Examinando por Autor "Fian, C."

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  • Miniatura
    Ítem
    Microlensing of the broad emission lines in 27 gravitationally lensed quasars Broad line region structure and kinematics
    (European Southern Observatory (ESO), 2021) Fian, C.; Mediavilla, E.; Motta, V.; Jiménez-Vicente, J.; Muñoz, J. A.; Chelouche, D.; Hanslmeier, A.
    Aims. We aim to study the structure and kinematics of the broad line region (BLR) of a sample of 27 gravitationally lensed quasars with up to five different epochs of observation. This sample is composed of ∼100 spectra from the literature plus 22 unpublished spectra of 11 systems. Methods. We measure the magnitude differences in the broad emission line (BEL) wings and statistically model the distribution of microlensing magnifications to determine a maximum likelihood estimate for the sizes of the C IV, C III], and Mg II emitting regions. Results. The BELs in lensed quasars are expected to be magnified differently owing to the different sizes of the regions from which they originate. Focusing on the most common BELs in our spectra (C IV, C III], and Mg II), we find that the low-ionization line Mg II is only weakly affected by microlensing. In contrast, the high-ionization line C IV shows strong microlensing in some cases, indicating that its emission region is more compact. Thus, the BEL profiles are deformed differently depending on the geometry and kinematics of the corresponding emitting region. We detect microlensing in either the blue or the red wing (or in both wings with different amplitudes) of C IV in more than 50% of the systems and find outstanding asymmetries in the wings of QSO 0957+561, SDSS J1004+4112, SDSS J1206+4332, and SDSS J1339+1310. This observation indicates that the BLR is, in general, not spherically symmetric and supports the existence of two regions in the BLR, one insensitive to microlensing and another that only shows up when it is magnified by microlensing. Disregarding the existence of these two regions, our estimate for Mg II, R1/2 = 67.3−15.7+3.8 √(M/M⊙) light-days, is in good agreement with previous results from smaller samples, while we obtain smaller sizes for the C III] and CIV lines, R1/2 = 31.0−4.0+1.9 √(M/M⊙) light-days and R1/2 = 15.5−3.9+0.8 √(M/M⊙) light-days, respectively.
  • Miniatura
    Ítem
    Revealing the structure of the lensed quasar Q 0957+561 I. Accretion disk size
    (European Southern Observatory (ESO), 2021) Fian, C.; Mediavilla, E.; Jiménez-Vicente, J.; Motta, V.; Muñoz, J. A.; Chelouche, D.; Goméz-Alvarez, P.; Rojas, K.; Hanslmeier, A.
    Aims. We aim to use signatures of microlensing induced by stars in the foreground lens galaxy to infer the size of the accretion disk in the gravitationally lensed quasar Q 0957+561. The long-term photometric monitoring of this system (which so far has provided the longest available light curves of a gravitational lens system) permits us to evaluate the impact of uncertainties on our recently developed method (controlled by the distance between the modeled and the experimental magnitude difference histograms between two lensed images), and thus to test the robustness of microlensing-based disk-size estimates. Methods. We analyzed the well-sampled 21-year GLENDAMA optical light curves of the double-lensed quasar and studied the intrinsic and extrinsic continuum variations. Using accurate measurements for the time delay between the images A and B, we modeled and removed the intrinsic quasar variability, and from the statistics of microlensing magnifications we used a Bayesian method to derive the size of the region emitting the continuum at λrest = 2558 Å. Results. Analysis of the Q 0957+561 R-band light curves show a slow but systematic increase in the brightness of the B relative to the A component during the past ten years. The relatively low strength of the magnitude differences between the images indicates that the quasar has an unusually big optical accretion disk of half-light radius: R1/2 = 17.6±6.1 √(M/0.3 M⊙) lt-days.