scholarly journals Simulations of stellar winds from X-ray bursts

2020 ◽  
Vol 638 ◽  
pp. A107
Author(s):  
Y. Herrera ◽  
G. Sala ◽  
J. José
Keyword(s):  
Neutron Star ◽  
Stellar Wind ◽  
Nuclear Reactions ◽  
Gravitational Energy ◽  
Model Parameters ◽  
Wind Model ◽  
X Ray ◽  
Physical Conditions ◽  
Free Parameters

Context. Photospheric radius expansion during X-ray bursts can be used to measure neutron star radii and help constrain the equation of state of neutron star matter. Understanding the stellar wind dynamics is important for interpreting observations, and therefore stellar wind models, though studied in past decades, have regained interest and need to be revisited with updated data and methods. Aims. Here, we study the radiative wind model in the context of X-ray bursts with modern techniques and physics input. We focus on characterization of the solutions and the study of observable magnitudes as a function of free model parameters. Methods. We implemented a spherically symmetric nonrelativistic wind model in a stationary regime, with updated opacity tables and modern numerical techniques. Total mass and energy outflows (Ṁ, Ė) were treated as free parameters. Results. A high-resolution parameter-space exploration was performed to allow better characterization of observable magnitudes. High correlation was found between different photospheric magnitudes and free parameters. For instance, the photospheric ratio of gravitational energy outflow to radiative luminosity is directly proportional to the photospheric wind velocity. Conclusions. The correlations found here could help determine the physical conditions of the inner layers, where nuclear reactions take place, by means of observable photospheric values. Further studies are needed to determine the range of physical conditions in which the correlations are valid.

Neutron-Star Accretion in a Stellar Wind: Model for a Pulsed X-Ray Source

1973 ◽  
Vol 179 ◽  
pp. 585 ◽  
Author(s):  
Kris Davidson ◽  
Jeremiah P. Ostriker
Keyword(s):  
Neutron Star ◽  
Stellar Wind ◽  
Wind Model ◽  
X Ray

scholarly journals Chemical Abundances of Early Type Stars

1998 ◽  
Vol 188 ◽  
pp. 224-225
Author(s):  
S. Tanaka ◽  
S. Kitamoto ◽  
T. Suzuki ◽  
K. Torii ◽  
M.F. Corcoran ◽  
...  
Keyword(s):  
Surface Layer ◽  
Stellar Wind ◽  
Nuclear Reactions ◽  
X Rays ◽  
Early Type ◽  
Chemical Abundances ◽  
X Ray ◽  
Low Metallicity ◽  
Early Type Stars

X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.

scholarly journals The confrontation of the shock-powered synchrotron maser model with the Galactic FRB 200428

2020 ◽  
Vol 500 (2) ◽  
pp. 2704-2710 ◽  
Author(s):  
Yun-Wei Yu ◽  
Yuan-Chuan Zou ◽  
Zi-Gao Dai ◽  
Wen-Fei Yu
Keyword(s):  
Line Of Sight ◽  
Model Parameters ◽  
Observational Constraints ◽  
Synchrotron Emission ◽  
Physical Processes ◽  
X Ray ◽  
Emission Efficiency ◽  
Free Parameters ◽  
Fast Radio Burst ◽  
Parameter Constraints

ABSTRACT The association of FRB 200428 with an X-ray burst (XRB) from the Galactic magnetar SGR 1935+2154 offers important implications for the physical processes responsible for the fast radio burst (FRB) phenomena. By assuming that the XRB emission is produced in the magnetosphere, we investigate the possibility that the FRB emission is produced by shock-powered synchrotron maser (SM), which is phenomenologically described with a number of free parameters. The observational constraints on the model parameters indicate that the model can in principle be consistent with the FRB 200428 observations, if the ejecta lunched by magnetar activities can have appropriate ingredients and structures and the shock processes occur on the line of sight. To be specific, a complete burst ejecta should consist of an ultra-relativistic and extremely highly collimated e± component and a sub-relativistic and wide-spreading baryonic component. The internal shocks producing the FRB emission arise from a collision between the e± ejecta and the remnant of a previous baryonic ejecta at the same direction. The parameter constraints depend on the uncertain spectrum and efficiency of the SM emission. While the spectrum is tentatively described by a spectral index of −2, we estimate the emission efficiency to be around 10−4 by requiring that the synchrotron emission of the shocked material cannot be much brighter than the magnetosphere XRB emission.

