Velocity-resolved Reverberation Mapping of Changing-look AGN NGC 2617

Abstract

NGC 2617 has attracted a lot of attention after the detection of the changes in spectral type, and its geometry and kinematics of broad-line region (BLR) are still ambiguous. In this paper, we present the high cadence ($\sim$ 2 days) reverberation mapping campaign of NGC 2617 from 2019 October to 2020 May undertaken at Lijiang 2.4 m telescope. For the first time, the velocity-resolved reverberation signature of the object was successfully detected. Both H$\alpha$ and H$\beta$ show an asymmetrical profile with a peak in the velocity-resolved time lags. For each of both lines, the lag of the line core is longer than those of the relevant wings, and the peak of the velocity-resolved lags is slightly blueshifted. These characteristics are not consistent with the theoretical prediction of the inflow, outflow or Keplerian disk model. Our observations give the time lags ofH$\alpha$, H$\beta$, H$\gamma$, and He I, with a ratio of ${\tau }_{\mathrm{H}\alpha }$:${\tau }_{\mathrm{H}\beta }$:${\tau }_{\mathrm{H}\gamma }$:${\tau }_{\mathrm{He}\mathrm{I}}$ = 1.27:1.00:0.89:0.20, which indicates a stratified structure in the BLR of the object. It is the first time that the lags of H$\alpha$ and He I are obtained. Assuming a virial factor of $f$ = 5.5 for dispersion width of line, the masses of black hole derived from H$\alpha$ and H$\beta$ are $23.8_{-2.7}^{+5.4}$ and $21.1_{-4.4}^{+3.8}\times 10^6{\mathrm{M}}_{\odot }$, respectively. Our observed results indicate the complexity of the BLR of NGC 2617.

19 pages, 5 figures, Accepted for publication in ApJ

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• The Lick AGN Monitoring Project 2016: Dynamical Modeling of Velocity-Resolved H\b{eta} Lags in Luminous Seyfert Galaxies
• Supermassive Black Hole and Broad-line Region in NGC~5548: Results from Five-season Reverberation Mapping
• Multi-Wavelength Monitoring and Reverberation Mapping of a Changing Look Event in the Seyfert Galaxy NGC 3516
• Investigating Changing-Look Active Galactic Nuclei with Long-term Optical and X-Ray Observations
• Galaxy morphoto-Z with neural Networks (GaZNets). I. Optimized accuracy and outlier fraction from Imaging and Photometry
• Velocity-resolved Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 4151 during Outburst Stage. II. Four Season Observation Results
• The H$\alpha$ broadband photometric reverberation mapping of four Seyfert 1 galaxies
• Measuring the Virial Factor in SDSS DR5 Quasars with Redshifted H$\beta$ and Fe ii Broad Emission Lines
• Velocity-Resolved Ionization Mapping of Broad Line Region. I. Insights into Diverse Geometry and Kinematics
• Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum
• Measuring the Virial Factor in SDSS DR7 AGNs with Redshifted H$\beta$ and H$\alpha$ Broad Emission Lines
• On the Relation between the Inclination Angle of the Accretion Disk and the Broad-line Region in Active Galactic Nuclei
• A magnetically-supported disk-corona model for Changing-Look AGN transitions
• Correcting the Contamination of Second-order Spectra: Improving Hα Measurements in Reverberation Mapping Campaigns