The shape of SN 1993J re-analysed

Stevance, H. F.; Baade, D.; Bruten, J. R.; Cikota, Aleksandar; Clocchiatti, A.; Hines, Dean C.; Höflich, Peter; Maund, Justyn R.; Patat, F.; Vallely, P.; Wheeler, J. C.

doi:10.1093/mnras/staa721

Cited by 7 publications

(5 citation statements)

References 74 publications

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“…To estimate the uncertainty for the light curves, we use SN 1998bw/GRB980425 as a proxy for the explosion of a massive stripped envelope SN (Hoeflich et al 1999). Detailed analysis of polarization spectra resulted in an axis ratio of 0.7 for SN 1998bw seen from an angle of 30 o (Hoeflich 1995) but with significant uncertainties as discussed in Stevance et al (2020). The possible effect of asymmetry on the V -band light curve of SN 2013ai is shown in Figure 17.…”

Section: Modeling Resultsmentioning

confidence: 96%

SN 2013ai: A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae

Davis

Pessi

Fraser

et al. 2021

ApJ

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Section: Modeling Resultsmentioning

confidence: 96%

SN 2013ai: A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae

Davis

Pessi

Fraser

et al. 2021

ApJ

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“…Unfortunately there is no unambiguous way to determine the ISP. A summary of the commonly used methods to estimate ISP has been provided by Stevance et al (2020). In this paper we estimate the ISPs by measuring them from the reliable, bright stars in our imaging polarimetry.…”

Section: Isp Correctionmentioning

confidence: 99%

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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“…The geometry of many SN explosions has been studied with the aid of spectropolarimetry -including the famous Type II SN 1987A (see e.g. Schwarz & Mundt 1987;Jeffery 1987;Cropper et al 1988) and Type IIb SN 1993J (Trammell et al 1993;Tran et al 1997;Stevance et al 2020) prehensive review of SN spectropolarimetry is provided by Patat (2017).…”

Section: Spectropolarimetrymentioning

confidence: 99%

“…Its presence is a constant nuisance for the determination of the intrinsic SN polarisation as there is no unique and unambiguous way to estimate and determine it. Stevance et al (2020) provides an educative summary of methods that have been employed in the past to estimate and remove ISP from observations of SNe. There is no single method that is 100% reliable in our case.…”

Section: Interstellar Polarisation: Alternatives and Implicationsmentioning

confidence: 99%

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

Pursiainen

Leloudas

Paraskeva

et al. 2022

A&A

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We present a spectroscopic analysis of the most nearby Type I superluminous supernova (SLSN-I), SN 2018bsz. The photometric evolution of SN 2018bsz has several surprising features, including an unusual pre-peak plateau and evidence for rapid formation of dust ≳ 200 d post-peak. We show here that the spectroscopic and polarimetric properties of SN 2018bsz are also unique. While its spectroscopic evolution closely resembles SLSNe-I, with early O ii absorption and C ii P-Cygni profiles followed by Ca, Mg, Fe, and other O features, a multi-component Hα profile appearing at ∼ 30 d post-maximum is the most atypical. The Hα is at first characterised by two emission components, one at ∼ +3000 km/s and a second at ∼ −7500 km/s, with a third, near-zero-velocity component appearing after a delay. The blue and central components can be described by Gaussian profiles of intermediate width (FWHM ∼ 2000 -6000 km/s), but the red component is significantly broader (FWHM ≳ 10000 km/s) and Lorentzian. The blue Hα component evolves towards a lower-velocity offset before abruptly fading at ∼ +100 d post-maximum brightness, concurrently with a light curve break. Multi-component profiles are observed in other hydrogen lines, including Paβ, and in lines of Ca ii and He i. Spectropolarimetry obtained before (10.2 d) and after (38.4 d) the appearance of the H lines shows a large shift on the Stokes Q -U plane consistent with SN 2018bsz undergoing radical changes in its projected geometry. Assuming the supernova is almost unpolarised at 10.2 d, the continuum polarisation at 38.4 d reaches P ∼ 1.8%, implying an aspherical configuration. We propose that the observed evolution of SN 2018bsz can be explained by highly aspherical, possibly disk-like, circumstellar material (CSM) with several emitting regions. After the supernova explosion, the CSM is quickly overtaken by the ejecta, but as the photosphere starts to recede, the different CSM regions re-emerge, producing the peculiar line profiles. Based on the first appearance of Hα, we can constrain the distance of the CSM to be less than ∼ 6.5 × 10 15 cm (430 AU), or even lower (≲ 87 AU) if the pre-peak plateau is related to an eruption that created the CSM. The presence of CSM has been inferred previously for other SLSNe-I, both directly and indirectly. However, it is not clear whether the rare properties of SN 2018bsz can be generalised for SLSNe-I, for example in the context of pulsational pair instability, or whether they are the result of an uncommon evolutionary path, possibly involving a binary companion.

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The shape of SN 1993J re-analysed

Cited by 7 publications

References 74 publications

SN 2013ai: A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae

SN 2013ai: A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae

Polarimetry of Hydrogen-Poor Superluminous Supernovae

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

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