TY - JOUR
T1 - Steep Hard-X-Ray Spectra Indicate Extremely High Accretion Rates in Weak Emission-line Quasars
AU - Marlar, Andrea
AU - Shemmer, Ohad
AU - Anderson, S. F.
AU - Brandt, W. N.
AU - Diamond-Stanic, A. M.
AU - Fan, X.
AU - Luo, B.
AU - Plotkin, R. M.
AU - Richards, Gordon T.
AU - Schneider, D. P.
AU - Wu, Jianfeng
N1 - Funding Information:
We gratefully acknowledge the financial support of NASA grants NNX13AB57G, NNX16AC06G, and NNX17AC67G (A.M., O.S.), the NASA ADAP program (W.N.B.), Curtin University through the Peter Curran Memorial Fellowship (R.P.M.), the National Key R & D Program of China grant 2016YFA0400702 and National Natural Science Foundation of China grant 11673010 (B.L.). Support for this work was also provided by the National Aeronautics and Space Administration through Chandra Award Number AR3-14009X and GO7-18110X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics and Space Administration under contract NAS8-03060 (G.T.R.). We thank an anonymous referee for a thoughtful and constructive report that helped in improving this manuscript. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, as well as NASAʼs Astrophysics Data System Bibliographic Services. This research has also made use of data provided by the High Energy Astrophysics Science Archive Research Center (HEA-SARC), which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory.
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/10/1
Y1 - 2018/10/1
N2 - We present XMM-Newton imaging spectroscopy of 10 weak emission-line quasars (WLQs) at , six of which are radio-quiet, and four that are radio-intermediate. The new X-ray data enabled us to measure the power-law photon index, at rest-frame energies >2 keV, in each source with relatively high accuracy. These measurements allowed us to confirm previous reports that WLQs have steeper X-ray spectra, suggesting higher accretion rates with respect to "typical" quasars. A comparison between the photon indices of our radio-quiet WLQs and those of a control sample of 85 sources shows that the first are significantly higher, at the 3σ level. Collectively, the four radio-intermediate WLQs have lower photon indices with respect to the six radio-quiet WLQs, as may be expected if the spectra of the first group are contaminated by X-ray emission from a jet. Therefore, in the absence of significant jet emission along our line of sight, these results are in agreement with the idea that WLQs constitute the extreme high end of the accretion-rate distribution in quasars. We detect soft excess emission in our lowest-redshift radio-quiet WLQ, in agreement with previous findings suggesting that the prominence of this feature is associated with a high accretion rate. We have not detected signatures of Compton reflection, Fe Kα lines, or strong variability between two X-ray epochs in any of our WLQs, which can be attributed to their relatively high luminosity.
AB - We present XMM-Newton imaging spectroscopy of 10 weak emission-line quasars (WLQs) at , six of which are radio-quiet, and four that are radio-intermediate. The new X-ray data enabled us to measure the power-law photon index, at rest-frame energies >2 keV, in each source with relatively high accuracy. These measurements allowed us to confirm previous reports that WLQs have steeper X-ray spectra, suggesting higher accretion rates with respect to "typical" quasars. A comparison between the photon indices of our radio-quiet WLQs and those of a control sample of 85 sources shows that the first are significantly higher, at the 3σ level. Collectively, the four radio-intermediate WLQs have lower photon indices with respect to the six radio-quiet WLQs, as may be expected if the spectra of the first group are contaminated by X-ray emission from a jet. Therefore, in the absence of significant jet emission along our line of sight, these results are in agreement with the idea that WLQs constitute the extreme high end of the accretion-rate distribution in quasars. We detect soft excess emission in our lowest-redshift radio-quiet WLQ, in agreement with previous findings suggesting that the prominence of this feature is associated with a high accretion rate. We have not detected signatures of Compton reflection, Fe Kα lines, or strong variability between two X-ray epochs in any of our WLQs, which can be attributed to their relatively high luminosity.
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U2 - 10.3847/1538-4357/aad812
DO - 10.3847/1538-4357/aad812
M3 - Article
AN - SCOPUS:85054849050
SN - 0004-637X
VL - 865
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 92
ER -