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Saxton, RD, Read, AM, Komossa, S, Lira, P, Alexander, KD, Steele, IA, Ocana, F, Berger, E and Blanchard, P (2019) XMMSL2 J144605.0+685735: a slow tidal disruption event. Astronomy & Astrophysics, 630. ISSN 1432-0746
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Abstract
Aims. We investigate the evolution of X-ray selected tidal disruption events.
Methods. New events are found in near real-time data from XMM-Newton slews, and are monitored by multi-wavelength facilities.
Results. In August 2016, X-ray emission was detected from the galaxy XMMSL2 J144605.0+685735 (also known as 2MASX 14460522+6857311), that was 20 times higher than an upper limit from 25 years earlier. The X-ray flux was flat for ∼100 days and then fell by a factor of 100 over the following 500 days. The UV flux was stable for the first 400 days before fading by a magnitude, while the optical (U,B,V) bands were roughly constant for 850 days. Optically, the galaxy appears to be quiescent, at a distance of 127 ± 4 Mpc (z = 0.029 ± 0.001) with a spectrum consisting of a young stellar population of 1–5 Gyr in age, an older population, and a total stellar mass of ∼6 × 109 M⊙. The bolometric luminosity peaked at Lbol ∼ 1043 ergs s−1 with an X-ray spectrum that may be modelled by a power law of Γ ∼ 2.6 or Comptonisation of a low-temperature thermal component by thermal electrons. We consider a tidal disruption event to be the most likely cause of the flare. Radio emission was absent in this event down to < 10 μJy, which limits the total energy of a hypothetical off-axis jet to E < 5 × 1050 ergs. The independent behaviour of the optical, UV, and X-ray light curves challenges models where the UV emission is produced by reprocessing of thermal nuclear emission or by stream-stream collisions. We suggest that the observed UV emission may have been produced from a truncated accretion disc and the X-rays from Compton upscattering of these disc photons.
| Item Type: | Article |
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| Uncontrolled Keywords: | 0201 Astronomical and Space Sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | EDP Sciences |
| Related URLs: | |
| Date Deposited: | 06 Jan 2020 11:47 |
| Last Modified: | 04 Sep 2021 08:13 |
| DOI or ID number: | 10.1051/0004-6361/201935650 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/11953 |
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