Institut für Astronomie und Astrophysik

Abteilung Astronomie

Preprint 06/95

RX J1940.1-1025 - A new asynchronous AM Her system

S. Friedrich(1), R. Staubert(1), G. Lamer(1), M. König(1), R. Geckeler(1), M. Bässgen(1), W. Kollatschny(2), R. Östreicher(3), S.D. James(4), and R.K. Sood(4)

(1)Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany
(2)Universitäts-Sternwarte, Geismarlandstr. 11, 37083 Göttingen, Germany
(3)Landessternwarte Königstuhl, D-69117 Heidelberg, Germany
(4)University of New South Wales, ADFA, Canberra, Australia

accepted by Astronomy & Astrophysics

Abstract. We present optical spectroscopy and white light photometry of RX J1940.1-1025 over a period of one year. From the photometry two periods can clearly be distinguished. The shorter one with 12116.3s is also the period of the radial velocities of the narrow emission line components and the period of narrow dips also seen in the X-ray data. This shorter period is interpreted as the orbital period. The longer period of 12151s is also present in the X-ray data and is interpreted as the spin period of the white dwarf. We find a phase modulation of the X-ray lightcurve with the beat period of 49.5days. Our measurement of circular polarization of about 2% confirms the conjecture that RX J1940.1-1025 is an AM Her system.

Key words: cataclysmic variables - stars: individual: RX J1940.1-1025 - stars: megnetic field - X-rays: stars

Paper (83k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de) Last updated 04-Aug-1997