@article{0ef89a69b59a437fb0091b71c2b9715c,
title = "Chandra X-Rays from the Redshift 7.54 Quasar ULAS J1342+0928",
abstract = "We present a 45 ks Chandra observation of the quasar ULAS J1342+0928 at z = 7.54. We detect counts from the quasar in the observed-frame energy range 0.5-7.0 keV (6σ detection), representing the most distant non-transient astronomical source identified in X-rays to date. The present data are sufficient only to infer rough constraints on the spectral parameters. We find an X-ray hardness ratio of between the 0.5-2.0 keV and 2.0-7.0 keV ranges and derive a power-law photon index of . Assuming a typical value for high-redshift quasars of Γ = 1.9, ULAS J1342+0928 has a 2-10 keV rest-frame X-ray luminosity of . Its X-ray-to-optical power-law slope is , consistent with the general trend indicating that the X-ray emission in the most bolometrically powerful quasars is weaker relative to their optical emission.",
keywords = "cosmology, individual (ULAS J134208.10+092838.61), observations-early universe-quasars",
author = "Eduardo Banados and Thomas Connor and Daniel Stern and John Mulchaey and Xiaohui Fan and Roberto Decarli and Farina, {Emanuele P.} and Chiara Mazzucchelli and Venemans, {Bram P.} and Fabian Walter and Feige Wang and Jinyi Yang",
note = "Funding Information: We thank the referee for useful comments that improved this Letter. We thank Silvia Martocchia for providing the data to produce Figure 3. The work of D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. B.P.V. and F. Walter acknowledge funding through ERC grants “Cosmic Dawn” and “Cosmic Gas.” The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory. This research has made use of software provided by the Chandra X-ray Center (CXC) in the application package CIAO. Facility: CXO. Software: Astropy (Astropy Collaboration et al. 2018). Publisher Copyright: {\textcopyright} 2018. The American Astronomical Society. All rights reserved..",
year = "2018",
month = apr,
day = "1",
doi = "10.3847/2041-8213/aab61e",
language = "English (US)",
volume = "856",
journal = "Astrophysical Journal Letters",
issn = "2041-8205",
publisher = "IOP Publishing Ltd.",
number = "2",
}