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Title: Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442

Abstract

We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He i lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. They were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, i.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would bemore » very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.« less

Authors:
; ; ; ; ; ;  [1];  [2]; ;  [3]
  1. Polar Research Institute of China, Jinqiao Road 451, Shanghai 200136 (China)
  2. Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan 650011 (China)
  3. Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China)
Publication Date:
OSTI Identifier:
22654445
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 843; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ACCRETION DISKS; BALMER LINES; HYDROGEN; OSCILLATOR STRENGTHS; OSCILLATORS; PHOTOIONIZATION; QUASARS; RESOLUTION; SPECTRA; TELESCOPES; VELOCITY; WAVELENGTHS

Citation Formats

Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA725E.
Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, & Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442. United States. doi:10.3847/2041-8213/AA725E.
Shi, Xi-Heng, Pan, Xiang, Zhang, Shao-Hua, Sun, Lu-Ming, Ji, Tuo, Liu, Bo, Zhou, Hong-Yan, Wang, Jian-Guo, Yang, Chen-Wei, and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn. Sat . "Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442". United States. doi:10.3847/2041-8213/AA725E.
@article{osti_22654445,
title = {Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442},
author = {Shi, Xi-Heng and Pan, Xiang and Zhang, Shao-Hua and Sun, Lu-Ming and Ji, Tuo and Liu, Bo and Zhou, Hong-Yan and Wang, Jian-Guo and Yang, Chen-Wei and Jiang, Ning, E-mail: zhouhongyan@pric.org.cn, E-mail: shixiheng@pric.org.cn},
abstractNote = {We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He i lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. They were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, i.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would be very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.},
doi = {10.3847/2041-8213/AA725E},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 843,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}