Extreme ultraviolet observations of G191-B2B and the local interstellar medium with the Hopkins Ultraviolet Telescope

1993 ◽  
Vol 404 ◽  
pp. 663 ◽  
Author(s):  
Randy A. Kimble ◽  
Arthur F. Davidsen ◽  
William P. Blair ◽  
Charles W. Bowers ◽  
W. Van Dyke Dixon ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Extreme Ultraviolet ◽  
Local Interstellar Medium ◽  
Ultraviolet Observations

High-resolution Na I Observations of the Local Interstellar Medium

1991 ◽  
Vol 9 (1) ◽  
pp. 122-123
Author(s):  
Barry Y. Welsh ◽  
Peter W. Vedder ◽  
John V. Vallerga
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Column Density ◽  
Velocity Structure ◽  
Extreme Ultraviolet ◽  
Sodium Absorption ◽  
Local Interstellar Medium ◽  
Neutral Gas ◽  
Hydrogen Column Density ◽  
Early Type Stars

AbstractWe present high-resolution absorption measurements (R ~ 150 000) of the interstellar Na I D-lines at 5890 Å observed towards 46 early-type stars. The distance to these stars ranges from 20–200 pc, allowing a probe of the local interstellar medium (LISM). The velocity structure, velocity dispersions and column densities of the various cloud components have been derived using an absorption line-fitting analysis. Sodium column densities have been determined for 23 of the 46 target stars. No sodium absorption was detected towards any of the stars with distances < 43 pc. Such null results imply a corresponding hydrogen column density limit, N(H), of ~ 2.5 × 1018cm−2 in many directions in the LISM. For three exceptionally vacant lines of sight (to β CMa, 36 Lyn and η Hya) this limit of low hydrogen column density can be placed out to a much further distance of > 150 pc.We have plotted the distribution of sodium column density in the LISM for a total of 118 stars in the form of three galactic maps. These maps qualitatively show that the present picture of the LISM, in which the first 50 pc is essentially free of dense clumps of neutral gas, is correct. Our map of sodium columns for stars with distances > 100 pc shows that the region within the galactic quadrant defined by 200° < l < 270° shows a conspicuous absence of any significant concentration of neutral gas. This region will be a prime direction of study for forthcoming soft X-ray and extreme ultraviolet satellite experiments.

scholarly journals Extreme Ultraviolet Observations of Hot White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 66-85 ◽  
Author(s):  
Stuart Bowyer
Keyword(s):  
Interstellar Medium ◽  
White Dwarfs ◽  
Thermal Emission ◽  
Extreme Ultraviolet ◽  
Upper Atmosphere ◽  
Wavelength Band ◽  
Upper Limits ◽  
Effective Temperatures ◽  
Ultraviolet Observations ◽  
The Universe

The term extreme ultraviolet (EUV or XUV) is employed in upper atmosphere physics and in solar work where it usually denotes the wavelength band between 100 and 1000 Å. Since thermal emission with 30,000 ≲ T ≲ 300,000 K peaks in this band, it might be expected that studies at these wavelengths would be especially useful for objects with effective temperatures in this range. In fact9 few such studies have been carried out. The reason for this anomaly is that very few EUV studies have been made at all, particularly because of unreasonably pessimistic estimates of the opacity of the interstellar medium and partially because of instrumental difficulties encountered at these wavelengths. The first search for extreme ultraviolet emitting objects was carried out in 1975 with instrumentation on the Apollo spacecraft in the Apollo-Soyuz mission. Four of approximately thirty preselected objects were detected with this instrumentation. The objects detected unquestionably are more a reflection of the prejudices of the investigators than they are a sampling of the contents of the universe. Nonetheless, two of the four objects detected were hot white dwarfs: HZ 43 and Feige 24. In addition, upper limits which turned out to be extremely useful were obtained on the Sirius A/B system. These results, plus more recent results obtained on hot white dwarfs will be discussed in this review.

Measuring EUV Line Emission from the Hot Interstellar Medium

1984 ◽  
Vol 81 ◽  
pp. 348-352
Author(s):  
Simon Labov ◽  
Christopher Martin ◽  
Stuart Bowyer
Keyword(s):  
Interstellar Medium ◽  
Extreme Ultraviolet ◽  
Line Emission ◽  
Grazing Incidence ◽  
Resolving Power ◽  
Sounding Rocket ◽  
Local Interstellar Medium ◽  
Diffuse Emission ◽  
Hot Gas ◽  
Under Construction

AbstractIn the local interstellar medium, the presence of hot gas (log T ~ 5 to 6) has been inferred from measurements of oxygen VI absorption in the ultraviolet, and from diffuse emission in the extreme ultraviolet (EUV) and soft X-ray regions. Here we describe a spectrometer that is very sensitive to gas in this temperature range. The spectrometer uses an array of plane-ruled gratings at grazing incidence in the extreme off plane mount. A set of Kirkpatrick-Baez mirrors focuses the conically diffracted light on to one of two microchannel plate detectors. The field of view of the instrument is 0.2° by 12°. The predicted sensitivity ranges from 50 to 200 ph/(cm2 sec str) with a resolving power (λ/Δλ) of 15 to 50 over the 50 to 700A wavelength band. The instrument is currently under construction for a sounding rocket flight.

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