Extreme Variability Quasars in Their Various States. I. The Sample Selection and Composite SDSS Spectra

Ren, Wenke; Wang, Junxian; Cai, Zhenyi; Guo, Hengxiao

doi:10.3847/1538-4357/ac3828

Extreme Variability Quasars in Their Various States. I. The Sample Selection and Composite SDSS Spectra

Journal Article · Mon Jan 24 23:00:00 EST 2022 · The Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/ac3828· OSTI ID:1983207

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Univ. of Science and Technology of China, Hefei (China)
Univ. of California, Irvine, CA (United States)

Extremely variable quasars (EVQs) are a population of sources showing large optical photometric variability revealed by time-domain surveys. The physical origin of such extreme variability is yet unclear. In this first paper of a series, we construct the largest-ever sample of 14,012 EVQs using more than 15 yr of photometric data from Sloan Digital Sky Survey (SDSS) and Pan-STARRS1. We divide the EVQs into five subsamples according to the relative brightness of each EVQ during SDSS spectroscopic observation compared with the mean brightness from photometric observations. Corresponding control samples of normal quasars are built with matched redshift, bolometric luminosity, and supermassive black hole mass. We obtain the composite SDSS spectra of EVQs in various states and their corresponding control samples. We find EVQs exhibit clearly bluer SDSS spectra during bright states and clearly redder spectra during dim states, consistent with the "bluer-when-brighter" trend widely seen in normal quasars. We further find that the line equivalent widths (EWs) of broad Mg II, C IV and [O III] (but not broad Hβ, which is yet puzzling) gradually decreases from the dim state to the bright state, similar to the so-called intrinsic Baldwin effect commonly seen in normal active galactic nuclei. In addition, EVQs have consistently larger line EWs compared with the control samples. We also see that EVQs show slight excess in the very broad line component compared with control samples. Possible explanations for the discoveries are discussed. Our findings support the hypothesis that EVQs are in the tail of a broad distribution of quasar properties but are not a distinct population.

View Accepted Manuscript (DOE)

Research Organization:: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)

Sponsoring Organization:: USDOE Office of Science (SC)

OSTI ID:: 1983207

Journal Information:: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 925; ISSN 0004-637X

