The Probable Progenitor of PSN J01364816+1545310 in M74

ATel #5229; S. D. Van Dyk (IPAC/Caltech), E. A. Petigura (UC Berkeley), S. B. Cenko (NASA/GSFC), W. Zheng, G. W. Marcy (UC Berkeley), A. W. Howard (U. Hawaii/IfA), R. J. Foley (Harvard/Smithsonian CfA), B. E. Tucker (ANU), P. L. Kelly, and A. V. Filippenko (UC Berkeley)
on 27 Jul 2013; 22:48 UT
Credential Certification: Schuyler D. Van Dyk (vandyk@ipac.caltech.edu)

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Schuyler D. Van Dyk (IPAC/Caltech), Erik A. Petigura (UC Berkeley), S. Bradley Cenko (NASA/GSFC), WeiKang Zheng, Geoffrey W. Marcy (UC Berkeley), Andrew W. Howard (U. Hawaii/IfA), Ryan J. Foley (Harvard/Smithsonian CfA), Brad E. Tucker (ANU/UC Berkeley), Patrick L. Kelly, and Alexei V. Filippenko (UC Berkeley) report the identification of the probable progenitor of PSN J01364816+1545310 in archival Hubble Space Telescope (HST) Advanced Camera for Surveys/Wide Field Channel (WFC) images in bands F435W, F555W, and F814W from 2003 November and 2005 June. The exact position of the PSN was located in the HST images via adaptive-optics NIRC2-NGS K'-band imaging at the Keck-II 10-m telescope on 2013 July 27 UT. A precise astrometric registration was performed between the HST F814W drizzled mosaic and a coaddition of the 15 1-sec NIRC2 wide-camera exposures. Even without applying a distortion correction to the NIRC2 frames before coaddition, using 10 stars in close proximity to the PSN in common between the two image sets we were able to achieve an uncertainty of 1.05 WFC pixels (52 milliarcsec) in the X-direction and 0.75 pixels (38 milliarcsec) in the Y-direction. We therefore found the PSN in the NIRC2 images to correspond directly in the HST images to a star which is particularly bright in F814W. After processing the 2003 HST images with Dolphot (Dolphin 2000, PASP, 112, 1383) we find that the star has B=25.03 (+/-0.02), V=24.65 (+/-0.02), and I=22.61 (+/-0.01) mag. Correcting for an assumed distance of 8.6 Mpc (Herrmann et al. 2008, ApJ, 683, 630) and for only the Galactic foreground extinction (Schlafly & Finkbeiner 2011, ApJ, 737, 103; A(V)=0.19 mag), we find that the star has M(V)_0=-5.2 and (V-I)_0=1.96 mag. These are consistent with the properties of an M-type red supergiant (RSG), which is not unexpected for the classification of the PSN as a young Type II SN (ATel 5228). We note, however, that (B-V)_0=0.32 mag, which is too blue for a RSG and may indicate that the profile of this star is contaminated by another, bluer object. M74 was also host to the Type Ic SN 2002ap and the Type II-P SN 2003gd. The probable progenitor of the PSN is apparently more luminous than the RSG progenitor of SN 2003gd (M[V]_0=-3.5 mag; e.g., Van Dyk, Li, & Filippenko 2003, PASP, 115, 1289). Further analysis is ongoing, and we encourage observations of this nearby PSN at all wavelengths.