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ATEL # 1168; S. Immler (NASA/GSFC/UMCP) and P. J. Brown (PSU), on behalf of the Swift satellite team
on 3 Aug 2007; 21:57 UT
Password Certification: Stefan Immler (firstname.lastname@example.org)
Subjects: Optical, Ultra-Violet, X-ray
Swift Ultraviolet/Optical Telescope (UVOT) and X-Ray Telescope (XRT) observed SN 2007gi (CBET #1017) on 2007-08-03.58 UT. The following UVOT magnitudes were measured: v = 14.6±0.1 (79 s exposure time), b = 15.0±0.1 (157 s), u = 15.2±0.1 (157 s), uvw1 [181-321nm] = 17.2±0.2 (472 s), uvm2 [166-268 nm] = 20.1±0.5 (875 s), and uvw2 [112-264 nm] = 18.5±0.2 (621 s). These magnitudes are on the UVOT photometric system (see GCN Circ. 6614) which in the optical is close to the Johnson UBV. They have not been corrected for extinction.
The red UV-optical colors are consistent with SNe Ia observed with Swift UVOT (e.g. Brown et al., 2005, ApJ, 635, 1192; Immler et al., 2006, ApJL, 648, 119).
No X-ray source is detected at the position of the SN in the merged 2.6 ks Swift XRT observation obtained simultaneously with the UVOT observations. The 3-sigma upper limit to the XRT net count rate is 6.8 E-03 cts/s, corresponding to an unabsorbed (0.2-10 keV band) X-ray flux of < 3.4 E-13 ergs/cm/cm/s and a luminosity of <1.7E40 ergs/s for an adopted thermal plasma spectrum with a temperature of kT = 10 keV, a Galactic foreground column density of N_H = 1.89E+20 (Dickey & Lockman, 1990, ARAA 28) and a distance of 20.4 Mpc (0.004820, NED; H_o = 71 km/s/Mpc, Omega_M = 1/3, Omega_L = 2/3).