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A. Dosaj, M.G. Garcia, W.R. Forman, C. Jones, A. Kong, F.A. Primini, R. Di Stefano, S.S. Murray (Harvard-Smithsonian CfA)
We will present analysis of the diffuse emission from the nucleus of M31 using a 40 ks Chandra ACIS-S observation. The observation was taken by Chandra on 5 October, 2001. This is a continuation of our work performed on a 5 ks observation with the Chandra ACIS-I detector, presented as a poster paper at the 2001 ASP conference. With this observation we performed spectral analysis of the diffuse emission in annuli whose radii increase with one arcminute increments. We reported that the diffuse emission is best described by a cool Mekal spectrum whose temperature varies radially from 0.5 to 0.26 keV ±5%. This emission is much softer than that of the point sources. The surface brightness profile was fit to a king model, S = So ( 1 + ( r/a)2)-3\beta + \frac{1}{2}, which yields \beta = 0.55, typical of galaxies. The inferred gas density distribution is a power law with exponent -1.65.
With this new observation we will be able to get better spectral fits, allowing us to determine gas temperatures to better than ±0% with 0.5 (rather than one) arcminute annuli. New calibration for the S3 chip coupled with the aimpoint being closer to the readout registers will reduce the effects of CTI suffered by the earlier observation. Further, unlike the ACIS-I observation the S3 chip will recieve better counting statistics for a soft source such as the the cool diffuse emission.
This research supported by NASA Contract NAS8-39073 to the Chandra\/ X-ray Center.