Long-term follow-up observations of extreme coronal line emitting galaxies

Clark, Peter, Or, Graur, Callow, Joseph, Aguilar, Jessica, Ahlen, Steven, Anderson, Joseph P., Berger, Edo, Muller-Bravo, Tomas E., Brink, Thomas G., Brooks, David, Chen, Ting-Wan, Claybaugh, Todd, de la Macorra, Axel, Doel, Peter, Filippenko, Alexi V., Forero-Romero, Jamie E., Gomez, Sebastian, Gromadzki, Mariuz, Honscheid, Klaus, Inserra, Cosimo ORCID: https://orcid.org/0000-0002-3968-4409, Kisner, Theodore, Landriau, Martin, Makrgianni, Lydia, Manera, Marc, Meisner, Aaron, Miquel, Ramon, Moustakas, John, Nicholl, Matt, Nie, Jundan, Onori, Francesca, Palmese, Antonella, Poppett, Claire, Reynolds, Thomas, Rezaie, Mehdi, Rossi, Graziano, Sanchez, Eusebio, Schubnell, Michael, Tarle, Gregory, Weaver, Benjamin A., Wevers, Thomas, Young, David R., Zheng, WeiKang and Zhou, Zhimin 2024. Long-term follow-up observations of extreme coronal line emitting galaxies. Monthly Notices of the Royal Astronomical Society 528 (4) , 7076–7102. 10.1093/mnras/stae460

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Abstract

We present new spectroscopic and photometric follow-up observations of the known sample of extreme coronal line-emitting galaxies (ECLEs) identified in the Sloan Digital Sky Survey (SDSS). With these new data, observations of the ECLE sample now span a period of two decades following their initial SDSS detections. We confirm the non-recurrence of the iron coronal line signatures in five of the seven objects, further supporting their identification as the transient light echoes of tidal disruption events (TDEs). Photometric observations of these objects in optical bands show little overall evolution. In contrast, mid-infrared (MIR) observations show ongoing long-term declines consistent with power-law decay. The remaining two objects had been classified as active galactic nuclei (AGNs) with unusually strong coronal lines rather than being TDE related, given the persistence of the coronal lines in earlier follow-up spectra. We confirm this classification, with our spectra continuing to show the presence of strong, unchanged coronal line features and AGN-like MIR colours and behaviour. We have constructed spectral templates of both subtypes of ECLE to aid in distinguishing the likely origin of newly discovered ECLEs. We highlight the need for higher cadence, and more rapid, follow-up observations of such objects to better constrain their properties and evolution. We also discuss the relationships between ECLEs, TDEs, and other identified transients having significant MIR variability.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	Oxford University Press
ISSN:	0035-8711
Date of First Compliant Deposit:	8 March 2024
Date of Acceptance:	7 February 2024
Last Modified:	18 Mar 2024 11:30
URI:	https://orca.cardiff.ac.uk/id/eprint/167041

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