The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle
Abstract
Among the various major subtypes of Type Ia supernovae (SNe), the luminous 1991T-like (Filippenko et al. 1992; Phillips et al. 1992) and 1999aa-like (Krisciunas et al. 2000; Garavini et al. 2004) events stand out as particularly important for constraining the explosion mechanism. Their white dwarf (WD) progenitors are thought to have masses close to or exceeding the Chandrasekhar limit. We present spectrophotometric and polarimetric time-series observations of the overluminous Type Ia SN2019vrq. Between -9 and +12 days relative to the light-curve peak, its continuum polarization is consistent with zero, as seen in most normal-bright SNeIa and despite a possible rise up to 0.2% toward longer wavelengths as seen in subluminous SNeIa. Polarization across major spectral features is marginal (≲0.3%) with the exception of the high-velocity CaII near-infrared triplet, which reaches ∼0.5%. This low polarization indicates a substantially spherically symmetric electron-scattering photosphere and minimal large-scale ejecta asymmetry. Early-time spectra reveal hot, doubly ionized ejecta dominated by SiIII and blended iron-group features. Intermediate-mass-element lines, such as CaII and SiII, are more clearly seen than in 91T-like events, though these lines remain weaker than in normal SNeIa. The intrinsically higher peak luminosity of overluminous 91T/99aa-like SNeIa (Yang et al. 2022; Phillips et al. 2024), their comparatively short formation timescale for a massive WD progenitor - a channel that becomes more common toward high redshift, and the moderate viewing-angle dependence of their spectrophotometric properties as inferred from their persistently low polarization, together suggest that this subclass may serve as a promising standard candle at high redshift.
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BibTeX
@misc{yang202691t99aalike,
title = {{The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle}},
author = {Yi Yang and Peter Hoeflich and J. Craig Wheeler and Dietrich Baade and Lifan Wang and Aleksandar Cikota and D. Andrew Howell and Curtis McCully and Alexei V. Filippenko and Ferdinando Patat and Chris Ashall and Mattia Bulla and Avishay Gal-Yam and Melissa. L. Graham and Daichi Hiramatsu and Divya Mishra and Estefania Padilla Gonzalez and Craig M. Pellegrino and Steve Schulze},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.31510},
eprint = {2609.31510},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.31510},
}
RIS
TY - UNPB
TI - The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle
AU - Yi Yang
AU - Peter Hoeflich
AU - J. Craig Wheeler
AU - Dietrich Baade
AU - Lifan Wang
AU - Aleksandar Cikota
AU - D. Andrew Howell
AU - Curtis McCully
AU - Alexei V. Filippenko
AU - Ferdinando Patat
AU - Chris Ashall
AU - Mattia Bulla
AU - Avishay Gal-Yam
AU - Melissa. L. Graham
AU - Daichi Hiramatsu
AU - Divya Mishra
AU - Estefania Padilla Gonzalez
AU - Craig M. Pellegrino
AU - Steve Schulze
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2609.31510
UR - https://arxiv.org/abs/2609.31510
AB - Among the various major subtypes of Type Ia supernovae (SNe), the luminous 1991T-like (Filippenko et al. 1992; Phillips et al. 1992) and 1999aa-like (Krisciunas et al. 2000; Garavini et al. 2004) events stand out as particularly important for constraining the explosion mechanism. Their white dwarf (WD) progenitors are thought to have masses close to or exceeding the Chandrasekhar limit. We present spectrophotometric and polarimetric time-series observations of the overluminous Type Ia SN2019vrq. Between -9 and +12 days relative to the light-curve peak, its continuum polarization is consistent with zero, as seen in most normal-bright SNeIa and despite a possible rise up to 0.2% toward longer wavelengths as seen in subluminous SNeIa. Polarization across major spectral features is marginal (≲0.3%) with the exception of the high-velocity CaII near-infrared triplet, which reaches ∼0.5%. This low polarization indicates a substantially spherically symmetric electron-scattering photosphere and minimal large-scale ejecta asymmetry. Early-time spectra reveal hot, doubly ionized ejecta dominated by SiIII and blended iron-group features. Intermediate-mass-element lines, such as CaII and SiII, are more clearly seen than in 91T-like events, though these lines remain weaker than in normal SNeIa. The intrinsically higher peak luminosity of overluminous 91T/99aa-like SNeIa (Yang et al. 2022; Phillips et al. 2024), their comparatively short formation timescale for a massive WD progenitor - a channel that becomes more common toward high redshift, and the moderate viewing-angle dependence of their spectrophotometric properties as inferred from their persistently low polarization, together suggest that this subclass may serve as a promising standard candle at high redshift.
ER -