AT2025ulz and S250818k: zooming in with the Hubble Space Telescope

arXiv:2510.18854 · astro-ph.HE, hep-ph · Submitted 2025-10-21 · Read on arXiv

astro-ph.HE, hep-ph

Submitted: 2025-10-21

Updated: 2025-12-17

Comments: 15 pages, 6 figures, 2 tables. Accepted for publication in ApJL

Journal ref: ApJL 996, L24 (2026)

DOI: 10.3847/2041-8213/ae2dea

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Hubble Space Telescope — 9× in this paper
• Gran Telescopio Canarias — 5× in this paper
• Aperture — 3× in this paper · explained in 1 episode
• Aperture Photometry — 2× in this paper · explained in 1 episode
• Consistency — 2× in this paper · explained in 3 episodes
• Mikulski Archive for Space Telescopes — 2× in this paper
• AMS and the European Regional Development Fund — 1× in this paper
• Bayesian Inference — 1× in this paper · explained in 5 episodes
• Benchmark — 1× in this paper · explained in 2 episodes
• Core — 1× in this paper · explained in 2 episodes
• Gaia Total Galactic Extinction — 1× in this paper
• Subsequent LIGO-Virgo-Kagra — 1× in this paper
• Target of Opportunity — 1× in this paper
• Trace — 1× in this paper · explained in 2 episodes

Sources

• Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-Significance Gravitational Wave Event S250818k
• Pan-STARRS follow-up of the gravitational-wave event S250818k and the lightcurve of SN 2025ulz
• AT2025ulz and S250818k: Leveraging DESI spectroscopy in the hunt for a kilonova associated with a sub-solar mass gravitational wave candidate
• AT2025ulz and S250818k: Deep X-ray and radio limits on off-axis afterglow emission and prospects for future discovery
• GWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run

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