Abstract
We present results of time-series analysis of the first year of the Fairall 9 intensive disc-reverberation campaign. We used Swift and the Las Cumbres Observatory global telescope network to continuously monitor Fairall 9 from X-rays to near-infrared at a daily to subdaily cadence. The cross-correlation function between bands provides evidence for a lag spectrum consistent with the τ ∝ λ4/3 scaling expected for an optically thick, geometrically thin blackbody accretion disc. Decomposing the flux into constant and variable components, the variable component's spectral energy distribution is slightly steeper than the standard accretion disc prediction. We find evidence at the Balmer edge in both the lag and flux spectra for an additional bound-free continuum contribution that may arise from reprocessing in the broad-line region. The inferred driving light curve suggests two distinct components, a rapidly variable (<4 d) component arising from X-ray reprocessing, and a more slowly varying (>100 d) component with an opposite lag to the reverberation signal.
| Original language | English |
|---|---|
| Pages (from-to) | 5399-5416 |
| Number of pages | 18 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 498 |
| Issue number | 4 |
| DOIs | |
| State | Published - Nov 1 2020 |
Bibliographical note
Publisher Copyright:© 2020 The Author(s)
Funding
We would like to thank the anonymous referee for their comments that greatly improved this paper. JVHS and KH acknowledge support from the Science and Technology Facilities Council grant ST/R000824/1. RE gratefully acknowledges support from National Aeronautics and Space Administration (NASA) Swift Key Project grant number 80NSSC19K0153. JMG gratefully acknowledges support from NASA under the ADAP award 80NSSC17K0126. AAB, KLP, and PAE acknowledge support from the UK Space Agency. Research by AJB was supported by National Science Foundation (NSF) grant AST-1907290. EMC gratefully acknowledges support from the NSF through grant AST-1909199. MV gratefully acknowledges financial support from the Independent Research Fund Denmark via grant number DFF 8021-00130. The authors appreciate the hard work and dedication of the Swift Observatory staff, who created a new UVOT mode in support of this project and put in considerable effort in scheduling this large program. This work makes use of observations from the LCO network, and of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research was made possible through the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund and NSF AST-1412587. This research also made use of ASTROPY, a community-developed core PYTHON package for astronomy (Astropy Collaboration et al. 2013), and MATPLOTLIB (Hunter 2007).
| Funders | Funder number |
|---|---|
| UK Space Agency | |
| UK Industrial Decarbonization Research and Innovation Centre | |
| National Science Foundation Arctic Social Science Program | AST-1907290, 1412587, 1907290, AST-1909199 |
| Science and Technology Facilities Council | ST/R000824/1 |
| Danmarks Frie Forskningsfond | DFF 8021-00130 |
| National Aeronautics and Space Administration | 80NSSC17K0126, 80NSSC19K0153 |
| IPAC | AST-1412587, 2013 |
Keywords
- Accretion
- Accretion discs
- Galaxies: active
- Quasars: individual: Fairall 9
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science