English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

47 Tuc X9 is a low mass X-ray binary (LMXB) in the globular cluster 47Tucanae, and was previously thought to be a cataclysmic variable. However,Miller-Jones et al. (2015) 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 reportsimultaneous observations of X9 performed by Chandra, Nustar and AustraliaTelescope Compact Array. We find a clear 28.18$\pm$0.02 min periodic modulationin the Chandra data, which we identify as the orbital period, confirming thissystem as an ultracompact X-ray binary. Our X-ray spectral fitting providesevidence for photoionized gas having a high oxygen abundance in this system,which indicates a C/O white dwarf donor. We also identify reflection featuresin the hard X-ray spectrum, making X9 the faintest LMXB to show X-rayreflection. We detect a $\sim$ 6.8 day modulation in the X-ray brightness by afactor of 10, in archival Chandra, Swift, and Rosat data. The simultaneousradio/X-ray flux ratio is consistent with either a black hole primary or aneutron star primary, if the neutron star is a transitional millisecond pulsar.Considering the measured orbital period (with other evidence of a white dwarfdonor), and the lack of transitional millisecond pulsar features in the X-raylight curve, we suggest that this could be the first ultracompact black holeX-ray binary identified in our Galaxy.

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