Periodic and secular variations in the lightcurve of dwarf nova EX Hydrae

Details Periodic and secular variations in the lightcurve of dwarf nova EX Hydrae Periodic and secular variations in the lightcurve of dwarf nova EX Hydrae

May 1980

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980a%26a....85..106v&link_type=abstract

Astronomy and Astrophysics, vol. 85, no. 1-2, May 1980, p. 106-112. Research supported by the Fonds de la Recherche Fondamental

Astronomy and Astrophysics

Astrophysics

47

Astronomical Photometry, Dwarf Stars, Light Curve, Novae, X Ray Sources, Binary Stars, Electrophotometry, Mass Transfer, Periodic Variations

Scientific paper

Extensive photoelectric observations of EX Hya were obtained between 1962 and 1976 at different telescopes and observatories. Evaluation of the data reveals a decrease of the orbital period at the rate of 5.2 x 10 to the -12th. This period change is likely caused by mass transfer with angular momentum exchange between orbital motion and disc rotation on a time scale which is considerably shorter than the corresponding Kelvin-Helmholtz time scale. Gravitational radiation losses are negligible in the evolution of EX Hya. Furthermore, the detection of a periodic modulation of the light curve with a period of 0.046546447 days and mean amplitudes between 0.2 and 0.4 magnitudes ('67-minute-cycle') is reported. This oscillation remained coherent over the 14 yr covered by observations. Either (1) asynchronous rotation or pulsations of the red component, (2) asynchronous rotation of the magnetic primary, or (3) resonances in the outer regions of the accretion disc are mentioned as possible sources for this periodicity.

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