EX Hydrae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 12h 52m 24.20s |
| Declination | -29° 14′ 56.0″ |
| Apparent magnitude (V) | 9.6 to 14 (variable) |
| Characteristics | |
| Spectral type | white dwarf + M4/M5: |
| Variable type | DQ Herculis |
| Details | |
| Mass | 0.55 ± 0.15[1] M☉ |
| Rotation | 67 minutes |
| Mass | 0.085 ± 0.015[1] M☉ |
| Astrometry | |
| Radial velocity (Rv) | −54[2] km/s |
EX Hydrae is a variable star classified as an eclipsing intermediate polar-type cataclysmic variable, specifically of the DQ Herculis type.[2] The system varies in apparent magnitude from 9.6 to 14.[3] 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.[1] The orbital period is 98.25696 minutes (0.068233846 days).[4] The system is 65±11 parsecs distant, making EX Hya one of the closest cataclysmic variable stars.[5] The cataclysmic outbursts appear to be caused by accretion of material from the M-star to the white dwarf.[4]
EX Hydrae also possess a 67-minute oscillation, believed to be caused by the spin period of the white dwarf component.[4] EX Hydrae's outbursts are unpredictable.
References
- 1 2 3 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
- 1 2 SIMBAD
- ↑ locator chart at AAVSO
- 1 2 3 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