Journal article
Compact Optical Counterparts of Ultraluminous X-ray Sources
The Astrophysical journal, Vol.737(2), 81
06/01/2011
DOI: 10.1088/0004-637X/737/2/81
Abstract
Using archival Hubble Space Telescope (HST) imaging data, we report the
multiband photometric properties of 13 ultraluminous X-ray sources (ULXs) that
have a unique compact optical counterpart. Both magnitude and color variation
are detected at time scales of days to years. The optical color, variability,
and X-ray to optical flux ratio indicate that the optical emission of most ULXs
is dominated by X-ray reprocessing on the disk, similar to that of low mass
X-ray binaries. For most sources, the optical spectrum is a power-law, $F_{\nu}
\propto \nu^{\alpha}$ with $\alpha$ in the range 1.0 to 2.0 and the optically
emitting region has a size on the order of 1e12 cm. Exceptions are NGC 2403 X-1
and M83 IXO 82, which show optical spectra consistent with direct emission from
a standard thin disk, M101 ULX-1 and M81 ULS1, which have X-ray to optical flux
ratios more similar to high-mass X-ray binaries, and IC 342 X-1, in which the
optical light may be dominated by the companion star. Inconsistent extinction
between the optical counterpart of NGC 5204 X-1 and the nearby optical nebulae
suggests that they may be unrelated.
Details
- Title: Subtitle
- Compact Optical Counterparts of Ultraluminous X-ray Sources
- Creators
- Lian Tao - Tsinghua UniversityHua Feng - Tsinghua UniversityFabien Grise - University of IowaPhilip Kaaret - University of Iowa
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.737(2), 81
- DOI
- 10.1088/0004-637X/737/2/81
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- Institute of Physics (IOP)
- Language
- English
- Date published
- 06/01/2011
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984200033702771
Metrics
9 Record Views