Pursiainen, M. orcid.org/0000-0003-4663-4300, Leloudas, G. orcid.org/0000-0002-8597-0756, Cikota, A. orcid.org/0000-0001-7101-9831 et al. (11 more authors) (2023) Polarimetry of hydrogen-poor superluminous supernovae. Astronomy & Astrophysics, 674. A81. ISSN 0004-6361
Abstract
We present linear polarimetry for seven hydrogen-poor superluminous supernovae (SLSNe-I) of which only one has previously published polarimetric data. The best-studied event is SN 2017gci, for which we present two epochs of spectropolarimetry at +3 d and +29 d post-peak in rest frame, accompanied by four epochs of imaging polarimetry up to +108 d. The spectropolarimetry at +3 d shows increasing polarisation degree P towards the redder wavelengths and exhibits signs of axial symmetry, but at +29 d, P ∼ 0 throughout the spectrum, implying that the photosphere of SN 2017gci evolved from a slightly aspherical configuration to a more spherical one in the first month post-peak. However, an increase of P to ∼0.5% at ∼ + 55 d accompanied by a different orientation of the axial symmetry compared to +3 d implies the presence of additional sources of polarisation at this phase. The increase in polarisation is possibly caused by interaction with circumstellar matter (CSM), as already suggested by a knee in the light curve and a possible detection of broad Hα emission at the same phase. We also analysed the sample of all 16 SLSNe-I with polarimetric measurements to date. The data taken during the early spectroscopic phase show consistently low polarisation, indicating at least nearly spherical photospheres. No clear relation between the polarimetry and spectral phase was seen when the spectra resemble Type Ic SNe during the photospheric and nebular phases. The light-curve decline rate, which spans a factor of eight, also shows no clear relation with the polarisation properties. While only slow-evolving SLSNe-I have shown non-zero polarisation, the fast-evolving ones have not been observed at sufficiently late times to conclude that none of them exhibit changing P. However, the four SLSNe-I with increasing polarisation degree also have irregular light-curve declines. For up to half of them, the photometric, spectroscopic, and polarimetric properties are affected by CSM interaction. As such, CSM interaction clearly plays an important role in understanding the polarimetric evolution of SLSNe-I.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | supernovae: general; polarization; techniques: polarimetric |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 06 Dec 2023 10:43 |
Last Modified: | 06 Dec 2023 10:43 |
Status: | Published |
Publisher: | EDP Sciences |
Refereed: | Yes |
Identification Number: | 10.1051/0004-6361/202345945 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:205901 |