Based on observations made with the ESO Telescopes at the La Silla Observatory under the programme ID 075.D-0634(B).
Evidence of an irradiated accretion disc in XTE J1818−245★
Article first published online: 24 JAN 2011
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Monthly Notices of the Royal Astronomical Society
Volume 413, Issue 1, pages 235–240, May 2011
How to Cite
Zurita Heras, J. A., Chaty, S., Cadolle Bel, M. and Prat, L. (2011), Evidence of an irradiated accretion disc in XTE J1818−245. Monthly Notices of the Royal Astronomical Society, 413: 235–240. doi: 10.1111/j.1365-2966.2010.18125.x
- Issue published online: 14 APR 2011
- Article first published online: 24 JAN 2011
- Accepted 2010 November 30. Received 2010 November 26; in original form 2009 November 18
- accretion, accretion discs;
- stars: individual: XTE J1818−245;
- X-rays: binaries
The X-ray transient source XTE J1818−245 went through an outburst in 2005 that was observed during a multiwavelength campaign from radio to soft γ-rays. Observations in V and R optical bands with the 1-m Swope telescope allowed the discovery of a new bright source. As we aimed to reveal the nature of the companion star, we performed new optical observations with the ESO/NTT telescope at La Silla, both in photometry and spectroscopy. We confirm the optical counterpart found by the Swope telescope, but the spectral type of the secondary star could not be identified. The spectrum showed a blue-dominated shape and an Hα emission line was detected, indicating that the optical emission was dominated by the presence of an accretion disc. The broad-band spectral energy distribution revealed that the outer parts of the accretion disc had to be irradiated by its inner parts to explain the optical emission. New observations of XTE J1818−245 in quiescence are needed to find the nature of the companion star. Moreover, radio-to-X-ray strictly simultaneous observations of transient black holes are needed to disentangle the importance of jets and irradiated accretion discs in the infrared–optical–ultraviolet domain.