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Disappearance of the Supergiant Progenitor of SN 2011dh in M51

ATel #4850; Schuyler D. Van Dyk (IPAC/Caltech), Alexei V. Filippenko, Ori Fox, Patrick Kelly (UC Berkeley), and Nathan Smith (University of Arizona)
on 2 Mar 2013; 22:28 UT
Credential Certification: Schuyler D. Van Dyk (vandyk@ipac.caltech.edu)

Subjects: Optical, Supernovae

Referred to by ATel #: 4912

We report that in Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations at F555W and F814W with the UVIS channel, conducted on 2013 March 2 UT as part of our Cycle 20 Snapshot program GO-13029 (PI: A. Filippenko), we have discovered that the yellow supergiant star, identified by Van Dyk et al. (2011, ApJ, 741, L28) and Maund et al. (2011, MNRAS, 739, L37) at the position of the Type IIb SN 2011dh in M51, has vanished. From preliminary photometry extracted from the 2013 images using Dolphot v2.0 (Dolphin 2000, PASP, 112, 1383), the HST flight-system magnitudes of the object seen at the position of the supergiant and SN are F555W = 23.20 +/- 0.02 and F814W = 22.51 +/- 0.02 mag. The brightness of the supergiant in, e.g., Van Dyk et al. (2011) was F555W = 21.86 +/- 0.01 and F814W = 21.22 +/- 0.01 mag. It is therefore evident that the yellow supergiant has disappeared, making it highly likely that it was the star that actually exploded (in agreement with the theoretical analyses by Bersten et al. 2012, ApJ, 757, 31 and Benvenuto, Bersten, & Nomoto 2013, ApJ, 762, 74, and the conclusions of Maund et al. 2011). Additionally, there is no obvious presence of a light echo around the SN in the 2013 images. Further analysis is ongoing.