The Origin of the Ultraluminous X-Ray Sources

Recently, several ultraluminous X-ray (ULX) sources were shown to host a neutron star (NS) accretor. We perform a suite of evolutionary calculations, which show that, in fact, NSs are the dominant type of ULX accretor. Although black holes (BH) dominate early epochs after the star-formation burst, N...

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Bibliographic Details
Published in:The Astrophysical journal 2017-09, Vol.846 (1), p.17
Main Authors: Wiktorowicz, Grzegorz, Sobolewska, Ma gorzata, Lasota, Jean-Pierre, Belczynski, Krzysztof
Format: Article
Language:English
Subjects:
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BLACK HOLES
COSMIC X-RAY SOURCES
LUMINOSITY
MAIN SEQUENCE STARS
METALLICITY
methods: statistical
NEUTRON STARS
Physics
Red giant stars
Star & galaxy formation
Star formation
stars: black holes
stars: neutron
STATISTICS
Stellar evolution
X ray sources
X-rays: binaries
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Summary:Recently, several ultraluminous X-ray (ULX) sources were shown to host a neutron star (NS) accretor. We perform a suite of evolutionary calculations, which show that, in fact, NSs are the dominant type of ULX accretor. Although black holes (BH) dominate early epochs after the star-formation burst, NSs outweigh them after a few 100 Myr and may appear as late as a few gigayears after the end of the star-formation episode. If star formation is a prolonged and continuous event (i.e., not a relatively short burst), NS accretors dominate the ULX population at any time in the solar metallicity environment, whereas BH accretors dominate when the metallicity is sub-solar. Our results show a very clear (and testable) relation between the companion/donor evolutionary stage and the age of the system. A typical NSULX consists of a NS and Red Giant. A typical BH ULX consists of a BH and main-sequence star. Additionally, we find that the very luminous ULXs ( erg s−1) are predominantly BH systems ( ) with Hertzsprung-gap donors ( ). Nevertheless, some NSULX systems may also reach extremely high X-ray luminosities ( 1041 erg s−1).
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aa821d