Evidence of an X-Ray-Ultraviolet Spectral Correlation in Ultraluminous X-Ray Sources

By comparing the ratio of flux densities in the X-ray and ultraviolet (UV) wavebands by way of the spectral optical-X-ray index, ox, we explore the relation between the emissions in the respective wavebands for a number of ultraluminous X-ray sources (ULXs) with known optical counterparts. We presen...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2019-03, Vol.873 (2), p.L12
Main Authors: Sonbas, E., Dhuga, K. S., Gö ü, E.
Format: Article
Language:English
Subjects:
Accretion disks
Active galactic nuclei
Corona
Correlation
Dwarf galaxies
Galaxies
galaxies: dwarf
Luminosity
methods: data analysis
Optical counterparts (astronomy)
Slopes
Spectral correlation
stars: black holes
Ultraviolet spectra
X ray sources
X-rays: binaries
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Summary:By comparing the ratio of flux densities in the X-ray and ultraviolet (UV) wavebands by way of the spectral optical-X-ray index, ox, we explore the relation between the emissions in the respective wavebands for a number of ultraluminous X-ray sources (ULXs) with known optical counterparts. We present a significant (anti)correlation between ox and the L(2500 )-UV luminosity. In comparison with low-z active galactic nuclei (AGNs) for which a similar correlation is observed, the ULX ox indices follow a steeper slope albeit with a large uncertainty. The results are also compared with a small sample of dwarf-galaxy data consisting of a mixture of broadline candidate AGNs and "composites." A number of these sources follow the steeper slope of the ULX data, potentially hinting at an intrinsic similarity of these sources to ULXs. We are able to reproduce the general trend of the ULX correlation with the use of a multicolor accretion disk coupled to a hot corona of Comptonizing electrons.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ab0a75