calculate the transonic accretion solutions which may contain discontinuous shock transitions. We investigate the effect of ζ –parameter (parametrizing the radial variation of the tor...
We present the global structure of magnetized advective accretion flow around the rotating black holes in presence of dissipation. By considering accretion flow to be threaded by toroidal magnetic fields and by assuming synchrotron radiative mechanism to be the dominant cooling process, we obtain global transonic accretion solutions in terms of dis...
We present the global structure of magnetized advective accretion flow around the rotating black holes in presence of dissipation. By considering accretion flow to be threaded by toroidal magnetic fields and by assuming synchrotron radiative mechanism to be the dominant cooling process, we obtain global transonic accretion solutions in terms of dis...
We explore the global structure of the accretion flow around a Schwarzschild black hole where the accretion disc is threaded by toroidal magnetic fields. The accretion flow is optically thin and advection dominated. Synchrotron radiation is considered to be the active cooling mechanism in the flow. With this, we obtain the global transonic accretio...
We explore the global structure of the accretion flow around a Schwarzschild black hole where the accretion disc is threaded by toroidal magnetic fields. The accretion flow is optically thin and advection dominated. Synchrotron radiation is considered to be the active cooling mechanism in the flow. With this, we obtain the global transonic accretio...
We investigate the global structure of the advection dominated accretion flow around a Schwarzschild black hole where the accretion disc is threaded by toroidal magnetic fields. We consider synchrotron radiative process as an effective cooling mechanism active in the flow. With this, we obtain the global transonic accretion solutions by exploring t...
We investigate the global structure of the advection dominated accretion flow around a Schwarzschild black hole where the accretion disc is threaded by toroidal magnetic fields. We consider synchrotron radiative process as an effective cooling mechanism active in the flow. With this, we obtain the global transonic accretion solutions by exploring t...
We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the domin...
We investigate a single-temperature, magnetized accretion disk around a Schwarzschild black hole. The global transonic accretion solutions including Rankine-Hugoniot (RH) shocks are studied in the presence of synchrotron cooling. We study the shock properties in terms of plasma β (= p gas /p mag , where p gas and p mag represent the gas pressure an...
We study the coupled disc-jet system around the black hole where the outflow
solutions are obtained in terms of the inflow parameters. We observe that an
advective accretion disc can eject outflows/jets for wide range of viscosity
parameter. However, such possibility is reduced if the cooling is active as the
energy dissipative process inside the d...
We self-consistently study the properties of the dissipative standing shock waves in an accrertion flow around a stationary black hole. We use analytical method to achieve our goal and identify an effective area in the parameter space spanned by the specific energy and the specific an-gular momentum which allows accretion flow to pass through shock...
In this report we shall discuss a number of models of the accretion disks including the advective disk paradigm which comprises the most complete solution presented so far. It incorporates accretion and outflows within the same framework, and takes into account angular momentum, viscosity, heating/cooling etc.
This paper presents a brief summary of the field of Xray astronomy with
special focus on Active Galactic Nuclei (AGN) studies. The paper begins with
an overview of Xray astronomy and deals with its history, importance and
different Xray satellites. The paper then discusses the Xray emission
processes and the various astrophysical Xray sour...
Questions
Questions (15)
Suppose, in a particular X-ray observation data set for a particular low-mass X-ray binary neutron star source, we find no QPO features, thermonuclear burst features or strong X-ray pulsations.
If neither of these features ( QPO, thermonuclear bursts or strong X-ray pulsations) are present in a given X-ray observation, then what other interesting features can be explored from the data set with the aim to get a suitable refereed publication?
Does the New Astronomy Journal charge fees for publishing accepted papers? Are there any page charges?
Or is it totally free like Research in Astronomy and Astrophysics Journal of IOP or Journal of Astrophysics and Astronomy of Springer?
Hi All!!
I have recently completed my PhD in theoretical astrophysics with work on accretion flow around black holes. Now I want to venture into some observational studies. I would like to know how I can make use of the VIRTUAL OBSERVATORIES to start some good quality research work in observations. I would be very glad if you could share some useful links or documents. Thanking you all...
A human being is such a complex organism, he has his emotions, various thoughts rise in his mind. Society again is an aggregate of individual human beings. So much of complexity just can't be grasped by studying the laws at the atomic or even deeper at the quark level.
Are there statistical physical laws which can explain our thoughts or the way we behave as members of a society?
Supermongo and IDL are also very popular among astrophysicists. Are Matlab, Mathematica, Xmgrace, Gnuplot also popular among some groups?
In the literature we find that relativistic e- - e+ jets are not possible. For truly relativistic jests, we need to have e- - p pairs.
The above relation has been used in the synchrotron cooling expression in the paper "Behaviour of dissipative accretion flows around black holes" 2007MNRAS.376.1659D.
We know that the electron thermal velocity is v_e = (k T_e/m_e)^0.5 and ion thermal velocity is v_i = (k T_i/m_i)^0.5. If we say that ions and electrons have same kinetic energy then...m_e (v_e^2) = m_i (v_i^2)...and we arrive at the ralation...
T_e = (m_e/m_i)T_i
But under what assumptions can we arrive at the relation T_e = (m_e/m_i)^0.5 T_i ??
Why does the outward increase of angular momentum in an accretion disk make the disk Rayleigh stable? Since the density profile in an accretion disk increases inward in the case of constant accretion rate, there should not be an instability in between consecutive rings. Is that the reason why they are Rayleigh stable?
