Unveiling the nature of ultraluminous X-ray sources via UV spectroscopy
Abstract
Our recent HST/Chandra study of the ultraluminous X-ray source {ULX} in NGC 5408 showed that the X-ray/UV/optical/NIR spectral energy distribution {SED} is consistent with emission from an irradiated accretion disk, while the UV/optical/NIR SED alone can also be explained as a B0I supergiant star. If the accretion disk dominates in the far-UV, then we expect to see a wealth of spectral lines features in the far-UV spectrum. If, instead, the far-UV light arises from an early B supergiant, we expect to see UV lines with strong P-Cygni profiles. To determine the physical origin of the UV/optical/NIR emission, we propose to take a deep look at the far-UV spectrum of the ULX using the unique capabilities of the Cosmic Origins Spectrograph. The spectrum obtained will definitively distinguish between an irradiated accretion disk and a supergiant companion star. Detection of UV lines is likely one of the only direct ways to constrain the physical nature of ultraluminous X-ray sources.
- Publication:
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HST Proposal
- Pub Date:
- October 2013
- Bibcode:
- 2013hst..prop13320G