TY - JOUR
T1 - Chandra detection of three x-ray bright quasars at z > 5
AU - Li, Jiang Tao
AU - Wang, Feige
AU - Yang, Jinyi
AU - Zhang, Yuchen
AU - Fu, Yuming
AU - Bian, Fuyan
AU - Bregman, Joel N.
AU - Fan, Xiaohui
AU - Li, Qiong
AU - Wu, Xue Bing
AU - Yu, Xiaodi
N1 - Publisher Copyright:
© 2021. The American Astronomical Society.
PY - 2021/1/10
Y1 - 2021/1/10
N2 - We report Chandra detection of three UV-bright radio-quiet quasars at z ≳5. We have collected a sufficient number of photons to extract an X-ray spectrum of each quasar to measure their basic X-ray properties, such as the X-ray flux, power-law photon index (Γ), and optical-to-X-ray spectral slope (αOX). J074749+115352 at z = 5.26 is the X-ray brightest radio-quiet quasar at z > 5. It may have a short timescale variation (on a timescale of ∼3800 s in the observer's frame, or ∼600 s in the rest frame), which is, however, largely embedded in the statistical noise. We extract phase folded spectra of this quasar. There are two distinguishable states: A "high soft"state with an average X-ray flux ∼2.7 times the "low hard"state, and a significantly steeper X-ray spectral slope (Γ = - 2.40+0.32 0.33 versus - 1.78+0.24 0.25). We also compare the three quasars detected in this paper to other quasar samples. We find that J074749+115352, with an SMBH mass of MSMBH ≈ 1.8 × 109Me and an Eddington ratio of λEdd ≈ 2.3, is extraordinarily X-ray bright. It has an average αOX = -1.46 ± 0.02 and a 2-10 keV bolometric correction factor of Lbol/L2-10 keV = 42.4 ± 5.8, both significantly depart from some well defined scaling relations. We compare Γ of the three quasars to other samples at different redshifts, and do not find any significant redshift evolution based on the limited sample of z > 5 quasars with reliable measurements of the X-ray spectral properties.
AB - We report Chandra detection of three UV-bright radio-quiet quasars at z ≳5. We have collected a sufficient number of photons to extract an X-ray spectrum of each quasar to measure their basic X-ray properties, such as the X-ray flux, power-law photon index (Γ), and optical-to-X-ray spectral slope (αOX). J074749+115352 at z = 5.26 is the X-ray brightest radio-quiet quasar at z > 5. It may have a short timescale variation (on a timescale of ∼3800 s in the observer's frame, or ∼600 s in the rest frame), which is, however, largely embedded in the statistical noise. We extract phase folded spectra of this quasar. There are two distinguishable states: A "high soft"state with an average X-ray flux ∼2.7 times the "low hard"state, and a significantly steeper X-ray spectral slope (Γ = - 2.40+0.32 0.33 versus - 1.78+0.24 0.25). We also compare the three quasars detected in this paper to other quasar samples. We find that J074749+115352, with an SMBH mass of MSMBH ≈ 1.8 × 109Me and an Eddington ratio of λEdd ≈ 2.3, is extraordinarily X-ray bright. It has an average αOX = -1.46 ± 0.02 and a 2-10 keV bolometric correction factor of Lbol/L2-10 keV = 42.4 ± 5.8, both significantly depart from some well defined scaling relations. We compare Γ of the three quasars to other samples at different redshifts, and do not find any significant redshift evolution based on the limited sample of z > 5 quasars with reliable measurements of the X-ray spectral properties.
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U2 - 10.3847/1538-4357/abc750
DO - 10.3847/1538-4357/abc750
M3 - Article
AN - SCOPUS:85100192173
SN - 0004-637X
VL - 906
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - abc750
ER -