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X-ray observations of the ultraluminous infrared galaxy IRAS 19254 2 7245 ( the Superantennae )
| Content Provider | Semantic Scholar |
|---|---|
| Author | Pappa, Athina Georgantopoulos, I. Stewart, Gerald |
| Copyright Year | 2000 |
| Abstract | We present ROSAT High Resolution Imager (HRI) and ASCA observations of the wellknown ultraluminous infrared galaxy (ULIRG) IRAS 1925427245 (the `Superantennae'). The object is not detected by ROSAT, implying a 3s upper limit of X-ray luminosity LX , 8 10 erg s in the 0.1±2 keV band. However, we obtain a clear detection by ASCA, yielding a luminosity in the 2±10 keV band of 2 10 erg s: The X-ray spectrum of IRAS 1925427245 is very hard, equivalent to a photon index of G 1:0 ^ 0:35: We therefore attempt to model the X-ray data using a `scatterer' model, in which the intrinsic X-ray emission along our line of sight is obscured by an absorbing screen while some fraction, f, is scattered into our line of sight by an ionized medium; this is the standard model for the X-ray emission in obscured (but non Compton-thick) Seyfert galaxies. We obtain an absorbing column density of NH 2 10 cm for a power-law photon index of G 1:9; an order of magnitude above the column estimated on the basis of optical observations; the percentage of the scattered emission is high (,20 per cent). Alternatively, a model where most of the X-ray emission comes from reflection on a Compton-thick torus NH . 10 cm22 cannot be ruled out. We do not detect an Fe line at 6.4 keV; however, the upper limit (90 per cent) to the equivalent width of the 6.4 keV line is high (,3 keV). Overall, the results suggest that most of the X-ray emission originates in a highly obscured Seyfert 2 |
| File Format | PDF HTM / HTML |
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| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
