Optical Monitoring of BL Lacertae Object S5 0716+714 with a Novel Multipeak Interference Filter

We at first introduce a novel photometric system, which consists of a Schmidttelescope, an objective prism, a CCD camera, and, especially, a multi-peakinterference filter. The multi-peak interference filter enables light in multipassbands to pass through it simultaneously. The light in different passbandsis differentially refracted by the objective prism and is focused on the CCDseparately, so we have multi "images" for each object on the CCD frames. Thissystem enables us to monitor blazars exactly simultaneously in multi wavebandson a single telescope, and to accurately trace the color change during thevariation. We used this novel system to monitor the BL Lacertae object S50716+714 during 2006 January and February and achieved a very high temporalresolution. The object was very bright and very active during this period. Twostrong flares were observed, with variation amplitudes of about 0.8 and 0.6mags in the $V'$ band, respectively. Strong bluer-when-brighter correlationswere found for both internight and intranight variations. No apparent time lagwas observed between the $V'$- and $R'$-band variations, and the observedbluer-when-brighter chromatism may be mainly attributed to the larger variationamplitude at shorter wavelength. In addition to the bluer-when-brighter trend,the object also showed a bluer color when it was more active. The observedvariability and its color behaviors are consistent with the shock-in-jet model.Comment: 30 pages, 22 figures, accepted by A