Evidence for Two Distinct Broad-line Regions from Reverberation Mapping of PG 0026+129

Authors: Hu, Chen; Li, Sha-Sha; Guo, Wei-Jian; Yang, Sen; Yang, Zi-Xu; Bao, Dong-Wei; Jiang, Bo-Wei; Du, Pu; Li, Yan-Rong; Xiao, Ming; Songsheng, Yu-Yang; Yu, Zhe; Bai, Jin-Ming; Ho, Luis C.; Bian, Wei-Hao; Brotherton, Michael S.; Yuan, Ye-Fei; Aceituno, Jesús; Winkler, Hartmut; Wang, Jian-Min; SEAMBH CollaborationWe report on the results of a new spectroscopic monitoring campaign of the quasar PG 0026+129 at the Calar Alto Observatory 2.2 m telescope from 2017 July to 2020 February. Significant variations in the fluxes of the continuum and broad emission lines, including Hβ and He ii, were observed in the first and third years, and clear time lags between them are measured. The broad Hβ line profile consists of two Gaussian components: an intermediate-width H with an FWHM of 1964 ± 18 and another very broad H with an FWHM of 7570 ± 83 . H has long time lags of ∼40-60 days in the rest frame, while H shows nearly zero time delay with respect to the optical continuum at 5100 Å. The velocity-resolved delays show consistent results: lags of ∼30-50 days at the core of the broad Hβ line and roughly zero lags at the wings. H has a redshift of ∼400 , which seems to be stable for nearly 30 yr by comparing with archived spectra, and may originate from an infall. The rms spectrum of H shows a double-peaked profile with brighter blue peak and extended red wing in the first year, which matches the signature of a thin disk. Both the double-peaked profile and the near-zero lag suggest that H comes from a region associated with the part of the accretion disk that emits the optical continuum. Adopting the FWHM (in the rms spectrum) and the time lag measured for the total Hβ line, and a virial factor of 1.5, we obtain a virial mass of for the central black hole in this quasar. © 2020. The American Astronomical Society. All rights reserved..We acknowledge the support of the staff of the CAHA 2.2 m telescope. This work is based on observations collected at the Centro Astronomico Hispanoen Andalucia (CAHA) at Calar Alto, operated jointly by the Andalusian Universities and the Instituto de Astrofisica de Andalucia (CSIC). This research is supported by the National Key R&D Program of China (2016YFA0400701, 2016YFA0400702), by the National Science Foundation of China (11721303, 11773029, 11833008, 11873048, 11922304, 11973029, 11991051, 11991052, 11991054, 12003036, 12022301), by the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (CAS; QYZDJ-SSW-SLH007), by the CAS Key Research Program (KJZDEW-M06), and by the Strategic Priority Research Program of the CAS (XDB23000000, XDB23010400). J.A. acknowledges financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709).Peer reviewe