期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 515, 期 3, 页码 3370-3382出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stac1768
关键词
binaries: close; stars: individual: J192054.50-200135.5; subdwarfs; white dwarfs
资金
- National Natural Science Foundation of China [12090040/3, 12125303, 11733008, 12103086]
- National Key R&D Program of China [2021YFA1600401/3]
- China Manned Space Project [CMS-CSST-2021-A10]
- Australian Research Council (ARC) [DP190100252]
- Grant Agency of the Czech Republic [GA.CR 22-34467S]
- Polish National Science Centre [UMO-2017/26/E/ST9/00703, UMO-2017/25/B/ST9/02218]
- National Aeronautics and Space Administration
- NASA Science Mission Directorate
- NASA [NAS 5-26555]
- Australian Research Council [LE130100104]
- Australian National University
- Swinburne University of Technology
- University of Queensland
- University of Western Australia
- University of Melbourne
- Curtin University of Technology
- Monash University,
- Australian Astronomical Observatory
- Astronomy Australia Limited (AAL)
- Australian Government through the Commonwealth's Education Investment Fund (EIF)
- National Collaborative Research Infrastructure Strategy (NCRIS)
- National eResearch Collaboration Tools and Resources (NeCTAR)
- Australian National Data Service Projects (ANDS)
- [RVO:67985815]
A hot subdwarf O (sdO) star and a white dwarf (WD) binary system, which has the capability of emitting low-frequency gravitational waves and possibly being the progenitor of Type Ia supernovae, has been discovered. Spectroscopy and light curve analysis provide information about the system, such as temperature, mass ratio, and disc characteristics. The binary system is believed to have originated from a common envelope ejection channel and might result in an R Coronae Borealis (R CrB) star.
Binaries consisting of a hot subdwarf star and an accreting white dwarf (WD) are sources of gravitational wave radiation at low frequencies and possible progenitors of Type Ia supernovae if the WD mass is large enough. Here, we report the discovery of the third binary known of this kind: It consists of a hot subdwarf O (sdO) star and a WD with an orbital period of 3.495 h and an orbital shrinkage of 0.1 s in 6 yr. The sdO star overfills its Roche lobe and likely transfers mass to the WD via an accretion disc. From spectroscopy, we obtain an effective temperature of T-eff = 54 240 +/- 1840 K and a surface gravity of log g = 4.841 +/- 0.108 for the sdO star. From the light curve analysis, we obtain an sdO mass of M-sdO = 0.55 M-circle dot and a mass ratio of q = M-WD/M-sdO = 0.738 +/- 0.001. Also, we estimate that the disc has a radius of similar to 0.41 R-circle dot and a thickness of similar to 0.18 R-circle dot. The origin of this binary is probably a common envelope ejection channel, where the progenitor of the sdO star is either a red giant branch star or, more likely, an early asymptotic giant branch star; the sdO star will subsequently evolve into a WD and merge with its WD companion, likely resulting in an R Coronae Borealis (R CrB) star. The outstanding feature in the spectrum of this object is strong Ca H&K lines, which are blue-shifted by similar to 200 km s(-1) and likely originate from the recently ejected common envelope, and we estimated that the remnant common envelope (CE) material in the binary system has a density similar to 6 x 10(-1)0 g cm(-3).
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