Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-26T05:09:26.424Z Has data issue: false hasContentIssue false
  • English
  • Français

Soft X-Ray Spectroscopy with Exosat

Published online by Cambridge University Press:  12 April 2016

R. Mewe
R. Mewe*
Affiliation:
Laboratory for Space Research Utrecht., The Netherlands

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

With the 500 and 1000 l/mm transmission gratings aboard the European x-ray Observatory SATellite (EXOSAT) we have measured medium-resolution (Δλ 5 A at 100 A) spectra of some ten objects of various categories such as isolated white dwarfs, cool stars with convective mantles, cataclysmic variables (e.g. AM Her) and a high-luminosity X-ray source (Sco X-1).

The Instrument configuration was mostly such that one low-energy telescope was used as a photometer, while the other telescope was used as a spectrometer with the 500 l/mm grating inserted.

The white dwarf spectra were measured between about 60 and 300 A. They show a continuum with no clear evidence of aborption and emission lines except for the He II absorption edge at 227 A in the spectrum of Feige 24. For the cooler (28 000 K) white dwarf Sirius B the emission is peaked between about 100 and 160 A and limited to about 200 A. which can be expected from atmospheric model spectra of DA white dwarfs. The soft X-ray emission of the hotter (> 60 000 K) DA white dwarfs (HZ43. Feige 24) is also interpreted in terms of photospheric emission. In the HZ43 spectrum the absorption edge is apparently absent which sets a stringent upper limit to the abundance ratio He/H of about 10−5. On the other hand the spectrum of Feige 24 shows a dominant absorption edge, implying He/H > 10−3. Moreover, here the shape of the continuum may be indicative of a stratification of element abundances in the outer atmosphere.

Type
Session 3. Non-Solar Astrophysics
Information
International Astronomical Union Colloquium , Volume 86: Eighth International Colloquium on Ultraviolet and X-ray Spectroscopy of Astrophysical and Laboratory Plasmas , 1984 , pp. 59 - 66
Copyright
Copyright © Naval Research Laboratory 1984. Publication courtesy of the Naval Research Laboratory, Washington, DC.

References

Brinkman, A.C., Dijkstra, J.H., Geeriings, W.F.P.A., van Rooijen, F.A., Timmerman, C., de Korte, P.A.J.: 1980. Appl. Optics 19, 1601.CrossRefGoogle Scholar
Brinkman, A.C. et al.: 1984. to be Publ, in COSPAR proc.Google Scholar
Bues, I.: 1970. Astron. Astrophys. 7, 91.Google Scholar
Dijkstra, J.H. Lantwaard, L.J.: 1975. Opt. Commun. 15, 3.CrossRefGoogle Scholar
Dijkstra, J.H.: 1976. Space Sci. Instr. 2, 363.Google Scholar
Dijkstra, J.H. Lantwaard, L.J. Timmerman, C.: 1978. in New Instrumentation for Space Astronomy (Eds. van der Hucht, K.A.. Vaiana, G.S.). Pergamon, London, p. 257.Google Scholar
Helse, J. et al.: 1984a. in preparation.Google Scholar
Heise, J. et al.: 1984b. to be Publ, in COSPAR proc.Google Scholar
Heise, J. et al.: 1984c. to be Publ, in proc. of Bologna (July) conf.Google Scholar
Kahn, S.M., Wesemael, F., Liebert, J., Raymond, J.C., Steiner, J.E. Shipman, H.L.: 1984. Astrophys. J. 278, 255.CrossRefGoogle Scholar
Malina, R.F., Bowyer, S., Basri, G.: 1982. Astrophys. J. 262, 717.CrossRefGoogle Scholar
Mewe, R., Gronenschild, E.H.B.M.: 1981. Astron. Astrophys. Suppl. Ser. 45, 11.Google Scholar
Mewe, R.: 1984. Physica Scripta T7, 5.CrossRefGoogle Scholar
Mewe, R. Gronenschild, E.H.B.M., Oord, G.H.J. van den: 1984. submitted to Astron. Astrophys. Suppl. Ser.Google Scholar
Schnopper, H.W., Van Speybroeck, L.P., Delvaiile, J.P., Epstein, A., Kaline, E., Babrach, R.Z., Dijkstra, J., Lantwaard, L.: 1977. Appl. Opt. 16. 1088.CrossRefGoogle Scholar
Schrijver, C.J.: 1983. Astron. Astrophys. 127, 289.Google Scholar
Schrijver, C.J., Mewe, R., Walter, F.M.: 1984. Astron. Astrophys. in press.Google Scholar
Seward, F.D. et al.: 1982. Appl. Opt. 21, 2012.CrossRefGoogle Scholar
Valana, G.S. et al.: 1981. Astrophys. J. 245, 163.Google Scholar
Wesemael, F., Auer, L.H., Van Horn, H.M., Savedoff, M.P.: 1980. Astrophys. J. Suppl. 43, 159.CrossRefGoogle Scholar