Publisher:: IOP PublishingCopyright Statement

Country of Publication:: United States

Language:: English

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THE TIMESCALE-DEPENDENT COLOR VARIABILITY OF QUASARS VIEWED WITHGALEX Zhu(朱飞凡), Fei-Fan; Wang(王俊贤), Jun-Xian; Cai(蔡振翼), Zhen-Yi The Astrophysical Journal, Vol. 832, Issue 1 https://doi.org/10.3847/0004-637X/832/1/75	journal	November 2016
The Sloan Digital Sky Survey Reverberation Mapping Project: The C iv Blueshift, Its Variability, and Its Dependence Upon Quasar Properties Sun, Mouyuan; Xue, Yongquan; Richards, Gordon T. The Astrophysical Journal, Vol. 854, Issue 2 https://doi.org/10.3847/1538-4357/aaa890	journal	February 2018
Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey Rumbaugh, N.; Shen, Yue; Morganson, Eric The Astrophysical Journal, Vol. 854, Issue 2 https://doi.org/10.3847/1538-4357/aaa9b6	journal	February 2018
EUCLIA—Exploring the UV/Optical Continuum Lag in Active Galactic Nuclei. I. A Model without Light Echoing Cai, Zhen-Yi; Wang, Jun-Xian; Zhu, Fei-Fan The Astrophysical Journal, Vol. 855, Issue 2 https://doi.org/10.3847/1538-4357/aab091	journal	March 2018
Identification of SDSS J141324.27+530527.0 as a New “Changing-look” Quasar with a “Turn-on” Transition Wang, J.; Xu, D. W.; Wei, J. Y. The Astrophysical Journal, Vol. 858, Issue 1 https://doi.org/10.3847/1538-4357/aab88b	journal	May 2018
A Mid-IR Selected Changing-look Quasar and Physical Scenarios for Abrupt AGN Fading Stern, Daniel; McKernan, Barry; Graham, Matthew J. The Astrophysical Journal, Vol. 864, Issue 1 https://doi.org/10.3847/1538-4357/aac726	journal	August 2018
Discovery of 21 New Changing-look AGNs in the Northern Sky Yang, Qian; Wu, Xue-Bing; Fan, Xiaohui The Astrophysical Journal, Vol. 862, Issue 2 https://doi.org/10.3847/1538-4357/aaca3a	journal	July 2018
Changing-look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars MacLeod, Chelsea L.; Green, Paul J.; Anderson, Scott F. The Astrophysical Journal, Vol. 874, Issue 1 https://doi.org/10.3847/1538-4357/ab05e2	journal	March 2019
1ES 1927+654: An AGN Caught Changing Look on a Timescale of Months Trakhtenbrot, Benny; Arcavi, Iair; MacLeod, Chelsea L. The Astrophysical Journal, Vol. 883, Issue 1 https://doi.org/10.3847/1538-4357/ab39e4	journal	September 2019
Initial Results from a Systematic Search for Changing-look Active Galactic Nuclei Selected via Mid-infrared Variability Sheng, Zhenfeng; Wang, Tinggui; Jiang, Ning The Astrophysical Journal, Vol. 889, Issue 1 https://doi.org/10.3847/1538-4357/ab5af9	journal	January 2020
Understanding Broad Mg ii Variability in Quasars with Photoionization: Implications for Reverberation Mapping and Changing-look Quasars Guo, Hengxiao; Shen, Yue; He, Zhicheng The Astrophysical Journal, Vol. 888, Issue 2 https://doi.org/10.3847/1538-4357/ab5db0	journal	January 2020
EUCLIA. II. On the Puzzling Large UV to X-Ray Lags in Seyfert Galaxies Cai, Zhen-Yi; Wang, Jun-Xian; Sun, Mouyuan The Astrophysical Journal, Vol. 892, Issue 1 https://doi.org/10.3847/1538-4357/ab7991	journal	March 2020
Time-delay Measurement of Mg ii Broad-line Response for the Highly Accreting Quasar HE 0413-4031: Implications for the Mg ii–based Radius–Luminosity Relation Zajaček, Michal; Czerny, Bożena; Martinez–Aldama, Mary Loli The Astrophysical Journal, Vol. 896, Issue 2 https://doi.org/10.3847/1538-4357/ab94ae	journal	June 2020
The Sloan Digital Sky Survey Reverberation Mapping Project: How Broad Emission Line Widths Change When Luminosity Changes Wang, Shu; Shen, Yue; Jiang, Linhua The Astrophysical Journal, Vol. 903, Issue 1 https://doi.org/10.3847/1538-4357/abb36d	journal	October 2020
The Extreme Red Excess in Blazar Ultraviolet Broad Emission Lines Punsly, Brian; Marziani, Paola; Berton, Marco The Astrophysical Journal, Vol. 903, Issue 1 https://doi.org/10.3847/1538-4357/abb950	journal	October 2020
High-redshift Extreme Variability Quasars from Sloan Digital Sky Survey Multiepoch Spectroscopy Guo, Hengxiao; Peng, Jiacheng; Zhang, Kaiwen The Astrophysical Journal, Vol. 905, Issue 1 https://doi.org/10.3847/1538-4357/abc2ce	journal	December 2020
Evidence for Two Distinct Broad-line Regions from Reverberation Mapping of PG 0026+129 Hu, Chen; Li, Sha-Sha; Guo, Wei-Jian The Astrophysical Journal, Vol. 905, Issue 1 https://doi.org/10.3847/1538-4357/abc2da	journal	December 2020
More Variable Quasars Have Stronger Emission Lines Kang, Wen-Yong; Wang, Jun-Xian; Cai, Zhen-Yi The Astrophysical Journal, Vol. 911, Issue 2 https://doi.org/10.3847/1538-4357/abeb69	journal	April 2021
Spectral Properties of Quasars from Sloan Digital Sky Survey Data Release 14: The Catalog Rakshit, Suvendu; Stalin, C. S.; Kotilainen, Jari The Astrophysical Journal Supplement Series, Vol. 249, Issue 1 https://doi.org/10.3847/1538-4365/ab99c5	journal	July 2020
A Sample Bias in Quasar Variability Studies Shen, Yue; Burke, Colin J. The Astrophysical Journal Letters, Vol. 918, Issue 1 https://doi.org/10.3847/2041-8213/ac1e2e	journal	August 2021

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