Journal Article

Microlensing-induced spectral variability in Q 2237 + 0305

G. F. Lewis, M. J. Irwin, P. C. Hewett and C. B. Foltz

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 295, issue 3, pages 573-586
Published in print April 1998 | ISSN: 0035-8711
Published online April 1998 | e-ISSN: 1365-2966 | DOI:
Microlensing-induced spectral variability in Q 2237 + 0305

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We present both photometry and spectra of the individual images of the quadruple gravitational lens system Q 2237 + 0305. Comparison of spectra obtained at two epochs, separated by ∼ 3 yr, shows evidence for significant changes in the emission line-to-continuum ratio of the strong ultraviolet C iv λ1549, C iii] λ1909 and Mg ii λ2798 lines. The short, ∼ 1 day, light-travel time differences between the sight lines to the four individual quasar images rule out any explanation based on intrinsic variability of the source. The spectroscopic differences thus represent direct detection of microlensing-induced spectroscopic differences in a quasar. The observations allow constraints to be placed on the relative spatial scales in the nucleus of the quasar, with the ultraviolet continuum arising in a region of ≲ 0.05 pc in extent, while the broad emission-line material is distributed on scales much greater than this.

Keywords: quasars: general; quasars: individual: Q 2237 + 0305; gravitational lensing

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Subjects: Astronomy and Astrophysics

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