J/A+A/706/A176 Fairall 9 ubvyI light curves (Mandal+, 2026)
HALO. I: Photometric continuum reverberation mapping of Fairall 9.
Mandal A.K., Pozo Nunez F., Jaiswal V.K., Naddaf M.H., Czerny B., Panda S.,
Karczmarek P., Pietrzynski G., Pandey S., Peterson B.M., Zajacek M.,
Dovciak M., Karas V., Narloch W., Kicia M., Gorski M., Kaluszynski M.,
Hajdu G., Wielgorski P., Zgirski B., Galan C., Pych W., Smolec R.,
Bakowska K., Gieren W., Kervella P.
<Astron. Astrophys. 706, A176 (2026)>
=2026A&A...706A.176M 2026A&A...706A.176M (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Photometry, SDSS ; Optical
Keywords: galaxies: active - galaxies: distances and redshifts -
galaxies: nuclei - galaxies: photometry - quasars: emission lines -
galaxies: Seyfert
Abstract:
We investigate the origin of inter-band continuum time delays in
active galactic nuclei (AGNs) to study the structure and
properties of their accretion disks.
We aim to measure the inter-band continuum time delays through
photometric monitoring of Seyfert galaxy Fairall 9 to con- struct the
lag-spectrum. Additionally, we explain the observed features in the
Fairall 9 lag-spectrum and discuss the potential drivers behind them,
based on our newly collected data from the Obserwatorium Cerro Murphy
(OCM) telescope.
We initiated a long-term, continuous AGN photometric monitoring
program in 2024, titled "Hubble constant constraints through AGN
Light curve Observations" (HALO) using intermediate and broad band
filters. Here, we present the first results from HALO, focusing on
photometric light curves and continuum time-delay measurements for
Fairall 9. To complement these observations and extend the wavelength
coverage of the lag-spectrum, we also reanalyzed archival Swift light
curves and spectroscopic data available in the literature.
Using HALO and Swift light curves, we measured inter-band continuum
delays to construct the lag-spectrum of Fairall 9. Excess lags appear
in the u and U bands (Balmer continuum contamination) and in the I
band (Paschen jump/dust emission from the torus). Overall, the
lag-spectrum deviates significantly from standard disk model
predictions.
We find that inter-band delays deviate from the power-law,
τλ∝λβ due to BLR scattering,
reprocessing, and dust contributions at longer wavelengths. Power-law
fits are therefore not well suited for characterizing the nature of
the time delays.
Description:
Light curves from OCM monitoring of Fairall 9
in the u, v, b, y, and I filters,
Objects:
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RA (2000) DE Designation(s)
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01 23 45.76 -58 48 20.8 Fairall 9 = QSO J0123-5848
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 29 1120 Fairall 9 observations in ubvyI from HALO
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See also:
J/A+AS/121/461 : UV variability of Fairall-9 (Recondo-Gonzalez+, 1997)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d MJD Modifier Julian date
14- 20 F7.4 Jy Flux Flux in Band
22- 27 F6.4 Jy e_Flux Uncertainty in Flux
29 A1 --- Band [ubvyI] Observed band
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Acknowledgements:
Amit Kumar Mandal, amitastro.am(at)gmail.com
(End) Patricia Vannier [CDS] 26-Jan-2026