{ital ORFEUS} {ital II} Far-Ultraviolet Spectroscopy of Am Herculis
- Lawrence Livermore National Laboratory, L-41, PO Box 808, Livermore, CA 94550 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Six high-resolution ({lambda}/{Delta}{lambda} {approx} 3000) far-UV ({lambda}{lambda} = 910{endash}1210 A) spectra of the magnetic cataclysmic variable AM Herculis were acquired in 1996 November during the flight of the {ital ORFEUS}-{ital SPAS} {ital II} mission. AM Her was in a high optical state at the time of the observations, and the spectra reveal emission lines of O vi {lambda}{lambda}1032, 1038, C iii {lambda}{lambda}977, 1176, and He ii {lambda}1085 superposed on a nearly flat continuum. Continuum flux variations can be described as per G{umlt a}nsicke et al. by a {approx}20 kK white dwarf with a {approx}37 kK hot spot covering a fraction {ital f} {approximately} 0.15 of the surface of the white dwarf, but we caution that the expected Lyman absorption lines are not detected. The O vi emission lines have a broad and narrow component structure similar to that of the optical emission lines, the C iii and He ii emission lines are dominated by the broad component, and the radial velocities of these lines are consistent with an origin of the narrow and broad components in the irradiated face of the secondary and the accretion funnel, respectively. The density of the narrow- and broad-line regions is {ital n}{sub nlr} {approximately} 3 {times} 10{sup 10} cm{sup {minus}3} and {ital n}{sub blr} {approximately} 1 {times} 10{sup 12} cm{sup {minus}3}, respectively, yet the narrow-line region is optically thick in the O vi line and the broad-line region is optically thin; apparently, the velocity shear in the broad-line region allows the O vi photons to escape, rendering the gas effectively optically thin. The orbital phase variations of the emission-line fluxes are unexplained. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}
- OSTI ID:
- 307222
- Journal Information:
- Astrophysical Journal, Vol. 505, Issue 2; Other Information: PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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