Reconstructing the Scene: New Views of Supernovae and Progenitors from the SNSPOL Project

Hoffman, Jennifer L.; Williams, G. G.; Leonard, Douglas C.; Bilinski, Christopher; Huk, Leah N.; Mauerhan, Jon C.; Milne, Peter; Porter, Amber L.; Smith, Nathan; Smith, Paul S.

doi:10.1017/s1743921317003052

Cited by 2 publications

(1 citation statement)

References 17 publications

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“…Such evolution in the polarization parameters of SN 2012au indicates that the ejecta were aspherical and/or clumpy during the early phases. Using spectropolarimetric data at several epochs for this event, Hoffman et al (2014Hoffman et al ( , 2017) also noticed similar evolution in the continuum position angle.…”

Section: Polarimetric Results and Comparisonsmentioning

confidence: 54%

Photometric, polarimetric, and spectroscopic studies of the luminous, slow-decaying Type Ib SN 2012au

Kumar

Anupama

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Optical, near-infrared (NIR) photometric and spectroscopic studies, along with the optical imaging polarimetric results for SN 2012au, are presented in this article to constrain the nature of the progenitor and other properties. Well-calibrated multiband optical photometric data (from –0.2 to +413 d since B-band maximum) were used to compute the bolometric light curve and to perform semi-analytical light-curve modelling using the minim code. A spin-down millisecond magnetar-powered model explains the observed photometric evolution of SN 2012au reasonably. Early-time imaging polarimetric follow-up observations (–2 to +31 d) and comparison with other similar cases indicate signatures of asphericity in the ejecta. Good spectral coverage of SN 2012au (from –5 to +391 d) allows us to trace the evolution of layers of SN ejecta in detail. SN 2012au exhibits higher line velocities in comparison with other SNe Ib. Late nebular phase spectra of SN 2012au indicate a Wolf–Rayet star as the possible progenitor for SN 2012au, with oxygen, He-core, and main-sequence masses of ∼1.62 ± 0.15 M⊙, ∼4–8 M⊙, and ∼17–25 M⊙, respectively. There is a clear absence of a first overtone of carbon monoxide (CO) features up to +319 d in the K-band region of the NIR spectra. Overall analysis suggests that SN 2012au is one of the most luminous slow-decaying Type Ib SNe, having comparatively higher ejecta mass (∼ 4.7–8.3 M⊙) and kinetic energy (∼ [4.8–5.4] × 1051 erg). Detailed modelling using mesa and the results obtained through stella and snec explosions also strongly support spin-down of a magnetar with mass of around 20 M⊙ and metallicity Z = 0.04 as a possible powering source of SN 2012au.

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Section: Polarimetric Results and Comparisonsmentioning

confidence: 54%

Photometric, polarimetric, and spectroscopic studies of the luminous, slow-decaying Type Ib SN 2012au

Kumar

Anupama

et al. 2021

Monthly Notices of the Royal Astronomical Society

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A High-velocity Scatterer Revealed in the Thinning Ejecta of a Type II Supernova

Leonard

Hillier

Pignata

et al. 2021

ApJL

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We present deep, nebular-phase spectropolarimetry of the Type II-P/L SN 2013ej, obtained 167 days after explosion with the European Southern Observatory’s Very Large Telescope. The polarized flux spectrum appears as a nearly perfect (92% correlation), redshifted (by ∼4000 km s−1) replica of the total flux spectrum. Such a striking correspondence has never been observed before in nebular-phase supernova spectropolarimetry, although data capable of revealing it have heretofore been only rarely obtained. Through comparison with 2D polarized radiative transfer simulations of stellar explosions, we demonstrate that localized ionization produced by the decay of a high-velocity, spatially confined clump of radioactive 56Ni—synthesized by and launched as part of the explosion with final radial velocity exceeding 4500 km s−1—can reproduce the observations through enhanced electron scattering. Additional data taken earlier in the nebular phase (day 134) yield a similarly strong correlation (84%) and redshift, whereas photospheric-phase epochs that sample days 8 through 97 do not. This suggests that the primary polarization signatures of the high-velocity scattering source only come to dominate once the thick, initially opaque hydrogen envelope has turned sufficiently transparent. This detection in an otherwise fairly typical core-collapse supernova adds to the growing body of evidence supporting strong asymmetries across nature’s most common types of stellar explosions, and establishes the power of polarized flux—and the specific information encoded by it in line photons at nebular epochs—as a vital tool in such investigations going forward.

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Reconstructing the Scene: New Views of Supernovae and Progenitors from the SNSPOL Project

Cited by 2 publications

References 17 publications

Photometric, polarimetric, and spectroscopic studies of the luminous, slow-decaying Type Ib SN 2012au

Photometric, polarimetric, and spectroscopic studies of the luminous, slow-decaying Type Ib SN 2012au

A High-velocity Scatterer Revealed in the Thinning Ejecta of a Type II Supernova

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