Broad-line Region of the Quasar PG 2130+099. II. Doubling the Size Over Four Years?

Kavli Affiliate: Luis C. Ho

| First 5 Authors: Zhu-Heng Yao, Sen Yang, Wei-Jian Guo, Yong-Jie Chen, Yu-Yang Songsheng

| Summary:

Over the past three decades, multiple reverberation mapping (RM) campaigns
conducted for the quasar PG 2130+099 have exhibited inconsistent findings with
time delays ranging from $sim$10 to $sim$200 days. To achieve a comprehensive
understanding of the geometry and dynamics of the broad-line region (BLR) in PG
2130+099, we continued an ongoing high-cadence RM monitoring campaign using the
Calar Alto Observatory 2.2m optical telescope for an extra four years from 2019
to 2022. We measured the time lags of several broad emission lines (including
He II, He I, H$beta$, and Fe II) with respect to the 5100 {AA} continuum, and
their time lags continuously vary through the years. Especially, the H$beta$
time lags exhibited approximately a factor of two increase in the last two
years. Additionally, the velocity-resolved time delays of the broad H$beta$
emission line reveal a back-and-forth change between signs of virial motion and
inflow in the BLR. The combination of negligible ($sim$10%) continuum change
and substantial time-lag variation (over two times) results in significant
scatter in the intrinsic $R_{rm Hbeta}-L_{rm 5100}$ relationship for PG
2130+099. Taking into account the consistent changes in the continuum
variability time scale and the size of the BLR, we tentatively propose that the
changes in the measurement of the BLR size may be affected by ‘geometric
dilution’.

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