The first spectroscopic IR reverberation programme on Mrk 509

J A J Mitchell*, M J Ward, 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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Near IR spectroscopic reverberation of Active Galactic Nuclei (AGN) potentially allows the 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 day 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 lightcurves are consistent with previous results, with a hot dust lag at >40 days in the K-band, clearly different from the accretion disc response at <20 days in the z-band. We place this limit of 40 days by demonstrating clearly that the modest variability that we do detect in the H and K-band does not reverberate on timescales of less than 40 days. We also extract the Paβ line lightcurve, and find a lag which is consistent with the optical BLR Hβ line of ∼70 − 90 days. 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.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date4 Apr 2024
Publication statusE-pub ahead of print - 4 Apr 2024


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