Shortening the baseline: characterising Type Ia supernovae using Δm10(X)

Velasco, JM, Mazzali, PA ORCID: 0000-0001-6876-8284, Ashall, C, Burns, CR, Phillips, MM, Galbany, L, Morrell, N, Stritzinger, MD, Hoeflich, P, Hsiao, EY and Uddin, SA (2026) Shortening the baseline: characterising Type Ia supernovae using Δm10(X). Monthly Notices of the Royal Astronomical Society, 552 (4). ISSN 0035-8711

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Abstract

An explorative study of Type Ia supernovae (SNe Ia) light curves is presented. (Formula presented) decline-rate metrics are used to evaluate alternative characterisations of light-curve diversity and the luminosity–width relation (LWR). Using a sample of 362 SNe Ia from the Carnegie Supernova Project (CSP-I and CSP-II), Gaussian process regression is used to fit B- and g-band light curves and measure decline-rates across multiple post-maximum time-scales. The LWR is calibrated using a clean subsample of SNe Ia with host-independent distance moduli and Fitzpatrick (1999) reddening corrections. Decline-rates (Formula presented) and (Formula presented) are found to capture the LWR effectively, while mitigating the severe degeneracy that affects longer time-scales for fast-declining ((Formula presented) ) events. Continuous, piecewise linear models are presented that seamlessly anchor the transition between normal and fast-declining regimes. The decline-rate (Formula presented) closely approximates the results of the more complex colour-stretch parameters, requiring less post-maximum temporal coverage than (Formula presented) or (Formula presented), and offers an even greater sensitivity for slow decliners. (Formula presented) provides a precise and practical tool for large-scale photometric surveys and real-time observer classification.

Item Type:	Article
Uncontrolled Keywords:	methods: data analysis; techniques: photometric; supernovae: general; cosmological parameters; 5109 Space Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Date of acceptance:	5 October 2026
Date of first compliant Open Access:	5 November 2026
Date Deposited:	05 Nov 2026 15:42
Last Modified:	05 Nov 2026 15:42
DOI or ID number:	10.1093/mnras/stag1907
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29835

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