AstroNote 2025-266

The BHTOM.space network coordinated an observing campaign to monitor SN 2025pht, 

reported on 2025/06/29 by the All Sky Automated Survey for SuperNovae (ASAS-SN) and designated as ASASSN-25cw. The event was spotted in the direction of the Eridanus constellation in the NGC 1637 spiral galaxy, some 10 Mpc from the Milky Way (Crowther 2013).

Observations commenced on Jul 5th, 2025, approx. a week after it was discovered, and are still ongoing. During this period, approximately 300 measurements were obtained using a 40-cm telescope from the ROAD Observatory (Chile). Photometric data were taken in B, V, and I filters and subsequently transformed into Gaia Synthetic Photometry (GaiaSP) for consistency.

A recent study by Kilpatrick et al. 2025 (https://arxiv.org/pdf/2508.10994) identifies this Type-II supernova progenitor with the use of JWST data. SN2025pht was previously classified by Stanek et al. (ASAS-SN) here: https://www.wis-tns.org/object/2025pht.

The SN2025pht event was also detected and reported by the ATLAS survey.

Observations of the object with BHTOM will continue until it disappears in the background. Further photometric observations with the use of larger telescopes are advised, as well as spectra taken during different phases of dimming.

Detailed light curves and associated statistics are presented on the webpage: https://bhtom.space/public/targets/SN2025pht. Further details and the full photometric dataset are available for download by registered users of the BHTOM.space platform. 

Acknowledgements: BHTOM.space is based on the open-source TOM Toolkit by LCO and has been supported by the European Union's research and innovation programmes under grant agreements No 101004719 (OPTICON-RadioNet Pilot, ORP) and 101131928 (ACME).