EX Hydrae

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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)
Spectral type white dwarf + M4/M5:
Variable type DQ Herculis
Radial velocity (Rv)−54[1] km/s
Mass0.55 ± 0.15[2] M
Rotation67 minutes
Mass0.085 ± 0.015[2] M
Other designations
1RXS J125224.7-291451, 2E 2876, RX J1252.4-2914, AAVSO 1247-28
Database references

EX Hydrae is a variable star classified as an eclipsing intermediate polar-type cataclysmic variable, specifically of the DQ Herculis type.[1] 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.[2] 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.


  1. ^ a b "V* EX Hya". SIMBAD. Centre de données astronomiques de Strasbourg.
  2. ^ a b c 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
  3. ^ locator chart at AAVSO
  4. ^ a b c AAVSO
  5. ^ Eisenbart, S., Beuermann, K., Reinsch, K., & Gansicke, B.T., 2002, "Multi-wavelength Spectrophotometry of EX Hydrae," A&A 382, 984, abstract available online here

External links[edit]