First X-ray polarization measurement confirms the low black-hole spin in LMC X-3

Abstract

X-ray polarization is a powerful tool to investigate the geometry of accreting material around black holes, allowing independent measurements of the black hole spin and orientation of the innermost parts of the accretion disk. We perform the X-ray spectro-polarimetric analysis of an X-ray binary system in the Large Magellanic Cloud, LMC X-3, that hosts a stellar-mass black hole, known to be persistently accreting since its discovery. We report the first detection of the X-ray polarization in LMC X-3 with the Imaging X-ray Polarimetry Explorer, and find the average polarization degree of 3.2% +- 0.6% and a constant polarization angle -42 deg +- 6 deg over the 2-8 keV range. Using accompanying spectroscopic observations by NICER, NuSTAR, and the Neil Gehrels Swift observatories, we confirm previous measurements of the black hole spin via the X-ray continuum method, a ~ 0.2. From polarization analysis only, we found consistent results with low black-hole spin, with an upper limit of a < 0.7 at a 90% confidence level. A slight increase of the polarization degree with energy, similar to other black-hole X-ray binaries in the soft state, is suggested from the data but with a low statistical significance.

14 pages, 8 figures, submitted to ApJ

References in corpus (11)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Modelling the behaviour of accretion flows in X-ray binaries
• A distance to the Large Magellanic Cloud that is precise to one per cent
• An Empirical Background Model for the NICER X-ray Timing Instrument
• ixpeobssim: a Simulation and Analysis Framework for the Imaging X-ray Polarimetry Explorer
• Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
• Thermal disc emission from a rotating black hole: X-ray polarization signatures
• Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-Timing Analysis
• Polarized X-rays from windy accretion in Cygnus X-1
• X-ray Polarimetry as a Tool to Measure the Black Hole Spin in Microquasars: Simulations of IXPE Capabilities
• Accretion Disc Evolution in GRO J1655-40 and LMC X-3 with Relativistic and Non-Relativistic Disc Models

Cited by in corpus (7)

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• X-ray polarization from accretion disk winds
• The population of NuSTAR Black Hole X-ray Binaries
• Investigating the consistency of the shape and flux of X-ray reflection spectra in the hard state with an accretion disk reaching close to the black hole
• Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray Observations