LQ Hydrae

LQ Hydrae

A visual band light curve for LQ Hydrae. The main plot (adapted from Berdyugina et al.[1]) shows the long-term variation, and the inset plot (adapted from Kiraga[2]) shows the periodic variation.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 09h 32m 25.568s[3]
Declination −11° 11′ 04.69″[3]
Apparent magnitude (V) 7.82[4] (7.79 to 7.86)[5]
Characteristics
Evolutionary stage Main sequence
Spectral type K1Vp[6]
B−V color index 0.933±0.021[4]
Variable type BY Dra[5]
Astrometry
Radial velocity (Rv)7.58±0.27[7] km/s
Proper motion (μ) RA: −248.040 mas/yr[3]
Dec.: 34.277 mas/yr[3]
Parallax (π)54.7362 ± 0.0244 mas[3]
Distance59.59 ± 0.03 ly
(18.269 ± 0.008 pc)
Absolute magnitude (MV)6.47[6]
Details
Mass0.81[8] M☉
Radius1.0[9] R☉
Luminosity0.282±0.001[3] L☉
Surface gravity (log g)4.57[8] cgs
Temperature4,812±39[8] K
Metallicity [Fe/H]0.32[8] dex
Rotation1.601[9] d
Rotational velocity (v sin i)25±2[10] km/s
AgeUnder 75[11] Myr
Other designations
LQ Hya, BD−10 2857, GC 13168, GJ 355, HD 82558, HIP 46816, SAO 155272, LTT 3510[12]
Database references
SIMBADdata

LQ Hydrae is a single[13] variable star in the equatorial constellation of Hydra. It is sometimes identified as Gl 355 from the Gliese Catalogue; LQ Hydrae is the variable star designation, which is abbreviated LQ Hya.[14] The brightness of the star ranges from an apparent visual magnitude of 7.79 down to 7.86,[5] which is too faint to be readily visible to the naked eye. Based on parallax measurements, this star is located at a distance of 59.6 light years from the Sun. It is drifting further away with a radial velocity of 7.6 km/s.[7]

During a 1981 survey of southern stars, W. P. Bidelman found the H and K lines of ionized calcium for LQ Hya were filled in with emission. (W. D. Heintz independently made the same observation.) In 1986, F. C. Fekel and associates determined this is a young, rapidly rotating BY Draconis-type variable.[13][15] A decade of photometry was used to determine a rotation period of 1.601136±0.000013 days (1 day, 14 hours, and 24 minutes) The star 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 undergoing differential rotation.[10]

The high lithium abundance and rapid rotation of this star indicate it is a zero age main sequence star, or possibly even a pre-main sequence star.[14] A strong flare event was observed on December 22, 1993, with an estimated energy release of ~5.7×1033 erg.[11] Additional flares were detected thereafter, with ROSAT X-ray data from 1992 showing a strong flare during that time period.[14] Observations from December 2000 and 2001 showed that the magnetic field of the star is dramatically changing its topology on a time frame of a year or less.[16]

The stellar classification of LQ Hya is K1Vp,[6] indicating it is a K-type main-sequence star with some peculiar features in the spectrum. In some respects it is considered an analog 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 of 8.8×1029 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 the solar cycle in the Sun.

  1. ^ a b Cite error: The named reference Berdyugina_et_al_2002 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Kiraga was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Houk_Swift_1999 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Halbwachs_et_al_2018 was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Luck2018 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Strassmeier2009 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Jetsu1993 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Montes_et_al_1999 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Fekel_et_al_1986b was invoked but never defined (see the help page).
  14. ^ a b c d e Cite error: The named reference Covino_et_al_2001 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Fekel_et_al_1986a was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference McIfor_et_al_2004 was invoked but never defined (see the help page).