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(gzipped) PostScript## Microlensing on different timescales in the lightcurves of QSO 0957+561 A,B
^{1} Tartu Observatory, EE-2444 Tõravere, Estonia^{2} Harvard-Smithsonian Center for Astrophysics, MS-19 60
Garden Street, Cambridge, MA 02138, USA^{3} Hamburger Sternwarte, Gojenbergsweg 112, D-21029
Hamburg-Bergedorf, Germany^{4} Institute of Theoretical Astrophysics, P.O. Box 1029,
Blindern, N-0315 Oslo, Norway^{5} Centre for Advanced Study, Drammensveien 78, N-0271,
Oslo, Norway
A statistical analysis of an extended data set on a time basis of
17 years of optical observations of the gravitationally lensed quasar
0957+561 is presented. We use all available photometry to estimate the
time delay between We show that masses down to about may explain this microlensing event. Solar mass objects alone can more or less be excluded. However, a distribution of compact objects with a small fraction () in solar mass objects, seems to be possible. The best constrained parameter is the radius of the source which roughly should be (within a factor of 3). With the present noise level an additional variability due to the
microlensing on shorter time scales (days to months) is difficult to
prove with a reasonable significance. All steps of the analysis are
carried out by using simple statistical tests and with as few
Online publication: July 27, 1998 |