SN 2018bsz: A Type I superluminous supernova with aspherical circumstellar material

Pursiainen, M.; Leloudas, G.; Paraskeva, E.; Cikota, Aleksandar; Anderson, J. P.; Angus, C.; Brennan, S.; Bulla, Mattia; Camacho-Iñiguez, E.; Charalampopoulos, P.; Chen, T. -W.; Mancheño, M. Delgado; Fraser, M.; Frohmaier, C.; Galbany, L.; Gutiérrez, C. P.; Gromadzki, M.; Inserra, C.; Maund, Justyn R.; Müller-Bravo, T. E.; Torres, S. Muñoz; Nicholl, Matt; Onori, F.; Patat, F.; Pessi, P. J.; Roy, R.; Spyromilio, J.; Wiseman, P.; Young, D. R.

doi:10.1051/0004-6361/202243256

Cited by 23 publications

(13 citation statements)

References 165 publications

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“…Given that the low-level polarisation at +29.0 d implies spherical symmetry, option iii) is unlikely the cause for the continuum polarisation at +3.0 d. Furthermore, Fiore et al (2021) identified broad C ii absorption lines in near-peak spectra of SN 2017gci. As shown in Figure C.6, these lines do not project loops on the Q -U plane -as was seen in SN 2018bsz (Pursiainen et al 2022) -nor do they follow the drawn dominant axis as would be expected if the polarisation properties at +3.3 d were caused by uneven distribution of absorbing material. Thus, option ii) does not seem to be the cause for the tendency of the data and we assume that the polarisation is caused by an inherently aspherical photosphere.…”

Section: Polarimetry Of Sn 2017gcimentioning

confidence: 57%

“…In the first epoch, the polarisation degree appears to increase towards the red (as in SN 2017gci) and at the second epochs towards the blue, following approxi- The SN showed low level of polarisation at near-peak with no particular line features, but at +185 d the level of continuum polarisation had increased to ∼ 0.8%. Finally, for SN 2018bsz the polarimetric evolution appears to be strongly affected by interaction with highly aspherical CSM (Pursiainen et al 2022), and comparison to SN 2017gci is not fruitful. While the spectropolarimetry shows a low level of polarisation at +29.0 d, the imaging polarimetry at ∼ +55 d shows that the polarisation degree has increased to P ∼ 0.5% in V band.…”

Section: Polarimetry Of Sn 2017gcimentioning

confidence: 97%

“…Recently, Pursiainen et al (2022) analyse two epochs of spectropolarimetry of SN 2018bsz -the most nearby SLSN-I to date at z = 0.0267 (see e.g. Anderson et al 2018;Chen et al 2021) -along an extensive spectroscopic data set.…”

Section: Introductionmentioning

confidence: 99%

“…Instead, CSM has been identified in a number of SLSNe-I (e.g. Yan et al 2015Yan et al , 2017Lunnan et al 2018;Pursiainen et al 2022) and the irregular light curves seen in many SLSNe-I (see e.g. Hosseinzadeh et al 2021;Chen et al 2022b) suggests that CSM interaction may play a role even in SLSNe-I that display no obvious spectral signatures attributed to CSM.…”

Section: Introductionmentioning

confidence: 99%

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Polarimetry of Hydrogen-Poor Superluminous Supernovae

Pursiainen¹,

G.²,

Cikota³

et al. 2023

Preprint

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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.

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Section: Polarimetry Of Sn 2017gcimentioning

confidence: 57%

Section: Polarimetry Of Sn 2017gcimentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Polarimetry of Hydrogen-Poor Superluminous Supernovae

Pursiainen¹,

G.²,

Cikota³

et al. 2023

Preprint

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“…This discovery allowed Nicholl et al (2016b) to suggest that such bumps may be usual/omnipresent features in SLSNe-I; however, this theory was refuted by Angus et al (2019), who carried out a detailed analysis of SLSNe-I from the Dark Energy Survey and found that only three SLSNe-I showed early bumps in their sample of 14 objects. Later on, PFT12dam (Vreeswijk et al 2017), and potentially SN 2018bsz (e.g., Anderson et al 2018;Chen et al 2021;Gutiérrez et al 2022;Pursiainen et al 2022) and SN 2018hti (Lin et al 2020;Fiore et al 2022) were revealed to show early LC undulations. Gutiérrez et al (2022) examined this topic in detail and found that some SLSNe-I that show smooth LC in their early phase can be characterized by slow photometric evolution (e.g., SN 2007bi, Gal-Yam et al 2009Young et al 2010;LSQ14an, Inserra et al 2017;SN 2015bn, Nicholl et al 2016a, 2016bSN 2017gci, Fiore et al 2021 in their sample).…”

Section: Premaximum Light-curve Undulationsmentioning

confidence: 99%

Premaximum Spectroscopic Diversity of Hydrogen-poor Superluminous Supernovae

Könyves-Tóth

2022

ApJ

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We search for the reasons behind the spectroscopic diversity of hydrogen-poor superluminous supernovae (SLSNe-I) in the premaximum phase. Our analysis is a continuation of the paper of Könyves-Tóth & Vinkó, who disclosed two new subtypes of SLSNe-I characterized by the presence/absence of a W-shaped absorption feature in their premaximum spectra between 4000 and 5000 Å (called Type W and Type 15bn, respectively). However, the physical cause of this bimodality is still uncertain. Here we present premaximum spectral synthesis of 27 SLSNe-I with special attention to the photospheric temperature (T phot) and velocity (v phot) evolution. We find that a T phot limit of 12,000 K separates the Type W and Type 15bn SLSNe-I: Type W objects tend to show T phot ≥ 12,000 K, while Type 15bn ones have T phot ≤ 12,000 K. This is consistent with the chemical composition of the studied objects. Another difference between these groups may be found in their ejecta geometry: Type W SLSNe-I may show null polarization, implying spherical symmetry, while the polarization of Type 15bn objects may increase in time. This suggests a two-component model with a spherical outer carbon–oxygen layer and an asymmetric inner layer containing heavier ions. The two subgroups may have different light-curve evolution as well, since six Type W objects show early bumps, unlike Type 15bn SLSNe-I. This feature, however, needs further study, as it is based on only a few objects at present.

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