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

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1 Citation (SciVal)

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 M_u_,AB = −23 mag, peak bolometric luminosity L_max = 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.

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 - 1 May 2024

Data Availability Statement

The Swift data underlying this article are available in the Swift archives at https://www.swift.ac.uk/swift_live/, https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/swift.pl, https://www.ssdc.asi.it/mmia/index.php?mission = swiftmastr. The photometry of J221951 is available in the online supplementary material. The ATCA data are available from the Australia Telescope Online Archive – https://atoa.atnf.csiro.au/. The HST and GALEX observations are available from the MAST Portal – https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. The X-shooter spectrum and GROND data are available from the ESO main archive – http://archive.eso.org/eso/eso_archive_main.html.

Funding

This research has made use of data obtained from the HEASARC and the Leicester Database and Archive Service, provided by NASA\u2019s Goddard Space Flight Center and the School of Physics and Astronomy, University of Leicester, UK, respectively. This publication makes use of data products from the WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI: 10.26093/cds/vizier). The original description of the VizieR service was published in 2000, A&AS, 143, 23. This research has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. Some of the observations reported in this paper were obtained with the SALT. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5\u201326555. These observations are associated with program #16076. The Australia Telescope Compact Array is part of the Australia Telescope National Facility ( https://ror.org/05qajvd42 ) which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the traditional owners of the ATCA observatory site. This research uses services or data provided by the Astro Data Lab at NSF\u2019s National Optical-Infrared Astronomy Research Laboratory. NOIRLab is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation. This publication uses the data from the AstroSat mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC). Part of the funding for GROND (both hardware as well as personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). This research made use of Astropy, a community-developed core python package for Astronomy (Astropy Collaboration ). AAB, NPMK, MJP, KLP, PAE, APB, and JPO acknowledge funding from the UK Space Agency. MDP acknowledges support for this work by the Scientific and Technological Research Council of Turkey (T\u00DCBITAK), grant number MFAG-119F073. RG and SBP acknowledge the financial support of ISRO under AstroSat archival Data utilization programme (DS2B-13013(2)/1/2021-Sec.2). RG and SBP are also thankful to the AstroSat UVIT team for helping with UVIT data analysis. EA, MGB, SC, GC, AD, PDA, AM, and GT acknowledge funding from the Italian Space Agency, contract ASI/INAF no. I/004/11/4. This work is also partially supported by a grant from the Italian Ministry of Foreign Affairs and International Cooperation Number MAE0065741. PDA acknowledges support from PRIN-MIUR 2017 (grant no.20179ZF5KS). DBM is supported by research grant no. 19\u2009054 from Villum Fonden. MN is supported by the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement no. 948381) and by a Fellowship from the Alan Turing Institute. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement no. 101004719. ET acknowledges support from the ERC under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement 101002761). DBM is supported by the ERC under the European Union\u2019s Horizon 2020 research and innovation programme (grant agreement no. 725246). The Cosmic Dawn Center is supported by the Danish National Research Foundation.

Funders	Funder number
Villum Fonden
National Aeronautics and Space Administration
Australian Government
European Space Agency
National Science Foundation
California Institute of Technology
Danmarks Grundforskningsfond
Commonwealth Scientific and Industrial Research Organisation
IPAC
Alan Turing Institute
UK Space Agency
European Research Council
Ministero degli Affari Esteri e della Cooperazione Internazionale	MAE0065741, 20179ZF5KS, 19 054
Horizon 2020 Framework Programme	948381
Space Telescope Science Institute	NAS 5–26555
Indian Space Research Organisation	DS2B-13013
Horizon 2020	101002761, 101004719, 725246
Space Science Data Center (SSDC) - Agenzia Spaziale Italiana (ASI)	I/004/11/4
Türkiye Bilimsel ve Teknolojik Araştırma Kurumu	MFAG-119F073
Deutsche Forschungsgemeinschaft	HA 1850/28-1

Keywords

black hole physics
galaxies: nuclei
gravitational waves
transients: tidal disruption events
ultraviolet: general

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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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

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 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

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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 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.",

keywords = "black hole physics, galaxies: nuclei, gravitational waves, transients: tidal disruption events, ultraviolet: general",

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 {De Pasquale}, M. 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{\`i}, {A. D.} and Avanzo, {P. D.} and Elia, {V. D.} and P. Giommi and Hartmann, {D. H.} and Krimm, {H. A.} and Malesani, {D. B.} and A. Melandri and Nousek, {J. A.} and Brien, {P. T.O.} 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",

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TY - JOUR

T1 - Swift/UVOT discovery of Swift J221951−484240

T2 - 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 - Aì, A. D.

AU - Avanzo, P. D.

AU - Elia, V. D.

AU - Giommi, P.

AU - Hartmann, D. H.

AU - Krimm, H. A.

AU - Malesani, D. B.

AU - Melandri, A.

AU - Nousek, J. A.

AU - Brien, P. T.O.

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 - 2024/5/1

Y1 - 2024/5/1

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 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.

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 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.

KW - black hole physics

KW - galaxies: nuclei

KW - gravitational waves

KW - transients: tidal disruption events

KW - ultraviolet: general

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U2 - 10.1093/mnras/stae795

DO - 10.1093/mnras/stae795

M3 - Article

AN - SCOPUS:85191195877

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VL - 530

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JO - Monthly Notices of the Royal Astronomical Society

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ER -

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

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