First hard X-ray observations of the blazar S5 0716+714 with NuSTAR during a multiwavelength campaign

TL;DR

This paper presents the first hard X-ray observations of blazar S5 0716+714 with NuSTAR during a multiwavelength campaign, revealing a high break energy and strong correlations across frequencies during a flare.

Contribution

It provides the first report of NuSTAR hard X-ray data for S5 0716+714 and analyzes its spectral and variability properties during a flaring state.

Findings

Highest reported break energy at 8 keV for the source.

Strong correlations between optical, UV, and gamma-ray emissions.

No time lag observed between different frequency bands.

Abstract

We report the results of a multifrequency campaign targeting S5 0716+714 in the flaring state of the source observed in 2015 January and February. The observations have been performed using the following instruments: Fermi/Large Area Telescope (LAT), Nuclear Spectroscopic Telescope Array, X-ray Telescope and Ultraciolet/Optical Telescope. The elevated flux level was visible in all frequencies and the outburst consists of five sub-flares. In this paper we focus on the analysis of the X-ray observations both in the soft and hard regimes for data collected with NuStar and Swift/XRT. This is the first time, when hard X-ray observations of the source collected with NuStar are reported. The studies reveal both low- and high-energy components clearly visible in the energy band, with the break energy of 8 keV, which is the highest break energy ever reported for S5 0716+714. The second part of this work is concentrated on multifrequency observations collected during the flaring activity period. The variability patterns recorded during the period are characterized using a fractional variability amplitude and description of the flare profiles. The correlation studies reveal strong and significant relation between the optical, ultraviolet and gamma-ray observations, and no time lag is found for any of the studied relations.