X-ray detectability of accreting isolated black holes in our Galaxy. Issue 1 (15th March 2018)

• Record Type: Journal Article
• Authors: Tsuna, Daichi; Kawanaka, Norita; Totani, Tomonori
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 477:Issue 1(2018)
• Page Start: 791
• Page End: 801
• Publication Date: 2018-03-15
• Subjects: accretion, accretion discs -- black hole physics -- Galaxy: general -- X-rays: ISM -- X-rays: stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty699
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: Detectability of isolated black holes (IBHs) without a companion star but emitting X-rays by accretion from dense interstellar medium (ISM) or molecular cloud gas is investigated. We calculate orbits of IBHs in the Galaxy to derive a realistic spatial distribution of IBHs for various mean values of kick velocity at their birth υavg . X-ray luminosities of these IBHs are then calculated considering various phases of ISM and molecular clouds for a wide range of the accretion efficiency λ (a ratio of the actual accretion rate to the Bondi rate) that is rather uncertain. It is found that detectable IBHs mostly reside near the Galactic Centre (GC), and hence taking the Galactic structure into account is essential. In the hard X-ray band, where identification of IBHs from other contaminating X-ray sources may be easier, the expected number of IBHs detectable by the past survey by NuSTAR towards GC is at most order unity. However, 30–100 IBHs may be detected by the future survey by FORCE with an optimistic parameter set of υavg = 50 km s −1 and λ = 0.1, implying that it may be possible to detect IBHs or constrain the model parameters.