next previous
Up: Abstract

A& A Supplement series, Vol. 121, January 1997, 119 - 138

Received March 18; accepted May 21, 1996

Optical photometric monitoring of tex2html_wrap_inline1888-ray loud blazars.

I. Observations from November 1994 to November 1995

M. Villatatex2html_wrap1914, C.M. Raiteritex2html_wrap1916, G. Ghisellinitex2html_wrap1918, G. De Francescotex2html_wrap1920, S. Bosiotex2html_wrap1922, G. Latinitex2html_wrap1924, B. Bucciarellitex2html_wrap1926, M. Chiabergetex2html_wrap1928, G. Chiumientotex2html_wrap1930, A. Coratex2html_wrap1932, L. Lanteritex2html_wrap1934, M.G. Lattanzitex2html_wrap1936, G. Massonetex2html_wrap1938, A. Peilatex2html_wrap1940, F. Racioppitex2html_wrap1942, R.L. Smarttex2html_wrap1944, F. Scaltrititex2html_wrap1946gif - E. Anderluccitex2html_wrap1948tex2html_wrap_inline1890

Send offprint request: M. Villata (

tex2html_wrap1950  Osservatorio Astronomico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (TO), Italy
tex2html_wrap1952  Istituto di Fisica Generale dell'Università, Via Pietro Giuria 1, I-10125 Torino, Italy


The results of the optical monitoring between November 1994 and November 1995 of twenty tex2html_wrap_inline1892-ray loud blazars included in the Torino blazar monitoring program are presented. All data were taken with the tex2html_wrap_inline1894 REOSC astrometric telescope of the Torino Astronomical Observatory, equipped with a tex2html_wrap_inline1896 pixels charge-coupled device (CCD) camera. Observations have been carried out in the standard B, V (Johnson), and R (Cousins) bands. Source magnitudes are calculated with respect to reference stars in the same frame. For half blazar fields it was possible to perform a photometric calibration through the observation of Landolt's fields during photometric nights. In the other cases either photometric sequences from the literature were adopted or, when lacking, magnitudes were simply normalized to their minimum value. Most of the monitored objects show a more or less pronounced brightness variability on both short and long time scales. In a few cases also noticeable intranight variations were detected. Data simultaneous to pointings of the Compton Gamma Ray Observatory (CGRO) are present in our light curves: when the tex2html_wrap_inline1904 data are available they will provide a useful information in order to understand the possible correlations between the optical and tex2html_wrap_inline1906-ray emissions. For one source (PKS 2254+074) we performed also photopolarimetry, deducing magnitudes, amount of polarization, and position angle in the UBVRI bands.

keywords: quasars: general -- gamma rays: theory

next previous
Up: Abstract

Copyright EDP Sciences