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)[1] and Reinsch and Beuermann (1990).[2] | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 12h 52m 24.22s[3] |
| Declination | −29° 14′ 56.0″[3] |
| Apparent magnitude (V) | 9.6 to 14.0[4] |
| Characteristics | |
| Spectral type | white dwarf + M4/M5: |
| Variable type | eclipsing intermediate polar[5] |
| Astrometry | |
| Radial velocity (Rv) | −21[6] km/s |
| Proper motion (μ) | RA: −119.473[3] mas/yr Dec.: +30.330[3] mas/yr |
| Parallax (π) | 17.5716±0.0166 mas[3] |
| Distance | 185.6 ± 0.2 ly (56.91 ± 0.05 pc) |
| Orbit[7] | |
| Period (P) | 6,894.4 s |
| Semi-major axis (a) | 0.68 R☉ |
| Inclination (i) | 78.0±0.2° |
| Semi-amplitude (K1) (primary) | 58.9±1.8 km/s |
| Semi-amplitude (K2) (secondary) | 432.4±4.8 km/s |
| Details | |
| White dwarf | |
| Mass | 0.788±0.025[7] M☉ |
| Radius | 0.011[7] R☉ |
| Rotation | 67 minutes |
| Red dwarf | |
| Mass | 0.1074±0.0047[7] M☉ |
| Radius | 0.1513[7] R☉ |
| Other designations | |
| 1RXS J125224.7-291451, 2E 2876, RX J1252.4-2914, AAVSO 1247-28[8] | |
| Database references | |
| SIMBAD | data |
EX Hydrae is an eclipsing intermediate polar (DQ Herculis) -type cataclysmic variable star that also undergoes eclipses. The system varies in apparent magnitude from 9.6 to 14.0.[9] 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.[10] The orbital period is 98.25696 minutes (0.068233846 days).[11] The system is 65±11 parsecs distant, making EX Hya one of the closest cataclysmic variable stars.[12] The cataclysmic outbursts appear to be caused by accretion of material from the M-star to the white dwarf.[11]
EX Hydrae also possess a 67-minute oscillation, believed to be caused by the spin period of the white dwarf component.[11] EX Hydrae's outbursts are unpredictable.
References
[edit]- ^ 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.
- ^ 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.
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
- ^ Beuermann, K.; Reinsch, K. (2024). "High-resolution spectroscopy of the intermediate polar EX Hydrae. II. The inner disk radius". Astronomy and Astrophysics. 686: A304. arXiv:2402.13834. Bibcode:2024A&A...686A.304B. doi:10.1051/0004-6361/202244473.
- ^ Duflot, M.; Figon, P.; Meyssonnier, N. (1995). "Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue". Astronomy and Astrophysics Supplement Series. 114: 269. Bibcode:1995A&AS..114..269D.
- ^ a b c d e Beuermann, K.; Reinsch, K. (2024). "Current and secular accretion rates of EX Hydrae". Astronomy and Astrophysics. 687: A273. arXiv:2412.13850. Bibcode:2024A&A...687A.273B. doi:10.1051/0004-6361/202450486.
- ^ "V* EX Hya". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ locator chart at AAVSO
- ^ 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.
- ^ a b c "AAVSO". Archived from the original on 2010-06-15. Retrieved 2009-04-24.
- ^ 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
[edit]- AAVSO Variable Star of the Month. EX Hydrae: April 2009 Archived 2010-06-15 at the Wayback Machine
