Clockwise evolution in the hardness-intensity diagram of the black hole X-ray binary Swift J1910.2-0546

Payaswini Saikia, David M. Russell, Saarah F. Pirbhoy, M. C. Baglio, D. M. Bramich, Kevin Alabarta, Fraser Lewis, Phil Charles

Research output: Contribution to journalArticlepeer-review


We present a detailed study of optical data from the 2012 outburst of the candidate black hole X-ray binary Swift J1910.2-0546 using the Faulkes Telescope and Las Cumbres Observatory (LCO). We analyse the peculiar spectral state changes of Swift J1910.2-0546 in different energy bands, and characterize how the optical and UV emission correlates with the unusual spectral state evolution. Using various diagnostic tools like the optical/X-ray correlation and spectral energy distributions, we disentangle the different emission processes contributing towards the optical flux of the system. When Swift J1910.2-0546 transitions to the pure hard state, we find significant optical brightening of the source along with a dramatic change in the optical colour due to the onset of a jet during the spectral state transition. For the rest of the spectral states, the optical/UV emission is mostly dominated by an X-ray irradiated disc. From our high cadence optical study, we have discovered a putative modulation. Assuming that this modulation arises from a superhump, we suggest Swift J1910.2-0546 to have an orbital period of 2.25-2.47 h, which would make it the shortest orbital period black hole X-ray binary known to date. Finally, from the state transition luminosity of the source, we find that the distance to the source is likely to be ∼4.5-20.8 kpc, which is also supported by the comparative position of the source in the global optical/X-ray correlation of a large sample of black hole and neutron star X-ray binaries.

Original languageEnglish (US)
Pages (from-to)4543-4553
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Sep 2023


  • ISM: jets and outflows
  • X-rays: individual: Swift J1910.2-0546
  • accretion, accretion discs
  • black hole physics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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