The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle
Year: 2026
Type: preprint
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 ($\lesssim$0.3%) with the exception of the high-velocity CaII near-infrared triplet, which reaches $\sim$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.
Source: arXiv (Cornell University)
Authors: Yang, Yi, Hoeflich, Peter, Wheeler, J. Craig, Baade, Dietrich, Wang, Lifan, Cikota, Aleksandar, Howell, D. Andrew, McCully, Curtis, Filippenko, Alexei V., Patat, Ferdinando, Ashall, Chris, Bulla, Mattia, Gal-Yam, Avishay, Graham, Melissa. L., Hiramatsu, Daichi, Mishra, Divya, Gonzalez, Estefania Padilla, Pellegrino, Craig M., Schulze, Steve
Institutions: Tsinghua University, Florida State University, The University of Texas at Austin, Mitchell Institute, Texas A&M University, NSF NOIRLab, International Gemini Observatory, Las Cumbres Observatory Global Telescope Network, University of California, Santa Barbara, University of California, Berkeley, University of Hawaiʻi at Mānoa, University of Hawaii System, University of Ferrara, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, National Institute for Astrophysics, Weizmann Institute of Science, University of Washington, University of Florida, Johns Hopkins University, Goddard Space Flight Center
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: Collaborative Research: Searching for the Expelled Envelope of Stripped-Envelope Supernovae, CDS&E: WoU-MMA: The Treasure Map, G433322167, Thermonuclear Supernovae: Geometry as the Rosetta Stone of Explosions and Progenitors, with Implications for Precision Cosmology, Speeding up the messenger: immediate detection of multimessenger transients with Las Cumbres Observatory, G58316358, G6273510985, Signatures of Type Ia Supernovae Explosions and their Cosmological Implications, G92095433
OpenAlex ID: W7214640635