A1 Refereed original research article in a scientific journal
Long-term follow-up observations of extreme coronal line emitting galaxies
Authors: Clark P, Graur O, Callow J, Aguilar J, Ahlen S, Anderson JP, Berger E, Müller-Bravo TE, Brink TG, Brooks D, Chen T, Claybaugh T, de la Macorra A, Doel P, Filippenko AV, Forero-Romero JE, Gomez S, Gromadzki M, Honscheid K, Inserra C, Kisner T, Landriau M, Makrygianni L, Manera M, Meisner A, Miquel R, Moustakas J, Nicholl M, Nie J, Onori F, Palmese A, Poppett C, Reynolds T, Rezaie M, Rossi G, Sanchez E, Schubnell M, Tarlé G, Weaver BA, Wevers T, Young DR, Zheng W, Zhou Z
Publisher: Oxford University Press
Publication year: 2024
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: Monthly Notices of the Royal Astronomical Society
Volume: 528
Issue: 4
First page : 7076
Last page: 7102
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stae460
Web address : https://doi.org/10.1093/mnras/stae460
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/387351417
Preprint address: https://arxiv.org/abs/2307.03182
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.
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