2026A&A...706A.324V

Query : 2026A&A...706A.324V

2026A&A...706A.324V - Astronomy and Astrophysics, volume 706A324 (2026/2-1)

Back from the dead: AT2019aalc as a candidate repeating tidal disruption event in an active galactic nucleus.

VERES P.M., FRANCKOWIAK A., VAN VELZEN S., ADEBAHR B., TAZIAUX S., NECKER J., STEIN R., KIER A., MULLER A., BOMANS D.J., JORDANA-MITJANS N., KOWALSKI M., HAMMERSTEIN E., MARCI-BOEHNCKE E., REUSCH S., GARRAPPA S., ROSE S. and DAS K.K.

Abstract (from CDS):

Context. To date, three nuclear transients have been associated with high-energy neutrino events. These transients are generally thought to be powered by tidal disruption events (TDEs) in stars caused by massive black holes. However, AT2019aalc, hosted in a Seyfert-1 galaxy, has not yet been classified due to a lack of multiwavelength observations. Interestingly, the source re-brightened 4 years after its discovery.
Aims. Our aim is to constrain the physical mechanism responsible for the second optical flare, which may also provide clues to the origin of the initial event.
Methods. We conducted a multiwavelength monitoring program (from radio to X-rays) of AT2019aalc during its re-brightening in 2023-2024.
Results. The observations revealed multiple X-ray flares during the second optical flaring episode of the transient and a uniquely bright UV counterpart. The second flare, similar to the first one, is accompanied by IR dust echo emission. A long-term radio flare was found with an inverted spectrum. Optical spectroscopic observations revealed the presence of Bowen fluorescence lines and strong high-ionization coronal lines, indicating an extreme level of ionization in the system.
Conclusions. The results suggest that the transient can be classified as a Bowen fluorescence flare (BFF), a relatively new sub-class of flaring active galactic nuclei (AGNs). AT2019aalc can be also classified as an extreme coronal line emitter (ECLE). We find that in addition to AT2019aalc, another BFF, AT2021loi, is spatially coincident with a high-energy neutrino event. We propose a repeating TDE scenario within an AGN framework to explain the multiwavelength properties of AT2019aalc and suggest a possible connection among ECLEs, BFFs, and TDEs occurring in AGNs.

Abstract Copyright: © The Authors 2026

Journal keyword(s): neutrinos - galaxies: active - galaxies: individual: AT2019aalc - quasars: emission lines - galaxies: Seyfert - radio continuum: galaxies

VizieR on-line data: <Available at CDS (J/A+A/706/A324): table1.dat table2.dat table3.dat table4.dat table5.dat>

Simbad objects: 41

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Number of rows : 41
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 AT 2022upj ev 00 23 56.846 -14 25 23.22           ~ 30 0
2 AT 2021loi ev 01 00 39.619 +39 42 30.31           ~ 12 0
3 IRAS 01003-2238 Sy2 01 02 49.9920152640 -22 21 57.262136544   18.62 18.9 17.83   ~ 192 0
4 2dFGRS TGS564Z081 Sy2 01 19 08.6635573080 -34 11 30.527946780   16.226   15.275   ~ 159 0
5 OGLE17aaj ev 01 56 24.93 -71 04 15.7           ~ 29 0
6 2MASS J01580475-0052221 Sy1 01 58 04.7506373016 -00 52 21.927742716   18.84 18.34     SNII 114 1
7 M 77 Sy2 02 42 40.7091669408 -00 00 47.859690204 9.70 9.61 8.87 10.1 9.9 ~ 4897 2
8 AT 2020afhd ev 03 13 35.700 -02 09 06.37           TDE 9 0
9 AT 2021dms ev 03 21 24.069 -11 08 45.71           ~ 7 0
10 AT 2019pev CV? 04 29 22.7162030809 +00 37 07.516251497           ~ 24 0
11 AT 2019qiz ev 04 46 37.880 -10 13 34.92           ~ 143 0
12 eRASSt J045650.3-203750 X 04 56 50.3 -20 37 50           ~ 40 0
13 ASASSN -14ko ev 05 25 18.13 -46 00 20.3           SNIIn 84 0
14 Z 119-12 SyG 08 13 16.9505119752 +22 38 53.905852212           ~ 156 0
15 AT 2019avd Sy1 08 23 36.80 +04 23 03.4           ~ 47 0
16 AT 2020vdq ev 10 08 53.440 +42 43 00.23           ~ 37 0
17 AT 2021acak ev 10 34 47.900 +15 29 22.38           ~ 7 0
18 ASASSN -22ci ev 12 20 45.010 +49 33 04.68           ~ 31 0
19 IC 3599 Sy1 12 37 41.1939398400 +26 42 27.484266888   15.7 16.5     ~ 191 0
20 RX J133157.6-324319 X 13 31 57.90 -32 43 21.2           ~ 19 0
21 AT 2021seu ev 14 21 34.622 +37 54 34.97           ~ 2 0
22 IceCube-191119A ev 15 20.4 +03 10           ~ 24 0
23 4C 04.51 rG 15 21 14.41846935 +04 30 21.6366133   18.2       ~ 103 1
24 Z 49-155 Sy1 15 24 16.6702264008 +04 51 19.027331064   16.70 16.26     ~ 70 0
25 AT 2022fpx ev 15 31 03.700 +53 24 19.26           ~ 19 0
26 AT 2018dyk ev 15 33 08.01 +44 32 08.2           ~ 33 0
27 IceCube-200410A ev 16 10.3 +11 37           ~ 16 0
28 2MASX J16105891-6055250 AG? 16 10 58.8863559654 -60 55 24.411688282           ~ 78 0
29 AT 2017bgt AGN 16 11 05.518 +02 34 02.14           ~ 35 0
30 AT 2021aeuk ev 16 12 59.842 +42 19 40.25           ~ 14 0
31 AT 2017gge ev 16 20 34.86 +24 07 25.6           ~ 30 0
32 IceCube-200530A ev 17 03.3 +26 48           ~ 31 0
33 SN 2019fdr SN* 17 09 06.859 +26 51 20.50           SLSN-II 48 0
34 AT 2021qth ev 20 11 38.926 -21 09 36.64           ~ 11 0
35 IceCube-191001A ev 20 56.3 +12 56           ~ 37 0
36 2MASX J20570298+1412165 G 20 57 02.9650698480 +14 12 16.295014080           ~ 162 0
37 AT 2021lwx ev 21 13 48.410 +27 25 50.38           ~ 16 0
38 AT 2018bcb ev 22 43 42.90 -16 59 08.1           ~ 39 0
39 AT 2018fyk ev 22 50 16.10 -44 51 53.5           ~ 114 0
40 AT 2024mvz ev 23 40 27.800 -07 00 51.66           ~ 1 0
41 IceCube-230511A ev ~ ~           ~ 4 0

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