Follow-up of SN 2025wny III: Spectroscopic Time-delay Measurements of a Strongly Gravitationally Lensed Superluminous Supernova

@misc{johansson2026followup,
  title = {{Follow-up of SN 2025wny III: Spectroscopic Time-delay Measurements of a Strongly Gravitationally Lensed Superluminous Supernova}},
  author = {Joel Johansson and Edvard Mörtsell and Ariel Goobar and Steve Schulze and Maggie L. Li and Yu-Jing Qin and Lin Yan and Hannah C. Turner and Suhail Dhawan and Alice Townsend and Jakob Nordin and Aleksandra Bochenek and Malte Busmann and Kaustav K. Das and Christoffer Fremling and Lluis Galbany and Alexa C. Gordon and Daniel Gruen and Mansi M. Kasliwal and Chang Liu and Zoë McGrath and Christopher Martin and Peter Massey and Martijn S. S. L. Oei and Daniel A. Perley and Andrés I. Ponte Pérez and Francisco Prada and Nikolaus Z. Prusinski and Nabeel Rehemtulla and R. Michael Rich and Surya Shivaprasad and Jesper Sollerman and Jacob L. Wise},
  howpublished = {arXiv},
  year = {2026},
  month = aug,
  doi = {10.48550/arxiv.2608.28416},
  eprint = {2608.28416},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.28416},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Follow-up of SN 2025wny III: Spectroscopic Time-delay Measurements of a Strongly Gravitationally Lensed Superluminous Supernova
AU  - Joel Johansson
AU  - Edvard Mörtsell
AU  - Ariel Goobar
AU  - Steve Schulze
AU  - Maggie L. Li
AU  - Yu-Jing Qin
AU  - Lin Yan
AU  - Hannah C. Turner
AU  - Suhail Dhawan
AU  - Alice Townsend
AU  - Jakob Nordin
AU  - Aleksandra Bochenek
AU  - Malte Busmann
AU  - Kaustav K. Das
AU  - Christoffer Fremling
AU  - Lluis Galbany
AU  - Alexa C. Gordon
AU  - Daniel Gruen
AU  - Mansi M. Kasliwal
AU  - Chang Liu
AU  - Zoë McGrath
AU  - Christopher Martin
AU  - Peter Massey
AU  - Martijn S. S. L. Oei
AU  - Daniel A. Perley
AU  - Andrés I. Ponte Pérez
AU  - Francisco Prada
AU  - Nikolaus Z. Prusinski
AU  - Nabeel Rehemtulla
AU  - R. Michael Rich
AU  - Surya Shivaprasad
AU  - Jesper Sollerman
AU  - Jacob L. Wise
PY  - 2026
DA  - 2026/08/28
PB  - arXiv
DO  - 10.48550/arxiv.2608.28416
UR  - https://arxiv.org/abs/2608.28416
AB  - We present spatially resolved spectra and infer the time-delays between the multiple images of the strongly gravitationally lensed superluminous supernova (SLSN) 2025wny at z=2.015. SN 2025wny is the first known spatially resolved strongly lensed SLSN and provides a unique opportunity to measure lensing delays through the temporal evolution of supernova spectra. We present a spectroscopic dataset spanning several months, including spatially resolved spectra of images A, B, C, D, and E. We identify and measure the wavelength evolution of spectral features using Gaussian-process modeling. The time delays are inferred by jointly fitting the temporal evolution of the spectral features, yielding Δt_AB=−10.3 ± 2.3, Δt_AC=0.1 ± 3.6, Δt_AD=−65.7 ± 3.5, and Δt_AE=3.7 ± 8.8 days (68% confidence intervals). These are the among most precise time-delay measurements obtained for a lensed supernova to date, whether from spectroscopic or photometric methods. The longest delay (Δt_AD) is particularly well constrained, with a ~5% precision. Combined with the lens model presented by Mörtsell et al. (2026), the spectroscopic time-delays give a Hubble constant H_0 = 70.2^+8.2_−6.1 km/s/Mpc. Our analysis demonstrates that spectroscopic evolution provides an independent and complementary route to time-delay measurements in lensed supernova systems, avoiding reliance on photometric light curves alone. As future surveys discover larger samples of lensed supernovae, spectroscopic time-delay measurements will provide an important avenue for precision cosmography.
ER  -