On the spin-down and X-ray luminosity of anomalous X-ray pulsars and soft gamma repeaters as white dwarfs

2017 ◽  
Author(s):  
Diego L. Caceres ◽  
Jorge A. Rueda
Keyword(s):  
White Dwarfs ◽  
X Ray ◽  
Soft Gamma Repeaters

scholarly journals X‐Ray Lines from Hot Flows around White Dwarfs: Application to SS Cygni

2001 ◽  
Vol 549 (1) ◽  
pp. 509-515 ◽  
Author(s):  
Kristen Menou ◽  
Rosalba Perna ◽  
John C. Raymond
Keyword(s):  
White Dwarfs ◽  
X Ray

scholarly journals Magneto–rotational and Thermal Evolution of Magnetars with Crustal Magnetic Fields

2000 ◽  
Vol 177 ◽  
pp. 681-684 ◽  
Author(s):  
U. Geppert ◽  
D. Page ◽  
M. Colpi ◽  
T. Zannias
Keyword(s):  
Magnetic Fields ◽  
Binary Systems ◽  
Thermal Evolution ◽  
Related Question ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Core Field ◽  
The Core ◽  
Crustal Field

The interpretation of Soft–Gamma–Repeaters (SGRs) and Anomalous X–Ray Pulsars (AXPs) as Magnetars (Thompson & Duncan 1996) raises again the issue of the generation of the ultra–strong magnetic fields (MFs) in neutron stars (NSs) and the related question of where these fields are anchored: in the core, penetrating the whole star, or confined to the crust. Recently, Heyl & Kulkarni (1998) considered the magneto–thermal evolution of magnetars with a core field. Since the assumption of a crustal field is at least not in disagreement with the observations of isolated pulsars (Urpin & Konenkov 1997) and of NSs in binary systems (Urpin, Geppert & Konenkov 1998, Urpin, Konenkov & Geppert 1998), here we would like to address the question whether the observations of SGRs and AXPs can be interpreted as magnetars having a crustal MF. Given the strength of the MF in magnetars we take into account, in an approximate manner, the strongly non–linear Hall effect on its decay. We intend to provide a contribution to an unified picture of NS MF evolution based on the crustal field hypothesis.

scholarly journals Neutron Star Formation by Collapse of White Dwarfs

1980 ◽  
Vol 58 ◽  
pp. 595-600
Author(s):  
R. Canal ◽  
J. Isern ◽  
J. Labay
Keyword(s):  
Neutron Star ◽  
White Dwarfs ◽  
Pure Oxygen ◽  
Type I ◽  
Solid Core ◽  
X Ray ◽  
Rate Of Increase ◽  
Central Regions ◽  
Central Oxygen ◽  
Mass Increase

Abstract.Mass-accreting carbon-oxygen white dwarfs become thermally and dynamically unstable when they reach high enough central densities. Carbon ignition at the star’s center likely propagates subsonically and, in the case of an initially solid core, leads to collapse if the rate of increase of the core’s mass is sufficiently fast. Recent results indicate, however, that solidification of the core induces carbon-oxygen separation. The central regions are then made of pure oxygen while carbon is rejected to lower-density layers. Carbon ignition happens only after neutronization of the central (oxygen) regions. Collapse to a neutron star is then independent from the rate of mass increase and the only possible restrictions are set by the behaviour of the outer, accreted layers. X-ray sources, pulsars and Type I supernovae are likely outcomes of this process.

scholarly journals AM Herculis Binaries

1996 ◽  
Vol 165 ◽  
pp. 403-414 ◽  
Author(s):  
K. Beuermann
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Close Binaries ◽  
Physical Processes ◽  
X Ray ◽  
Sky Survey

AM Herculis binaries contain mass accreting magnetic white dwarfs which appear as bright X-ray sources in the ROSAT All Sky Survey. About 52 systems are presently known which allow detailed studies of the evolution of magnetic close binaries and of fundamental plasma-physical processes in the accretion region on the white dwarf.

Helium Abundance in the Photospheres of Hot Da White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 188-193 ◽  
Author(s):  
J. B. Holberg ◽  
K. Kidder ◽  
J. Liebert ◽  
F. Wesemael
Keyword(s):  
White Dwarfs ◽  
Uv Spectroscopy ◽  
Helium Abundance ◽  
Apparent Contradiction ◽  
X Ray ◽  
Upper Limits

AbstractWe have used optical and UV spectroscopy to determine He abundances and upper limits to He abundances in the photospheres of a selected sample of very hot hydrogen-rich white dwarfs. He abundances in the range log(He/H) -3 to -1.5 are observed in several of these DAs and upper limits of -3 determined for the remainder. In apparent contradiction to the relatively large He abundances inferred from soft X-ray observations for the hot DA G191 B2B, we find no evidence of He in the optical and UV.

scholarly journals AM CVn Systems as Optical, X-Ray and GWR Sources

2004 ◽  
Vol 194 ◽  
pp. 117-119
Author(s):  
L. Yungelson ◽  
G. Nelemans ◽  
S. F. Portegies Zwart
Keyword(s):  
Gravitational Waves ◽  
White Dwarfs ◽  
X Ray

AbstractWe discuss the model for the Galactic sample of the AM CVn systems with Porb, ≤ 1500 s that can be detected in the optical and/or X-ray bands and may be resolved by the gravitational waves detector LISA. At 3 ≲ P ≲ 10 min all detectable systems are X-ray sources. At P ≳ 10 min most systems are only detectable in the V-band. About 30% of the X-ray sources is also detectable in the V-band. About 10,000 AM CVn systems might be resolved by LISA: this is comparable to the number of detached double white dwarfs that can be resolved. Several hundreds of AM CVn LISA sources might be also detectable in the V- and/or X-ray bands.

The Effect of CNO Metal Abundances on the Soft X-Ray Emission from He Rich White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 202-205
Author(s):  
M.A. Barstow
Keyword(s):  
Effective Temperature ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
X Ray ◽  
Metal Abundances

AbstractPredicted soft X-ray fluxes for model atmospheres containing varying concentrations of CNO metals are compared with those observed by EXOSAT for the planetary nebula nucleus K1-16. An effective temperature in the range ≈ 125000 − 180000K is determined for K1-16 and a limit on the concentration of CNO in the atmosphere (between 0.02 and 20 ×solar relative to He) obtained. Some comments on the application of the models to the apparently metal rich star H1504+65 are included.

Sign in / Sign up

Export Citation Format

Share Document