Optical Counterpart to the Ultraluminous X-Ray Source in the UGC6456 Galaxy

Abstract

We report the identification of the optical counterpart to the transient ultraluminuos X-ray source in the blue dwarf galaxy UGC6456 (VII Zw 403). The source is highly variable in both the X-ray (more 100 times, 0.3-10 keV) and optical (more 3 times, V band) ranges. The peak X-ray luminosity of UGC6456 ULX exceeds $10^{40}$ erg/s; the absolute magnitude when the source is optically bright is M${}_V=-8.24\pm 0.11$, which makes this source one of the brightest ULXs in the optical range. We found a correlation between the optical and X-ray fluxes (with a coefficient of $0.9\pm 0.3$), which may indicate that the optical emission is produced by re-processing of the X-rays in outer parts of the optically-thick wind coming from the supercritical accretion disk. Optical spectra of UGC6456 ULX show broad and variable hydrogen and helium emission lines, which also confirms the presence of the strong wind.

arXiv comment5 pages, 3 figure, 1 table. Published in The Astrophysical Journal Letters

References in corpus (25)

• Gaia Data Release 2. Summary of the contents and survey properties
• An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
• Cosmicflows-2: The Data
• The Nature of Accreting Black Holes in Nearby Galaxy Nuclei
• An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907
• The Ultraluminous State
• The SCORPIO focal reducer
• Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
• The Charge Transfer Efficiency and Calibration of WFPC2
• Discovery of pulsations from NGC 300 ULX1 and its fast period evolution
• The ultraluminous state revisited: fractional variability and spectral shape as diagnostics of super-Eddington accretion
• Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
• A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source
• Puzzling accretion onto a black hole in the ultraluminous X-ray source M101 ULX-1
• The discovery of weak coherent pulsations in the ultraluminous X-ray source NGC 1313 X-2
• Evidence for Pulsar-like Emission Components in the Broadband ULX Sample
• Supercritical Accretion Discs in Ultraluminous X-ray Sources and SS 433
• Compact Optical Counterparts of Ultraluminous X-ray Sources
• Optical counterparts of the nearest ultraluminous X-ray sources
• On the association of the ultraluminous X-ray sources in the Antennae galaxies with young stellar clusters
• A tale of two periods: determination of the orbital ephemeris of the super-Eddington pulsar NGC 7793 P13
• Discovery of a red supergiant donor star in SN2010da/NGC 300 ULX-1
• The supergiant optical counterpart of ULX P13 in NGC7793
• No Strong Geometric Beaming in the Ultraluminous Neutron Star Binary NGC 300 ULX-1 (SN 2010da) from Swift and Gemini
• Transition of an X-ray binary to the hard ultraluminous state in the blue compact dwarf galaxy VII Zw 403

Cited by in corpus (4)

• Ultraluminous X-Ray Sources
• Long-Term X-Ray/UV Variability in ULXs
• Simultaneous X-ray/UV observations of ultraluminous X-ray source Holmberg II X-1 with Indian space mission AstroSat
• Exploring the nature of an ultraluminous X-ray source in NGC 628