Early rise and quiescent detection of V462 Lupi (AT 2025nlr) as observed by GOTO

ATel #17237; B. Godson, D. Steeghs (Warwick), A. Kumar (RHUL), D. O'Neill (Birmingham), K. Ulaczyk, K. Ackley (Warwick), M. Dyer, D. Jarvis (Sheffield) and G. Ramsay (Armagh) on behalf of the GOTO collaboration.
on 19 Jun 2025; 13:58 UT
Credential Certification: Danny Steeghs (D.T.H.Steeghs@warwick.ac.uk)

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AT 2025nlr was discovered as a g=8.7 mag source on 2025-06-12 20:52:48 UT (JD 2460839.37) by the All Sky Automated Survey for SuperNovae (ASAS-SN) and promptly classified as a galactic classical nova (ATel #17228).

We report on observations with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022; Dyer et al. 2024) of AT 2025nlr prior to its discovery by ASAS-SN. 

The position of AT 2025nlr was observed by GOTO-South as part of its all-sky survey on 2025-05-23 08:52:45 UT (JD 2460818.86997) at an increased brightness level. Difference imaging identified a flux excess at J2000 RA = 15:08:03.27 and Dec = -40:08:35.15, approximately 6" from the reported position of AT 2025nlr, with a magnitude of L=17.98 +/- 0.05 in the GOTO L-band. The L-band is approximately g+r combined, and no colour-term corrections were applied. Several additional detections were made before the source saturated in our images, slowly rising to L=17.74 +/- 0.14 on 2025-06-05 10:09:09 UT (JD 2460831.92303).

The source is also detected pre-outburst on numerous epochs between 2023 and 2025, suggesting a pre-outburst counterpart at L=19.2 with some evidence of variability. Furthermore, the GOTO position matches a G=18.3 GAIA source (DR3 6005352160949679104) to within 0.1". We believe the astrometric offset from the reported ASAS-SN is consistent with the fact that the source was already very bright in the ASAS-SN images.

Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. These values were measured directly from the science images rather than template-subtracted photometry as the source was detected in the template.

GOTO (goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).