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UV Variability of IRAS 13224-3809

Published online by Cambridge University Press:  10 November 2010

G. Tenorio-Tagle
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife
J. M. Mas-Hesse
Affiliation:
Laboratorio de Astrofísica Espacial y Física Fundamental, POB 50727, E-28080 Madrid, Spain
P. M. Rodriguez-Pascual
Affiliation:
ESA IUE Observatory, POB 50727, E-28080 Madrid, Spain
L. Sanz Fernandez De Cordoba
Affiliation:
Laboratorio de Astrofísica Espacial y Física Fundamental, POB 50727, E-28080 Madrid, Spain
Th. Boller
Affiliation:
Max-Planck-Institut für extraterrestrische Physik, D-85740 Garching, Germany
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Summary

Cross-correlation of the ROSAT All Sky Survey and the IRAS Point Source Catalog has provided a sample of 244 galaxies with strong emission at both far-infrared and soft X-ray ranges. IRAS 13224-3809 appeared as an outstanding object within this sample due to its extreme X-ray luminosity (Lx = 3 · 1044 erg s−1), steep X-ray spectrum and rapid X-ray variability, with a doubling timescale of only 800 s (Boiler et al. 1993). We have performed repeated IUE observations of this object in January, February and May 1993, looking for variable features in its spectrum, having detected a strong variability in the Lyα line. While a relatively broad Lyα component (FWHM ∼ 5000 km s−1) remains essentially constant over the three IUE observations, the initially strong and narrow core emission component vanishes completely becoming a strong absorption. A maximum variation of 50% has also been detected in the UV continuum level. IRAS 13224-3809 has a deficit of UV emission when compared to Seyfert 1 galaxies. The UV-X-ray energy distribution suggests that the UV bump frequently found in these galaxies might be present at higher energies, well within the ROSAT band (0.1–2.4 keV). If this bump is due to thermal emission of a heated accretion disk, as proposed by several authors, its temperature should be significantly higher than in other similar objects (blackbody temperature kT ∼ 100 eV).

Type
Chapter
Information
Violent Star Formation
From 30 Doradus to QSOs
, pp. 256 - 257
Publisher: Cambridge University Press
Print publication year: 1994

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