Abstract

Contributed Talk - Splinter AGN   (MW-1250)

Broad line region echo from highly accreting intermediate-mass black hole SDSS J144850.08+160803.1

Mariia Demianenko1, 2, 3, Anton Afanasiev4, 5, Evgenii Rubtsov5, Victoria Toptun6, Jörg-Uwe Pott1, Alexandr Belinski5, Franz E. Bauer7, Igor V. Chilingarian3, 5, Kirill A. Grishin8, 5, Marina Burlak5, Natalia Ikonnikova5
1 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany, e-mail: demianenko@mpia.de 2 Department for Physics and Astronomy, Heidelberg University, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany 3 Center for Astrophysics — Harvard and Smithsonian, 60 Garden Street MS09, Cambridge, MA 02138, USA 4 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France 5 Sternberg Astronomical Institute, Moscow M.V. Lomonosov State University, Universitetskij pr., 13, Moscow, 119234, Russia 6 European Southern Observatory, Karl-Schwarzschildstr. 2, 85748, Garching bei München, Germany 7 Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica, Chile 8 Université Paris Cité, CNRS(/IN2P3), Astroparticule et Cosmologie, F-75013 Paris, France

The first reverberation-mapping and intra-night variability campaigns on highly accreting IMBHs using 0.6-2.5m telescopes secured 568 hours of observing time from March 2024 to March 2027, and already allowed the first BLR radius estimate of $ au_{GPCC}=1.31^{+2.66}_{-0.56}$~lt.days for a previously unexplored part of the parameter space. This result probably suggests that the $R_{Heta}-L_{5100}$ relation of Bentz+13, inputting $L_{5100}$ prediction from the Sloan&Netzer AD model as an extension of classic thin disk, is a reasonable approximation for the highly-accreting IMBH regime. However, there is an importance of accounting for the Eddington rate. In the broader astrophysical context, our time-lag estimate spans a previously unexplored region of the $R_{Halpha}-L_{Halpha}$ relation. The radius--luminosity relation provides the basis for single-epoch virial black-hole mass estimators, which are widely applied beyond the local Universe, including in high-redshift AGN studies. Recent high-redshift observations have revealed populations of low-mass and, in some cases, apparently overmassive black holes, highlighting the need to test whether locally calibrated virial mass estimators can be extrapolated to poorly explored low-mass and high-accretion regimes. Under the definition (M_{ m BH}<2 imes10^5,M_odot), J1448+16 is, to our knowledge, the second active IMBH in a galaxy center with a BLR reverberation-mapping measurement, after NGC~4395, and the first one BLR-mapped in the high-accretion-rate regime.