SN 2024bfu, SN 2025qe, and the early light curves of type Iax supernovae

Magee, M R, Killestein, T L, Pursiainen, M, Godson, B, Jarvis, D, Jiménez-Palau, C, Lyman, J D, Steeghs, D, Warwick, B, Anderson, J P, Butterley, T, Chen, T-W, Dhillon, V S, Galbany, L, González-Gaitán, S, Gromadzki, M, Inserra, C ORCID: https://orcid.org/0000-0002-3968-4409, Kelsey, L, Kumar, A, Leloudas, G, Mattila, S, Moran, S, Müller-Bravo, T E, Noysena, K, Ramsay, G, Srivastav, S, Starling, R, Wilson, R W, Young, D R, Ackley, K, Breton, R P, Velázquez, J Casares, Dyer, M J, Galloway, D K, Kankare, E, Kotak, R, Nuttall, L K, O’Neill, D, Pessi, P, Pollacco, D, Ulaczyk, K and Yaron, O 2025. SN 2024bfu, SN 2025qe, and the early light curves of type Iax supernovae. Monthly Notices of the Royal Astronomical Society , staf1675. 10.1093/mnras/staf1675

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Abstract

Type Iax supernovae (SNe Iax) are one of the most common subclasses of thermonuclear supernova and yet their sample size, particularly those observed shortly after explosion, remains relatively small. In this paper we present photometric and spectroscopic observations of two SNe Iax discovered shortly after explosion, SN 2024bfu and SN 2025qe. Both SNe were observed by multiple all-sky surveys, enabling tight constraints on the moment of first light and the shape of the early light curve. Our observations of SN 2025qe begin <2 d after the estimated time of first light and represent some of the earliest observations of any SN Iax. Spectra show features consistent with carbon absorption throughout the evolution of SN 2025qe, potentially indicating the presence of unburned material throughout the ejecta. We gather a sample of SNe Iax observed by ATLAS, GOTO, and ZTF shortly after explosion and measure their rise times and early light curve power-law rise indices. We compare our results to a sample of normal SNe Ia and find indications that SNe Iax show systematically shorter rise times, consistent with previous work. We also find some indication that SNe Iax show systematically lower rise indices than normal SNe Ia. The low rise indices observed among SNe Iax are qualitatively consistent with extended 56Ni distributions and more thoroughly-mixed ejecta compared to normal SNe Ia, similar to predictions from pure deflagration explosions.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2025-10-03
Publisher:	Oxford University Press
ISSN:	0035-8711
Date of First Compliant Deposit:	15 October 2025
Date of Acceptance:	28 September 2025
Last Modified:	15 Oct 2025 10:45
URI:	https://orca.cardiff.ac.uk/id/eprint/181679

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