Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars

TL;DR

This paper reports XMM-Newton X-ray observations of nine gravitationally lensed quasars from Gaia DR2, providing spectral analysis, luminosities, and identifying notable sources for future studies and discovery prospects.

Contribution

First X-ray spectral analysis of a sample of Gaia DR2 lensed quasars, including flux, luminosity, and variability insights, aiding future gravitational lensing research.

Findings

Eight quasars strongly detected in X-ray

Identification of a variable flux quasar

Discovery of the most closely-separated X-ray lensed sources

Abstract

We present XMM-Newton X-ray observations of nine confirmed lensed quasars at $1 \lesssim z \lesssim 3$ identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3--8.0 keV fluxes $F_{0.3-8.0} \gtrsim 5 \times 10^{-14}\ {\rm erg}\ {\rm cm}^{-2}\ {\rm s}^{-1}$. Modeling the X-ray spectra with an absorbed power law, we derive power law photon indices and 2--10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic crossing events, we also identify three quasars of interest: a quasar that shows evidence of flux variability from previous ROSAT observations, the most closely-separated individual lensed sources resolved by XMM-Newton, and one of the X-ray brightest quasars known at $z>3$. These sources represent the tip of discovery that will be enabled by SRG/eROSITA.