Discovery of the Dust-Enshrouded Progenitor of SN 2008S with Spitzer
Abstract
We report the discovery of the progenitor of the recent Type IIn SN 2008S in the nearby galaxy NGC 6946. Surprisingly, it was not found in deep, preexplosion optical images of its host galaxy taken with the Large Binocular Telescope, but only through examination of archival Spitzer mid-IR data. A source coincident with the SN 2008S position is clearly detected in the 4.5, 5.8, and 8.0 μm IRAC bands, showing no evident variability in the 3 years prior to the explosion, yet is undetected at 3.6 and 24 μm. The distinct presence of ~440 K dust, along with stringent LBT limits on the optical fluxes, suggests that the progenitor of SN 2008S was engulfed in a shroud of its own dust. The inferred luminosity of ≈3.5 × 104 L⊙ implies a modest mass of ~10 M⊙. We conclude that objects like SN 2008S are not exclusively associated with the deaths or outbursts of very massive η Carinae-like objects. This conclusion holds based solely on the optical flux limits even if our identification of the progenitor with the mid-IR source is incorrect.
Based in part on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia.- Publication:
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The Astrophysical Journal
- Pub Date:
- July 2008
- DOI:
- 10.1086/589922
- arXiv:
- arXiv:0803.0324
- Bibcode:
- 2008ApJ...681L...9P
- Keywords:
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- stars: evolution;
- supernovae: general;
- surveys;
- Astrophysics
- E-Print:
- ApJ letters, in press