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Register a new userQ2237+0305 in X-rays: spectra and variability with XMM-Newton
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E.V. Fedorova
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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. 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. The total X-ray flux from all the images of this quadruple gravitational lens system is 6 x 10^{-13} 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 Gamma=1.82+0.07/-0.08. The X-ray lightcurves obtained after background subtraction are compatible with the hypothesis of a stationary flux from the source.
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We present the results of the first long-term (2.2 years) spectroscopic monitoring of a gravitationally lensed quasar, namely the Einstein Cross Q2237+0305. We spatially deconvolve deep VLT/FORS1 spectra to accurately separate the spectrum of the lensing galaxy from the spectra of the quasar images. Accurate cross-calibration of the observations at 31 epochs from October 2004 to December 2006 is carried out using foreground stars observed simultaneously with the quasar. The quasar spectra are further decomposed into a continuum component and several broad emission lines. We find prominent microlensing events in the quasar images A and B, while images C and D are almost quiescent on a timescale of a few months. The strongest variations are observed in the continuum, and their amplitude is larger in the blue than in the red, consistent with microlensing of an accretion disk. Variations in the intensity and profile of the broad emission lines are also reported, most prominently in the wings of the CIII] and in the center of the CIV emission lines. During a strong microlensing episode observed in quasar image A, the broad component of the CIII] is more magnified than the narrow component. In addition, the emission lines with higher ionization potentials are more magnified than the lines with lower ionization potentials, consistent with the stratification of the broad line region (BLR) infered from reverberation mapping observations.
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First results from high-resolution coronal spectroscopy of flares with the Reflection Grating Spectrometers on board the textit{XMM-Newton} satellite are reviewed. Rotational modulation in the X-ray light curve of HR 1099 is discussed. Results from time-dependent spectroscopy of flares in the active stars HR 1099, AB Dor, YY Gem are also presented. Variations in the shape of the emission measure distributions, in the abundances and in the average density of the cool plasma are discussed.
We present the results of the first long-term (2.2 years) spectroscopic monitoring of a gravitationally lensed quasar, namely the Einstein Cross Q2237+0305. The goal of this paper is to present the observational facts to be compared in follow-up papers with theoretical models to constrain the inner structure of the source quasar. We spatially deconvolve deep VLT/FORS1 spectra to accurately separate the spectrum of the lensing galaxy from the spectra of the quasar images. Accurate cross-calibration of the 58 observations at 31-epoch from October 2004 to December 2006 is carried out with non-variable foreground stars observed simultaneously with the quasar. The quasar spectra are further decomposed into a continuum component and several broad emission lines to infer the variations of these spectral components. We find prominent microlensing events in the quasar images A and B, while images C and D are almost quiescent on a timescale of a few months. The strongest variations are observed in the continuum of image A. Their amplitude is larger in the blue (0.7 mag) than in the red (0.5 mag), consistent with microlensing of an accretion disk. Variations in the intensity and profile of the broad emission lines are also reported, most prominently in the wings of the CIII] and center of the CIV emission lines. During a strong microlensing episode observed in June 2006 in quasar image A, the broad component of the CIII] is more highly magnified than the narrow component. In addition, the emission lines with higher ionization potentials are more magnified than the lines with lower ionization potentials, consistent with the results obtained with reverberation mapping. Finally, we find that the V-band differential extinction by the lens, between the quasar images, is in the range 0.1-0.3 mag.
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