ROSAT observations of the dwarf starforming galaxy Holmberg II ( UGC 4305 )
نویسندگان
چکیده
We present ROSAT PSPC and HRI observations of the dwarf irregular galaxy Holm-berg II (UGC4305). This is one of the most luminous dwarf galaxies (L x ∼ 10 40 erg s −1) detected in the ROSAT All-Sky Survey. The X-ray emission comes from a single unresolved point source, coincident with a large HII region which emits intense radio emission. The source is variable on both year and day timescales, clearly favouring accretion into a compact object rather than a supernova remnant or a superbubble interpretation for the origin of the X-ray emission. However, its X-ray spectrum is well-fit by a a Raymond-Smith spectrum with kT∼0.8 keV, lower than the temperature of X-ray binaries in nearby spiral galaxies.
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