Q2237+0305 in X-rays: spectra and variability with XMM-Newton^*

¹ Astronomical Observatory of Kyiv Shevchenko University, Observatorna St. 3, Kiev, UA- 04053, Ukraine e-mail: elena_f@mail.univ.kiev.ua; zhdanov@observ.univ.kiev.ua
² Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: [cristian.vignali;giorgio.palumbo]@unibo.it

Received: 25 September 2007
Accepted: 23 August 2008

Abstract

Aims. X-ray observations of gravitationally lensed quasars may allow us to probe the inner structure of the central engine of a quasar. Observations of Q2237+0305 (Einstein Cross) in X-rays may be used to constrain the inner structure of the X-ray emitting source.

Methods. Here we analyze the XMM-Newton observation of the quasar in the gravitational lens system Q2237+0305 taken during 2002. Combined spectra of the four images of the quasar in this system were extracted and modelled with a power-law model. Statistical analysis was used to test the variability of the total flux.

Results. The total X-ray flux from all the images of this quadruple gravitational lens system is  erg/(cm² s) in the range 0.2–10 keV, showing no significant X-ray spectral variability during almost 42 ks of the observation time. Fitting of the cleaned source spectrum yields a photon power-law index of . The X-ray lightcurves obtained after background subtraction are compatible with the hypothesis of a stationary flux from the source.