期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 437, 期 2, 页码 1681-1697出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt2007
关键词
binaries: close; binaries: eclipsing; binaries: spectroscopic; stars: individual: 1SWASP J024743.37-251549.2; stars: individual: EL CVn
资金
- European Research Council under the European Community [227224 (PROSPERITY)]
- Research Council of the University of Leuven [GOA/2013/012]
- Science and Technology Facilities Council [ST/I001719/1, ST/J001384/1]
- Deutsche Forschungsgemeinschaft (DFG) [HE1356/49-1, HE1356/62-1]
- STFC [ST/J000035/1, PP/F000065/1, PP/D000955/1, PP/F000057/1, ST/J001651/1, ST/I001719/1, ST/J001384/1, ST/G002355/1, ST/H005307/1] Funding Source: UKRI
- Science and Technology Facilities Council [PP/F000065/1, ST/J001651/1, ST/H005307/1, PP/F000057/1, ST/J000035/1, PP/D000955/1, ST/G002355/1] Funding Source: researchfish
The star 1SWASP J024743.37-251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP 0247-25 B). The remnant is in a rarely observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low mass white dwarf composed almost entirely of helium, i.e. it is a pre-helium white dwarf (pre-He-WD). We have used the photometric database from the Wide Angle Search for Planets (WASP) to find 17 eclipsing binary stars with orbital periods P = 0.7-2.2 d with similar light curves to 1SWASP J024743.37-251549.2. The only star in this group previously identified as a variable star is the brightest one, EL CVn, which we adopt as the prototype for this class of eclipsing binary star. The characteristic light curves of EL CVn-type stars show a total eclipse by an A-type dwarf star of a smaller, hotter star and a secondary eclipse of comparable depth to the primary eclipse. We have used new spectroscopic observations for six of these systems to confirm that the companions to the A-type stars in these binaries have very low masses (approximate to 0.2 M-circle dot). This includes the companion to EL CVn which was not previously known to be a pre-He-WD. EL CVn-type binary star systems will enable us to study the formation of very low mass white dwarfs in great detail, particularly in those cases where the pre-He-WD star shows non-radial pulsations similar to those recently discovered in WASP0247-25 B.
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