Accretion Rates and Beaming in Ultraluminous X-ray Sources

Abstract

I show that extreme beaming factors $b$ are not needed to explain ULXs as stellar--mass binaries. For neutron star accretors one typically requires $b\sim 0.13$, and for black holes almost no beaming ($b\sim 0.8$). The main reason for the high apparent luminosity is the logarithmic increase in the limiting luminosity for super--Eddington accretion. The required accretion rates are explicable in terms of thermal--timescale mass transfer from donor stars of mass $6 - 10\msun$, or possibly transient outbursts. Beaming factors $\la 0.1$ would be needed to explain luminosities significantly above $10^{40}{L}_{40}$ erg s${}^{-1}$, but these requirements are relaxed somewhat if the accreting matter has low hydrogen content.

MNRAS Letters, in press

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• A Population of Ultraluminous X-ray Sources with An Accreting Neutron Star
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• Milliarcsec-scale radio emission of ultraluminous X-ray sources: steady jet emission from an intermediate-mass black hole?
• Orbital decay in M82 X-2
• X-ray emission from BH+O star binaries expected to descend from the observed galactic WR+O binaries
• Combined Analysis of Hubble and VLT Photometry of the Intermediate Mass Black Hole ESO 243-49 HLX-1
• Population synthesis on high-mass X-ray binaries: prospects and constraints from the universal X-ray luminosity function
• Associated Spectral and Temporal State Transition of the bright ULX NGC1313 X-1
• Formation and Evolution of Ultraluminous X-ray Pulsar Binaries to Pulsar-Neutron Star and Pulsar-White Dwarf Systems
• ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole mass determination
• X-Ray Spectroscopy of Newly Identified ULXs Associated With M87's Globular Cluster Population
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• Possible Periodic Dips in the Pulsating Ultraluminous X-ray Source M51 ULX-7
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• Broad and Luminous [OIII] and [NII] in Globular Cluster ULXs
• AT2018lqh: Black Hole Born from a Rotating Star?
• Spitzer IRAC observations of IR excess in Holmberg IX X-1: A circumbinary disk or a variable jet?
• Constraining the mass of accreting black holes in ultraluminous X-ray sources with ultrafast outflows
• Simultaneous NICER and NuSTAR observations of the Ultraluminous source NGC 4190 ULX-1
• Investigation of the timing and spectral properties of an Ultra-luminous X-ray pulsar NGC 7793 P13
• Mid-Infrared and X-ray luminosity correlations of X-ray point sources in NGC 1399
• Observational limits on the X-ray emission from the bubble nebula surrounding Ho IX X-1
• Multiwavelength modeling the SED of Luminous Supersoft X-ray Sources in Large Magellanic Cloud and Small Magellanic Cloud