An elliptical accretion disk following the tidal disruption event AT 2020zso

T. Wevers; M. Nicholl; M. Guolo; P. Charalampopoulos; M. Gromadzki; T. M. Reynolds; E. Kankare; G. Leloudas; J. P. Anderson; I. Arcavi; G. Cannizzaro; T. W. Chen; N. Ihanec; C. Inserra; C. P. Gutiérrez; P. G. Jonker; A. Lawrence; M. R. Magee; T. E. Müller-Bravo; F. Onori; E. Ridley; S. Schulze; P. Short; D. Hiramatsu; M. Newsome; J. H. Terwel; S. Yang; D. Young

doi:10.1051/0004-6361/202142616

An elliptical accretion disk following the tidal disruption event AT 2020zso

T. Wevers, M. Nicholl, M. Guolo, P. Charalampopoulos, M. Gromadzki, T. M. Reynolds, E. Kankare, G. Leloudas, J. P. Anderson, I. Arcavi, G. Cannizzaro, T. W. Chen, N. Ihanec, C. Inserra, C. P. Gutiérrez, P. G. Jonker, A. Lawrence, M. R. Magee, T. E. Müller-Bravo, F. OnoriE. Ridley, S. Schulze, P. Short, D. Hiramatsu, M. Newsome, J. H. Terwel, S. Yang, D. Young

Physics and Astronomy

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Abstract

Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.

Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.

Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 10¹⁵ cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 10⁵ M_⊙) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (R_in = several 100 R_g and R_out = several 1000 R_g) accretion disk.

Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 10⁶ M_⊙ and disk viscosity α ≳ 0.1.

Original language	English
Article number	A6
Number of pages	30
Journal	Astronomy and Astrophysics
Volume	666
Issue number	October 2022
Early online date	27 Sept 2022
DOIs	https://doi.org/10.1051/0004-6361/202142616
Publication status	Published - 1 Oct 2022

Bibliographical note

Funding Information:
We are grateful to T. Hung for sharing a Python implementation of the relativistic accretion disk model, and we thank T. Ricci, J. Schimoia, and G. Couto for providing spectra of NGC 4958, NGC 1097 and Arp102B. We also thank J. Krolik, T. Piran and T. Ryu for insightful comments, and the anonymous referee for comments and suggestions that improved the paper. This work is based on observations collected at the European Southern Observatory under ESO programmes 106.216C, 106.2169.001 and 106.2169.002 (PI: Inserra). The spectra will be made publicly available through WISErep. We thank the Swift team for scheduling the requested ToO observations. The Swift data are publicly available from the Swift science archive. This work is partly based on the NUTS2 programme carried out at the NOT. NUTS2 is funded in part by the Instrument Centre for Danish Astrophysics (IDA). Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This work makes use of observations from the Las Cumbres Observatory global telescope network. Based on data products created from observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 179.A-2010 and made use of data from the VISTA Hemisphere survey (McMahon et al. 2013). T.M.B. was funded by the CONICYT PFCHA/DOCTORADOBECAS CHILE/2017-72180113. S.Y. is funded through the GREAT research environment grant 2016-06012. P.C. is supported by a research grant (19054) from VILLUM FONDEN. T.-W.C. acknowledges the EU Funding under Marie Skłodowska-Curie grant H2020-MSCA-IF-2018-842471. The LCO team was supported by National Science Foundation (NSF) grants AST-1313484, AST-1911225, and AST-1911151, as well as by National Aeronautics and Space Administration (NASA) grant 80NSSC19kf1639. M.N. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 948381). N.I. is partially supported by Polish NCN DAINA grant No. 2017/27/L/ST9/03221. S.S. acknowledges support from the G.R.E.A.T research environment, funded by Vetenskapsrådet, the Swedish Research Council, project number 2016-06012. IA is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that program, from the ERC under the European Union’s Horizon 2020 research and innovation program (grant agreement number 852097), from the Israel Science Foundation (grant number 2752/19), from the United States – Israel Binational Science Foundation (BSF), and from the Israeli Council for Higher Education Alon Fellowship.

