0 Assigned ID: 849 ----- Attempting Submission 1 (Fri Apr 11 21:18:35 GMT 2014) ----- HST Phase I Proposal 849 (iPTF13bvn.apt) successfully submitted. ----- Attempting Submission 2 (Fri Apr 11 23:33:11 GMT 2014) ----- HST Phase I Proposal 849 (iPTF13bvn.apt) successfully submitted. ----- Attempting Submission 3 (Fri Apr 11 23:54:35 GMT 2014) ----- 0 ----- Attempting Submission 1 (Thu Jul 03 17:43:34 GMT 2014) ----- Determining the nature of the progenitor stars responsible for core-collapse supernovae (SNe) is a vital problem for massive stellar evolution and, e.g., the chemical history of galaxies. Up to this point, the progenitor, or progenitor systems, responsible for the stripped-envelope Type Ib and Ic SNe are still not understood unambiguously. For the recent Type Ib SN iPTF13bvn in the spiral galaxy NGC 5806, a putative progenitor star was identified at the exact SN position in pre-SN, multi-band HST ACS images. The luminosity and colors for this object have been characterized as being consistent with a single, massive (M_initial > 31--35 Msun) Wolf-Rayet star. Notwithstanding uncertainties in the measurements of the object's brightness and also its host galaxy properties, such as distance and inclination, the progenitor of iPTF13bvn has been suggested by others, instead, to be much less massive and possibly in an interacting binary system. We propose here to deeply reimage the SN site in B and V with WFC3 to determine the status of the putative progenitor, when the SN itself has faded well below the brightness of the progenitor. We will be testing the Wolf-Rayet progenitor scenario and, at the same time, placing constraints on the interacting binary scenario. This can be done in Cycle 22 and only with HST. We will observe the site of the Type Ib SN iPTF13bvn once again, this time quite deeply, in F438W and F555W with WFC3/UVIS. The total exposure times will be 5720 and 5610 s, respectively. These will allow us not only to determine whether the putative Wolf-Rayet star progenitor has vanished, which is one progenitor scenario, but also to undertake an investigation of the other possible scenario, an interacting binary system. If the progenitor's binary companion has brightness V ~ 27.5 mag (and approx the color of a A0I star), we should then be able to detect it at S/N~5 and 7, respectively. We should be able to put a strict (3-sigma) constraint of V>28.4 mag for anything remaining at the SN site. The galaxy NGC 5806 has already been host to two other recent SNe, so it could host other future SNe. These images will be the deepest available in these two bands for this galaxy, so the data will have archival value for the entire community for a variety of studies. For these reasons, we are imaging much of the entire galaxy, placing the pointing center at UVIS-CENTER, line dithering to fill both the chip gap (using a POS TARG offset between exposure pairs) and to subsample the PSF as well in each band. Scheduling these observations in the 2015 June 11 to September 16 visibility window should be sufficient, since the SN itself should have faded to at least V ~ 28.6 mag, if not fainter. HOT STARS 0 false false false false false SUPPORTED STAR SUPERNOVA TYPE IB This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 B=26.0 WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F555W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 3 false 1404751025560 The scheduling data was generated by CASM 22.2. 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