scholarly journals Modelling decretion discs in Be/X-ray binaries

2019 ◽  
Author(s):  
R O Brown ◽  
M J Coe ◽  
W C G Ho ◽  
A T Okazaki
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Major Axis ◽  
High Mass ◽  
Model Parameters ◽  
Be Stars ◽  
Semi Major Axis ◽  
X Ray ◽  
Smoothed Particle ◽  
X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

scholarly journals On the origin of Supergiant Fast X-ray Transients

2018 ◽  
Vol 14 (S346) ◽  
pp. 193-196
Author(s):  
Swetlana Hubrig ◽  
Lara Sidoli ◽  
Konstantin A. Postnov ◽  
Markus Schöller ◽  
Alexander F. Kholtygin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Stellar Wind ◽  
Longitudinal Magnetic Field ◽  
High Mass ◽  
Large Telescope ◽  
X Ray ◽  
Very Large Telescope ◽  
Low X ◽  
X Ray Binaries

Abstract. A fraction of high-mass X-ray binaries are supergiant fast X-ray transients. These systems have on average low X-ray luminosities, but display short flares during which their X-ray luminosity rises by a few orders of magnitude. The leading model for the physics governing this X-ray behaviour suggests that the winds of the donor OB supergiants are magnetized. In agreement with this model, the first spectropolarimetric observations of the SFXT IGR J11215-5952 using the FORS 2 instrument at the Very Large Telescope indicate the presence of a kG longitudinal magnetic field. Based on these results, it seems possible that the key difference between supergiant fast X-ray transients and other high-mass X-ray binaries are the properties of the supergiant’s stellar wind and the physics of the wind’s interaction with the neutron star magnetosphere.

On the nature of the 35-day cycle in the X-ray binary Her X-1/HZ Her

2018 ◽  
Vol 14 (S346) ◽  
pp. 281-287
Author(s):  
N. Shakura ◽  
D. Kolesnikov ◽  
K. Postnov ◽  
I. Volkov ◽  
I. Bikmaev ◽  
...  
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Orbital Plane ◽  
Outer Edge ◽  
Model Parameters ◽  
Free Precession ◽  
X Ray ◽  
Synchronization Mechanism ◽  
Optical Star ◽  
Optical Flux

AbstractThe X-ray binary Her X-1 consists of an accreting neutron star and the optical companion HZ Her. The 35-day X-ray variability of this system is known since its discovery in 1972 by the UHURU satellite and is believed to be caused by forced precession of the warped accretion disk tilted to the orbital plane. We argue that the observed features of the optical variability of HZ Her can be explained by free precession of the neutron star with a period close to that of the forced disk precession. The model parameters include a) the intensity (power) of the stream of matter flowing out of the optical star; b) the X-ray luminosity of the neutron star; c) the optical flux of the accretion disk; d) the X-ray irradiation pattern on the donor star; e) the tilt of the inner and outer edge of the accretion disk. A possible synchronization mechanism based on the coupling between the neutron star free precession and the dynamical action of non-stationary gas streams is discussed shortly.

scholarly journals Proposed wavelength measurements of silicon X-ray spectra: Application to Vela X-1

2008 ◽  
Vol 86 (1) ◽  
pp. 183-189 ◽  
Author(s):  
D A Liedahl ◽  
G V Brown
Keyword(s):  
Neutron Star ◽  
Stellar Wind ◽  
Large Scale ◽  
Radiation Transport ◽  
Three Dimensional ◽  
Mass Transfer Process ◽  
Gravitational Potential Energy ◽  
X Ray ◽  
Close Orbit ◽  
Mass Capture

