BVRI observations of dwarf novae in outburst

I. AL Comae Berenices, V544 Herculis, V660 Herculis, V516 Cygni and DX Andromedae

Cattedra di Astrofisica, Università di Perugia, Via A. Pascoli I-06123 Perugia, Italy

Received: 18 March 1997
Accepted: 26 January 1998

Abstract

In this paper we report photometric observations of AL Com, V544 Her, V660 Her, V516 Cyg and DX And taken during the descending phase after an outburst. For four of these variables we calibrated comparison stars in the field of view. Our observations cover the period in which AL Com showed the larger optical outburst since 1974, and V660 Her showed the larger outburst ever reported in the literature (). The optical spectral distribution of DX And, AL Com and V660 Her shows that the model of the steady–state accretion disk does not provide a good representation of the optical continuum during the decline phase of a dwarf nova outburst.