Low metallicity natal environments and black hole masses in Ultraluminous X-ray Sources - Astrophysics > High Energy Astrophysical PhenomenaReport as inadecuate




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Abstract: We review the available estimates of the masses of the compact object inUltraluminous X-ray Sources ULXs and critically reconsider the stellar-massversus intermediate-mass black hole interpretations. Black holes of severalhundreds to thousands of $M \odot$ are not required for the majority of ULXs,although they might be present in the handful of known hyper-luminous $\sim10^{41}$ erg s$^{-1}$ objects and-or some sources showing timing features intheir power density spectra. At the same time, however, stellar mass BHs may bequite a reasonable explanation for ULXs below $\sim 10^{40}$ erg s$^{-1}$, butthey need super-Eddington accretion and some suitable dependence of the beamingfactor on the accretion rate in order to account for ULXs above thisisotropic luminosity. We investigate in detail a -third way- in which aproportion of ULXs contain $\approx 30-90 M \odot$ black holes formed in a lowmetallicity environment and accreting in a slightly critical regime and findthat it can consistently account for the properties of bright ULXs. Surveys ofULX locations looking for a statistically meaningful relationship between ULXposition, average luminosity and local metallicity will provide a definitivetest of our proposal.



Author: L. Zampieri, T. P. Roberts

Source: https://arxiv.org/



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