AstroNote 2023-194

We report the discovery of a second flare from the candidate TDE [1], AT2019aalc. The transient was first observed with the Zwicky Transient Facility (ZTF) in January 2019. The first flare started in the middle of April 2019, lasted ~60 days and peaked in the r-band at 16.7 mag (M = −19.4). Based on ZTF observations, we report a significant re-brightening that started mid-May this year, roughly 4 years after the first flare. The new flare is evolving slightly faster than the original one. From the beginning of the new flare (the source was detected anew on 2023-05-11 at r ~ 19.3 mag after several non-detections), a 2.8 mag rise can be seen till the last observation (2023-07-02 with r ~ 16.5 mag), on a timescale of roughly 50 days. The new flare evolves with constant color and is still ongoing.

Furthermore, AT2019aalc was associated with the high-energy neutrino event IC191119A [2], detected by the IceCube Observatory about 150 days after the peak of the first flare [1].

We note that the host galaxy of AT2019aalc, SDSS J152416.66+045119.0 (z=0.03557, [3]), is a known Seyfert 1 galaxy. Consequently, an AGN origin for the flare cannot be excluded.

Multi-wavelength follow-up has been triggered.

[1] van Velzen et al., arXiv e-prints, arXiv:2111.09391 (2021)

[2] E. Blaufuss, GCN Circular 26258 (2019)

[3] Ahn et al., The Astrophysical Journal Supplement, Volume 203, Issue 2, article id. 21, 13 pp. (2012)