期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 442, 期 2, 页码 1157-1165出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu884
关键词
accretion, accretion discs; X-rays: binaries
资金
- NASA [NNX11AD08G]
- Science and Technology Facilities Council [1233534] Funding Source: researchfish
- NASA [NNX11AD08G, 148671] Funding Source: Federal RePORTER
We present spectroscopic X-ray data of two candidate ultracompact X-ray binaries (UCXBs): 4U 0614+091 and 4U 1543-624. We confirm the presence of a broad O viii Ly alpha reflection line (at a parts per thousand 18 angstrom) using XMM-Newton and Chandra observations obtained in 2012 and 2013. The donor star in these sources is a carbon-oxygen or oxygen-neon-magnesium white dwarf. Hence, the accretion disc is enriched with oxygen which makes the O viii Ly alpha line particularly strong. Modelling the X-ray reflection off a carbon- and oxygen-enriched, hydrogen- and helium-poor disc with models assuming solar composition likely biases several of the best-fitting parameters. In order to describe the X-ray reflection spectra self-consistently, we modify the currently available xillver reflection model. We present initial grids that can be used to model X-ray reflection spectra in UCXBs with carbon-oxygen-rich (and hydrogen- and helium-poor) accretion disc. We find that the new reflection model provides a better overall description of the reflection spectra of 4U 0614+091 and 4U 1543-624 than the reflection models that assume solar abundances.
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