SUPERSOFT X-RAY PHASE OF SINGLE DEGENERATE TYPE Ia SUPERNOVA PROGENITORS IN EARLY-TYPE GALAXIES
- Department of Earth Science and Astronomy, College of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902 (Japan)
- Department of Astronomy, Keio University, Hiyoshi 4-1-1, Kouhoku-ku, Yokohama 223-8521 (Japan)
- Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8583 (Japan)
In the single degenerate (SD) scenario for Type Ia supernova (SN Ia) progenitors, an accreting white dwarf (WD) is expected to undergo a supersoft X-ray source (SSS) phase. Recently, Gilfanov and Bogdan (hereafter GB10) claimed that observed X-ray fluxes of early-type galaxies would be too low to be consistent with the prediction of the SD scenario based on rather simple assumptions. We present realistic evolutionary models of SD systems and calculate durations of SSS phases. In most cases, accreting WDs spend a large fraction of time in the optically thick wind phase and the recurrent nova phase rather than the SSS phase. Thus, the SSS phase lasts only for a few hundred thousand years. This is by a factor of {approx}10 shorter than those adopted by GB10 where the SN Ia progenitor WD was assumed to spend most of its life as an SSS. The theoretical X-ray luminosity of the SSS has a large uncertainty because of the uncertain atmospheric model of mass-accreting WDs and absorption of soft X-rays by the companion star's cool wind material. We thus adopt an average of the observed fluxes of existing symbiotic SSSs, i.e., {approx}0.4 x 10{sup 36} erg s{sup -1} for 0.3-0.7 keV. Using these SSS duration and soft X-ray luminosity, we show that the observed X-ray flux obtained by GB10 is rather consistent with our estimated flux in early-type galaxies based on the SD scenario. This provides strong support for the SD scenario as a main contributor of SNe Ia in early-type galaxies.
- OSTI ID:
- 21452634
- Journal Information:
- Astrophysical Journal Letters, Vol. 724, Issue 2; Other Information: DOI: 10.1088/2041-8205/724/2/L212; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ABSORPTION
COSMIC X-RAY SOURCES
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
SOFT X RADIATION
SUPERNOVAE
WHITE DWARF STARS
BINARY STARS
COSMIC RAY SOURCES
DWARF STARS
ELECTROMAGNETIC RADIATION
ERUPTIVE VARIABLE STARS
EVOLUTION
IONIZING RADIATIONS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SORPTION
STARS
VARIABLE STARS
X RADIATION