EXPLORATORY X-RAY MONITORING OF LUMINOUS RADIO-QUIET QUASARS AT HIGH REDSHIFT: INITIAL RESULTS

• Published in: The Astrophysical journal Vol. 783; no. 2; pp. 1 - 18
• Main Authors: Shemmer, Ohad, Brandt, W N, Paolillo, Maurizio, Kaspi, Shai, Vignali, Cristian, Stein, Matthew S, Lira, Paulina, Schneider, Donald P, Gibson, Robert R
• Format: Journal Article
• Language: English
• Published: United States 10.03.2014
• Subjects: Accessibility; Active galactic nuclei; Assessments; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Benchmarking; BENCHMARKS; COMPARATIVE EVALUATIONS; DESIGN; ENERGY SPECTRA; EXTRAPOLATION; GALAXY NUCLEI; LUMINOSITY; Monitoring; QUASARS; RED SHIFT; X RADIATION; X-RAY GALAXIES; X-rays
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/783/2/116

We present initial results from an exploratory X-ray monitoring project of two groups of comparably luminous radio-quiet quasars (RQQs). The first consists of four sources at 4.10 [< or =, slant] z [< or =, slant] 4.35, monitored by Chandra, and the second is a comparison sample of three sources at 1.33 [< or =, slant] z [< or =, slant] 2.74, monitored by Swift. Six of these sources show significant X-ray variability over rest-frame timescales of ~10 super(2)-10 super(3) days; three of these also show significant X-ray variability on rest-frame timescales of ~1-10 days. The X-ray variability properties of our variable sources are similar to those exhibited by nearby and far less luminous active galactic nuclei (AGNs). This result may be attributed to luminous sources at the highest redshifts having relatively high accretion rates. This project is designed to provide a basic assessment of the X-ray variability properties of RQQs at the highest accessible redshifts that will serve as a benchmark for more systematic monitoring of such sources with future X-ray missions.