南方基地知识库

NGC 2617 attracted a lot of attention after the detection of changes in its spectral type; the geometry and kinematics of the broad-line region (BLR) are still ambiguous. In this paper, we present the high cadence (similar to 2 days) reverberation mapping campaign of NGC 2617 from 2019 October to 2020 May undertaken at the 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 both of the 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 of H alpha, H beta, H gamma, and He I, with a ratio of tau(H alpha): tau(H beta): tau(H gamma): tau(He) (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 the dispersion width of the line, the masses of the black holes derived from H alpha and H beta are 23.8(-207)(+5.4) and 21.1(-4.4)(+3.8) x 10(6)M(circle dot), respectively. Our observed results indicate the complexity of the BLR of NGC 2617.