Detection of Chromatic Microlensing in Q 2237 + 0305 A

Mosquera, A. M.; Muñoz, J. A.; Mediavilla, E.
Bibliographical reference

The Astrophysical Journal, Volume 691, Issue 2, pp. 1292-1299 (2009).

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2
2009
Number of authors
3
IAC number of authors
1
Citations
35
Refereed citations
35
Description
We present narrowband images of the gravitational lens system Q 2237 + 0305 made with the Nordic Optical Telescope in eight different filters covering the wavelength interval 3510-8130 Å. Using point-spread function photometry fitting we have derived the difference in magnitude versus wavelength between the four images of Q 2237 + 0305. At λ = 4110 Å, the wavelength range covered by the Strömgren-v filter coincides with the position and width of the C IV emission line. This allows us to determine the existence of microlensing in the continuum and not in the emission lines for two images of the quasar. Moreover, the brightness of image A shows a significant variation with wavelength which can only be explained as a consequence of chromatic microlensing. To perform a complete analysis of this chromatic event, our observations were used together with Optical Gravitational Lensing Experiment light curves. Both data sets cannot be reproduced by the simple phenomenology described under the caustic crossing approximation; using more realistic representations of microlensing at high optical depth, we found solutions consistent with simple thin disk models (rs vprop λ4/3) however, other accretion disk size-wavelength relationships also lead to good solutions. New chromatic events from the ongoing narrowband photometric monitoring of Q 2237 + 0305 are needed to accurately constrain the physical properties of the accretion disk for this system.
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Relativistic and Theoretical Astrophysics
Introduction Gravitational lenses are a powerful tool for Astrophysics and Cosmology. The goals of this project are: i) to obtain a robust determination of the Hubble constant from the time delay measured between the images of a lensed quasar; ii) to study the individual and statistical properties of dark matter condensations in lens galaxies from
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