TY - JOUR

T1 - Long-term follow-up observations of extreme coronal line emitting galaxies

AU - Clark, Peter

AU - Graur, Or

AU - Callow, Joseph

AU - Aguilar, Jessica

AU - Ahlen, S.P.

AU - Anderson, Joseph

AU - Berger, Edo

AU - Müller-Bravo, Tomás E.

AU - Brink, Thomas G.

AU - Brooks, David

AU - Chen, Ting-Wan

AU - Claybaugh, Todd

AU - Pettersson, Axel de la Macorra

AU - Doel, Peter

AU - Filippenko, Alexei

AU - Forero-Romero, Jaime

AU - Gomez, Sebastian

AU - Gromadzki, Mariusz

AU - Honscheid, Klaus

AU - Inserra, Cosimo

AU - Kisner, Theodore

AU - Landriau, Martin

AU - Makrygianni, Lydia

AU - Manera, Marc

AU - Meisner, Aaron

AU - Miquel, Ramon

AU - Moustakas, John

AU - Nicholl, Matt

AU - Nie, Jundan

AU - Onori, Francesca

AU - Palmese, Antonella

AU - Poppett, Claire

AU - Reynolds, Thomas

AU - Rezaie, Mehdi

AU - Rossi, Graziano

AU - Sanchez, E.

AU - Schubnell, Michael

AU - Tarlé, Gregory

AU - Weaver, Benjamin A

AU - Wevers, Thomas

AU - Young, David

AU - Zheng, Weikang

AU - Zhou, Zhimin

PY - 2024/3/31

Y1 - 2024/3/31

N2 - 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.

AB - 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.

U2 - 10.1093/mnras/stae460

DO - 10.1093/mnras/stae460

M3 - Journal article

VL - 528

SP - 7076

EP - 7102

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -