The old nova DQ Her (1934)

The eclipse of the triple-peaked H_α profile

¹ University of Padova, Department of Astronomy, vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: bianchini@pd.astro.it
² Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA
³ On leave from Lycoming College, Williamsport, PA, USA

Received: 1 June 2004
Accepted: 7 July 2004

Abstract

We performed time resolved spectroscopy of the old-nova intermediate-polar DQ Her during an eclipse of its WD primary. The eclipse of the H_α and HeIλ6678 emission lines is reminiscent of that of an accretion disk. However, H_α shows a triple-peaked profile and is only partially eclipsed. The three stationary peaks shown by H_α could be produced by the accretion stream overflowing the disk, some material near the barycenter of the binary system, the surface of the secondary facing the WD, a wind and/or a jet from the disk. Some contamination by the nova ejecta is also possible. The presence of stationary components in the emission line profiles is reminiscent of other CVs like the dwarf nova IP Peg. The broad component of the H_α emission seems to be produced by the accretion disk as this component is the only one to show radial velocity variations modulated by the orbital motion of the WD. The O–C value derived from the eclipse of the continuum confirms the cyclical behavior of the O–C vs. JD diagram and suggests a main secular periodicity slightly longer than ~22 yr, possibly due to magnetic activity cycles of the secondary.