@article{AlcaldeMediavillaMoreauetal.2002,
  author    = {Alcalde, D. and Mediavilla, E. and Moreau, O. and De Rop, Y. and Barrena, R. and Gil-Merino, Rodrigo and McLeod, B. A. and Motta, V. and Oscoz, Alejandro and Serra-Ricart, M.},
  title     = {QSO 2237+0305 VR light curves from Gravitational Lenses International Time Project optical monitoring},
  year      = {2002},
  abstract  = {We present VR observations of QSO 2237+0305 conducted by the Gravitational Lensing International Time Project collaboration from 1999 October 1 to 2000 February 3. The observations were made with the 2.56 m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma (Spain). The point-spread function (PSF) fitting method and an adapted version of the ISIS subtraction method have been used to derive the VR light curves of the four components (A-D) of the quasar. The mean errors range in the intervals 0.01-0.04 mag (PSF fitting) and 0.01-0.02 mag (ISIS subtraction), with the faintest component (D) having the largest uncertainties. We address the relatively good agreement between the A and D light curves derived using different filters, photometric techniques, and telescopes. The new VR light curves of component A extend the time coverage of a high-magnification microlensing peak, which was discovered by the OGLE team.},
  language  = {en}
}
@article{GilMerinoGoicoecheaSerraRicartetal.2001,
  author    = {Gil-Merino, Rodrigo and Goicoechea, Luis Julian and Serra-Ricart, M. and Oscoz, Alejandro and Alcalde, D. and Mediavilla, E.},
  title     = {Short time-scale fluctuations in the difference light curves of QSO 0957+561A,B: microlensing or noise?},
  year      = {2001},
  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 330d 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 -33mmag 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.},
  language  = {en}
}
@article{GoicoecheaGilMerinoSerraRicartetal.2001,
  author    = {Goicoechea, Luis Julian and Gil-Merino, Rodrigo and Serra-Ricart, M. and Oscoz, Alejandro and Alcalde, D. and Mediavilla, E.},
  title     = {IAC gravitational lenses monitoring program : difference signals from 2.5 years of QSO 0957+561 observations},
  isbn      = {0-7923-6974-2},
  year      = {2001},
  language  = {en}
}
@article{PugaAlcaldeBarrenaetal.2001,
  author    = {Puga, E. and Alcalde, D. and Barrena, R. and Mediavilla, E. and Motta, V. and Munoz, J. A. and Oscoz, Alejandro and Serra-Ricart, M. and Gil-Merino, Rodrigo and Goicoechea, Luis Julian and Lewis, G. f and Libbrecht, C. and Moreau, O. and Surdej, J. and Wambsganß, Joachim},
  title     = {Daily monitoring of the gravitational lens QSO 2237+0305 at the Nordic Optical Telescope},
  isbn      = {0-7923-6974-2},
  year      = {2001},
  language  = {en}
}
@article{GoicoecheaGilMerinoSerraRicartetal.2001,
  author    = {Goicoechea, Luis Julian and Gil-Merino, Rodrigo and Serra-Ricart, M. and Mediavilla, E. and Oscoz, Alejandro and Alcalde, D.},
  title     = {The nature of dark matter in elliptical (cD) galaxies : main lens galaxy of Q0957+561},
  isbn      = {1-583-81074-9},
  year      = {2001},
  language  = {en}
}