Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient

S R Oates; N P M Kuin; M Nicholl; F Marshall; E Ridley; K Boutsia; A A Breeveld; D A H Buckley; S B Cenko; M De Pasquale; P G Edwards; M Gromadzki; R Gupta; S Laha; N Morrell; M Orio; S B Pandey; M J Page; K L Page; T Parsotan; A Rau; P Schady; J Stevens; P J Brown; P A Evans; C Gronwall; J A Kennea; N J Klingler; M H Siegel; A Tohuvavohu; E Ambrosi; S D Barthelmy; A P Beardmore; M G Bernardini; C Bonnerot; S Campana; R Caputo; S Ciroi; G Cusumano; A D’Aì; P D’Avanzo; V D’Elia; P Giommi; D H Hartmann; H A Krimm; D B Malesani; A Melandri; J A Nousek; P T O’Brien; J P Osborne; C Pagani; D M Palmer; M Perri; J L Racusin; T Sakamoto; B Sbarufatti; J E Schlieder; G Tagliaferri; E Troja; D Xu

doi:10.1093/mnras/stae795

Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient

S R Oates, N P M Kuin, M Nicholl, F Marshall, E Ridley, K Boutsia, A A Breeveld, D A H Buckley, S B Cenko, M De Pasquale, P G Edwards, M Gromadzki, R Gupta, S Laha, N Morrell, M Orio, S B Pandey, M J Page, K L Page, T ParsotanA Rau, P Schady, J Stevens, P J Brown, P A Evans, C Gronwall, J A Kennea, N J Klingler, M H Siegel, A Tohuvavohu, E Ambrosi, S D Barthelmy, A P Beardmore, M G Bernardini, C Bonnerot, S Campana, R Caputo, S Ciroi, G Cusumano, A D’Aì, P D’Avanzo, V D’Elia, P Giommi, D H Hartmann, H A Krimm, D B Malesani, A Melandri, J A Nousek, P T O’Brien, J P Osborne, C Pagani, D M Palmer, M Perri, J L Racusin, T Sakamoto, B Sbarufatti, J E Schlieder, G Tagliaferri, E Troja, D Xu

School of Mathematics and Physics

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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 $L_{max}=1.1\times 10^{45}~{\rm erg\, s}^{-1}$ 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.

Original language	English
Pages (from-to)	1688-1710
Number of pages	23
Journal	Monthly Notices of the Royal Astronomical Society
Volume	530
Issue number	2
Early online date	19 Mar 2024
DOIs	https://doi.org/10.1093/mnras/stae795
Publication status	Published - May 2024

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Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient
Copyright 2024 the authors. This is an open access article published under a Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
Final published version, 16.1 MBLicence: CC BY

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Oates, S. R., Kuin, N. P. M., Nicholl, M., Marshall, F., Ridley, E., Boutsia, K., Breeveld, A. A., Buckley, D. A. H., Cenko, S. B., De Pasquale, M., Edwards, P. G., Gromadzki, M., Gupta, R., Laha, S., Morrell, N., Orio, M., Pandey, S. B., Page, M. J., Page, K. L., ... Xu, D. (2024). Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient. Monthly Notices of the Royal Astronomical Society, 530(2), 1688-1710. https://doi.org/10.1093/mnras/stae795

@article{e79f1e703227464891db1d5c253645ce,

title = "Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient",

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 \$L\_\{max\}=1.1\textbackslash{}times 10\textasciicircum{}\{45\}\textasciitilde{}\{\textbackslash{}rm erg\textbackslash{}, s\}\textasciicircum{}\{-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.",

