Ultraviolet spectroscopy of V Sagittae in high, intermediate and low states from HST and IUE satellites
Abstract
We present the first phase resolved ultraviolet spectroscopic study of V Sge in high, intermediate and low states observed with the Hubble Space Telescope High Resolution Spectrograph (HST HRS) and International Ultraviolet Explorer (IUE) during the period 1978-1996 to diagnose the ultraviolet fluxes of C IV 1550 Å and He II 1640 Å emission lines originating in the accretion disk during different orbital phases. Different spectra showing the variations in line fluxes at different orbital phases are presented. The reddening of V Sge is determined from the 2200 Å feature. We concentrated on calculating the line fluxes of C IV & He II emission lines. From HST and IUE data, we derived an accretion luminosity and an accretion rate for V Sge. The average temperature of the outer rim of the accretion disk {∼}10000 K. Our results show that there are variations in line fluxes, accretion luminosities and accretion rates with time for V Sge. These variations are attributed to the variations of both density and temperature as a result of a changing rate of mass transfer from the secondary star to the white dwarf. These results from the HST and IUE observations are consistent with the binary model consisting of a white dwarf, a disk around the white dwarf, and a lobe-filling main-sequence companion (Hachisu & Kato, Astrophys. J. 598:527H, 2003).
- Publication:
-
Astrophysics and Space Science
- Pub Date:
- November 2015
- DOI:
- 10.1007/s10509-015-2542-x
- Bibcode:
- 2015Ap&SS.360...31S
- Keywords:
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- Binaries: close;
- Cataclysmic variables;
- Accretion;
- accretion disk;
- Stars: Individual: (V Sagittae);
- Ultraviolet: stars