Keywords

Accretion
Accretion disks
Galaxies: active
Quasars: supermassive black holes

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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Wevers, T., Nicholl, M., Guolo, M., Charalampopoulos, P., Gromadzki, M., Reynolds, T. M., Kankare, E., Leloudas, G., Anderson, J. P., Arcavi, I., Cannizzaro, G., Chen, T. W., Ihanec, N., Inserra, C., Gutiérrez, C. P., Jonker, P. G., Lawrence, A., Magee, M. R., Müller-Bravo, T. E., ... Young, D. (2022). An elliptical accretion disk following the tidal disruption event AT 2020zso. Astronomy and Astrophysics, 666(October 2022), Article A6. Advance online publication. https://doi.org/10.1051/0004-6361/202142616

@article{36b111d9a3d74139a29029970df8674c,

title = "An elliptical accretion disk following the tidal disruption event AT 2020zso",

abstract = "Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 105 M⊙) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (Rin = several 100 Rg and Rout = several 1000 Rg) accretion disk.Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 106 M⊙ and disk viscosity α ≳ 0.1.",

keywords = "Accretion, Accretion disks, Galaxies: active, Quasars: supermassive black holes",

author = "T. Wevers and M. Nicholl and M. Guolo and P. Charalampopoulos and M. Gromadzki and Reynolds, {T. M.} and E. Kankare and G. Leloudas and Anderson, {J. P.} and I. Arcavi and G. Cannizzaro and Chen, {T. W.} and N. Ihanec and C. Inserra and Guti{\'e}rrez, {C. P.} and Jonker, {P. G.} and A. Lawrence and Magee, {M. R.} and M{\"u}ller-Bravo, {T. E.} and F. Onori and E. Ridley and S. Schulze and P. Short and D. Hiramatsu and M. Newsome and Terwel, {J. H.} and S. Yang and D. Young",

note = "Funding Information: We are grateful to T. Hung for sharing a Python implementation of the relativistic accretion disk model, and we thank T. Ricci, J. Schimoia, and G. Couto for providing spectra of NGC 4958, NGC 1097 and Arp102B. We also thank J. Krolik, T. Piran and T. Ryu for insightful comments, and the anonymous referee for comments and suggestions that improved the paper. This work is based on observations collected at the European Southern Observatory under ESO programmes 106.216C, 106.2169.001 and 106.2169.002 (PI: Inserra). The spectra will be made publicly available through WISErep. We thank the Swift team for scheduling the requested ToO observations. The Swift data are publicly available from the Swift science archive. This work is partly based on the NUTS2 programme carried out at the NOT. NUTS2 is funded in part by the Instrument Centre for Danish Astrophysics (IDA). Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This work makes use of observations from the Las Cumbres Observatory global telescope network. Based on data products created from observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 179.A-2010 and made use of data from the VISTA Hemisphere survey (McMahon et al. 2013). T.M.B. was funded by the CONICYT PFCHA/DOCTORADOBECAS CHILE/2017-72180113. S.Y. is funded through the GREAT research environment grant 2016-06012. P.C. is supported by a research grant (19054) from VILLUM FONDEN. T.-W.C. acknowledges the EU Funding under Marie Sk{\l}odowska-Curie grant H2020-MSCA-IF-2018-842471. The LCO team was supported by National Science Foundation (NSF) grants AST-1313484, AST-1911225, and AST-1911151, as well as by National Aeronautics and Space Administration (NASA) grant 80NSSC19kf1639. M.N. acknowledges support from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme (grant agreement No. 948381). N.I. is partially supported by Polish NCN DAINA grant No. 2017/27/L/ST9/03221. S.S. acknowledges support from the G.R.E.A.T research environment, funded by Vetenskapsr{\aa}det, the Swedish Research Council, project number 2016-06012. IA is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that program, from the ERC under the European Union{\textquoteright}s Horizon 2020 research and innovation program (grant agreement number 852097), from the Israel Science Foundation (grant number 2752/19), from the United States – Israel Binational Science Foundation (BSF), and from the Israeli Council for Higher Education Alon Fellowship.",

year = "2022",

month = oct,

day = "1",

doi = "10.1051/0004-6361/202142616",

language = "English",

volume = "666",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

number = "October 2022",

}

Wevers, T, Nicholl, M, Guolo, M, Charalampopoulos, P, Gromadzki, M, Reynolds, TM, Kankare, E, Leloudas, G, Anderson, JP, Arcavi, I, Cannizzaro, G, Chen, TW, Ihanec, N, Inserra, C, Gutiérrez, CP, Jonker, PG, Lawrence, A, Magee, MR, Müller-Bravo, TE, Onori, F, Ridley, E, Schulze, S, Short, P, Hiramatsu, D, Newsome, M, Terwel, JH, Yang, S & Young, D 2022, 'An elliptical accretion disk following the tidal disruption event AT 2020zso', Astronomy and Astrophysics, vol. 666, no. October 2022, A6. https://doi.org/10.1051/0004-6361/202142616

TY - JOUR

T1 - An elliptical accretion disk following the tidal disruption event AT 2020zso

AU - Wevers, T.

