Abstract
We present seven epochs of spectropolarimetry of the Type IIb supernova (SN IIb) 2011dh in M51, spanning 86 d of its evolution. The first epoch was obtained 9 d after the explosion, when the photosphere was still in the depleted hydrogen layer of the stripped-envelope progenitor. Continuum polarization is securely detected at the level of P ≈ 0.5 per cent through day 14 and appears to diminish by day 30, which is different from the prevailing trends suggested by studies of other core-collapse SNe. Time-variable modulations in P and position angle are detected across P-Cygni line features. H α and He I polarization peak after 30 d and exhibit position angles roughly aligned with the earlier continuum, while O I and Ca II appear to be geometrically distinct. We discuss several possibilities to explain the evolution of the continuum and line polarization, including the potential effects of a tidally deformed progenitor star, aspherical radioactive heating by fast-rising plumes of 56Ni from the core, oblique shock breakout, or scattering by circumstellar material. While these possibilities are plausible and guided by theoretical expectations, they are not unique solutions to the data. The construction of more detailed hydrodynamic and radiative-transfer models that incorporate complex aspherical geometries will be required to further elucidate the nature of the polarized radiation from SN 2011dh and other SNe IIb.
| Original language | English |
|---|---|
| Pages (from-to) | 4467-4484 |
| Number of pages | 18 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 453 |
| Issue number | 4 |
| DOIs | |
| State | Published - Nov 11 2015 |
| Externally published | Yes |
Funding
We thank the anonymous referee for their insightful commentary and helpful suggestions. We are grateful to the staffs at Lick, Palo-mar, and Steward Observatories for their excellent assistance, as well as J. Chuck Horst, Julienne Sumandal, and Chris Salvo for help with the Palomar observations. Hien Tran and Ryan Chornock supplied spectropolarimetric data on SN 1993J and SN 2008ax for our comparison. JCM acknowledges Dan Kasen and Paul Duffell at U.C. Berkeley for insightful discussions. AVF’s group at U.C. Berkeley is supported by Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, the Christopher R. Redlich Fund, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. Support was provided by NSF grants AST-1210599 (U. Arizona), AST-1211916 (U.C. Berkeley), AST-1009571 and AST-1210311 (SDSU), and AST-1210372 (U. Denver). JMS is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. AG-Y is supported by the EU/FP7 via ERC grant no. 307260, the Quantum Universe I-Core programme by the Israeli Committee for Planning and Budgeting and the ISF; by Minerva and ISF grants; by the Weizmann-UK ‘making connections’ programme; and by Kimmel and ARCHES awards. 1IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation (NSF). 2015), in some cases potentially forming stripped-envelope Wolf– Rayet stars before exploding. These hypotheses are supported by the direct detection of the progenitor stars and their candidate companions in respective pre-and post-explosion images from the Hubble Space Telescope (HST; Maund et al. 2004; Van Dyk et al. 2011, 2013; Fox et al. 2014). We thank the anonymous referee for their insightful commentary and helpful suggestions. We are grateful to the staffs at Lick, Palomar, and Steward Observatories for their excellent assistance, as well as J. Chuck Horst, Julienne Sumandal, and Chris Salvo for help with the Palomar observations. Hien Tran and Ryan Chornock supplied spectropolarimetric data on SN 1993J and SN 2008ax for our comparison. JCM acknowledges Dan Kasen and Paul Duffell at U.C. Berkeley for insightful discussions. AVF's group at U.C. Berkeley is supported by Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, the Christopher R. Redlich Fund, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. Support was provided by NSF grantsAST-1210599 (U.Arizona), AST-1211916 (U.C.Berkeley), AST-1009571 and AST-1210311 (SDSU), and AST-1210372 (U. Denver). JMS is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. AG-Y is supported by the EU/FP7 via ERC grant no. 307260, theQuantum Universe I-Core programme by the Israeli Committee for Planning and Budgeting and the ISF; by Minerva and ISF grants; by the Weizmann-UK 'making connections' programme; and by Kimmel and ARCHES awards.
| Funders | Funder number |
|---|---|
| Christopher R. Redlich Fund | |
| EU/FP7 | |
| Hubble Space Telescope | |
| NSF grantsAST-1210599 | grantsAST-1210599 |
| TABASGO Foundation | |
| U.C. Berkeley | |
| U.C.Berkeley | |
| Weizmann-UK | |
| National Science Foundation | 1211916, 1210372, 307260, 1210599, 1302771, 1009571, 1210311 |
| National Sleep Foundation | AST-1211916, AST-1210599, AST-1009571, AST-1210311 |
| San Diego State University | AST-1210372, AST-1302771 |
| Association of Canadian Universities for Research in Astronomy | |
| Iowa Science Foundation | |
| American Venous Forum | |
| European Research Council | |
| Minerva Foundation | |
| Planning and Budgeting Committee of the Council for Higher Education of Israel |
Keywords
- Supernovae: general
- Supernovae: individual: SN 2011dh