Mid-IR progenitor of AT 2017eaw in NGC 6946

ATel #10373; Rubab Khan (University of Washington)
on 14 May 2017; 19:45 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Rubab Khan (khan@astronomy.ohio-state.edu)

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We report the Spitzer/IRAC flux of a bright mid-IR source coincident with the position of the transient AT 2017eaw in the nearby galaxy NGC 6946 discovered by Patrick Wiggins and confirmed by ATel #10372. The candidate mid-IR progenitor is present at RA=20:34:44.29, DEC=+60:11:36.02 in the catalog of mid-IR sources in nearby galaxies published in Khan 2017 (ApJ S, 228, 5). The cataloged object is at <0.76" from the reported location of the transient, on the same IRAC native pixel (1.2") and the SINGS mosaic (0.75", Kennicutt et al. 2003) on which PSF fitting photometry measurements were done. The mosaic was constructed from images obtained with Spitzer/IRAC on November 11, 2004 (PI: R. Kennicutt). This is well within one PSF FWHM (~1.45") of IRAC1 and IRAC2 (3.6um and 4.5um). The candidate progenitor has IRAC1/2 (3.6um/4.5um) fluxes of 18.02/17.75 Vega magnitudes, which translates to 0.0174/0.0143 mJy and implies luminosities of ~15,000 and ~10,000 solar luminosities at a distance of 5.7 Mpc (Sahu et al. 2006). Significantly higher fluxes at 5.8/8.0/24um reported in Table-8 of Khan 2017 for this source are not primarily associated with the location of the 3.6/4.5um detection and are contaminated by other sources in a crowded region. The Spitzer 4.5um image (SINGS mosaic; red: transient, green: cataloged) is posted at https://www.dropbox.com/s/1cp00r3r13ubky6/AT2017eaw.png