Structure of the pre-outburst accretion disk in SS Cygni

¹ Institute of Astronomy of the Russian Academy of Sciences, 48, Pyatnitskaya str., 119017 Moscow, Russia
² INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica – Roma, Area di Ricerca di Tor Vergata, via del Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: franco.giovannelli@iasf-roma.inaf.it
³ INAF Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

Received: 15 December 2010
Accepted: 10 November 2011

Abstract

We present results of spectroscopic observations of SS Cygni performed at the 1.5 m telescope of the Loiano Observatory in June 2009, three days before a long outburst. Using results of these observations, we computed Doppler tomograms in three Balmer lines H_β, H_γ, and H_δ. Analyzing the tomograms, we identified gas dynamic features existing in the system. It is shown that in the pre-outburst disk a number of shock waves exist. These waves are “hot line” a wave produced by the interaction between the circum-disk halo and the stream from the inner Lagrangian point L₁, and two arms of the spiral tidal shock and bow shock caused by the motion of the accretor and disk in the gas of the circum-binary envelope. We also found that before the outburst the density and size of the disk increase.