DRAFT
2026-02-25 09:36:19
Type: Object/s-Data/Analysis
Bibcode: 2026TNSAN..46....1P
AT 2025agpz / ATLAS25pny / LSST-P-DO-313761043604045880: SLSN candidate in the first Rubin / LSST alerts
Authors: I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), D. Aguado (IAC and ULL), A. López-Oramas (IAC and ULL), C. Jiménez Ángel (GRANTECAN), R. Shirley (MPE), R. Marques-Chaves (Univ. of Geneva), and S. Geier (GRANTECAN & IAC)
Source Group: SGLF
Keywords: Time-domain, Transient, Supernova
Abstract:
We report on a candidate SLSN, first discovered by ATLAS (ATLAS25pny, AT 2025agpz) and with a well defined light curve (object LSST-P-DO-313761043604045880) in the first Rubin alerts.

The transient ATLAS25pny was discovered by ATLAS on 2025-12-10 at 21:37:31 UT at cyan-ATLAS = 19.739 +/ - 0.194 and reported to the TNS (AT 2025agpz, Tonry et al., TNS Astronomical Transient Report No. 280310). Using the Lasair LSST broker we find that this transient has a well defined LSST light curve in the first public Rubin / LSST alerts (object LSST-P-DO-313761043604045880) with a first detection on 2025-11-24 at 08:04:49 UT at an LSST r-band magnitude of 23.89 +/- 0.18.

The slow evolution of the light curve, with an observed rise time in the r-band of about 80 days, the colour evolution, and the faint likely host galaxy with Legacy Imaging Surveys DR10 magnitudes of g=24.16, r=23.75, i=23.35, and z=23.41 suggests that this transient is a superluminous supernova. The LS DR9 photometric redshift of the likely host galaxy is z = 0.796 +/- 0.471.

We encourage photometric and spectroscopic follow up.

LSST photometry is available at the LSST brokers, e.g.: 

Lasair

Show current TNS values
Catalog Name Reported RA Reported DEC Reported Obj-Type Reported Redshift Host Name Host Redshift Remarks TNS RA TNS DEC TNS Obj-Type TNS Redshift
TNS 2025agpz [ATLAS25pny] 04:07:51.568 -48:42:47.65 04:07:51.557 -48:42:48.40

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