Swift observations of SN2011hs

ATel #3768; R. Margutti, A. M. Soderberg, D. Milisavljevic (Harvard Univ.)
on 16 Nov 2011; 18:42 UT
Credential Certification: Raffaella Margutti (rmargutti@cfa.harvard.edu)

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The spectral properties of SN2011hs show a good match to the energetic type-IIb 'hypernova' 2003bg approximately 15 days before maximum light (Milisavljevic CBET 2902). A Swift-ToO was executed to observe the field of SN2011hs starting from 2011-11-15T16:28:36 UT. No X-ray source is detected at the optical position of the transient (RA=22:57:11.77 dec=-43:23:4.8) with a 3 sigma upper limit of 2.3d-3 cts/s in the 0.3-10 keV energy band (total exposure= 9.3 ks). The Galactic neutral hydrogen column density in the direction of the event is 1.22d20 1/cm2 (Kalberla 2005). Assuming a spectral photon index ~2, this translates into an absorbed flux of 1.2d-13 erg/s/cm2 (corresponding to a luminosity limit of 9d39 erg/s for a luminosity distance of 26 Mpc). 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, V, W1 and W2 band. Including possible contamination from the host galaxy, we measure the following preliminary magnitudes (UVOT photometric system Breeveld et al. 2011, arXiv:1102.4717): V=16.44 +\- 0.04; B=17.07 +\- 0.05; U=16.80+\-0.07; W1= 17.90+/-0.08; W2=18.67 +/- 0.09. The source is seen faintly in the uvm2 filter. Magnitudes are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.019 in the direction of the transient (Schlegel et al. 1998). We thank the Swift team for scheduling these ToO observations.