Continuum Reverberation Mapping of Mrk 876 over Three Years with Remote Robotic Observatories

Miller, Jake A.; Cackett, Edward M.; Goad, Michael R.; Horne, Keith; Barth, Aaron J.; Romero-Colmenero, Encarni; Fausnaugh, Michael; Gelbord, Jonathan; Korista, Kirk T.; Landt, Hermine; Treu, Tommaso; Winkler, Hartmut

Abstract

Continuum reverberation mapping probes the size scale of the optical continuum-emitting region in active galactic nuclei (AGN). Through 3 yr of multiwavelength photometric monitoring in the optical with robotic observatories, we perform continuum reverberation mapping on Mrk 876. All wave bands show large-amplitude variability and are well correlated. Slow variations in the light curves broaden the cross-correlation function (CCF) significantly, requiring detrending in order to robustly recover interband lags. We measure consistent interband lags using three techniques (CCF, JAVELIN, and PyROA), with a lag of around 13 days from u to z. These lags are longer than the expected radius of 12 days for the self-gravitating radius of the disk. The lags increase with wavelength roughly following λ4/3, as would be expected from thin disk theory, but the lag normalization is approximately a factor of 3 longer than expected, as has also been observed in other AGN. The lag in the i band shows an excess that we attribute to variable Hα broad-line emission. A flux–flux analysis shows a variable spectrum that follows fν ∝ λ−1/3, as expected for a disk, and an excess in the i band that also points to strong variable Hα emission in that band.

Citation

Miller, J. A., Cackett, E. M., Goad, M. R., Horne, K., Barth, A. J., Romero-Colmenero, E., …Winkler, H. (2023). Continuum Reverberation Mapping of Mrk 876 over Three Years with Remote Robotic Observatories. Astrophysical Journal, 953(2), Article 137. https://doi.org/10.3847/1538-4357/ace342

• Journal Article Type: Article
• Acceptance Date: Jun 29, 2023
• Online Publication Date: Aug 11, 2023
• Publication Date: Aug 20, 2023
• Deposit Date: Oct 25, 2023
• Publicly Available Date: Oct 25, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 953
• Issue: 2
• Article Number: 137
• DOI: https://doi.org/10.3847/1538-4357/ace342
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/1817397