Abstract
We present photometry, spectra, and spectropolarimetry of supernova (SN) 2012ab, mostly obtained over the course of ~300 d after discovery. SN 2012ab was a Type IIn (SN IIn) event discovered near the nucleus of spiral galaxy 2MASXJ12224762+0536247. While its light curve resembles that of SN 1998S, its spectral evolution does not. We see indications of CSM interaction in the strong intermediate-width emission features, the high luminosity (peak at absolute magnitude M = -19.5), and the lack of broad absorption features in the spectrum. The Hα emission undergoes a peculiar transition. At early times it shows a broad blue emission wing out to -14 000 km s-1 and a truncated red wing. Then at late times (>100 d) it shows a truncated blue wing and a very broad red emission wing out to roughly +20 000 km s-1. This late-time broad red wing probably arises in the reverse shock. Spectra also show an asymmetric intermediate-width Hα component with stronger emission on the red side at late times. The evolution of the asymmetric profiles requires a density structure in the distant CSM that is highly aspherical. Our spectropolarimetric data also suggest asphericity with a strong continuum polarization of ~1-3 per cent and depolarization in the Hα line, indicating asphericity in the CSM at a level comparable to that in other SNe IIn. We estimate a mass-loss rate of M˙ = 0.050M⊙ yr-1 for vpre = 100 km s-1 extending back at least 75 yr prior to the SN. The strong departure from axisymmetry in the CSM of SN 2012ab may suggest that the progenitor was an eccentric binary system undergoing eruptive mass loss.
| Original language | English |
|---|---|
| Article number | stx3214 |
| Pages (from-to) | 1104-1120 |
| Number of pages | 17 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 475 |
| Issue number | 1 |
| DOIs | |
| State | Published - Mar 21 2018 |
| Externally published | Yes |
Funding
We thank the staffs at the MMT, Bok, Lick, and Keck Observatories for their assistance with the observations. Observations using Steward Observatory facilities were obtained as part of the large observing programme AZTEC: Arizona Transient Exploration and Characterization. Some observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Research at Lick Observatory is partially supported by a generous gift from Google. This work was supported by NSF grant AST-1210599. NS received additional support from NSF grants AST-1312221 and AST-1515559, and by a Scialog grant from the Research Corporation for Science Advancement. JMS was supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. The work of A.V.F.’s supernova group at UC Berkeley has been generously supported by NSF grant AST-1211916, the TABASGO Foundation, Gary and Cynthia Bengier, the Christopher R. Redlich Fund, the Richard & Rhoda Goldman Fund, and the Miller Institute for Basic Research in Science (U.C. Berkeley). JCW’s SN group at UT Austin was supported by NSF grant AST-1109881. ROTSE-III was supported by NASA grant NNX-08AV63G, NSF grant PhY-0801007, the Australian Research Council, the University of New South Wales, the University of Texas, and the University of Michigan. DCL acknowledges support from NSF grants AST-1009571 and AST-1210311, under which part of this research was carried out.
| Funders | Funder number |
|---|---|
| Christopher R. Redlich Fund | |
| Richard & Rhoda Goldman Fund | AST-1109881 |
| TABASGO Foundation | |
| University of Texas | |
| National Science Foundation | AST-1515559, AST-1210599, AST-1312221 |
| National Aeronautics and Space Administration | PhY-0801007, NNX-08AV63G |
| W. M. Keck Foundation | |
| Research Corporation for Science Advancement | AST-1211916, AST-1302771 |
| University of California | |
| University of Michigan | AST-1009571, AST-1210311 |
| Australian Research Council | |
| University of New South Wales |
Keywords
- Supernovae: individual: Type IIn