Avisual bandlight curve for LQ Hydrae. The main plot (adapted from Berdyuginaet al.[1]) shows the long-term variation, and the inset plot (adapted from Kiraga[2]) shows the periodic variation.
During a 1981 survey of southern stars,W. P. Bidelman found theH and K lines of ionized calcium for LQ Hya were filled in withemission. (W. D. Heintz independently made the same observation.) In 1986,F. C. Fekel and associates determined this is a young, rapidly rotatingBY Draconis-type variable.[13][15] A decade of photometry was used to determine arotation period of 1.601136±0.000013 days (1 day, 14 hours, and 24 minutes) Thestar spots on the surface showed significant evolution over time scales of a few months. Variations in rotational modulation of surface activity suggested the star is undergoingdifferential rotation.[10]
The highlithium abundance and rapid rotation of this star indicate it is azero age main sequence star, or possibly even apre-main sequence star.[14] A strongflare event was observed on December 22, 1993, with an estimated energy release of~5.7×1033 erg.[11] Additional flares were detected thereafter, withROSATX-ray data from 1992 showing a strong flare during that time period.[14] Observations from December 2000 and 2001 showed that themagnetic field of the star is dramatically changing its topology on a time frame of a year or less.[16]
Thestellar classification of LQ Hya is K1Vp,[6] indicating it is aK-type main-sequence star with some peculiar features in the spectrum. In some respects it is considered ananalog of a young Sun around the age of 60 million years.[1] It shows strong emission of ultraviolet and has been detected in the X-ray band, showing an X-ray emission of8.8×1029 erg/s and indicating high chromospheric activity levels.[14] The star shows dual magnetic activity cycles with period of 6.8 and 11.4 years,[14] which are somewhat comparable to thesolar cycle in the Sun.
^abBerdyugina, S. V.; et al. (November 2002), "Magnetic activity in the young solar analog LQ Hydrae. I. Active longitudes and cycles",Astronomy and Astrophysics,394 (2):505–515,Bibcode:2002A&A...394..505B,doi:10.1051/0004-6361:20021179.
^abcHouk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars",Michigan Spectral Survey,5,Bibcode:1999MSS...C05....0H.
^abFekel, F. C.; et al. (November 1986), "Chromospherically active stars. II. HD 82558, a young single BY Draconis variable",Astronomical Journal,92:1150–1154,Bibcode:1986AJ.....92.1150F,doi:10.1086/114246.
Kõvári, Zs.; Weber, M. (June 2004), Forgács-Dajka, E.; Petrovay, K.; Erdélyi, R. (eds.), "Differential rotation of LQ Hya and IL Hya from Doppler imaging",Proceedings of the British-Hungarian N+N Workshop for Young Researchers On Computer processing and use of satellite data in astronomy and astrophysics and 3rd Workshop of Young Researchers in Astronomy & Astrophysics; Hungary, 3-7 February 2004, vol. 14, Publications of the Astronomy Department of the Eötvös University (PADEU), pp. 221–232,Bibcode:2004PADEU..14..221K.
Saar, S. H.; et al. (1994), Caillault, J.-P. (ed.), "Multiple Epoch Magnetic Surface Images of LQ Hya",The Eighth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Astronomical Society of the Pacific Conference Series, vol. 64, pp. 661–663,Bibcode:1994ASPC...64..661S.
Strassmeier, K. G.; et al. (February 1993), "Surface features of the lower atmosphere of HD 82558 (=LQ Hydrae)",Astronomy and Astrophysics,268:671–684,Bibcode:1993A&A...268..671S.
Saar, S. H.; et al. (1992), Giampapa, M. S.; Bookbinder, J. A. (eds.), "Magnetic Surface Images of the BY DRA Star HD 82558",The Seventh Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Astronomical Society of the Pacific Conference Series, vol. 26, pp. 255–258,Bibcode:1992ASPC...26..255S.
