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Swift observations of SN2011it

ATel #3804; R. Margutti, A. M. Soderberg, D. Milisavljevic (Harvard Univ.)
on 12 Dec 2011; 15:30 UT
Credential Certification: Raffaella Margutti (rmargutti@cfa.harvard.edu)

Subjects: Ultra-Violet, X-ray, Supernovae

SN2011it has been recently classified as a broad-line type-Ic supernova (Tomasella, CBET 2938). A Swift-ToO was executed to observe the field of SN2011it starting from 2011-12-08T00:22:48 UT, with the primary aim to constrain the off-axis X-ray emission from the SN. No X-ray source is detected at the optical position of the transient with a 3 sigma upper limit of 2.4d-3 cts/s in the 0.3-10 keV energy band (total exposure= 8.3 ks). The Galactic neutral hydrogen column density in the direction of the event is 8.46d20 1/cm2 (Kalberla 2005). Assuming a spectral photon index ~2, this translates into a de-absorbed flux of 1.1d-13 erg/s/cm2, corresponding to a luminosity limit of 6d40 erg/s for a luminosity distance of 68 Mpc (i.e. adopting for the host galaxy a redshift of z = 0.015894 de Vaucouleurs et al. 1991, RC3 catalogue, via NED). For comparison SN1998bw (broad line Ic associated with GRB980425) was detected at a level ~3d40 erg/sec at a similar epoch (Pian 2000 Apj 536 778). Contemporary Swift-UVOT observations have been obtained in the 6 optical/UV filters. The source is seen faintly in the V filter but not clearly in the other filters. Including important contamination from the host galaxy, we measure a preliminary magnitude (UVOT photometric system Breeveld et al. 2011, arXiv:1102.4717) v= 16.7 +\- 0.1 (value not corrected for the Galactic extinction due to the reddening of E(B-V) =0.118 mag in the direction of the transient according to Schlegel et al. 1998). We thank the Swift team for scheduling these ToO observations.