An XMM-Newton catalogue of BL Lacs

TL;DR

This paper presents a comprehensive XMM-Newton catalogue of BL Lac objects, analyzing their X-ray, optical, and UV properties, variability, and spectral models, and integrating multi-wavelength data for a large sample over 20 years.

Contribution

It provides the first homogeneous analysis of BL Lac X-ray and optical/UV data from XMM-Newton, including spectral fitting, variability assessment, and multi-wavelength cataloging.

Findings

Log parabola model is preferred at higher fluxes, indicating intrinsic curvature.

Detected X-ray counterparts for 103 BL Lacs from 1151 in the catalog.

The catalogue includes spectral, variability, and multi-wavelength data for the sample.

Abstract

We present an XMM-Newton catalogue of BL Lac X-ray, optical, and UV properties based on cross-correlation with the 1151 BL Lacs listed in the fifth edition of the Roma-BZCAT. We searched for the X-ray counterparts to these objects in the field of view of all pointed observations in the XMM-Newton archive over nearly 20 years of mission. The cross-correlation yields a total of 310 XMM-Newton fields which correspond to 103 different BL Lacs. We homogeneously analysed data from the three EPIC cameras (X-ray) and OM(optical/UV) using the XMM-Newton SAS software, and produced images, light curves, and spectral products for BL Lacs detected in any of the three EPIC cameras. We tested two different phenomenological models, log parabola and power law, with different variations of the absorbing column density and extracted their parameters. We derived time-variability information from the light curves following well-established statistical methods and quantified variability through statistical indicators. OM magnitudes and fluxes were computed wherever possible. We see that the log parabola model is preferred over the power law model for sources showing higher fluxes, which might indicate that curvature is intrinsic to BL Lacs and is only seen when the flux is high. We present the results of our analysis as a catalogue of X-ray spectral properties of the sample in the 0.2-10 keV energy band as well as in the optical/UV band. We complete the catalogue with multi-wavelength information at radio and gamma-ray energies.