eprintid: 10192060 rev_number: 6 eprint_status: archive userid: 699 dir: disk0/10/19/20/60 datestamp: 2024-05-14 13:40:06 lastmod: 2024-05-14 13:40:06 status_changed: 2024-05-14 13:40:06 type: article metadata_visibility: show sword_depositor: 699 creators_name: Oates, SR creators_name: Kuin, NPM creators_name: Nicholl, M creators_name: Marshall, F creators_name: Ridley, E creators_name: Boutsia, K creators_name: Breeveld, AA creators_name: Buckley, DAH creators_name: Cenko, SB creators_name: De Pasquale, M creators_name: Edwards, PG creators_name: Gromadzki, M creators_name: Gupta, R creators_name: Laha, S creators_name: Morrell, N creators_name: Orio, M creators_name: Pandey, SB creators_name: Page, MJ creators_name: Page, KL creators_name: Parsotan, T creators_name: Rau, A creators_name: Schady, P creators_name: Stevens, J creators_name: Brown, PJ creators_name: Evans, PA creators_name: Gronwall, C creators_name: Kennea, JA creators_name: Klingler, NJ creators_name: Siegel, MH creators_name: Tohuvavohu, A creators_name: Ambrosi, E creators_name: Barthelmy, SD creators_name: Beardmore, AP creators_name: Bernardini, MG creators_name: Bonnerot, C creators_name: Campana, S creators_name: Caputo, R creators_name: Ciroi, S creators_name: Cusumano, G creators_name: Aì, AD creators_name: Avanzo, PD creators_name: Elia, VD creators_name: Giommi, P creators_name: Hartmann, DH creators_name: Krimm, HA creators_name: Malesani, DB creators_name: Melandri, A creators_name: Nousek, JA creators_name: Brien, PTO creators_name: Osborne, JP creators_name: Pagani, C creators_name: Palmer, DM creators_name: Perri, M creators_name: Racusin, JL creators_name: Sakamoto, T creators_name: Sbarufatti, B creators_name: Schlieder, JE creators_name: Tagliaferri, G creators_name: Troja, E creators_name: Xu, D title: Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F63 keywords: Black hole physics, gravitational waves, galaxies: nuclei, ultraviolet: general, transients: tidal disruption events note: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ abstract: We report the discovery of Swift J221951−484240 (hereafter: J221951), a luminous slow-evolving blue transient that was detected by the Neil Gehrels Swift Observatory Ultraviolet/Optical Telescope (Swift/UVOT) during the follow-up of gravitational wave alert S190930t, to which it is unrelated. Swift/UVOT photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with an approximately constant temperature of T ∼ 2.5 × 104 K. At a redshift z = 0.5205, J221951 had a peak absolute magnitude of Mu,AB = −23 mag, peak bolometric luminosity Lmax = 1.1 × 1045 erg s−1 and a total radiated energy of E > 2.6 × 1052 erg. The archival Wide-field Infrared Survey Explorer IR photometry shows a slow rise prior to a peak near the discovery date. Spectroscopic UV observations display broad absorption lines in N V and O VI, pointing towards an outflow at coronal temperatures. The lack of emission in the higher H α lines, N I and other neutral lines is consistent with a viewing angle close to the plane of the accretion or debris disc. The origin of J221951 cannot be determined with certainty but has properties consistent with a tidal disruption event and the turn-on of an active galactic nucleus. date: 2024-05-01 date_type: published publisher: Oxford University Press (OUP) official_url: http://dx.doi.org/10.1093/mnras/stae795 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 2273655 doi: 10.1093/mnras/stae795 lyricists_name: Breeveld, Alice lyricists_name: Kuin, Nicolaas lyricists_id: AABRE89 lyricists_id: NPMKU93 actors_name: Flynn, Bernadette actors_id: BFFLY94 actors_role: owner full_text_status: public publication: Monthly Notices of the Royal Astronomical Society volume: 530 number: 2 pagerange: 1688-1710 citation: Oates, SR; Kuin, NPM; Nicholl, M; Marshall, F; Ridley, E; Boutsia, K; Breeveld, AA; ... Xu, D; + view all <#> Oates, SR; Kuin, NPM; Nicholl, M; Marshall, F; Ridley, E; Boutsia, K; Breeveld, AA; Buckley, DAH; Cenko, SB; De Pasquale, M; Edwards, PG; Gromadzki, M; Gupta, R; Laha, S; Morrell, N; Orio, M; Pandey, SB; Page, MJ; Page, KL; Parsotan, T; Rau, A; Schady, P; Stevens, J; Brown, PJ; Evans, PA; Gronwall, C; Kennea, JA; Klingler, NJ; Siegel, MH; Tohuvavohu, A; Ambrosi, E; Barthelmy, SD; Beardmore, AP; Bernardini, MG; Bonnerot, C; Campana, S; Caputo, R; Ciroi, S; Cusumano, G; Aì, AD; Avanzo, PD; Elia, VD; Giommi, P; Hartmann, DH; Krimm, HA; Malesani, DB; Melandri, A; Nousek, JA; Brien, PTO; Osborne, JP; Pagani, C; Palmer, DM; Perri, M; Racusin, JL; Sakamoto, T; Sbarufatti, B; Schlieder, JE; Tagliaferri, G; Troja, E; Xu, D; - view fewer <#> (2024) Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient. Monthly Notices of the Royal Astronomical Society , 530 (2) pp. 1688-1710. 10.1093/mnras/stae795 <https://doi.org/10.1093/mnras%2Fstae795>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10192060/1/stae795.pdf