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Swift observations of SN2011hg

ATel #3738; R. Margutti, A. M. Soderberg, D. Milisavljevic (Harvard University)
on 6 Nov 2011; 15:17 UT
Credential Certification: Raffaella Margutti (rmargutti@cfa.harvard.edu)

Subjects: Ultra-Violet, X-ray, Supernovae

The spectral properties of 2011hg have been recently demonstrated to show a good match to the energetic type-IIb 'hypernova' 2003bg approximately 7 days before maximum light (Marion, CBET 2894). A Swift-ToO was executed to observe the field of 2011hg starting from 2011-11-04T05:00:08 UT. No X-ray source is detected at the optical position of the transient (RA=23:11:48.73 dec=3:00:59.3) with a 3 sigma upper limit of 8.8d-3 cts/s in the 0.3-10 keV energy band (total exposure= 4.3 ks). The Galactic neutral hydrogen column density in the direction of the event is 5.72d20 1/cm2 (Kalberla 2005). Assuming a spectral photon index ~2, this translates into an absorbed flux of 4.4d-13 erg/s/cm2 (corresponding to a luminosity limit of 6d41 erg/s for a luminosity distance of 109 Mpc, Willick et al., 1997, ApJS, 109, 333). Contemporary Swift-UVOT observations have been obtained in the 6 optical/UV filters. A source is detected at the transient position in the U, B and V band. Including possible contamination from the host galaxy, we measure the following preliminary magnitudes (UVOT photometric system Breeveld et al. 2011, arXiv:1102.4717): U=18.37 +\- 0.10; B= 18.47 +\- 0.10; V=17.92 +\- 0.10. The source is seen faintly in the uvw1 filter but not clearly in the uvm2 or uvw2 filters. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) =0.075 in the direction of the transient (Schlegel et al. 1998). We thank the Swift team for scheduling these ToO observations.