J/A+A/702/A202 SDSS J144850.08+160803.1 g + Ha light curves (Demianenko+, 2025)
Broad line region echo from highly accreting intermediate-mass black hole
candidate SDSS J144850.08+160803.1.
First probe of intra-night variability and reverberation mapping.
Demianenko M., Afanasiev A., Rubtsov E., Toptun V., Pott J.-U., Belinski A.,
Bauer F.E., Chilingarian I.V., Grishin K.A., Burlak M., Ikonnikova N.
<Astron. Astrophys. 702, A202 (2025)>
=2025A&A...702A.202D 2025A&A...702A.202D (SIMBAD/NED BibCode)
ADC_Keywords: X-ray sources ; Photometry ; Active gal. nuclei ; Accretion
Keywords: black hole physics - galaxies: active - galaxies: nuclei -
galaxies: photometry - galaxies: Seyfert
Abstract:
Elusive intermediate-mass black holes (IMBHs;
100M☉≤MBH≤2x105M☉) can be used as time-squeezing
machines, enabling studies of active galactic nucleus (AGN) geometry
via reverberation mapping (RM) on much shorter timescales than their
supermassive siblings.
Constraints on the broad line region (BLR) radius for IMBH candidates
across a broad range of Eddington ratios help probe the unexplored
faint end of the radius-luminosity (R-L) relation in AGNs. This
development opens up the opportunity to build a more robust MBH
estimator. The present study is aimed at: (a) confirming a highly
accreting IMBH candidate and (b) demonstrating the feasibility of the
first photometric BLR RM campaign for IMBHs with high Eddington rates.
SDSS J144850.08+160803.1 (J1448+16) was identified as an IMBH
candidate from a broad Hα-selected spectroscopic sample from
SDSS. We carried out XMM-Newton X-ray observations to confirm its AGN
status, along with narrowband Hα and broadband SDSS g'
monitoring over five months (March-July 2024) using a 60-cm
telescope at the Caucasus Mountain Observatory. These time series
allowed us both to probe the short-timescale variability and extract
the time lag between the BLR and accretion disk (AD) continuum.
XMM-Newton detected J1448+16 as a bright X-ray point source with a
photon index of {GAMMA}=2.32+0.15-0.13 and X-ray luminosity of
L2-10keV=(3.3+0.5-0.4)x1041erg/s, confirming its AGN activity.
From the SDSS optical spectrum and X-ray properties, we estimated a BH
mass of ~(0.9-2.4)x105M☉ and Eddington rate of ∼37-112%. We
report high-amplitude ∼55% intra-night (∼1.7h) Ha variability for this
highly accreting IMBH and extract a tentative BLR RM radius estimate
of ∼1-8 days.
This work offers a proof of concept for further high-Eddington-rate
IMBH variability studies and BLR RM campaigns, which will be essential
for an efficient calibration of the R-L relation at the faint end.
Description:
Light curve of SDSS J144850.08+160803.1 in Hα and SDSS g-bands,
was observed at Caucasus Mountain Observatory, PI: Demianenko
Website with parent sample, which consists of 2k low-mass AGNs
http://lc-dev.voxastro.org/valc.html
Objects:
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RA (2000) DE Designation(s)
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14 48 50.08 +16 08 03.1 J1448+16 = SDSS J144850.08+160803.1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 129 138 Light curve of SDSS J144850.08+160803.1
in Hα and SDSS g-bands
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d MJD Modified Julian Date
20- 21 A2 --- Band Photometric band (g or Ha)
23- 41 F19.16 ct Count Number of extracted photons in 3 arcsec
aperture before flux calibration
43- 62 F20.13 10-20W/m2 Flux AGN flux (in 10-17erg/cm2/s)
64- 83 F20.14 10-20W/m2 e_Flux Error of the AGN flux
(in 10-17erg/cm2/s)
85-106 F22.17 10-20W/m2 FCorr Relative correction term (median variation
of the calibration star)
(in 10-17erg/cm2/s)
109-126 F18.16 --- Airmass Airmass during the individual exposure
128-129 I2 % Humidity Humidity during the individual exposure
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Acknowledgements:
Mariia V. Demianenko, demianenko(at)mpia.de, qur_x(at)mail.ru
(End) M. Demianenko [Max Planck Inst. for Astron.], P. Vannier [CDS] 07-Oct-2025