Wednesday, July 31, 2013

1307.7755 (Nancy Elias-Rosa et al.)

On the progenitor of the Type Ic SN 2013dk in the Antennae Galaxies    [PDF]

Nancy Elias-Rosa, Andrea Pastorello, Justyn R. Maund, Katalin Takáts, Morgan Fraser, Stephen J. Smartt, Stefano Benetti, Giuliano Pignata, David Sand, Stefano Valenti
We report the results of our search for the progenitor candidate of SN 2013dk, a Type Ic supernova (SN) that exploded in NGC 4038 in the Antennae Galaxy system (distance 22.3 Mpc). We compare pre-explosion archival images taken with the Hubble Space Telescope (HST) with SN images obtained using adaptive optics images taken with the ESO Very Large Telescope+Naos-Conica. We isolate the SN position to within 3 sigma uncertainty radius of 0.02", and show that there is no detectable point source in any of the HST filter images within the error circle. We set an upper limit to the absolute magnitude of the progenitor to be M_F555W > -5.7. In isolation, this does not allow Wolf-Rayet (WR) star progenitors to be ruled out but SN 2013dk joins the list of undetected supernova Ib/c progenitors. A bright source appears 0.17" away, which is either a single bright supergiant or compact cluster. Although the core is not obviously more extended than other point-like sources, we consider it most likely that it is a compact cluster given its absolute magnitude of M_F555W = -9.02 +- 0.28 extended wings and complex environment. It is detected in five filters from F336W to F814W and we fit a stellar population model to estimate its age. The spectral energy distribution (SED) fit is not excellent, but it favours an age of around 15-22 Myrs corresponding to a turn-off mass of 10-15 solar masses. Even if this is a cluster, the spatial displacement of SN 2013dk means that its membership is not assured. The strongest statement we can make is that in the immediate environment of SN 2013dk (within 10 pc or so) we find no clear evidence of either a point source coincident with the SN or a young stellar cluster that could host a massive WR progenitor.
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