Swift observations of high-redshift radio-loud quasars

Abstract

We report on Swift observations of four z>2 radio-loud quasars (0212+735, 0537-286, 0836+710, and 2149-307), classified as blazars. The sources, well-known emitters at soft-medium X-rays, were detected at >5sigma with the BAT experiment in 15-150 keV. No flux variability was detected within the XRT and BAT exposures, with the exception of 0836+710 which shows an increase of a factor 4 of the 15-150 keV flux on a timescale of one month. The 0.3-10 keV spectra are well fitted by power law models, with rather hard continua (photon indices Gamma_XRT ~1.3-1.5); similarly, the 15-150 keV spectra are described by power laws with Gamma_BAT ~1.3-1.8. The XRT data exhibit spectral curvature, which can be modeled either in terms of excess absorption along the line of sight, or a downward-curved broken power law. In the former case, if the excess N_H is at the rest-frame of the source, columns of N_H^z=(0.3-6)x10^22 cm^-2 are measured. Modeling of the SEDs of the four quasars shows that the emission at the higher frequencies, >~ 10^16 Hz, is dominated by the jet, while the steep optical-to-UV continua, observed with the UVOT, can be attributed to thermal emission from the accretion disk. The disk luminosity is between 1% and 10% the jet power, similar to other powerful blazars.

Accepted for publication in ApJ; 22 pages, 4 figures

References in corpus (5)

• INTEGRAL observations of the blazar 3C454.3 in outburst
• Bulk Comptonization spectra in blazars
• Low energy cut-offs and hard X-ray spectra in high-z radio-loud quasars: the Suzaku view of RBS315
• Discovery of an Extreme MeV Blazar with the Swift Burst Alert Telescope
• Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217

Cited by in corpus (10)

• The spectrum of the Broad Line Region and the high-energy emission of powerful blazars
• First detection of hard X-ray photons in the soft X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed by Swift
• NuSTAR and multifrequency study of the two high-redshift blazars S5 0836+710 and PKS 2149-306
• The High Redshift Blazar S5 0836+71: A Broadband Study
• High-redshift blazar identification for Swift J1656.3-3302
• The changing look of PKS 2149-306
• Radio VLBA polarization and multi-band monitoring of the high-redshift quasar S5 0836+710 during a high activity period
• Understanding the Broadband Emission Process of 3C 279 through Longterm Spectral Analysis
• Breaks in the X-ray spectra of high redshift blazars and the intervening medium
• Investigating the variability of Swift-BAT blazars with NICER