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Title:
Ultraviolet Spectroscopy of BL Hyi and EF Eri in High and Intermediate States
Authors:
Sanad, M. R.; Abdel-Sabour, M. A.
Affiliation:
AA(Astronomy Department, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt), AB(Astronomy Department, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt; Department of Physics and Astronomy, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia)
Publication:
The Astronomical Journal, Volume 152, Issue 2, article id. 37, 10 pp. (2016). (AJ Homepage)
Publication Date:
08/2016
Origin:
IOP
Astronomy Keywords:
line: profiles, stars: individual: BL Hyi, EF Eri, ultraviolet: stars, white dwarfs
DOI:
10.3847/0004-6256/152/2/37
Bibliographic Code:
2016AJ....152...37S

Abstract

We present the first phase-resolved ultraviolet spectroscopy of two polar systems, BL Hyi and EF Eri, in high and intermediate states from the International Ultraviolet Explorer (IUE) during the periods between 1982-1995 and 1979-1991, respectively. The flux curves for the C IV and He II emission lines for both systems showing variations in their fluxes at different orbital phases are presented. The emission lines are produced in the accretion stream. The reddening for the two polars is found to be 0.00. Our results show that there are variations of the line fluxes with time, similar to the light curves found for both BL Hyi and EF Eri in the optical, infrared, ultraviolet, and X-ray bands. IUE observations support a radiative shock model of BL Hyi with the heating of matter by radiation from the accretion shock and cooling by the electrons scattering off ultraviolet photons from the surface of the white dwarf. EF Eri observations support a two-temperature white dwarf model producing sufficient ultraviolet flux for orbital modulations.
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