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Possible Detection of SN 2007pk in X-Rays with Swift

ATel #1284; S. Immler (NASA/CRESST/GSFC), D. Pooley (U of Wisconsin), P. J. Brown (PSU), W. Li, and A. V. Filippenko (UC Berkeley), on behalf of the Swift satellite team
on 16 Nov 2007; 19:12 UT
Credential Certification: Stefan Immler (immler@milkyway.gsfc.nasa.gov)

Subjects: Optical, Ultra-Violet, X-ray, Supernovae

Swift Ultraviolet/Optical Telescope (UVOT) and X-Ray Telescope (XRT) observed the type-IIn SN 2007pk (CBET #1129, ATel #1271) on 2007-11-13.09, 2007-11-14.04, 2007-11-15.44, and 2007-11-16.04 UT. A bright X-ray source is detected at the position of the SN within a 10 image pixel (23.5-arcsec) aperture centered on the SN, which includes the nucleus of the host galaxy NGC 579 (8-arcsec offset from the SN) in the merged 7.3 ks Swift XRT observations. Inspection of the XRT raw image indicates that some of the X-ray flux might be due to the SN, although the results are not conclusive due to the large point-spread-function of the XRT instrument (18-arcsec half-power diameter at 1.5 keV). The XRT net count rate (including the nucleus of the galaxy and the position of the SN) is (5.4+/-1.0)E-03 cts/s, corresponding to an unabsorbed (0.2-10 keV band) X-ray flux of (2.9+/-0.5)E-13 erg/cm/cm/s and a luminosity of (1.7+/-0.3)E40 erg/s for an adopted thermal plasma spectrum with a temperature of kT = 10 keV, a Galactic foreground column density of N_H = 4.7E+20 (Dickey & Lockman, 1990, ARAA 28) and a distance of 71 Mpc (z= 0.016655, NED; H_o = 71 km/s/Mpc, Omega_M = 1/3, Omega_L = 2/3). We note that no X-ray source is visible at that position in ROSAT All-Sky Survey (RASS) X-ray images down to the limit of the RASS, but NGC 579 is a radio bright galaxy and detected in the NRAO VLA Sky Survey (P. Chandra, private communication).

The following UVOT magnitudes were measured in observations on 2007-11-16: v = 15.8±0.1 (237 s exposure time), b = 15.9±0.1 (237 s), u = 14.9±0.1 (236 s), uvw1 [181-321nm] = 14.7±0.1 (476 s), uvm2 [166-268 nm] = 14.7±0.1 (654 s), and uvw2 [112-264 nm] = 15.0±0.1 (951 s). These magnitudes are on the UVOT photometric system (see Poole et al., 2007, MNRAS, accepted [astro-ph/0708.2259] ) which in the optical is close to the Johnson UBV system. They have not been corrected for extinction. The photometric behavior compared to the previous observations shows the optical magnitudes roughly constant and a decay in the UV of about 0.1 mag/day.

Observations in other wavelength regimes are encouraged.