X-ray reflection in oxygen-rich accretion discs of ultracompact X-ray binaries

O. K. Madej, Jeronimo Garcia, P. G. Jonker, M. L. Parker, R. Ross, A. C. Fabian, Jérôme Chenevez

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

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.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume442
Issue number2
Pages (from-to)1157-1165
Number of pages9
ISSN0035-8711
DOIs
Publication statusPublished - 2014

Keywords

  • ASTRONOMY
  • SOLAR-SYSTEM ABUNDANCES
  • 4U 0614+091
  • BLACK-HOLE
  • INTERSTELLAR-MEDIUM
  • SPECTRA
  • 4U-1543-624
  • ELEMENTS
  • STAR
  • SPECTROSCOPY
  • LINES
  • accretion, accretion discs
  • X-rays: binaries
  • X-ray reflection

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