scholarly journals Rapid Mass Accretion in the Symbiotic Star AG Dra

1987 ◽  
Vol 93 ◽  
pp. 759-762
Author(s):  
T. Iijima
Keyword(s):  
White Dwarf ◽  
Accretion Rate ◽  
Symbiotic Star ◽  
Mass Accretion Rate ◽  
Accretion Process ◽  
Rapid Mass

AbstractThe mass accretion process onto the hot component of AG Dra and its explosive phenomena are discussed. The hot component seems to be a massive white dwarf (M > 1 M⊙). The mass accretion rate is estimated to be about 10−7M⊙/year. Many properties of the explosive phenomena agree with those of mild hydrogen flashes expected from this rapid mass accretion.

scholarly journals The formation of bimodal dust species in nova ejecta – I. Chemical conditions

2019 ◽  
Vol 488 (1) ◽  
pp. 525-535 ◽  
Author(s):  
Chunhua Zhu ◽  
Helei Liu ◽  
Guoliang Lü ◽  
Zhaojun Wang ◽  
Lin Li
Keyword(s):  
Amorphous Carbon ◽  
White Dwarf ◽  
Accretion Rate ◽  
Carbon Number ◽  
Number Density ◽  
Chemical Profile ◽  
Chemical Abundances ◽  
Mixing Depth ◽  
Mass Accretion Rate ◽  
Chemical Conditions

Abstract It is still not known whether or not bimodal dust species (namely the silicate and amorphous carbon dust grains that are observed in a nova eruption) are formed in nova ejecta. Using the Modules for Experiments in Stellar Astrophysics code and considering the effects of the white dwarf mass, the mass-accretion rate and the chemical profile, which are described by a new parameter (the mixing depth), on the chemical abundances of nova ejecta, we investigate the possibility that bimodal dust species are produced in a nova eruption. We find that the C/O (the ratio of the carbon number density to the oxygen number density) of nova ejecta is affected by the mixing depth. For a model with a small mixing depth, the C/O of nova ejecta can evolve from greater than 1.0 to less than 1.0 over the course of an eruption, thereby providing the chemical conditions for the formation of bimodal dust species.

Clumpy wind accretion in Supergiant X-ray Binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 34-39
Author(s):  
Ileyk El Mellah ◽  
Andreas A. C. Sander ◽  
Jon O. Sundqvist ◽  
Rony Keppens
Keyword(s):  
Neutron Star ◽  
Accretion Rate ◽  
Recent Analysis ◽  
Line Of Sight ◽  
Time Variability ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Accretion Process ◽  
The Impact ◽  
X Ray Binaries

AbstractSupergiant X-ray Binaries host a compact object, generally a neutron star, orbiting an evolved O/B star. Mass transfer proceeds through the intense radiatively-driven wind of the stellar donor, a fraction of which is captured by the gravitational field of the neutron star. The subsequent accretion process onto the neutron star is responsible for the abundant X-ray emission from those systems. They also display variations in time of the X-ray flux by a factor of a few 10, along with changes in the hardness ratios believed to be due to varying absorption along the line-of-sight. We used the most recent results on the inhomogeneities (aka clumps) in the non-stationary wind of massive hot stars to evaluate their impact on the time-variable accretion process. We ran three-dimensional simulations of the wind in the vicinity of the accretor to witness the formation of the bow shock and follow the inhomogeneous flow over several spatial orders of magnitude, down to the neutron star magnetosphere. In particular, we show that the impact of the clumps on the time-variability of the intrinsic mass accretion rate is severely damped by the crossing of the shock, compared to the purely ballistic Bondi-Hoyle-Lyttleton estimation. We also account for the variable absorption due to clumps passing by the line-of-sight and estimate the final effective variability of the mass accretion rate for different orbital separations. These results are confronted to recent analysis of Vela X-1 observations with Chandra by Grinberg et al. (2017). It shows that clumps account well for time-variability at low luminosity but can not generate, per se, the high luminosity activity observed.

scholarly journals Temperaments of young stars: rapid mass accretion rate changes in T Tauri and Herbig Ae stars

2014 ◽  
Vol 440 (4) ◽  
pp. 3444-3461 ◽  
Author(s):  
G. Costigan ◽  
Jorick S. Vink ◽  
A. Scholz ◽  
T. Ray ◽  
L. Testi
Keyword(s):  
Accretion Rate ◽  
Young Stars ◽  
Mass Accretion Rate ◽  
T Tauri ◽  
Herbig Ae Stars ◽  
Rapid Mass

scholarly journals On the accretion onto the white dwarfs in symbiotic binaries: A test with the Thomson scattering process

2012 ◽  
Vol 8 (S290) ◽  
pp. 305-306
Author(s):  
Matej Sekeráš ◽  
Augustin Skopal
Keyword(s):  
Optical Depth ◽  
Electron Scattering ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accretion Rate ◽  
Thomson Scattering ◽  
Symbiotic Star ◽  
Scattering Process ◽  
Symbiotic Binaries ◽  
Different Levels

