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Detection of accretion X-rays from QS Vir : cataclysmic or a lot of hot air?
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Matranga, Marco, Drake, Jeremy J., Kashyap, Vinay and Steeghs, D. (2012) Detection of accretion X-rays from QS Vir : cataclysmic or a lot of hot air? The Astrophysical Journal, Vol.747 (No.2). p. 132. doi:10.1088/0004-637X/747/2/132 ISSN 0004-637X.
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WRAP_Steeghs_Detaection_1201.2682v1.pdf - Accepted Version Download (318Kb) | Preview |
Official URL: http://dx.doi.org/10.1088/0004-637X/747/2/132
Abstract
An XMM-Newton observation of the nearby "pre-cataclysmic" short-period (P orb = 3.62 hr) binary QS Vir (EC 13471-1258) revealed regular narrow X-ray eclipses when the white dwarf passed behind its M2-4 dwarf companion. The X-ray emission provides a clear signature of mass transfer and accretion onto the white dwarf. The low-resolution XMM-Newton EPIC spectra are consistent with a cooling flow model and indicate an accretion rate of yr–1. At 48 pc distant, QS Vir is then the second nearest accreting cataclysmic variable known, with one of the lowest accretion rates found to date for a non-magnetic system. To feed this accretion through a wind would require a wind mass-loss rate of yr–1 if the accretion efficiency is of the order of 10%. Consideration of likely mass-loss rates for M dwarfs suggests this is improbably high and pure wind accretion unlikely. A lack of accretion disk signatures also presents some difficulties for direct Roche lobe overflow. We speculate that QS Vir is on the verge of Roche lobe overflow, and that the observed mass transfer could be supplemented by upward chromospheric flows on the M dwarf, analogous to spicules and mottles on the Sun, that escape the Roche surface to be subsequently swept up into the white dwarf Roche lobe. If so, QS Vir would be in a rare evolutionary phase lasting only a million years. The X-ray luminosity of the M dwarf estimated during primary eclipse is LX = 3 × 1028 erg s–1, which is consistent with that of rapidly rotating "saturated" K and M dwarfs.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QB Astronomy | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Library of Congress Subject Headings (LCSH): | Cataclysmic variable stars | ||||
Journal or Publication Title: | The Astrophysical Journal | ||||
Publisher: | Institute of Physics Publishing Ltd. | ||||
ISSN: | 0004-637X | ||||
Official Date: | 2012 | ||||
Dates: |
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Volume: | Vol.747 | ||||
Number: | No.2 | ||||
Page Range: | p. 132 | ||||
DOI: | 10.1088/0004-637X/747/2/132 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Date of first compliant deposit: | 21 December 2015 | ||||
Date of first compliant Open Access: | 21 December 2015 | ||||
Funder: | United States. National Aeronautics and Space Administration (NASA) | ||||
Grant number: | NNG06GD34G (NASA), NAS8-39073 (NASA) |
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