TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5157 SUBJECT: XMM-Newton observation of GRB060510b DATE: 06/05/23 14:45:56 GMT FROM: Sergio Campana at INAF-OAB Sergio Campana (INAF/OAB) and Andrea DeLuca (INAF/IASF Milano) report: We have analyzed the XMM-Newton observation of the field of GRB060510B, discovered by Swift/BAT on May 10 2006, 08:22:14 UT (Krimm et al., GCN 5096). The XMM-Newton observation started ~5 hours after the GRB trigger and lasted for ~40 ks. The observation is affected by a high particle background, resulting in about 17 ks of usable data. We report here on data collected by the EPIC/pn camera. The afterglow of GRB060510B is detected at the following coordinates: RA(J2000): 15h 56m 29s.2, Dec(J2000): +78d 34' 12.0", with an uncertainty of 1.5 arcsec (1sigma), fully consistent with the reported Swift/XRT (Krimm et al.) and optical (Mirabal et al. GCN5097) positions. Extracting source events from a circle of 30 arcsec radius, the pn time-averaged, background-subtracted count rate in the 0.5-8 keV range is of 0.11+/-0.003 cts/s. The source is clearly fading with a power law decay with alpha=-0.7+/-0.1 (error at 90% c.l. for a single parameter) with reduced chi2=1.3, 16 d.o.f. The time-integrated X-ray spectrum is well fit (reduced chi2=1.0, 72 d.o.f.) by a power law absorbed by a column NH=(9.4+/-3.5)x10^20 cm^-2 (error at 90% confidence level), slightly larger than the Galactic value of NH_gal=3.8x10^20 cm^-2 (Dickey & Lockman 1990), and with a photon index Gamma=2.7+/-0.3. Since the redshift of the GRB afterglow is known we consider also an intrinsic absorption at z=4.9 (Price, GCN5104). The fit is similarly good (reduced chi2=0.99, 72 d.o.f.) with NH_z=(2.1+/-1.2)x10^22 cm^-2 and Gamma=2.5+/-0.2. The observed flux (0.5-10 keV) is of 1.4x10^-13 erg cm^-2 s^-1, corresponding to an unabsorbed flux of 1.8x10^-13 erg cm^-2 s^-1. No spectral evolution as a function of time (first 16 ks vs. remaining 22 ks of data) has been observed.