HALO

Context. We investigate the origin of inter-band continuum time delays in active galactic nuclei (AGNs) in order to study the structure and properties of their accretion disks. Aims. We aim to measure the inter-band continuum time delays through photometric monitoring of Seyfert galaxy Fairall 9 to construct 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. Methods. 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 broadband 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. Results. 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 and dust emission from the torus). Overall, the lag-spectrum deviates significantly from standard disk model predictions. Conclusions. We find that inter-band delays deviate from the power law, τ λ ∝ λ β , due to broad-line region scattering, reprocessing, and dust contributions at longer wavelengths. Power-law fits are therefore not well suited to characterizing the nature of the time delays.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-12-20
DOI
https://doi.org/10.1051/0004-6361/202557795
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

HALO

Mohammad-Hassan Naddaf, Michal Dovčiak, F. Pozo Núñez, R. Smolec et al.
Astronomy and Astrophysics
Galaxies: Formation, Evolution, Phenomena
article

HALO

Mohammad-Hassan Naddaf, Michal Dovčiak, F. Pozo Núñez, R. Smolec, Marek Górski, Michal Zajaček, B. Czerny, Piotr Wielgórski, V. Karas, C. Gałan, G. Hajdu, K. Bąkowska, P. Kervella, Vikram Kumar Jaiswal, W. Narloch, W. Pych, Bartłomiej Zgirski, Mikołaj Kałuszyński, Amit Kumar Mandal, Shivangi Pandey, Swayamtrupta Panda, W. Gieren, Grzegorz Pietrzyński, Mirosław Kicia
article en

Abstract

Context. We investigate the origin of inter-band continuum time delays in active galactic nuclei (AGNs) in order to study the structure and properties of their accretion disks. Aims. We aim to measure the inter-band continuum time delays through photometric monitoring of Seyfert galaxy Fairall 9 to construct 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. Methods. 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 broadband 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. Results. 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 and dust emission from the torus). Overall, the lag-spectrum deviates significantly from standard disk model predictions. Conclusions. We find that inter-band delays deviate from the power law, τ λ ∝ λ β , due to broad-line region scattering, reprocessing, and dust contributions at longer wavelengths. Power-law fits are therefore not well suited to characterizing the nature of the time delays.

Astronomy and AstrophysicsVol. 706
Centre National de la Recherche Scientifique (FR), M.J.P. Rohilkhand University (IN), University of Concepción (CL), Université Paris Cité (FR), Czech Academy of Sciences, Astronomical Institute (CZ), Institut d'Astrophysique de Paris (FR), Aryabhatta Research Institute of Observational Sciences (IN), Center for Theoretical Physics (PL), Sorbonne Université (FR), Chinese Academy of Science South America Center for Astronomy (CL), Sorbonne Paris Cité (FR), Millennium Institute of Astrophysics (CL), Turner Consulting Group (United States) (US), Centre for Theoretical Physics and Astrophysics (UZ), Institute of Astronomy (RU), Gemini South Observatory (CL), Centre de Recherche en Astronomie Astrophysique et Géophysique (DZ), Nicolaus Copernicus Astronomical Center (PL), Heidelberg Institute for Theoretical Studies (DE), Polish Academy of Sciences (PL)
National Science Foundation, European Commission, Grantová Agentura České Republiky, Klaus Tschira Stiftung
Openalex Percentile: Top 71%
Galaxies: Formation, Evolution, Phenomena
DOIOpen Access PDFOpenAlex
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