AAS 197, January 2001
Session 92. Star Formation in Nearby Galaxies
Oral, Wednesday, January 10, 2001, 10:30am-12:00noon, Royal Palm 3/4

## [92.04] XMM-Newton Observations of NGC 253: Resolving the Soft and Hard X-ray Emission

A. Ptak (CMU), W. Pietsch (MPE), K. Borozdin (LANL), G. Branduardi-Raymont (MSSL), M. Cappi (ITeSRE/CNR), M. Ehle (XMM-Newton SOC), P. Ferrando (CEA), M. Freyberg (MPE), S. Kahn (Columbia), T. Ponman (Birmingham), A. Read (MPE), T. Roberts (Leicester), M. Sako (Columbia), R. Shirey (UCSB), M. Ward (Leicester)

We present the first XMM-Newton observation of the nearby starburst galaxy NGC 253. The high throughput and ~10" resolution of XMM-Newton resulted in high signal-to-noise spectra, images, and light curves of the disk, halo and point-source features known from previous X-ray studies and a high resolution reflection grating spectrum of the nuclear region. The grating spectrum suggests temperatures ranging from 0.3-1.7 \times 107K and an electron density on the order of 0.1 cm-3. CCD images reveal that the limb-brightening of the plume (reported previously by Chandra) is mostly seen in high ionization emission lines, while in the lower ionization lines and below 0.5 keV the plume is more homogeneous. We detect the 6.7 keV emission line first discovered with BeppoSAX. A new, transient source detected 70" SSW of the nucleus exhibits the hardest spectrum of the point sources in NGC 253. The brightest (LX ~1039 \rm \ ergs \ s-1) X-ray source, 30" S of the nucleus, is variable by a factor of 2 within the XMM-Newton observation and has a spectrum consistent with a column density of ~3 \times 1021 \rm cm-2 and a thermal model with T~6 \times 107K or a power-law model with an energy index of ~1, suggesting that this source is a black hole X-ray binary. The implications of these results for models of starburst galaxies will be discussed.