Epoch J2000 Equinox J2000
|Right ascension||12h 52m 24.20s|
|Declination||-29° 14′ 56.0″|
|Apparent magnitude (V)||9.6 to 14 (variable)|
|Spectral type||white dwarf + M4/M5:|
|Variable type||DQ Herculis|
|Mass||0.55 ± 0.15 M☉|
|Mass||0.085 ± 0.015 M☉|
|Radial velocity (Rv)||−54 km/s|
EX Hydrae is a variable star classified as an eclipsing intermediate polar-type cataclysmic variable, specifically of the DQ Herculis type. The system varies in apparent magnitude from 9.6 to 14. The system consists of a white dwarf primary and an M-type secondary, of masses of 0.4–0.7 M☉ and 0.07–0.10 M☉ respectively. The orbital period is 98.25696 minutes (0.068233846 days). The system is 65±11 parsecs distant, making EX Hya one of the closest cataclysmic variable stars. The cataclysmic outbursts appear to be caused by accretion of material from the M-star to the white dwarf.
EX Hydrae also possess a 67-minute oscillation, believed to be caused by the spin period of the white dwarf component. EX Hydrae's outbursts are unpredictable.
- Beuermann, K., Harrison, T.E., MacArthur, B.E., Benedict, G.F., & Gansicke, B.T., 2003, "A Precise HST Parallax of the Cataclysmic Variable EX Hydrae, its System Parameters, and Accretion Rate," A&A 412, 821, abstract available online here
- locator chart at AAVSO
- Eisenbart, S., Beuermann, K., Reinsch, K., & Gansicke, B.T., 2002, "Multi-wavelength Spectrophotometry of EX Hydrae," A&A 382, 984, abstract available online here