AbstractWe tested the origin of the nebular radiation in the symbiotic star AG Dra, during different levels of its activity. We modeled the broad wings of the OVI 1032, 1038 Å resonance lines and HeII 1640 Å line by the Thomson scattering process, and determined the electron-scattering optical depth, τe, of the symbiotic nebula. The increase of τe during active phases results from an increase in the accretion rate onto the white dwarf.

scholarly journals Discovery of an X-Ray Off-State in the Supersoft Source CAL 83

1997 ◽  
Vol 163 ◽  
pp. 730-731
Author(s):  
P. Kahabka
Keyword(s):  
White Dwarf ◽  
Accretion Rate ◽  
X Rays ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Upper Limit ◽  
Linear Decline

AbstractAn X-ray off state of CAL 83 has been observed in April 1996 with the ROSAT HRI three weeks after a normal on state. An upper limit for a linear decline time of the observed flux of ~20 days (and of an efolding decline time of ~6 days) is deduced. This decline may be due to the response of the white dwarf envelope to a temporary increased mass accretion rate giving rise to an envelope expansion. CAL 83 may resemble the recurrent supersoft LMC transient RX J0513.9–6951 with episodes of disappearance in X-rays.

scholarly journals The relativistic mass accretion rate for accretion disk in the equatorial of rapidly rotating neutron stars

2021 ◽  
Vol 1869 (1) ◽  
pp. 012156
Author(s):  
A Yasrina ◽  
N Widianingrum ◽  
N S Risdianto ◽  
D Andra ◽  
N A Pramono ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Accretion Disk ◽  
Accretion Rate ◽  
Mass Accretion Rate ◽  
Relativistic Mass

A radio jet associated with the symbiotic star CH Cygni

1986 ◽  
Vol 64 (4) ◽  
pp. 520-522 ◽  
Author(s):  
E. R. Seaquist ◽  
A. R. Taylor
Keyword(s):  
Electron Density ◽  
White Dwarf ◽  
Transverse Velocity ◽  
Stellar Object ◽  
Symbiotic Star ◽  
Ionized Gas ◽  
Radio Outburst ◽  
Supercritical Accretion ◽  
End To End ◽  
Red Giant

We present observations that show that the symbiotic star CH Cygni recently underwent a strong radio outburst that produced a radio-emitting thermal jet. The jet is two-sided and is expanding lengthwise at an observed rate (end to end) of 1 arcsec/year, corresponding to a transverse velocity of 1100 km∙s−1 in each direction. The electron density on January 22, 1985 exceeded 2 × 106 cm−3, and the mass of the (ionized) gas exceeded [Formula: see text]. The emergence of the jet coincided with a decline in the visual luminosity of [Formula: see text].The data are consistent with a jet produced by supercritical accretion in a binary containing a red giant and a [Formula: see text] white dwarf. The discovery of a jet in such a system provides confirming evidence of the role played by accretion in determining the optical and radio properties of this system. It is also the first expanding jet found to be associated with an evolved stellar object.

scholarly journals Recurrent Novae — A Review

2015 ◽  
Vol 2 (1) ◽  
pp. 246-251 ◽  
Author(s):  
K. Mukai
Keyword(s):  
Accretion Rate ◽  
Current Understanding ◽  
X Rays ◽  
Symbiotic Star ◽  
Classical Novae ◽  
Extensive Data ◽  
Star Evolution ◽  
Wide Range ◽  
Multi Wavelength ◽  
Recurrent Nova

In recent years, recurrent nova eruptions are often observed very intensely in wide range of wavelengths from radio to optical to X-rays. Here I present selected highlights from recent multi-wavelength observations. The enigma of T Pyx is at the heart of this paper. While our current understanding of CV and symbiotic star evolution can explain why certain subset of recurrent novae have high accretion rate, that of T Pyx must be greatly elevated compared to the evolutionary mean. At the same time, we have extensive data to be able to estimate how the nova envelope was ejected in T Pyx, and it turns to be a rather complex tale. One suspects that envelope ejection in recurrent and classical novae in general is more complicated than the textbook descriptions. At the end of the review, I will speculate that these two may be connected.

scholarly journals Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 395-396 ◽  
Author(s):  
Swetlana Hubrig ◽  
C. Grady ◽  
M. Schöller ◽  
O. Schütz ◽  
B. Stelzer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Survey ◽  
Accretion Rate ◽  
Be Stars ◽  
General Correlation ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Debris Disk ◽  
Magnetic Nature

AbstractWe present the results of a new magnetic field survey of Herbig Ae/Be and A debris disk stars. They are used to determine whether magnetic field properties in these stars are correlated with the mass-accretion rate, disk inclinations, companion(s), Silicates, PAHs, or show a more general correlation with age and X-ray emission as expected for the decay of a remnant dynamo.

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