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EX Hydrae

A light curve for EX Hydrae. The top two panels show the variation when the star is in its quiescent state. Red arrows mark the times of maximum eclipse. The bottom panel shows the brightness change caused by a flare. Adapted from Warner and McGraw (1981) and Reinsch and Beuermann (1990).
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
Astrometry
Radial velocity (Rv)	−54 km/s
Details
Mass	0.55 ± 0.15 M☉
Rotation	67 minutes
Mass	0.085 ± 0.015 M☉
Other designations
1RXS J125224.7-291451, 2E 2876, RX J1252.4-2914, AAVSO 1247-28
Database references
SIMBAD	data

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.

References

1. Warner, B.; McGraw, J. T. (August 1981). "EX Hyd : modulated mass transfer of intermediate polar?". Monthly Notices of the Royal Astronomical Society. 196: 59P – 63P. Bibcode:1981MNRAS.196P..59W. doi:10.1093/mnras/196.1.59P.
2. Reinsch, K.; Beuermann, K. (December 1990). "Photometric observations of the intermediate polar EX Hydrae in outburst". Astronomy and Astrophysics. 240: 360–364. Bibcode:1990A&A...240..360R.
3. ^ "V* EX Hya". SIMBAD. Centre de données astronomiques de Strasbourg.
4. ^ Beuermann, K.; Harrison, Th. E.; McArthur, B. E.; Benedict, G. F.; Gänsicke, B. T. (2003). "A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate". Astronomy & Astrophysics. 412 (3): 821–827. arXiv:astro-ph/0309530. Bibcode:2003A&A...412..821B. doi:10.1051/0004-6361:20031498. S2CID 3167825.
5. locator chart at AAVSO
6. ^ "AAVSO". Archived from the original on 2010-06-15. Retrieved 2009-04-24.
7. Eisenbart, S.; Beuermann, K.; Reinsch, K.; Gänsicke, B. T. (2002). "Multi-wavelength spectrophotometry of EX Hydrae". Astronomy & Astrophysics. 382 (3): 984–998. arXiv:astro-ph/0111459. Bibcode:2002A&A...382..984E. doi:10.1051/0004-6361:20011655. S2CID 12934377.

External links

• AAVSO Variable Star of the Month. EX Hydrae: April 2009 Archived 2010-06-15 at the Wayback Machine

• Objects with variable star designations
• Hydra (constellation)
• White dwarfs
• Intermediate polars