SUPERSOFT X-RAY PHASE OF SINGLE DEGENERATE TYPE Ia SUPERNOVA PROGENITORS IN EARLY-TYPE GALAXIES
SUPERSOFT X-RAY PHASE OF SINGLE DEGENERATE TYPE Ia SUPERNOVA PROGENITORS IN EARLY-TYPE GALAXIES
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DOI：
10.1088/2041-8205/724/2/l212
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发表时间：
2010-10
期刊：
影响因子：
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通讯作者：
I. Hachisu;M. Kato;K. Nomoto
中科院分区：
文献类型：
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作者：
I. Hachisu;M. Kato;K. Nomoto
在Ia型超新星(SN Ia)前体的单一简并(SD)情景中，吸积白矮星(WD)预计将经历一个超软X射线源(SSS)阶段。最近，Gilfan ov&Bogdán(以下简称GB10)声称，观测到的早期类型星系的X射线通量将太低，与基于相当简单的假设的SD场景的预测不一致。我们提出了SD系统的现实演化模型，并计算了SSS阶段的持续时间。在大多数情况下，吸积的wd花了很大一部分时间在光学厚风阶段和反复出现的新星阶段，而不是SSS阶段。因此，SSS阶段只持续了几十万年。这比GB10中采用的∼要短10倍，在GB10中，假设SNIa的前身WD大部分时间都是作为社会保障人员度过的。SSS的理论X射线光度有很大的不确定性，因为质量吸积WDS的大气模型和伴星冷风物质对软X射线的吸收是不确定的。因此，我们采用现有共生SSs的观测通量的平均值，即∼0.4×1036erg S−1，能量为0.3-0.7keV。利用这些SSS持续时间和软X射线光度，我们表明，GB10观测到的X射线通量与我们基于SD情景估计的早期类型星系的X射线通量相当一致。这为SD情景提供了强有力的支持，它是早期类型星系中SNE Ia的主要贡献者。
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 & Bogdán (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 ∼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., ∼0.4 × 1036 erg s−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.