Related papers: Testing the cooling flow model in the intermediate…
Cooling ages of white dwarfs are routinely determined by mapping effective temperatures and masses to ages using evolutionary models. Typically, the reported uncertainties on cooling ages only consider the error propagation of the…
We study the accretion flow of a hot gas captured by the black hole gravity in the presence of a thin cold accretion disk. Such geometrical arrangement is expected in Active Galactic Nuclei (AGN) and in galactic X-ray binary systems because…
We obtained thermal equilibrium solutions for optically thin, two-temperature black hole accretion disks incorporating magnetic fields. The main objective of this study is to explain the bright/hard state observed during the bright/slow…
As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the…
We observed the intermediate polar RX J0558+53 with the 4.2m WHT and find in the pulsed emission lines, a ``corkscrew'' pattern, which indicates a two-pole white dwarf accretion. The ``corkscrew'' pattern consists of two emission-line…
Based on the X-ray observations from XMM-Newton and Swift, and optical observations from Transiting Exoplanet Survey Satellite (TESS) and AAVSO, we present temporal and spectral properties of probable intermediate polar SWIFT J0503.7-2819.…
We present a reanalysis of the HeII Lyman alpha absorption towards the quasars HS1700+6416 and HE2347-4342 using new high S/N, optical observations. An alternative analysis method is applied, which fits the high quality, optical HI data…
To understand the origin of hard X-ray emissions from black hole X-ray binaries during their low/hard states, we calculate the X-ray spectra of black-hole accretion flow for the following three configurations of hot and cool media: (a) an…
We study the usage of the X-ray light curve, column density toward the hard X-ray source, and emission measure (density square times volume), of the massive binary system Eta Carinae to determine the orientation of its semi-major axis. The…
An accurate assessment of white dwarf cooling times is paramount to place white dwarf cosmochronology of Galactic populations on more solid grounds. This issue is particularly relevant in view of the enhanced observational capabilities…
White dwarfs are almost completely degenerate objects that cannot obtain energy from thermonuclear sources, so their evolution is just a gravothermal cooling process. Recent improvements in the accuracy and precision of the luminosity…
Context. White dwarfs (WDs) in cataclysmic variables (CVs) are important experimental laboratories where the electron degeneracy is taking place on a macroscopic scale. Magnetic CVs increase in number especially in the hard X-ray band (>10…
We present an analysis of 30 archival ASCA and RXTE X-ray observations of 16 intermediate polars to investigate the nature of their orbital modulation. We show that X-ray orbital modulation is widespread amongst these systems, but not…
In many clusters of galaxies, the cooling time at the core of the intracluster medium is much less than the age of the system, suggesting that the the gas should continually lose energy by radiation. Simple thermodynamic arguments then…
We present the X-ray analysis of dwarf nova EY Cyg using the 45 ks \textit{XMM-Newton} observatory archival data obtained in quiescence. We find orbital modulations in X-rays. We simultaneously fitted EPIC pn, MOS1 and MOS2 data using a…
We test models for the generation of X-rays in accreting T Tauri stars (TTS), using X-ray data from the classical TTS T Tau. High-resolution spectroscopy from the Reflection Grating Spectrometers on XMM-Newton is used to infer electron…
We discuss two temperature accretion disk flows around rotating black holes. As we know that to explain observed hard X-rays the choice of Keplerian angular momentum profile is not unique, we consider the sub-Keplerian regime of the disk.…
Hydrodynamic simulations of the stellar winds from Wolf-Rayet stars within the Galactic Center can provide predictions for the X-ray spectrum of supermassive black hole Sgr A*. Herein, we present results from updated smooth particle…
Two-dimensional numerical simulations of an accretion flow in a close binary system are performed by solving the Euler equations with radiative transfer. In the present study, the specific heat ratio is assumed to be constant while…
We present new cooling models for carbon-oxygen white dwarfs with both H- and He-atmospheres, covering the whole relevant mass range, to extend our updated BaSTI (a Bag of Stellar Tracks and Isochrones) stellar evolution archive. They have…