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Attempt at Progenitor Identification of PSN J12545218-1014502 in NGC 4790

ATel #3971; Schuyler D. Van Dyk (Spitzer Science Center/Caltech), S. Bradley Cenko, Jeffrey M. Silverman, Adam A. Miller, Alexei V. Filippenko, Joshua S. Bloom (UC Berkeley), Peter E. Nugent (LBNL)
on 16 Mar 2012; 04:54 UT
Credential Certification: S. Bradley Cenko (cenko@astro.berkeley.edu)

Subjects: Optical, Supernovae

We report on our attempt to identify the progenitor of the Type Ib PSN J12545218-1014502 (ATEL #3967, #3968) in archival Hubble Space Telescope WFPC2 images taken with the F450W, F606W, and F814W filters (GO-9042; PI S. Smartt). We obtained short-exposure (1 s), g-band and R-band exposures of the SN on 2012 March 15.51 UT, using the Low Resolution Imaging Spectrometer on the Keck-I 10 m telescope. We astrometrically registered these images to the WFPC2 image mosaics, using 6 fiducial stars in common between the two image sets. We isolated the SN position on the WFPC2 mosaics with a 1-sigma uncertainty of about 1.7 WFC pixel (0.17 arcsec). We do not detect any source at this position to F450W > 24.8, F606W > 25.8, and F814W > 25.1 mag (3-sigma limits). If we arbitrarily increase our uncertainty in the astrometric solution to 2 pixels, a blue source is detected with m_F450W = 24.4 mag, using the package Dolphot v2.0 (Dolphin 2000, PASP, 112, 1383). This source then has an absolute B magnitude of about -7.5, assuming a Virgo-infall-corrected distance modulus of 31.7 mag to the host galaxy and a value of A_B = 0.21 mag (from the NASA/IPAC Extragalactic Database). This source is not detected by Dolphot in F606W and F814W, although it is marginally seen in the images in both bands. If this source is not the progenitor (which is likely the case), the SN progenitor, from the limits above, is not detected to roughly M_B > -7.1, M_V > -6.1, and M_I > -6.7 mag. Additional, higher-resolution images of the SN, as well as an estimate of the actual total extinction to the SN, are required. Further studies of this SN and its progenitor are ongoing.