Issue |
A&A
Volume 689, September 2024
|
|
---|---|---|
Article Number | A350 | |
Number of page(s) | 29 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202449296 | |
Published online | 24 September 2024 |
The fast transient AT 2023clx in the nearby LINER galaxy NGC 3799 as a tidal disruption of a very low-mass star
1
Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
2
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
3
European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
4
DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Kgs. Lyngby, Denmark
5
European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile
6
Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
7
Institute for Gravitational Wave Astronomy, University of Birmingham, Birmingham B15 2TT, UK
8
School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
9
Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
10
Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, København N DK-2200, Denmark
11
Millennium Institute of Astrophysics MAS, Nuncio Monsenor Sotero Sanz 100, Off. 104, Providencia, Santiago, Chile
12
School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
13
Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, P.R. China
14
Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, P.R. China
15
International Centre of Supernovae, Yunnan Key Laboratory, Kunming 650216, P.R. China
16
Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, 32001 Jhongli, Taiwan
17
Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis Bd Arago 75014 Paris, France
18
Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, E-08193 Barcelona, Spain
19
Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
20
Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, PL-00-478 Warszawa, Poland
21
Isaac Newton Group of Telescopes, ING, 38700 La Palma, S.C. Tenerife, Spain
22
Finnish Centre for Astronomy with ESO (FINCA), FI-20014 University of Turku, Finland
23
The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
24
Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
25
Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
26
School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
27
INAF-Osservatorio Astronomico d’Abruzzo, Via M. Maggini snc, I-64100 Teramo, Italy
28
Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
29
National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100101, China
30
Physics & Astronomy, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
Received:
20
January
2024
Accepted:
28
June
2024
We present an extensive analysis of the optical and ultraviolet (UV) properties of AT 2023clx, the closest optical/UV tidal disruption event (TDE) to date (z = 0.01107), which occurred in the nucleus of the interacting low-ionization nuclear emission-line region (LINER) galaxy, NGC 3799. After correcting for the host reddening (E(B − V)h = 0.179 mag), we find its peak absolute g-band magnitude to be −18.03 ± 0.07 mag, and its peak bolometric luminosity to be Lpk = (1.57 ± 0.19)×1043 erg s−1. AT 2023clx displays several distinctive features: first, it rose to peak within 10.4 ± 2.5 days, making it the fastest rising TDE to date. Our SMBH mass estimate of M̄BH ≈ 106.0 M⊙ –estimated using several standard methods– rules out the possibility of an intermediate-mass BH as the reason for the fast rise. Dense spectral follow-up reveals a blue continuum that cools slowly and broad Balmer and He II lines as well as weak He Iλλ5876,6678 emission features that are typically seen in TDEs. The early, broad (width ∼15 000 km s−1) profile of Hα matches theoretical expectations from an optically thick outflow. A flat Balmer decrement (LHα/LHβ ∼ 1.58) suggests that the lines are collisionally excited rather than being produced via photoionisation, in contrast to typical active galactic nuclei. A second distinctive feature, seen for the first time in TDE spectra, is a sharp, narrow emission peak at a rest wavelength of ∼6353 Å. This feature is clearly visible up to 10 d post-peak; we attribute it to clumpy material preceding the bulk outflow, which manifests as a high-velocity component of Hα (−9584 km s−1). Its third distinctive feature is the rapid cooling during the first ∼20 days after peak, reflected as a break in the temperature evolution. Combining these findings, we propose a scenario for AT 2023clx involving the disruption of a very low-mass star (≲0.1 M⊙) with an outflow launched in our line of sight and with disruption properties that led to efficient circularisation and prompt accretion disc formation, observed through a low-density photosphere.
Key words: black hole physics / methods: observational / galaxies: nuclei
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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