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A cluster or association close to SN 2012fh

ATel #4507; M. Fraser, S. J. Smartt, R. Kotak, J. R. Maund (Queens University Belfast), S. Benetti, L. Tomasella, M. Turatto (INAF Osservatorio Astronomico di Padova)
on 22 Oct 2012; 10:07 UT
Credential Certification: Morgan Fraser (mfraser02@qub.ac.uk)

Subjects: Infra-Red, Optical, Supernovae

Referred to by ATel #: 4544

We have aligned a 60s V-band image of SN 2012fh (obtained with the 1.82m Ekar telescope + AFOSC) to the 2004 Spitzer + IRAC 3.6 micron image of NGC 3344 in which Prieto (ATEL #4502) identified a progenitor candidate. We find that the position of the SN is offset by ~1" to the south of the center of the source identified by Prieto. Furthermore, we find that the source has a full-width half-maximum which is broader than surrounding isolated point sources. We suggest, therefore, that the source seen in IRAC images is not a single stellar progenitor, but rather an OB association, stellar cluster, or an otherwise unresolved group of stars.

There is a paucity of optical images of NGC 3344. However, using 12 fiducial sources we aligned an SDSS DR7 r' image of NGC 3344 to our AFOSC image of SN 2012fh. The source close to the progenitor position is seen to be extended, and as in the IRAC images, the transformed SN position lies to the south of the brightest pixel. The source has an SDSS g' magnitude of 18 (M_r ~ -11), which at the distance of NGC 3344 (~7Mpc) is too bright to be a single star.

While these pre-explosion images are of little use for constraining the progenitor of the SN in NGC 3344, its proximity to an apparent stellar association raises the appealing prospect of studying the surrounding stellar population after the SN fades, and hence obtaining an indirect constraint on the SN progenitor mass.