[72.03] The X-ray source population in M33

AAS 207th Meeting, 8-12 January 2006
Session 72 Neutron Stars and X-ray Binaries
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[72.03] The X-ray source population in M33

H.-J. Grimm, J.C. McDowell, A. Zezas, D.-W. Kim, G. Fabbiano (SAO/CfA)

We present source list, variability and spectra for 3 Chandra observations of the Local Group galaxy M33. The observations are centered on the nucleus and on the starforming region NGC 604. We detect a total of 261 sources in an area of ~ 0.2 square degree down to a flux limit of 3 times 10^-16 erg s^-1 cm^-2 which corresponds to a luminosity of ~2 times 10³⁴ erg s^-1 at a distance of 840 kpc. From the source list we construct the luminosity functions of sources observed in M33. Taking into account contamination by background AGN the luminosity functions are consistent with those of other star forming galaxies. The combination of X-ray color analysis and the existence of ``blue'' optical counterparts strongly indicate a young X-ray point source population in M33. Above 3 times 10³⁵ erg s^-1 there are few X-ray sources in the locus of the X-ray hardness ratio diagram that is generally populated by LMXBs.

For a total of 38 sources the number of counts is sufficient for detailed spectral fitting. 25 of these sources have been observed in more than one observation. There is no evidence for spectral variability between observations. Of the total, 198 sources have been detected in at least two observations. We find that 48 of 198 sources show variability between observations above 3 sigma. None of the intrinsic M33 sources show any short-timescale X-ray variability.

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