When a stellar wind from a massive star is captured by a neutron star in close orbit, gravitational potential energy is converted into hard X-radiation near the surface of the neutron star. The X-radiation, in turn, modifies the wind through heating and photoionization, which affects the dynamics of mass capture. We have begun a project to further elucidate this process, which involves time-dependent three-dimensional hydrodynamics, large-scale atomic physics calculations, and radiation transport, integrated in an attempt to derive a self-consistent “first principles” description of the mass transfer process. We anticipate that the high-resolution silicon X-ray spectrum, produced by innershell photoionization and photoexcitation, as measured by the Chandra observatory, will provide benchmarks for these calculations. However, theoretical wavelengths, which are required in order to draw inferences concerning the velocity field of the wind, are uncertain at the level of the likely Doppler shifts in the stellar wind. EBIT measurements could lead to a reliable set of wavelengths, thereby providing observational constraints on the physics that powers some of the brightest X-ray sources in the Galaxy. PACS Nos.: 32.30.Rj, 32.80.Fb, 32.80.Hd, 52.25.Os, 52.72.+v, 97.10.Me, 97.80.Jp

scholarly journals Physical Conditions Inside White Dwarfs and Type I Supernovae

1983 ◽  
Vol 72 ◽  
pp. 149-153
Author(s):  
E. Schatzman
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Beta Decay ◽  
White Dwarfs ◽  
Nuclear Reactions ◽  
Type I ◽  
Physical Conditions

After the first suggestion by Schatzman (1963) that accreting white dwarfs, close to the limiting mass, might be the progenitors of type I Supernovae, the problem was not studied until Schatzman (1974) described the competition between collapse dominated by beta decay, which would lead to neutron star formation and collapse dominated by nuclear reactions leading to stellar disruption.

scholarly journals The Evolutionary History of X-Ray Binaries

1977 ◽  
Vol 4 (1) ◽  
pp. 145-153
Author(s):  
E.P.J. van den Heuvel ◽  
G.J. Savonije
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Stellar Wind ◽  
Evolutionary History ◽  
Main Sequence ◽  
Early Type ◽  
Main Sequence Stars ◽  
X Ray ◽  
History Of ◽  
X Ray Binaries

The most important recent observational discoveries in the field of X-ray binaries are probably those of the slow pulsars and of the winds of normal early-type main-sequence stars. These facts yield key information on the evolutionary history of the X-ray binaries and on the rotational slow-down mechanism for a neutron star in a stellar wind, as will be pointed out in section 3. In the theoretical field, the X-ray binaries have triggered much fundamental work, notably on the detailed processes of mass transfer and on tidal evolution, which will be considered in sections 2, 4 and 5.

scholarly journals Modelling of 35-d superorbital cycle of B and V light curves of IMXB HZ Her/Her X-1

2020 ◽  
Vol 499 (2) ◽  
pp. 1747-1757
Author(s):  
D A Kolesnikov ◽  
N I Shakura ◽  
K A Postnov ◽  
I M Volkov ◽  
I F Bikmaev ◽  
...  
Keyword(s):  
Neutron Star ◽  
Orbital Plane ◽  
Accretion Disc ◽  
Light Curves ◽  
Model Parameters ◽  
Free Precession ◽  
X Ray ◽  
Synchronization Mechanism ◽  
Gas Streams ◽  
Optical Flux

ABSTRACT The X-ray binary Her X-1 consists of an accreting neutron star and the optical component HZ Her. The 35-d X-ray superorbital variability of this system is known, since its discovery in 1972 by the Uhuru satellite and is believed to be caused by forced precession of a warped accretion disc tilted to the orbital plane. We argue that the observed features of the 35-d optical variability of HZ Her can be explained by free precession of the neutron star with a period close to that of the forced disc. The model parameters include (a) the X-ray luminosity of the neutron star; (b) the optical flux from the accretion disc; and (c) the tilt of the inner and outer edges of the accretion disc. A possible synchronization mechanism based on the coupling between the neutron star free precession and the dynamical action of non-stationary gas streams is discussed.

Sign in / Sign up

Export Citation Format

Share Document