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Two new young, wide, magnetic + non-magnetic double-degenerate binary systems

Citation

Dobbie, PD and Baxter, R and Kulebi, B and Parker, QA and Koester, D and Jordan, S and Lodieu, N and Euchner, F, Two new young, wide, magnetic + non-magnetic double-degenerate binary systems, Monthly Notices of the Royal Astronomical Society, 421, (1) pp. 202-212. ISSN 0035-8711 (2012) [Refereed Article]

Copyright Statement

Copyright 2012 The Authors Monthly Notices of the Royal Astronomical Society Copyright 2012 RAS

DOI: doi:10.1111/j.1365-2966.2012.20291.x

Abstract

We report the discovery of two, new, rare, wide, double-degenerate binaries that each contain a magnetic and a non-magnetic star. The components of SDSS J092646.88+132134.5 + J092647.00+132138.4 and of SDSS J150746.48+521002.1 + J150746.80+520958.0 have angular separations of only 4.6 arcsec (a ∼ 650 au) and 5.1 arcsec (a ∼ 750 au), respectively. They also appear to share common proper motions. Follow-up optical spectroscopy has revealed each system to consist of a DA and a H-rich high-field magnetic white dwarf (HFMWD). Our measurements of the effective temperatures and the surface gravities of the DA components reveal both to have larger masses than is typical of field white dwarfs. By assuming that these degenerates have evolved essentially as single stars, owing to their wide orbital separations, we can use them to place limits on the total ages of the stellar systems. These suggest that in each case the HFMWD is probably associated with an early-type progenitor (Minit > 2 M⊙). We find that the cooling time of SDSS J150746.80+520958.0 (DAH) is lower than might be expected had it followed the evolutionary path of a typical single star. This mild discord is in the same sense as that observed for two of the small number of other HFMWDs for which progenitor mass estimates have been made, RE J0317-853 and EG 59. The mass of the other DAH, SDSS J092646.88+132134.5, appears to be smaller than expected on the basis of single-star evolution. If this object was/is a member of a hierarchical triple system it may have experienced greater mass loss during an earlier phase of its life as a result of its having a close companion. The large uncertainties on our estimates of the parameters of the HFMWDs suggest that a larger sample of these objects is required to firmly identify any trends in their inferred cooling times and progenitor masses. This should shed further light on their formation and on the impact magnetic fields have on the late stages of stellar evolution. To serve as a starting point, we highlight two further candidate young, wide magnetic + non-magnetic double-degenerate systems within SDSS, CBS 229 and SDSS J074853.07+302543.5 + J074852.95+302543.4, which should be subjected to detailed (resolved) spectroscopic follow-up studies.

Item Details

Item Type:Refereed Article
Keywords:binaries:general; stars: magnetic fields; white dwarfs
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Stellar Astronomy and Planetary Systems
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Dobbie, PD (Dr Paul Dobbie)
ID Code:80976
Year Published:2012
Web of Science® Times Cited:14
Deposited By:Mathematics and Physics
Deposited On:2012-11-19
Last Modified:2013-06-26
Downloads:0

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