LensWatch. II. Improved Photometry and Time-delay Constraints on the Strongly Lensed Type Ia Supernova 2022qmx (“SN Zwicky”) with Hubble Space Telescope Template Observations

Larison, C ORCID: 0000-0003-2037-4619, Pierel, JDR ORCID: 0000-0002-2361-7201, Newman, MJB ORCID: 0000-0002-8092-2077, Jha, SW ORCID: 0000-0001-8738-6011, Gilman, D ORCID: 0000-0002-5116-7287, Hayes, EE ORCID: 0000-0003-3847-0780, Agrawal, A ORCID: 0009-0008-1965-9012, Arendse, N ORCID: 0000-0001-5409-6480, Birrer, S ORCID: 0000-0003-3195-5507, Bronikowski, M ORCID: 0000-0002-1537-6911, Chakrabarti, S ORCID: 0000-0001-6711-8140, Della Costa, JM ORCID: 0000-0003-0928-2000, Coulter, DA ORCID: 0000-0003-4263-2228, Courbin, F ORCID: 0000-0003-0758-6510, Dalrymple, KA ORCID: 0000-0001-8737-9700, Dhawan, S ORCID: 0000-0002-2376-6979, Diego, JM ORCID: 0000-0001-9065-3926, Gall, C ORCID: 0000-0002-8526-3963, Goobar, A ORCID: 0000-0002-4163-4996, Hjorth, J ORCID: 0000-0002-4571-2306 et al (2025) LensWatch. II. Improved Photometry and Time-delay Constraints on the Strongly Lensed Type Ia Supernova 2022qmx (“SN Zwicky”) with Hubble Space Telescope Template Observations. The Astrophysical Journal, 980 (2). ISSN 0004-637X

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Abstract

Strongly lensed supernovae (SNe) are a rare class of transient that can offer tight cosmological constraints that are complementary to methods from other astronomical events. We present a follow-up study of one recently discovered strongly lensed SN, the quadruply imaged type Ia SN 2022qmx (aka “SN Zwicky”), at z = 0.3544. We measure updated, template-subtracted photometry for SN Zwicky and derive improved time delays and magnifications. This is possible because SNe are transient, fading away after reaching their peak brightness. Specifically, we measure point-spread-function photometry for all four images of SN Zwicky in three Hubble Space Telescope WFC3/UVIS passbands (F475W, F625W, and F814W) and one WFC3/IR passband (F160W), with template images taken ∼11 months after the epoch in which the SN images appear. We find consistency to within 2σ between lens-model-predicted time delays (≲1 day) and measured time delays with HST colors (≲2 days), including the uncertainty from chromatic microlensing that may arise from stars in the lensing galaxy. The standardizable nature of SNe Ia allows us to estimate absolute magnifications for the four images, with images A and C being elevated in magnification compared to lens model predictions by about 6σ and 3σ, respectively, confirming previous work. We show that millilensing or differential dust extinction is unable to explain these discrepancies, and we find evidence for the existence of microlensing in images A, C, and potentially D that may contribute to the anomalous magnification.

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date of acceptance:	18 December 2024
Date of first compliant Open Access:	5 June 2026
Date Deposited:	05 Jun 2026 13:46
Last Modified:	05 Jun 2026 13:46
DOI or ID number:	10.3847/1538-4357/ada776
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28751

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