| Autor: |
Mariko Kato, Izumi Hachisu |
| Jazyk: |
angličtina |
| Rok vydání: |
2024 |
| Předmět: |
|
| Zdroj: |
The Astrophysical Journal, Vol 973, Iss 2, p 160 (2024) |
| Druh dokumentu: |
article |
| ISSN: |
1538-4357 |
| DOI: |
10.3847/1538-4357/ad6d67 |
| Popis: |
A helium nova occurs on a white dwarf (WD) accreting hydrogen-deficient matter from a helium star companion. When the mass of a helium envelope on the WD reaches a critical value, unstable helium burning ignites to trigger a nova outburst. A bright soft X-ray phase appears in an early outbursting phase of a helium nova before it optically rises toward maximum. Such an X-ray bright phase is called the X-ray flash. We present theoretical light curves of X-ray flashes for 1.0, 1.2, and 1.35 M _☉ helium novae with mass accretion rates of (1.6–7.5) × 10 ^−7 M _☉ yr ^−1 . Long durations of the X-ray flashes (100 days–10 yr) and high X-ray luminosities (∼10 ^38 erg s ^−1 ) indicate that X-ray flashes are detectable as a new type of X-ray transient or persistent X-ray sources. An X-ray flash is a precursor of optical brightening, so that the detection of X-ray flashes on helium novae enables us to plan arranged observation for optical premaximum phases that have been one of the frontiers of the study of novae. We found a candidate object of helium-burning X-ray flash from the literature on extragalactic X-ray surveys. This X-ray transient source is consistent with our X-ray flash model of a 1.35 M _⊙ WD. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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