NuSTAR and Swift observations of Swift J1357.2-0933 during an early phase of its 2017 outburst

Abstract

We present a detailed spectral analysis of Swift and NuSTAR observations of the very faint X-ray transient and black hole system Swift J1357.2-0933 during an early low hard state of its 2017 outburst. Swift J1357.2-0933 was observed at $\sim$0.02% of the Eddington luminosity (for a distance of 2.3 kpc and a mass of 4 M${}_{\odot }$). Despite the low luminosity, the broadband X-ray spectrum between 0.3 and 78 keV requires the presence of a disk blackbody component with an inner disk temperature of T${}_{\mathrm{in}}$ $\sim$ 0.06 keV in addition to a thermal Comptonization component with a photon index of Γ $\sim$ 1.70. Using a more physical model, which takes strong relativistic effects into account, and assuming a high inclination of 70${}^{\circ }$, which is motivated by the presence of dips in optical light curves, we find that the accretion disk is truncated within a few RISCO from the black hole, independent of the spin.

11 pages, 5 figures, accepted for publication in ApJ

References in corpus (9)

• The role of the reflection fraction in constraining black hole spin
• A Long, Hard Look at the Low-Hard State in Accreting Black Holes
• X-ray irradiation in XTE J1817-330 and the inner radius of the truncated disc in the hard state
• Reprocessing of X-rays in the outer accretion disc of the black hole binary XTE J1817--330
• No Time for Dead Time: Timing analysis of bright black hole binaries with NuSTAR
• A Black Hole Nova Obscured by an Inner Disk Torus
• Broadband X-ray Spectra of GX 339-4 and the Geometry of Accreting Black Holes in the Hard State
• NuSTAR and XMM-Newton observations of the 2015 outburst decay of GX 339-4
• GRS 1739-278 observed at very low luminosity with XMM-Newton and NuSTAR

Cited by in corpus (3)

• The black hole X-ray transient Swift J1357.2-0933 as seen with Swift and NuSTAR during its 2017 outburst
• Puzzling Blue Dips in the Black Hole Candidate Swift J1357.2-0933, from ULTRACAM, SALT, ATCA, Swift and NuSTAR
• Global Accretion Properties of Black Hole X-Ray Binaries: A Phenomenological Perspective