LMC nova candidate ASASSN-24by (AT 2024epj): LCOGT follow-up

ATel #16543; I. Perez-Fournon and F. Poidevin (IAC and ULL)
on 20 Mar 2024; 13:16 UT
Credential Certification: Ismael Perez-Fournon (ipf@iac.es)

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We report on LCOGT follow-up observations of the LMC Nova candidate ASASSN-24by (AT 2024epj), discovered by K. Z. Stanek, for the ASAS-SN team, at g-Sloan = 10.2 on 2024-03-18 01:55:12 UT. We obtained short (5-sec) observations in the SDSS g', r', i', and Pan-STARRS zs filters with one of the 1-m LCOGT telescopes at the LCOGT Sutherland Observatory node, starting on 2024-03-18 18:34:24 UT. The images were astrometrically calibrated with Gaia DR3 stars, with rms of 0.1". For the photometric calibration we used the Gaia DR3 synthetic photometry from Gaia low-resolution spectra (Gaia Collaboration, Montegriffo et al. 2023, A&A 674, A33) and measured: g' = 11.56 +/- 0.05, r' = 11.08 +/- 0.02, i' = 11.10 +/- 0.02, and zs = 10.95 + 0.05.

We detect this LMC nova candidate at RA (J2000) = 04:55:03.930, Dec (J2000) = -65:55:57.02, that is offset by 1" from the reported ASAS-SN position. The nova candidate is likely associated with Gaia star 4662206589167459968, with Gmag = 20.541 +/- 0.020 and position RA (J2000) = 04:55:03.9284, Dec (J2000) = -65:55:56.938, that is 0.08" from the LCOGT position.

The ASAS-SN Sky Patrol forced photometry tool (Kochanek et al. 2017, PASP, 129, 4502) shows that the nova is fading rapidly, with g = 11.983 +/- 0.007 on 2024-03-19.08798 UT. The ATLAS forced photometry tool (Shingles et al. 2021, AstroNote 2021-7) shows detections in the ATLAS orange band with magnitudes from 11.3309 to 11.644 on 2024-03-19.00207 to 2024-03-19.03513.

Follow-up is strongly encourauged, in particular the spectroscopic classification.

The ASAS-SN light curve is available at:

https://asas-sn.osu.edu/sky-patrol/coordinate/de43c513-7d2a-42bf-a93e-89d1318a6b09

This work makes use of observations from the Las Cumbres Observatory global telescope network (program IAC2024A-008).

LCOGT finding chart