AU - Nicholl, M.

AU - Guolo, M.

AU - Charalampopoulos, P.

AU - Gromadzki, M.

AU - Reynolds, T. M.

AU - Kankare, E.

AU - Leloudas, G.

AU - Anderson, J. P.

AU - Arcavi, I.

AU - Cannizzaro, G.

AU - Chen, T. W.

AU - Ihanec, N.

AU - Inserra, C.

AU - Gutiérrez, C. P.

AU - Jonker, P. G.

AU - Lawrence, A.

AU - Magee, M. R.

AU - Müller-Bravo, T. E.

AU - Onori, F.

AU - Ridley, E.

AU - Schulze, S.

AU - Short, P.

AU - Hiramatsu, D.

AU - Newsome, M.

AU - Terwel, J. H.

AU - Yang, S.

AU - Young, D.

N1 - Funding Information: We are grateful to T. Hung for sharing a Python implementation of the relativistic accretion disk model, and we thank T. Ricci, J. Schimoia, and G. Couto for providing spectra of NGC 4958, NGC 1097 and Arp102B. We also thank J. Krolik, T. Piran and T. Ryu for insightful comments, and the anonymous referee for comments and suggestions that improved the paper. This work is based on observations collected at the European Southern Observatory under ESO programmes 106.216C, 106.2169.001 and 106.2169.002 (PI: Inserra). The spectra will be made publicly available through WISErep. We thank the Swift team for scheduling the requested ToO observations. The Swift data are publicly available from the Swift science archive. This work is partly based on the NUTS2 programme carried out at the NOT. NUTS2 is funded in part by the Instrument Centre for Danish Astrophysics (IDA). Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. This work makes use of observations from the Las Cumbres Observatory global telescope network. Based on data products created from observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 179.A-2010 and made use of data from the VISTA Hemisphere survey (McMahon et al. 2013). T.M.B. was funded by the CONICYT PFCHA/DOCTORADOBECAS CHILE/2017-72180113. S.Y. is funded through the GREAT research environment grant 2016-06012. P.C. is supported by a research grant (19054) from VILLUM FONDEN. T.-W.C. acknowledges the EU Funding under Marie Skłodowska-Curie grant H2020-MSCA-IF-2018-842471. The LCO team was supported by National Science Foundation (NSF) grants AST-1313484, AST-1911225, and AST-1911151, as well as by National Aeronautics and Space Administration (NASA) grant 80NSSC19kf1639. M.N. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 948381). N.I. is partially supported by Polish NCN DAINA grant No. 2017/27/L/ST9/03221. S.S. acknowledges support from the G.R.E.A.T research environment, funded by Vetenskapsrådet, the Swedish Research Council, project number 2016-06012. IA is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that program, from the ERC under the European Union’s Horizon 2020 research and innovation program (grant agreement number 852097), from the Israel Science Foundation (grant number 2752/19), from the United States – Israel Binational Science Foundation (BSF), and from the Israeli Council for Higher Education Alon Fellowship.

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 105 M⊙) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (Rin = several 100 Rg and Rout = several 1000 Rg) accretion disk.Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 106 M⊙ and disk viscosity α ≳ 0.1.

AB - Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 105 M⊙) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (Rin = several 100 Rg and Rout = several 1000 Rg) accretion disk.Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 106 M⊙ and disk viscosity α ≳ 0.1.

KW - Accretion

KW - Accretion disks

KW - Galaxies: active

KW - Quasars: supermassive black holes

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DO - 10.1051/0004-6361/202142616

M3 - Article

AN - SCOPUS:85139879493

SN - 0004-6361

VL - 666

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

IS - October 2022

M1 - A6

ER -

An elliptical accretion disk following the tidal disruption event AT 2020zso

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Keywords

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