A clean sightline to quiescence: Multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2-0933

Richard M. Plotkin, Elena Gallo, Peter G. Jonker, James C.A. Miller-Jones, Jeroen Homan, Teo Muñoz-Darias, Sera Markoff, Montserrat Armas Padilla, Rob Fender, Anthony P. Rushton, David M. Russell, Manuel A.P. Torres

Research output: Contribution to journalArticle

Abstract

We present coordinated multiwavelength observations of the high Galactic latitude (b=+50°) black holeX-ray binary (BHXB)Swift J1357.2-0933 in quiescence. Our broad-band spectrum includes strictly simultaneous radio and X-ray observations, and near-infrared, optical, and ultraviolet data taken 1-2 d later. We detect Swift J1357.2-0933 at all wavebands except for the radio (f5 GHz < 3.9 μJy beam-1; 3σrms). Given current constraints on the distance (2.3-6.3 kpc), its 0.5-10 keV X-ray flux corresponds to an Eddington ratio LX/LEdd = 4 × 10-9-3 × 10-8 (assuming a black hole mass of 10M). The broad-band spectrum is dominated by synchrotron radiation from a relativistic population of outflowing thermal electrons, which we argue to be a common signature of short-period quiescent BHXBs. Furthermore, we identify the frequency where the synchrotron radiation transitions from optically thick-to-thin (vb ≈ 2-5 × 1014 Hz), which is the most robust determination of a 'jet break' for a quiescent BHXB to date. Our interpretation relies on the presence of steep curvature in the ultraviolet spectrum, a frequency window made observable by the low amount of interstellar absorption along the line of sight. High Galactic latitude systems like Swift J1357.2-0933 with clean ultraviolet sightlines are crucial for understanding black hole accretion at low luminosities.

Original languageEnglish (US)
Pages (from-to)2707-2716
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume456
Issue number3
DOIs
StatePublished - Mar 1 2016

Keywords

  • Accretion, accretion discs
  • ISM: jets and outflows
  • Stars: individual: Swift J1357.2-0933
  • X-rays: binaries

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Plotkin, R. M., Gallo, E., Jonker, P. G., Miller-Jones, J. C. A., Homan, J., Muñoz-Darias, T., Markoff, S., Padilla, M. A., Fender, R., Rushton, A. P., Russell, D. M., & Torres, M. A. P. (2016). A clean sightline to quiescence: Multiwavelength observations of the high Galactic latitude black hole X-ray binary Swift J1357.2-0933. Monthly Notices of the Royal Astronomical Society, 456(3), 2707-2716. https://doi.org/10.1093/mnras/stv2861