Kupfer, T., van Roestel, J., Brooks, J. et al. (19 more authors) (2017) PTF1 J082340.04+081936.5: A hot subdwarf B star with a low-mass white dwarf companion in an 87-minute orbit. Astrophysical Journal, 835 (2). 131. ISSN 0004-637X
Abstract
We present the discovery of the hot subdwarf B star (sdB) binary PTF1 J082340.04+081936.5. The system has an orbital period of P orb = 87.49668(1) minutes (0.060761584(10) days), making it the second-most compact sdB binary known. The light curve shows ellipsoidal variations. Under the assumption that the sdB primary is synchronized with the orbit, we find a mass of M sdB = 0.45 +0.09 -0.07 M ⊙ , a companion white dwarf mass of M WD = 0.46 + 0.12 -0.09 M ⊙ , and a mass ratio of q = M WD /M sdB = 1.03 +0.10 -0.08 . The future evolution was calculated using the MESA stellar evolution code. Adopting a canonical sdB mass of M sdB = 0.47 M ⊙ , we find that the sdB still burns helium at the time it will fill its Roche lobe if the orbital period was less than 106 minutes at the exit from the last common envelope (CE) phase. For longer CE exit periods, the sdB will have stopped burning helium and turned into a C/O white dwarf at the time of contact. Comparing the spectroscopically derived log g and T eff with our MESA models, we find that an sdB model with a hydrogen envelope mass of 5 × 10 -4 M ⊙ matches the measurements at a post-CE age of 94 Myr, corresponding to a post-CE orbital period of 109 minutes, which is close to the limit to start accretion while the sdB is still burning helium.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017 The American Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | binaries: close; stars: individual (PTF1 J082340.04+081936.5); subdwarfs; white dwarfs |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 14 Dec 2016 16:22 |
Last Modified: | 22 Feb 2018 12:32 |
Published Version: | https://doi.org/10.3847/1538-4357/835/2/131 |
Status: | Published |
Publisher: | American Astronomical Society / IOP Publishing |
Refereed: | Yes |
Identification Number: | 10.3847/1538-4357/835/2/131 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:109196 |