scholarly journals Dynamics of Low Luminosity Accretion onto Neutron Stars: Spherically Symmetric Models

1997 ◽  
Vol 163 ◽  
pp. 824-825
Author(s):  
John C. L. Wang ◽  
Ralph S. Sutherland
Keyword(s):  
Interstellar Medium ◽  
Neutron Stars ◽  
Flow Dynamics ◽  
Stellar Surface ◽  
Spherically Symmetric ◽  
Atomic Processes ◽  
High Luminosity ◽  
Strongly Coupled ◽  
Accretion Flow ◽  
The Galaxy

The ~ 108−109 old neutron stars in the Galaxy may be undergoing low luminosity accretion from the interstellar medium (Ostriker et al. 1970; Shvartsman 1971). It was first recognized by Shvartsman (1971) that the accretion induced radiation from the stellar surface can heat the infalling material, which in turn inhibits further accretion. This preheating instability has been studied in detail in the high luminosity regime where equilibrium ionization and heating holds (e.g., Buff & McCray 1974; Ostriker et al. 1976; Cowie et al. 1978). In the low luminosity regime, however, dynamical timescales are typically much shorter than atomic timescales so the accretion flow dynamics is strongly coupled to non-equilibrium (NEQ) atomic processes (cf. Blaes et al. 1995).

scholarly journals Bursting X-Ray Sources: A Theoretical Framework for Accretion Models

1977 ◽  
Vol 4 (1) ◽  
pp. 125-125
Author(s):  
F.K. Lamb ◽  
A.C. Fabian ◽  
J.E. Pringle ◽  
D. Q. Lamb
Keyword(s):  
Neutron Star ◽  
Theoretical Framework ◽  
Stellar Surface ◽  
Spherically Symmetric ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow

We consider spherically symmetric accretion flow onto a strongly magnetized neutron star. We show that, under certain conditions, the flow is intermittent and that the resultant accretion luminosity (X-rays) from the stellar surface is akin to that observed in the bursting X-ray sources. We investigate the properties of such burst flows under a variety of conditions, in the hopes of providing a basic theoretical framework on which realistic models of the observed bursting sources can be built. This work was supported in part by NSF Grant PHY75-08790.

scholarly journals Abundances in the Gaseous Galactic Halo

1998 ◽  
Vol 11 (1) ◽  
pp. 86-89
Author(s):  
Ulysses J. Sofia
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
High Velocity ◽  
Galactic Halo ◽  
Solar Neighborhood ◽  
Local Interstellar Medium ◽  
The Galaxy ◽  
Metal Abundances ◽  
High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

scholarly journals Astrophysical MHD turbulence: confluence of observations, simulations, and theory

2012 ◽  
Vol 8 (S294) ◽  
pp. 325-336 ◽  
Author(s):  
Blakesley Burkhart ◽  
Alex Lazarian
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Magnetic Reconnection ◽  
Particle Transport ◽  
Recent Progress ◽  
Critical Component ◽  
Dynamo Theory ◽  
Mhd Turbulence ◽  
The Galaxy

AbstractMagnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

scholarly journals DIBs, Interstellar Dust, and Extinction

2013 ◽  
Vol 9 (S297) ◽  
pp. 147-152 ◽  
Author(s):  
G. C. Clayton
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Dust Grains ◽  
Weak Correlation ◽  
Interstellar Clouds ◽  
The Galaxy ◽  
The Relationship

AbstractThe relationship between DIBs and dust is still unknown. The correlation between reddening and DIB strength means that the DIBs are mixed in with the dust and gas in interstellar clouds. The DIBs are relatively stronger in the diffuse interstellar medium than in dense clouds. There is only a weak correlation between the DIBs and the UV extinction parameters including the 2175 Å bump strength and the far-UV rise. In addition, the bump dust grains are sometimes polarized, while the DIBs are not. However, observations of DIBs in the SMC show that when the 2175 Å bump is weak or missing so are the DIBs. Two of the four sightlines that deviate strongly from the CCM UV extinction in the Galaxy show weak DIBs.

The Unidentified Infrared Bands in the Diffuse Interstellar Medium across the Galaxy Based on theInfrared Telescope in SpaceMid‐Infrared Spectrometer Observation

2004 ◽  
Vol 609 (1) ◽  
pp. 203-219 ◽  
Author(s):  
Itsuki Sakon ◽  
Takashi Onaka ◽  
Daisuke Ishihara ◽  
Takafumi Ootsubo ◽  
Issei Yamamura ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
The Galaxy ◽  
Infrared Spectrometer

The evolution of the z distribution of normal neutron stars in the Galaxy

2010 ◽  
Vol 331 (8) ◽  
pp. 817-831
Author(s):  
Y.-C. Wei ◽  
C.-M. Zhang ◽  
Y.-H. Zhao ◽  
Q.-H. Peng ◽  
X.-J. Wu ◽  
...  
Keyword(s):  
Neutron Stars ◽  
The Galaxy

scholarly journals Two-temperature Radiative Hot Accretion Flow around Neutron Stars

2020 ◽  
Vol 890 (2) ◽  
pp. 116 ◽  
Author(s):  
De-Fu Bu ◽  
Erlin Qiao ◽  
Xiao-Hong Yang
Keyword(s):  
Neutron Stars ◽  
Accretion Flow ◽  
Two Temperature

scholarly journals Unidentified infrared bands in the interstellar medium across the Galaxy

2003 ◽  
Vol 405 (3) ◽  
pp. 999-1012 ◽  
Author(s):  
J. Kahanpää ◽  
K. Mattila ◽  
K. Lehtinen ◽  
C. Leinert ◽  
D. Lemke
Keyword(s):  
Interstellar Medium ◽  
The Galaxy

scholarly journals Accretion onto Relativistic Objects

1974 ◽  
Vol 64 ◽  
pp. 194-212
Author(s):  
M. J. Rees
Keyword(s):  
Black Holes ◽  
Interstellar Medium ◽  
Neutron Stars ◽  
Binary Systems ◽  
Compact Object ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Compact Objects ◽  
X Ray ◽  
Intergalactic Space

The physics of spherically symmetrical accretion onto a compact object is briefly reviewed. Neither neutron stars nor stellar-mass black holes are likely to be readily detectable if they are isolated and accreting from the interstellar medium. Supermassive black holes in intergalactic space may however be detectable. The effects of accretion onto compact objects in binary systems are then discussed, with reference to the phenomena observed in variable X-ray sources.

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