A white dwarf with a low magnetic field in the IP RXJ0028.8+5917/V709Cas

Abstract

We report the first detailed spectroscopic observations of the recently identified intermediate polar RXJ0028.8+5917/V709 Cas. We discovered that the system shows significant EW ~ (2-4)A broad absorptions, affecting the Balmer lines from Hdelta to Hbeta. These broad absorptions are interpreted as the contribution of an underlying DA logg=8 white dwarf at a temperature of ~ 23 000 K, contributing ~ 17 % (at 4500 A) to the overall flux. This is the first direct detection of a white dwarf in an intermediate polar system. The absence of significant Zeeman splitting indicates a magnetic field lower than 10 MG, confirming that, at least in some cases, intermediate polars have weaker fields than polars.

paper presented at the conference "The Physics of Cataclysmic Variables and Related Objects", 5-10 August, 2001, Gottingen, Germany, 2 pages, no figure. to be published in ASP Conferences Series, eds B.T. Gansicke, K. Beuermann, K. Reinsch