A Preliminary Search for the Progenitor Candidate of PSN J12015272-1852183 in the Antennae Galaxies (NGC 4038)

ATel #5162; N. Elias-Rosa (ICE-IEEC/CSIC Barcelona), A. Pastorello, S. Benetti, E. Cappellaro (INAF - Padova Astronomical Observatory), G. Pignata, K. Takats (Universidad Andres Bello), S. Valenti (University of California at Santa Barbara and Las Cumbres Observatory), A. Harutyunyan (Telescopio Nazionale Galileo, TNG)
on 25 Jun 2013; 17:24 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: N. Elias-Rosa (nelias@ice.cat)

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We report the identification of potential candidates for the progenitor star of the Type Ic PSN J12015272-1852183 discovered by the CHASE survey (CBAT TOCP) from archival Hubble Space Telescope (HST) WFPC2 images in F555W (~V), and F814W (~I). These images were obtained from 2008-12-02 to 2009-02-09 UT for the HST proposal 11962, PI: A. Riess. We used a good-quality, acquisition image of the SN obtained at TNG Telescope (+Dolores) on June 23.88 UT to geometrically match the HST mosaics. A broad source (labelled as ``A'' in the figure http://www.ice.csic.es/personal/elias/ProgCandSNAntenneaG.jpg ) is seen within the 0.15" total positional uncertainty (red circle in figure), and also detected by the package Dolphot (Dolphin 2000, PASP, 112, 1383). The estimated magnitude for this source is F555W = 25.75 +- 0.03 and F814W = 24.22 +- 0.07. The Milky Way component to the line-of-sight extinction is A_V = 0.13 mag and A_I = 0.07 mag (Schlafly & Finkbeiner, 2011, ApJ, 737, 103). From the classification spectrum (Harutyunyan et al. 2013; http://sngroup.oapd.inaf.it/ ), we detected the narrow interstellar Na ID lines both at the rest wavelength and at the redshift of the host galaxy, with the latter having an equivalent width which is a factor 2 higher than the Galactic component. We will therefore assume that the host galaxy extinction is twice the Galactic one. Assuming a distance modulus value to NGC 4038 of 31.46 mag as provided in the NASA/IPAC Extragalactic Database (NED), this results the absolute magnitudes of -6.10 and -7.45 in (~) V and I respectively, and a intrinsic colour of V-I = 1.35 mag for the star. Two additional stars are close enough to our candidate to be considered also potential progenitors. Their magnitudes are 24.85 (candidate ``B'') and 25.54 (candidate ``C'') in F555W, and 23.71 (candidate ``B'') and 23.74 (candidate ``C'') in F814W band. We note that all sources seems to be better detectable in the bluer band than in the red one, which we consider could be due to the fact our candidate is not a point source but rather a star wrapped in a more complex environment (strong signs of HII regions were detected in the classification spectrum). Further observations at higher resolution are request to confirm the progenitor candidate. Also observations at all wavelengths are encouraged.