The old nova HR Del M. Friedjung 1 , M. Dennefeld 1 , I. Voloshina 2

1. The old nova HR Del M. Friedjung 1, M. Dennefeld 1, I. Voloshina 2 1 Institut d’Astrophysique de Paris, UMR 7095, CNRS Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France 2 Sternberg Astronomical Institute, Moscow State university, Universitetskij prospect 13, 119992 Moscow, Russia Abstract.HR Del was studied both by photometry and by obtaining high resolution profiles in H alpha. The photometric variations can be understood as due to varying visibility of the irradiated mass loser, while the H alpha profile shows a non-classical S wave. Introduction Nova HR Del (1967) is a classical nova with unusual properties. During its outburst it brightened to a visual magnitude near 5, where it remained for about five months, before its brightness passed through a brief maximum at magnitude 3.5, followed by slow irregular fading. After the return to its pre outburst magnitude, it was exceptionally bright in the visual but especially in the UV compared with other old novae (Selvelli & Friedjung, 2003). More recently photo-ionisation modelling of the emission by the ejected nebula in 2002 led Moraes and Diaz (2009) to conclude that the ionising source had then still an exceptional luminosity of 10 36 ergs s -1, emitted by a disk source. Like other classical novae, HR Del is understood as being a cataclysmic binary with a mass gaining white dwarf and a not very luminous mass losing cool star. It appears that the white dwarf component of the binary has a rather low mass for one of a classical nova of 0.55-0.75 Msun (Selvelli and Friedjung, 2003), so through like classical novae in general it is expected to have large numbers of repeated large outbursts, with each outburst being the precursor of another one, it seems according to present ideas unlikely to become massive enough, to explode as a SN Ia. However such a white dwarf could still have low level nuclear burning long after its outburst according to Sion and Starrfield (1994). It was in such a framework interesting to make new observations of HR Del. . Observations and… Both photoelectric and CCD photometry was mainly performed at the Crimean Station of Sternberg Astronomical Institute The CCD V magnitudes containing time series of closely spaced observations can be used to look for orbital variations and the period. Night to night variations as well as periodic variations having a period of 0d.214164 were found, the period being very close to the spectroscopic one of 0d.214165 of Kurster and Barwig (1988). We concentrate here on the photometry in V, which when folded on the mean light curve with the photomet- ric period, is shown in Fig.1 … Results A sine wave fit gives a semi-amplitude in V of 0.043 +/- 0.002. High resolution profiles of Halpha were obtained using the AURELIE spectrograph on the 1.52 m telescope of the Haute Provence Observatory with a resolution of 0.30 A. These profils have a clear narrow central component, an example being shown in Fig.2.When profiles are averaged over 0.1 of the orbital period in different time spans, a clear S wave is found, which has the same phase dependence, an example being shown in Fig.3 Fig 1. Light curve of HR Del versus photometric phase in the V band from observations obtained during the 2005-2009. The average orbital sine wave is superposed on the data Discussion and conclusion The periodic variations in V are most easily understood as due to varying visibility of mass loser irradiated by the luminous ionising source. Then photometric minimum should occur at inferior conjunction of the mass loser. The central part of the H alpha profile can be understood as being produced by the outer parts of an accretion disk, while the wings come from other regions, including a non-negligible contribution due to the expanding nebula.We can compare the photometric phases with the spectroscopic S wave. The Kurster and Barwig phases are not the true ones; the error in the period makes the true phases at the time of our observations uncertain. However if our explanation of the photometric variations is correct, the S wave would appear to be due to an Hα bright spot on the side of the accretion disk around the mass gaining dwarf, opposite the mass loser. Such a bright spot is not classical in cataclysmic binaries. Fig.3. Series of averaged H alpha profiles during 2008, averaged in 10 bins of 0.1 in phase. The phases go from 0-0.1 in the bottom bin to 0.9-1.0 in the top bin. References 1. Kurster, M., Barwig, H. 1988, A&A, 199, 201 2. Moraes, M., Diaz, M., 2009, AJ , 138, 1541 3. Selvelli, P.L., Friedjung, M., 2003, A&A, 401, 297 4. Sion, E.M., Starrfield, S. G., 1994, ApJ, 421, 261 Fig 2. Example of a high dispersion spectrum of the H alpha region obtained on November 1st 2003 at Haute Provence Observatory. The core and the low intensity wings of H alpha are easily distinguishable XXVI IAP Annual Colloquium “Progenitors and environments ofstellar explosions”,June 28-July 2, 2010, Paris, France