Abstract
Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed the typical signs of an optical-UV transient class commonly believed to be TDEs. Optical spectra were obtained 428, 481, and 828 rest-frame days after optical light-curve peak, and a UV/X-ray observation coincided with the later spectrum. The optical spectra show strong coronal emission lines, including [Fe vii], [Fe x], [Fe xi], and [Fe xiv]. The Fe lines rise and then fall, except [Fe xiv] that appears late and rises. We observe increasing flux of narrow H α and H β and a decrease in broad H α flux. The coronal lines have full width at half-maximum ranging from ∼150-300 km s-1, suggesting they originate from a region between the broad- and narrow-line emitting gas. Between the optical flare and late-time observation, the X-ray spectrum softens dramatically. The 0.3-1 keV X-ray flux increases by a factor of ∼50, while the hard X-ray flux decreases by a factor of ∼6. Wide-field Infrared Survey Explorer fluxes also rose over the same period, indicating the presence of an infrared echo. With AT2017gge, AT2019qiz is one of two examples of a spectroscopically confirmed optical-UV TDE showing delayed coronal line emission, supporting speculations that Extreme Coronal Line Emitters in quiescent galaxies can be echos of unobserved past TDEs. We argue that the coronal lines, narrow lines, and infrared emission arise from the illumination of pre-existing material likely related to either a previous TDE or active galactic nucleus activity.
| Original language | English |
|---|---|
| Pages (from-to) | 1568-1587 |
| Number of pages | 20 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 525 |
| Issue number | 1 |
| Early online date | 26 Jul 2023 |
| DOIs | |
| Publication status | Published - 31 Oct 2023 |
Bibliographical note
RRS statement in Acknowledgements section.Funding Information:
MN is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 948381) and by funding from the UK Space Agency. MJW acknowledges support of a Leverhulme Emeritus Fellowship, EM-2021-064, during the preparation of this paper. TMR acknowledges the financial support of the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish academy of Science and Letters. SM acknowledges support from the Academy of Finland project 350458. IA is a Canadian Institute for Advanced Research (CIFAR) Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that programme, from the European Research Council (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. AC would like to thank the Leverhulme Trust for their support via the Leverhulme Early Career Fellowship scheme. PC and GL are supported by a research grant (19054) from VILLUM FONDEN. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement no. 101004719. FO acknowledges support from the Italian Ministry of Education, University and Research (MIUR), Research Projects of National Relevance (PRIN) 2017 (grant 20179ZF5KS) ‘The new frontier of the Multi-Messenger Astrophysics: follow-up of electromagnetic transient counterparts of gravitational wave sources’ and the support of HORIZON2020: AHEAD2020 grant agreement no. 871158. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.
Funding
MN is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 948381) and by funding from the UK Space Agency. MJW acknowledges support of a Leverhulme Emeritus Fellowship, EM-2021-064, during the preparation of this paper. TMR acknowledges the financial support of the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish academy of Science and Letters. SM acknowledges support from the Academy of Finland project 350458. IA is a Canadian Institute for Advanced Research (CIFAR) Azrieli Global Scholar in the Gravity and the Extreme Universe Program and acknowledges support from that programme, from the European Research Council (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. AC would like to thank the Leverhulme Trust for their support via the Leverhulme Early Career Fellowship scheme. PC and GL are supported by a research grant (19054) from VILLUM FONDEN. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement no. 101004719. FO acknowledges support from the Italian Ministry of Education, University and Research (MIUR), Research Projects of National Relevance (PRIN) 2017 (grant 20179ZF5KS) ‘The new frontier of the Multi-Messenger Astrophysics: follow-up of electromagnetic transient counterparts of gravitational wave sources’ and the support of HORIZON2020: AHEAD2020 grant agreement no. 871158. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.
Keywords
- accretion, accretion discs
- black hole physics
- transients: tidal disruption events
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science