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The first spectroscopic IR reverberation programme on Mrk 509

Mitchell, J A J; Ward, M J; Kynoch, D; Santisteban, J V Hernández; Horne, K; Pott, J -U; Esser, J; Mercatoris, P; Packham, C; Ferland, G J; Lawrence, A; Fischer, T; Barth, A J; Villforth, C; Winkler, H

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Jake Mitchell
PGR Student Doctor of Philosophy

D Kynoch

J V Hernández Santisteban

K Horne

J -U Pott

J Esser

P Mercatoris

C Packham

G J Ferland

A Lawrence

T Fischer

A J Barth

C Villforth

H Winkler


Near IR spectroscopic reverberation of Active Galactic Nuclei (AGN) potentially allows the infrared (IR) broad line region (BLR) to be reverberated alongside the disc and dust continua, while the spectra can also reveal details of dust astro-chemistry. Here, we describe results of a short pilot study (17 near-IR spectra over a 183 d period) for Mrk 509. The spectra give a luminosity-weighted dust radius of 〈Rd,lum〉 = 186 ± 4 light-days for blackbody (large grain dust), consistent with previous (photometric) reverberation campaigns, whereas carbon and silicate dust give much larger radii. We develop a method of calibrating spectral data in objects where the narrow lines are extended beyond the slit width. We demonstrate this by showing our resultant photometric band light curves are consistent with previous results, with a hot dust lag at >40 d in the K band, clearly different from the accretion disc response at <20 d in the z band. We place this limit of 40 d by demonstrating clearly that the modest variability that we do detect in the H and K band does not reverberate on time-scales of less than 40 d. We also extract the Pa β line light curve, and find a lag which is consistent with the optical BLR H β line of ∼70–90 d. This is important as direct imaging of the near-IR BLR is now possible in a few objects, so we need to understand its relation to the better studied optical BLR.


Mitchell, J. A. J., Ward, M. J., Kynoch, D., Santisteban, J. V. H., Horne, K., Pott, J. .-U., …Winkler, H. (2024). The first spectroscopic IR reverberation programme on Mrk 509. Monthly Notices of the Royal Astronomical Society, 529(4), 4824-4839.

Journal Article Type Article
Acceptance Date Mar 8, 2024
Online Publication Date Mar 18, 2024
Publication Date 2024-04
Deposit Date Jul 4, 2024
Publicly Available Date Jul 4, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 529
Issue 4
Pages 4824-4839
Public URL


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