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The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9.
- Source :
-
Monthly Notices of the Royal Astronomical Society . May2017, Vol. 467 Issue 2, p2199-2216. 18p. - Publication Year :
- 2017
-
Abstract
- 47 Tuc X9 is a low-mass X-ray binary (LMXB) in the globular cluster 47 Tucanae and was previously thought to be a cataclysmic variable. However, Miller-Jones et al. recently identified a radio counterpart to X9 (inferring a radio/X-ray luminosity ratio consistent with black hole LMXBs) and suggested that the donor star might be a white dwarf. We report simultaneous observations of X9 performed by Chandra, NuSTAR and Australia Telescope Compact Array. We find a clear 28.18 ± 0.02-min periodic modulation in the Chandra data, which we identify as the orbital period, confirming this system as an ultracompact X-ray binary. Our X-ray spectral fitting provides evidence for photoionized gas having a high oxygen abundance in this system, which indicates a C/O white dwarf donor. We also identify reflection features in the hard X-ray spectrum, making X9 the faintest LMXB to show X-ray reflection. We detect an ∼6.8-d modulation in the X-ray brightness by a factor of 10, in archival Chandra, Swiftand ROSAT data. The simultaneous radio/X-ray flux ratio is consistent with either a black hole primary or a neutron star primary, if the neutron star is a transitional millisecond pulsar. Considering the measured orbital period (with other evidence of a white dwarf donor) and the lack of transitional millisecond pulsar features in the X-ray light curve, we suggest that this could be the first ultracompact black hole X-ray binary identified in our Galaxy. [ABSTRACT FROM AUTHOR]
- Subjects :
- *X-ray binaries
*BLACK holes
*NEUTRON stars
*PULSARS
*GALAXIES
Subjects
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 467
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 129380252
- Full Text :
- https://doi.org/10.1093/mnras/stx166