Photometry and spectroscopy of short-period cataclysmic variables

Abstract

Broad-band UBVJHK photometric measurements on 20 dwarf novae and nine nova-like systems and 10 A resolution spectrophotometry from 3500 to 5400 A of 15 cataclysmic variables are presented, with emphasis on the quiescent values of the dwarf novae and on the normal states of the nova-like systems. These data are used together with values from the literature to make a comparison of the colors and line strengths of the systems with orbital periods below the 2-3 hr period gap (mostly SU UMa stars) with those systems in the 3-4 hr period group (including VY Scl stars, dwarf novae, and nova-like systems). The results show the largest difference in the mean and spread of equivalent width between the two sides of the period gap, and linear trends are apparent in bluer V J and U - B colors and increasing strength of He II lambda 4686 as the period gap is approached from the ultrashort-period end.