The kinematics of cool metal-line white dwarfs and accretion in the local interstellar medium

1985 ◽  
Vol 90 ◽  
pp. 1832 ◽  
Author(s):  
P. A. Aannestad ◽  
E. M. Sion
Keyword(s):  
Interstellar Medium ◽  
White Dwarfs ◽  
Local Interstellar Medium ◽  
Metal Line

scholarly journals The Interstellar and Circumstellar Environment of White Dwarfs

1997 ◽  
Vol 166 ◽  
pp. 69-74
Author(s):  
M.A. Barstow ◽  
P.D. Dobbie ◽  
J.B. Holberg
Keyword(s):  
Interstellar Medium ◽  
White Dwarfs ◽  
Column Density ◽  
Line Of Sight ◽  
Local Distribution ◽  
Local Interstellar Medium ◽  
Weighted Mean ◽  
Ionization Fraction ◽  
Absorbing Material ◽  
Circumstellar Environment

AbstractWe have studied the EUV spectra of 13 DA white dwarfs, observed by the EUVE satellite, paying attention to the possible sources of absorbing material along the lines-of-sight in both the local interstellar medium and in the photospheres of the stars themselves. The range of interstellar column densities seen are consistent with our previous understanding of the local distribution of material. Absorption from interstellar He II is found in the direction of five stars, allowing us to measure directly the He ionization fraction and estimate, indirectly, that of H. The weighted mean ionization fractions along these lines-of-sight are 0.27 ± 0.04 and 0.35 ± 0.1 respectively. Where He II is directly detected, the observed ionization fractions are not correlated with direction or with the volume/column density of material along the line-of-sight. Furthermore, the limits on the amount of He II established in all other directions completely encompass the range of observed values. Indeed, all the data can be consistent with more or less constant He and H ionization fractions throughout the local ISM. However, observation of very hot DA stars, indicating higher He II columns, might contradict this picture if the material is not photospheric or circumstellar.

scholarly journals White Dwarf Probes of Interstellar Deuterium

2000 ◽  
Vol 198 ◽  
pp. 485-486
Author(s):  
Wayne Landsman
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accurate Determination ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Space Telescope ◽  
Imaging Spectrograph

We review the advantages of using hot white dwarfs (WDs) as probes of the deuterium abundance in the local interstellar medium. We then discuss advantages of the Space Telescope Imaging Spectrograph (STIS) for such observations, as compared with earlier observations with the Goddard High Resolution Spectrograph (GHRS). The GHRS Ly α profile of the white dwarf HZ 43 is probably modified by the hot ‘hydrogen wall’ surrounding the Sun; but despite this complication, the sightline remains a promising one for an accurate determination of the deuterium abundance in the local interstellar medium.

Kinematical Structure of the Local Interstellar Medium: The Galactic Center Hemisphere

1997 ◽  
Vol 484 (2) ◽  
pp. 761-778 ◽  
Author(s):  
Ricardo Genova ◽  
John E. Beckman ◽  
Stuart Bowyer ◽  
Thomas Spicer
Keyword(s):  
Interstellar Medium ◽  
Galactic Center ◽  
Local Interstellar Medium
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