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The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9

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dc.contributor.authorBahramian, Arash
dc.contributor.authorHeinke, Craig O.
dc.contributor.authorTudor, Vlad
dc.contributor.authorMiller-Jones, James. C. A.
dc.contributor.authorBogdanov, Slavko
dc.contributor.authorMaccarone, Thomas J.
dc.contributor.authorKnigge, C.
dc.contributor.authorSivakoff, Gregory Robert
dc.contributor.authorChomiuk, Laura
dc.contributor.authorStrader, Jay
dc.contributor.authorGarcia, Javier A.
dc.contributor.authorKallman, Timothy
dc.date.accessioned2025-05-01T12:26:51Z
dc.date.available2025-05-01T12:26:51Z
dc.date.issued2017-01-01
dc.description47 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.
dc.identifier.doihttps://doi.org/10.7939/r3-k559-k505
dc.language.isoen
dc.relationhttps://doi.org/10.1093/mnras/stx166
dc.relation.isversionofBahramian, Arash., Heinke, Craig O., Tudor, Vlad., Miller-Jones, James. C. A., Bogdanov, Slavko., Maccarone, Thomas J., Knigge, C., Sivakoff, Gregory Robert., Chomiuk, Laura., Strader, Jay., Garcia, Javier A., & Kallman, Timothy. (2017). The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9. Monthly Notices of the Royal Astronomical Society, 467(2), 2199-2216. https://doi.org/10.1093/mnras/stx166
dc.rightsThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
dc.subjectGlobular Clusters: Individual: 47 Tuc
dc.subjectStars: Neutron
dc.subjectAccretion
dc.subjectStars: Black Holes
dc.subjectAccretion Discs
dc.subjectX-Rays: Binaries
dc.titleThe ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9
dc.typehttp://purl.org/coar/resource_type/c_6501 http://purl.org/coar/version/c_970fb48d4fbd8a85
ual.jupiterAccesshttp://terms.library.ualberta.ca/public

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