TITLE: GCN CIRCULAR NUMBER: 6287 SUBJECT: GRB 070412: Swift-XRT refined analysis DATE: 07/04/12 12:50:16 GMT FROM: Pat Romano at OAB-Swift P. Romano (Univ. Bicocca & INAF-OAB), A. Moretti (INAF-OAB), C. Guidorzi (Univ. Bicocca & INAF-OAB) report on behalf of the Swift Team: We have analysed the first 4 orbits of XRT data from GRB 070412 (trigger=275119; Romano et al., GCN Circ. 6273), which include 40s in WT and 2.4ks in PC mode. The refined XRT position is RA,Dec=181.5426 +40.1438: RA(J2000) =12h 06m 10.2s Dec(J2000) =+40d 08' 37.8" with an uncertainty of 4 arcsec (90% containment, see GCN Circ. 6282). The 0.3-10 keV X-ray light curve can be fit with a simple power-law with a decay slope of 0.98+/-0.05, although the initial descent could be due to a flare or the tail of the prompt emission (slope of ~-3.5). The X-ray spectrum from the XRT/WT data (40s starting from T+67.8) can be fit by an absorbed power-law with a photon index of 2.2+/-0.5 and column density of (1.8-0.9+1.1)E21 cm**-2, higher than the Galactic column density in the direction of the source (1.95E20 cm**-2). The unabsorbed (absorbed) 0.3-10 keV flux for this spectrum is 3.3E-10 (2.2E-10) erg/cm**2/s. The XRT/PC data (2.4ks starting from T+3386) can be fit by an absorbed power-law with a photon index of 2.3-0.5+0.6 and column density of (2.5-1.2+1.4)E21 cm**-2, consistently with the WT data. The unabsorbed (absorbed) 0.3-10 keV flux for this spectrum is 6.1E-12 (3.3E-12) erg/cm**2/s. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10 keV XRT count rate of 5.6E-3 count/s at T+24hr, which corresponds to an observed 0.3-10 keV flux of 2.8E-13 erg/cm**2/s. This circular is an official product of the Swift XRT Team.