Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is pre- sented .
Monitoring of Q2237+0305 in July-October 2000 , made at nearly daily basis , did not reveal rapid ( night-to-night and intranight ) variations of brightness of the components during this time period .
Rather slow changes of magnitudes of the components were observed , such as 0.08m fading of B and C components and 0.05m brightening of D in R band during July 23 - October 7 , 2000 .
By good luck three nights of observation in 1999 were almost at the time of the strong brightness peak of image C , and approximately in the middle of the ascending slope of the image A brightness peak .
The C component was the most blue one in the system in 1998 and 1999 , having changed its ( V-I ) color from 0.56m to 0.12m since August 1997 , while its brightness increased almost 1.2m during this time period .
The A component behaved similarly between August 1998 and August 2000 , having become 0.47m brighter in R , and at the same time , 0.15m bluer .
A correlation between the color variations and variations of magnitudes of the components is demonstrated to be significant and reaches 0.75 , with a regression line slope of 0.33 .
A color ( V-I ) vrs color ( V-R ) plot shows the components settled in a cluster , stretched along a line with a slope of 1.31 .
Both slopes are noticeably smaller than those expected if a standard galactic interstellar reddening law were responsible for the differences between the colors of images and their variations over time .
We attribute the brightness and color changes to microlensing of the quasar ’ s structure , which we conclude is more compact at shorter wavelengths , as predicted by most quasar models featuring an energizing central source .