author = "Oates, \{S R\} and Kuin, \{N P M\} and M Nicholl and F Marshall and E Ridley and K Boutsia and Breeveld, \{A A\} and Buckley, \{D A H\} and Cenko, \{S B\} and M De Pasquale and Edwards, \{P G\} and M Gromadzki and R Gupta and S Laha and N Morrell and M Orio and Pandey, \{S B\} and Page, \{M J\} and Page, \{K L\} and T Parsotan and A Rau and P Schady and J Stevens and Brown, \{P J\} and Evans, \{P A\} and C Gronwall and Kennea, \{J A\} and Klingler, \{N J\} and Siegel, \{M H\} and A Tohuvavohu and E Ambrosi and Barthelmy, \{S D\} and Beardmore, \{A P\} and Bernardini, \{M G\} and C Bonnerot and S Campana and R Caputo and S Ciroi and G Cusumano and A D{\textquoteright}A{\`i} and P D{\textquoteright}Avanzo and V D{\textquoteright}Elia and P Giommi and Hartmann, \{D H\} and Krimm, \{H A\} and Malesani, \{D B\} and A Melandri and Nousek, \{J A\} and O{\textquoteright}Brien, \{P T\} and Osborne, \{J P\} and C Pagani and Palmer, \{D M\} and M Perri and Racusin, \{J L\} and T Sakamoto and B Sbarufatti and Schlieder, \{J E\} and G Tagliaferri and E Troja and D Xu",

year = "2024",

month = may,

doi = "10.1093/mnras/stae795",

language = "English",

volume = "530",

pages = "1688--1710",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "2",

}

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, D’Aì, A, D’Avanzo, P, D’Elia, V, Giommi, P, Hartmann, DH, Krimm, HA, Malesani, DB, Melandri, A, Nousek, JA, O’Brien, PT, Osborne, JP, Pagani, C, Palmer, DM, Perri, M, Racusin, JL, Sakamoto, T, Sbarufatti, B, Schlieder, JE, Tagliaferri, G, Troja, E & Xu, D 2024, 'Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient', Monthly Notices of the Royal Astronomical Society, vol. 530, no. 2, pp. 1688-1710. https://doi.org/10.1093/mnras/stae795

TY - JOUR

T1 - Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient

AU - Oates, S R

AU - Kuin, N P M

AU - Nicholl, M

AU - Marshall, F

AU - Ridley, E

AU - Boutsia, K

AU - Breeveld, A A

AU - Buckley, D A H

AU - Cenko, S B

AU - De Pasquale, M

AU - Edwards, P G

AU - Gromadzki, M

AU - Gupta, R

AU - Laha, S

AU - Morrell, N

AU - Orio, M

AU - Pandey, S B

AU - Page, M J

AU - Page, K L

AU - Parsotan, T

AU - Rau, A

AU - Schady, P

AU - Stevens, J

AU - Brown, P J

AU - Evans, P A

AU - Gronwall, C

AU - Kennea, J A

AU - Klingler, N J

AU - Siegel, M H

AU - Tohuvavohu, A

AU - Ambrosi, E

AU - Barthelmy, S D

AU - Beardmore, A P

AU - Bernardini, M G

AU - Bonnerot, C

AU - Campana, S

AU - Caputo, R

AU - Ciroi, S

AU - Cusumano, G

AU - D’Aì, A

AU - D’Avanzo, P

AU - D’Elia, V

AU - Giommi, P

AU - Hartmann, D H

AU - Krimm, H A

AU - Malesani, D B

AU - Melandri, A

AU - Nousek, J A

AU - O’Brien, P T

AU - Osborne, J P

AU - Pagani, C

AU - Palmer, D M

AU - Perri, M

AU - Racusin, J L

AU - Sakamoto, T

AU - Sbarufatti, B

AU - Schlieder, J E

AU - Tagliaferri, G

AU - Troja, E

AU - Xu, D

PY - 2024/5

Y1 - 2024/5

N2 - 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 $L_{max}=1.1\times 10^{45}~{\rm erg\, s}^{-1}$ 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.

AB - 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 $L_{max}=1.1\times 10^{45}~{\rm erg\, s}^{-1}$ 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.

U2 - 10.1093/mnras/stae795

DO - 10.1093/mnras/stae795

M3 - Article

SN - 0035-8711

VL - 530

SP - 1688

EP - 1710

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

Swift/UVOT discovery of Swift J221951−484240: a UV luminous ambiguous nuclear transient

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