Short time-scale fluctuations in the difference light curves of QSO 0957+561A,B: microlensing or noise? |
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| Authors: | R Gil-Merino L J Goicoechea M Serra-Ricart A Oscoz D Alcalde E Mediavilla |
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| Institution: | Departamento de Física Moderna, Universidad de Cantabria, Avda. Los Castros s/n, E-39005 Santander, Spain;Lehrstuhl Astrophysik, Institut für Physik, Universität Potsdam, Am Neuen Palais 10, D-14469 Potsdam, Germany;Instituto de Astrofísica de Canarias, Via Láctea s/n, La Laguna, E-38200, Spain |
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| Abstract: | From optical R -band data of the double quasar QSO 0957+561A,B, we made two new difference light curves (with an overlap of about 330 d between the time-shifted light curve for the A image and the magnitude-shifted light curve for the B image). We observed noisy behaviours around the zero line and no short time-scale events (with a duration of months), where the term 'event' refers to a prominent feature that may be a result of microlensing or another source of variability. Only one event lasting two weeks and rising ?33 mmag was found . Measured constraints on the possible microlensing variability can be used to obtain information on the granularity of the dark matter in the main lensing galaxy and the size of the source. In addition, one can also test the ability of the observational noise to cause the rms averages and the local features of the difference signals. We focused on this last issue. The combined photometries were related to a process consisting of an intrinsic signal plus a Gaussian observational noise. The intrinsic signal has been assumed to be either a smooth function (polynomial), a smooth function plus a stationary noise process, or a correlated stationary process . Using these three pictures without microlensing, we derived some models totally consistent with the observations. We finally discussed the sensitivity of our telescope (at Teide Observatory) to several classes of microlensing variability. |
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| Keywords: | gravitational lensing galaxies: elliptical and lenticular cD quasars: individual: Q0957+561 dark matter |
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