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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2508.08720 |
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| _version_ | 1866909733975228416 |
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| author | Gonzalez-Buitrago, Diego Barth, Aaron J. Edelson, Rick Santisteban, Jorge V. Hernández Horne, Keith Schmidt, Thomas Li, Yan-Rong Guo, Hengxiao Joner, Michael D. Cackett, Edward Gelbord, Jonathan Bentz, Misty C. Brandt, W. N. Goad, Mike Korista, Kirk Vestergaard, Marianne Villforth, Christina Breeveld, Amanda Brink, Thomas G. Corsini, Enrico M. Bontà, Enrico Dalla Ferland, Gary J. Filippenko, Alexei V. García-Díaz, Ma. Teresa Hallum, Michael Horst, James C. Kim, Minjin Krongold, Yair Kruger, Jacob Kuhn, Brian Kumar, Sanjaya Mehdipour, Missagh Morelli, Leonardo Mathur, Smita Netzer, Hagai Ochner, Paolo Pagotto, Ilaria Pizzella, Alessandro Sand, David J. Siviero, Andrea Spencer, Michael Sung, Hyun-Il Vaughan, Simon Winkler, Hans Zheng, Weidong |
| author_facet | Gonzalez-Buitrago, Diego Barth, Aaron J. Edelson, Rick Santisteban, Jorge V. Hernández Horne, Keith Schmidt, Thomas Li, Yan-Rong Guo, Hengxiao Joner, Michael D. Cackett, Edward Gelbord, Jonathan Bentz, Misty C. Brandt, W. N. Goad, Mike Korista, Kirk Vestergaard, Marianne Villforth, Christina Breeveld, Amanda Brink, Thomas G. Corsini, Enrico M. Bontà, Enrico Dalla Ferland, Gary J. Filippenko, Alexei V. García-Díaz, Ma. Teresa Hallum, Michael Horst, James C. Kim, Minjin Krongold, Yair Kruger, Jacob Kuhn, Brian Kumar, Sanjaya Mehdipour, Missagh Morelli, Leonardo Mathur, Smita Netzer, Hagai Ochner, Paolo Pagotto, Ilaria Pizzella, Alessandro Sand, David J. Siviero, Andrea Spencer, Michael Sung, Hyun-Il Vaughan, Simon Winkler, Hans Zheng, Weidong |
| contents | We present ground-based, multi-band light curves of the AGN Mrk~509, NGC\,4151, and NGC\,4593 obtained contemporaneously with \sw\, monitoring. We measure cross-correlation lags relative to \sw\, UVW2 (1928~Å) and test the standard prediction for disk reprocessing, which assumes a geometrically thin, optically thick accretion disk where continuum interband delays follow the relation \( τ(λ) \propto λ^{4/3} \). For Mrk~509 the 273-d \sw\, campaign gives well-defined lags that increase with wavelength as $τ(λ)\proptoλ^{2.17\pm0.2}$, steeper than the thin-disk prediction, and the optical lags are a factor of $\sim5$ longer than expected for a simple disk-reprocessing model. This ``disk-size discrepancy'' as well as excess lags in the $u$ and $r$ bands (which include the Balmer continuum and H$α$, respectively) suggest a mix of short lags from the disk and longer lags from nebular continuum originating in the broad-line region. The shorter \sw\, campaigns, 69~d on NGC\,4151 and 22~d on NGC\,4593, yield less well-defined, shorter lags $<2$~d. The NGC\,4593 lags are consistent with $τ(λ) \propto λ^{4/3}$ but with uncertainties too large for a strong test. For NGC\,4151 the \sw\, lags match $τ(λ) \propto λ^{4/3}$, with a small $U$-band excess, but the ground-based lags in the $r$, $i$, and $z$ bands are significantly shorter than the $B$ and $g$ lags, and also shorter than expected from the thin-disk prediction. The interpretation of this unusual lag spectrum is unclear. Overall these results indicate significant diversity in the $τ-λ$ relation across the optical/UV/NIR, which differs from the more homogeneous behavior seen in the \sw\, bands. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_08720 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Departures from Standard Disk Predictions in Intensive Ground-Based Monitoring of Three AGN Gonzalez-Buitrago, Diego Barth, Aaron J. Edelson, Rick Santisteban, Jorge V. Hernández Horne, Keith Schmidt, Thomas Li, Yan-Rong Guo, Hengxiao Joner, Michael D. Cackett, Edward Gelbord, Jonathan Bentz, Misty C. Brandt, W. N. Goad, Mike Korista, Kirk Vestergaard, Marianne Villforth, Christina Breeveld, Amanda Brink, Thomas G. Corsini, Enrico M. Bontà, Enrico Dalla Ferland, Gary J. Filippenko, Alexei V. García-Díaz, Ma. Teresa Hallum, Michael Horst, James C. Kim, Minjin Krongold, Yair Kruger, Jacob Kuhn, Brian Kumar, Sanjaya Mehdipour, Missagh Morelli, Leonardo Mathur, Smita Netzer, Hagai Ochner, Paolo Pagotto, Ilaria Pizzella, Alessandro Sand, David J. Siviero, Andrea Spencer, Michael Sung, Hyun-Il Vaughan, Simon Winkler, Hans Zheng, Weidong Astrophysics of Galaxies We present ground-based, multi-band light curves of the AGN Mrk~509, NGC\,4151, and NGC\,4593 obtained contemporaneously with \sw\, monitoring. We measure cross-correlation lags relative to \sw\, UVW2 (1928~Å) and test the standard prediction for disk reprocessing, which assumes a geometrically thin, optically thick accretion disk where continuum interband delays follow the relation \( τ(λ) \propto λ^{4/3} \). For Mrk~509 the 273-d \sw\, campaign gives well-defined lags that increase with wavelength as $τ(λ)\proptoλ^{2.17\pm0.2}$, steeper than the thin-disk prediction, and the optical lags are a factor of $\sim5$ longer than expected for a simple disk-reprocessing model. This ``disk-size discrepancy'' as well as excess lags in the $u$ and $r$ bands (which include the Balmer continuum and H$α$, respectively) suggest a mix of short lags from the disk and longer lags from nebular continuum originating in the broad-line region. The shorter \sw\, campaigns, 69~d on NGC\,4151 and 22~d on NGC\,4593, yield less well-defined, shorter lags $<2$~d. The NGC\,4593 lags are consistent with $τ(λ) \propto λ^{4/3}$ but with uncertainties too large for a strong test. For NGC\,4151 the \sw\, lags match $τ(λ) \propto λ^{4/3}$, with a small $U$-band excess, but the ground-based lags in the $r$, $i$, and $z$ bands are significantly shorter than the $B$ and $g$ lags, and also shorter than expected from the thin-disk prediction. The interpretation of this unusual lag spectrum is unclear. Overall these results indicate significant diversity in the $τ-λ$ relation across the optical/UV/NIR, which differs from the more homogeneous behavior seen in the \sw\, bands. |
| title | Departures from Standard Disk Predictions in Intensive Ground-Based Monitoring of Three AGN |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.08720 |