A progress report on the study of the optical variability of the old nova HR Del

Abstract

The cataclysmic variable and old nova HR Del has been studied using ground-based photometry and spectroscopy over a period of more than 6 years. Some long term variations have been found, but no clear correlation established up to now between photometric, and spectroscopic changes. HR Del (or Nova Del 1967) was a bright classical nova with however unusual properties. It brightened in July 1967 to a magnitude near 5 m .5 from pre-outburst magnitude of about 12 m . After remaining 5 months near this magnitude, it brightened to a maximum mv ∼ 3.5, followed by an extremely slow irregular decline. The unusual nature of this nova might be due to the presence of a wind which was optically thin in the continuum before maximum, and whose velocity decreased during that stage, unlike that of the optically thick winds normally seen after maximum of classical novae (Friedjung 1992). The mass of the white dwarf component is low -(0.55 ÷ 0.75)M -, while the orbital period is 0 d .214165 (Kürster & Barwig 1988). HR Del was unusually bright both before and long after its outburst (Selvelli & Friedjung 2003). Two kinds of photometric observations were made:• To construct the overall light curve, daily estimates of HR Del's magnitude were made with the UBV photometer on the 60-cm telescope of the Sternberg Astronomical Institute in Crimea (time resolution 10 s). They covered the years 2001 -2006, with more than 1000 measurements in 3 bands.• To study the short-term variability of HR Del, observations with an Ap47 CCD detector on the same telescope were obtained in 2005 -2006, covering 23 nights, and containing more than 3500 measurements, with a time resolution of 30 s in the V band.• High-resolution spectroscopic observations of the region of the Hα line were obtained with the 152-cm telescope of the Haute Provence Observatory.