A Wind-Disk Self-Irradiation Model For Supercritical Accretion

Abstract

Optical emission from actively accreting X-ray binaries is dominated by X-ray reprocessing on the outer disk. In the regime of supercritical accretion, strong radiation will power a massive wind that is optically thick and nearly spherical, and will occult the central hard X-rays from irradiating the outer disk. Instead, thermal emission from the wind will act as a new source of irradiation. Here, we construct a self-irradiation model, in which the inner disk (within the wind photosphere) is completely blocked by the wind, the middle part (between the wind photosphere and scattersphere) is heated by the wind directly, and the outer disk (beyond the wind scattersphere) is heated by photons leaving the scattersphere. The model can adequately fit the UV/optical SED of NGC 247 X-1, a candidate source with supercritical accretion, while the standard irradiation model fails to produce a self-consistent result. The best-fit parameters suggest that the source contains a stellar mass black hole with an accretion rate roughly 100 times the critical value. Remarkably, the UV/optical fitting predicts a wind photosphere that is well consistent with X-ray measurements, although it is an extrapolation over 3 orders of magnitude in wavelength. This implies that supercritical accretion does power a massive wind and the UV/optical data are useful in constraining the wind structure.

Accepted for publication in ApJ Letters

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Cited by in corpus (12)

• Ultraluminous X-ray sources
• Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1
• Thermally driven winds in ULXs
• Linking soft excess in ultraluminous X-ray sources with optically thick wind driven by supercritical accretion
• The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
• Detection of 125.5-day Optical Periodic Modulation of the Neutron Star M51 ULX-8
• Identification of a Helium Donor Star in NGC 247 ULX-1
• Optical Counterparts of ULXs in NGC 1672
• Constraining soft and hard X-ray irradiation in ultraluminous X-ray sources
• The First Glimpse of ULXs Through the Near-Infrared Images Captured by the James Webb Space Telescope
• Comprehensive X-ray and Multiwavelength Study of ULXs in NGC 1566
• Possible optical counterparts of ULXs in NGC 1672