Gone with the wind? Potential gas inflow in the broad-line region of a QSO at z=0.287 traced by time-varying Balmer absorption
Abstract
We report spectroscopic observations of a remarkable QSO, J115724.80-000455.56 at z=0.287 from the Dark Energy Spectroscopic Instrument (DESI) survey. This QSO exhibits variability in its hydrogen Balmer absorption over a time interval of 10 months in the observed frame between 2021 and 2022. The observed Balmer absorption can be decomposed into two components with distinct kinematics: a non-varying, "stationary" component and a varying, "dynamic" component. Both absorbers have gas column densities of NH∼ 1022 cm−2 and likely have densities of nH≳ 108 cm−3. We inferred small effective physical sizes of ≲ 10−3 pc for the absorbers, which, together with the time variability, suggests that the absorption occurs in the broad-line region (BLR). The reshifted centroid velocities of both absorbers imply an inflow, where the inferred mass inflow rate is comparable to the single-epoch mass accretion rate of this QSO. The 2022 epoch of this QSO further reveals a 10% change in the column density over 2 months, indicating the gas inflow might be continuous. We also obtained new X-ray observations using the it Einstein Probe, which reveals an X-ray-to-bolometric luminosity ratio significantly below the general AGN population. The X-ray weakness is consistent with strong gas obscuration with NH= 4.0+ 1.6− 1.5×1023 cm−2. The substantially higher gas obscuration seen in the X-rays compared to the optical possibly indicates a warm absorber inside the BLR or merger-driven enhancement of the galactic scale obscuration consistent with optical imaging. This QSO might thus represent an active feeding phase after a recent gas-rich merger.
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BibTeX
@misc{ji2026gone,
title = {{Gone with the wind? Potential gas inflow in the broad-line region of a QSO at $z=0.287$ traced by time-varying Balmer absorption}},
author = {Xihan Ji and Dominic J. Walton and Francesco D'Eugenio and Ignas Juodžbalis and Vasily Belokurov and Andrew C. Fabian and Roberto Maiolino and Jiamu Huang and Douglas N. C. Lin},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25224},
eprint = {2609.25224},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25224},
}
RIS
TY - UNPB
TI - Gone with the wind? Potential gas inflow in the broad-line region of a QSO at z=0.287 traced by time-varying Balmer absorption
AU - Xihan Ji
AU - Dominic J. Walton
AU - Francesco D'Eugenio
AU - Ignas Juodžbalis
AU - Vasily Belokurov
AU - Andrew C. Fabian
AU - Roberto Maiolino
AU - Jiamu Huang
AU - Douglas N. C. Lin
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25224
UR - https://arxiv.org/abs/2609.25224
AB - We report spectroscopic observations of a remarkable QSO, J115724.80-000455.56 at z=0.287 from the Dark Energy Spectroscopic Instrument (DESI) survey. This QSO exhibits variability in its hydrogen Balmer absorption over a time interval of 10 months in the observed frame between 2021 and 2022. The observed Balmer absorption can be decomposed into two components with distinct kinematics: a non-varying, "stationary" component and a varying, "dynamic" component. Both absorbers have gas column densities of N_H∼ 10^22 cm^−2 and likely have densities of n_H≳ 10^8 cm^−3. We inferred small effective physical sizes of ≲ 10^−3 pc for the absorbers, which, together with the time variability, suggests that the absorption occurs in the broad-line region (BLR). The reshifted centroid velocities of both absorbers imply an inflow, where the inferred mass inflow rate is comparable to the single-epoch mass accretion rate of this QSO. The 2022 epoch of this QSO further reveals a 10% change in the column density over 2 months, indicating the gas inflow might be continuous. We also obtained new X-ray observations using the it Einstein Probe, which reveals an X-ray-to-bolometric luminosity ratio significantly below the general AGN population. The X-ray weakness is consistent with strong gas obscuration with N_H= 4.0^+ 1.6_− 1.5×10^23 cm^−2. The substantially higher gas obscuration seen in the X-rays compared to the optical possibly indicates a warm absorber inside the BLR or merger-driven enhancement of the galactic scale obscuration consistent with optical imaging. This QSO might thus represent an active feeding phase after a recent gas-rich merger.
ER -