26-30 June 2023
Centro Congressi Federico II
Europe/Rome timezone

Changing-look AGN in the BAT AGN Spectroscopic Survey

29 Jun 2023, 10:15
Aula Magna (Centro Congressi Federico II)

Aula Magna

Centro Congressi Federico II

Via Partenope, 36, Napoli, Italy


Matthew Temple


Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. I will present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. We have discovered eight new CL events, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combined with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14-195 keV light curve coverage, and five of these CL events can be associated with significant changes in their 14-195 keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration, and instead must be due to changes in the structure of the accretion disk and broad line region. We derive a CL rate of 0.7-6.2 per cent on 10-25 yr time-scales, and show that many transitions happen within at most a few years. Our results motivate further multiwavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs.

Primary author

Presentation Materials

Your browser is out of date!

Update your browser to view this website correctly. Update my browser now