Follow-up of SN 2025wny IV: Photometric Time-delay Measurements of a Strongly Lensed Superluminous Supernova

@misc{townsend2026followup,
  title = {{Follow-up of SN 2025wny IV: Photometric Time-delay Measurements of a Strongly Lensed Superluminous Supernova}},
  author = {Alice Townsend and Suhail Dhawan and Erin E. Hayes and Maggie L. Li and Joel Johansson and Edvard Mörtsell and Ariel Goobar and Lin Yan and Charlotte Ward and Veena Krishnaraj and Steve Schulze and Jacob Osman Hjortlund and Yu-Jing Qin and Hannah C. Turner and Peter Massey and Jakob Nordin and Jule Augustin and Aleksandra Bochenek and Malte Busmann and Christoffer Fremling and Daniel Gruen and Xander J. Hall and K. -R. Hinds and Ezequiel J. Marchesini and Zoë McGrath and Conor M. B. Omand and Eliana Palazzi and Daniel A. Perley and Andrea Rossi and Killa Santer and Jesper Sollerman and Chiara Ventura and Jacob L. Wise and Tracy X. Chen and Steven L. Groom and Mansi M. Kasliwal and Josiah Purdum},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.28427},
  eprint = {2608.28427},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.28427},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Follow-up of SN 2025wny IV: Photometric Time-delay Measurements of a Strongly Lensed Superluminous Supernova
AU  - Alice Townsend
AU  - Suhail Dhawan
AU  - Erin E. Hayes
AU  - Maggie L. Li
AU  - Joel Johansson
AU  - Edvard Mörtsell
AU  - Ariel Goobar
AU  - Lin Yan
AU  - Charlotte Ward
AU  - Veena Krishnaraj
AU  - Steve Schulze
AU  - Jacob Osman Hjortlund
AU  - Yu-Jing Qin
AU  - Hannah C. Turner
AU  - Peter Massey
AU  - Jakob Nordin
AU  - Jule Augustin
AU  - Aleksandra Bochenek
AU  - Malte Busmann
AU  - Christoffer Fremling
AU  - Daniel Gruen
AU  - Xander J. Hall
AU  - K. -R. Hinds
AU  - Ezequiel J. Marchesini
AU  - Zoë McGrath
AU  - Conor M. B. Omand
AU  - Eliana Palazzi
AU  - Daniel A. Perley
AU  - Andrea Rossi
AU  - Killa Santer
AU  - Jesper Sollerman
AU  - Chiara Ventura
AU  - Jacob L. Wise
AU  - Tracy X. Chen
AU  - Steven L. Groom
AU  - Mansi M. Kasliwal
AU  - Josiah Purdum
PY  - 2026
DA  - 2026/08/28
PB  - arXiv
DO  - 10.48550/arxiv.2608.28427
UR  - https://arxiv.org/abs/2608.28427
AB  - We present photometric time-delay measurements of SN 2025wny, the first strongly lensed Type I superluminous supernova (SLSN-I), discovered at z = 2.015. Time-delay measurements from strongly lensed supernovae provide an independent probe of cosmology and the Hubble constant, H_0, without reliance on the local distance ladder. Using multi-facility imaging data, we performed scene-modelling photometry to deblend four of the lensed images (A-D) and construct grizJ-band light curves. We modelled the resolved light curves with Gaussian process regression using GausSN (Hayes et al. 2024) to infer relative time delays and magnifications between the lensed images. We found that a constant magnification model provides a suboptimal description of the data, motivating a time-dependent sigmoid magnification model to account for evolving relative magnification of image A. We measured time delays of Δt_AB = −10.6^+2.2_−2.5 days and Δt_AC = 1.2^+2.7_−2.6 days (68% credible intervals), consistent with independent spectroscopic measurements from Johansson et al. (2026). Combining the photometric time delays with the lens model of Mörtsell et al. (2026) gives H_0, photo = 80.5^+26.4_−16.7 km s^−1 Mpc^−1, while including the spectroscopic time delays as well yields H_0, comb = 70.8^+8.2_−6.1 km s^−1 Mpc^−1. Our results further demonstrate the potential of strongly lensed supernovae as independent probes of H_0.
ER  -