Astronomy:LQ Hydrae

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Short description: Star in the constellation Hydra
LQ Hydrae
LQHyaLightCurve.png
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
Equinox J2000.0]] (ICRS)
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[3] mas/yr
Dec.: 34.277[3] mas/yr
Parallax (π)54.7362 ± 0.0244[3] mas
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.

References

  1. ↑ 1.0 1.1 Berdyugina, 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, doi:10.1051/0004-6361:20021179, Bibcode: 2002A&A...394..505B. 
  2. ↑ Kiraga, M. (March 2012). "ASAS Photometry of ROSAT Sources. I. Periodic Variable Stars Coincident with Bright Sources from the ROSAT All Sky Survey". Acta Astronomica 62 (1): 67–95. Bibcode: 2012AcA....62...67K. http://acta.astrouw.edu.pl/Vol62/n1/pdf/pap_62_1_4.pdf. Retrieved 23 June 2022. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  5. ↑ 5.0 5.1 5.2 Samus', N. N et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1 61 (1): 80, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  6. ↑ 6.0 6.1 6.2 Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey 5, Bibcode: 1999MSS...C05....0H. 
  7. ↑ 7.0 7.1 Halbwachs, J. -L. et al. (2018), "Multiplicity among solar-type stars. IV. The CORAVEL radial velocities and the spectroscopic orbits of nearby K dwarfs", Astronomy and Astrophysics 619: A81, doi:10.1051/0004-6361/201833377, Bibcode: 2018A&A...619A..81H. 
  8. ↑ 8.0 8.1 8.2 8.3 Luck, R. Earle (March 2018), "Abundances in the Local Region. III. Southern F, G, and K Dwarfs", The Astronomical Journal 155 (3): 31, doi:10.3847/1538-3881/aaa9b5, 111, Bibcode: 2018AJ....155..111L. 
  9. ↑ 9.0 9.1 Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review 17 (3): 251–308, doi:10.1007/s00159-009-0020-6, Bibcode: 2009A&ARv..17..251S. 
  10. ↑ 10.0 10.1 Jetsu, L. (September 1993), "A decade of photometry of LQ Hydrae", Astronomy and Astrophysics 276: 345–352, Bibcode: 1993A&A...276..345J. 
  11. ↑ 11.0 11.1 Montes, D. et al. (May 1999), "Optical and ultraviolet observations of a strong flare in the young, single K2 dwarf LQ Hya", Monthly Notices of the Royal Astronomical Society 305 (1): 45–60, doi:10.1046/j.1365-8711.1999.02373.x, Bibcode: 1999MNRAS.305...45M. 
  12. ↑ "LQ Hya". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LQ+Hya. 
  13. ↑ 13.0 13.1 Fekel, F. C. et al. (November 1986), "Chromospherically active stars. II. HD 82558, a young single BY Draconis variable", Astronomical Journal 92: 1150–1154, doi:10.1086/114246, Bibcode: 1986AJ.....92.1150F. 
  14. ↑ 14.0 14.1 14.2 14.3 14.4 Covino, S. et al. (June 2001), "Quiescent and flare analysis for the chromospherically active star Gl 355 (LQ Hya)", Astronomy and Astrophysics 371 (3): 973–985, doi:10.1051/0004-6361:20010454, Bibcode: 2001A&A...371..973C. 
  15. ↑ Fekel, F. C. et al. (February 1986), "A Survey of Chromospherically Active Stars", Astrophysical Journal Supplement 60: 551, doi:10.1086/191097, Bibcode: 1986ApJS...60..551F. 
  16. ↑ McIvor, T. et al. (December 2004), "The changing corona of LQ Hya", Monthly Notices of the Royal Astronomical Society 355 (4): 1066–1072, doi:10.1111/j.1365-2966.2004.08391.x, Bibcode: 2004MNRAS.355.1066M. 

Further reading

  • Cole-Kodikara, Elizabeth M. et al. (September 2019), "Spot evolution on LQ Hya from 2006-2017: temperature maps based on SOFIN and FIES data", Astronomy & Astrophysics 629: 9, doi:10.1051/0004-6361/201935729, A120, Bibcode: 2019A&A...629A.120C. 
  • Cole, E. M. et al. (September 2015), "Doppler imaging of LQ Hydrae for 1998-2002", Astronomy & Astrophysics 581: 9, doi:10.1051/0004-6361/201425440, A69, Bibcode: 2015A&A...581A..69C. 
  • Zhang, Liyun et al. (October 2014), "Chromospheric activity on late-type star LQ Hya", New Astronomy 32: 1–5, doi:10.1016/j.newast.2014.02.010, Bibcode: 2014NewA...32....1Z. 
  • Cao, Dong-tao et al. (February 2014), "Chromospheric Activity and Rotational Modulation on the Young, Single K2 Dwarf LQ Hya", The Astronomical Journal 147 (2): 10, doi:10.1088/0004-6256/147/2/38, 38, Bibcode: 2014AJ....147...38C. 
  • 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 (Publications of the Astronomy Department of the Eötvös University (PADEU)) 14: pp. 221–232, Bibcode: 2004PADEU..14..221K. 
  • Livshits, M. A.; Alekseev, I. Yu.; Katsova, M. M. (July 2003), "Butterfly Diagram for Starspots on LQ Hya", Astronomy Reports 47 (7): 562–572, doi:10.1134/1.1592835, Bibcode: 2003ARep...47..562L. 
  • Alekseev, I. Yu.; Kozlova, O. V. (January 2003), "Spots and Active Regions on Emission Stars. III. LQ Hya", Astrophysics (English Translation of Astrofizika) 46 (1): 28–45, doi:10.1023/A:1022959419060, Bibcode: 2003Ap.....46...28A. 
  • Donati, J. -F. (January 1999), "Magnetic cycles of HR 1099 and LQ Hydrae", Monthly Notices of the Royal Astronomical Society 302 (3): 457–481, doi:10.1046/j.1365-8711.1999.02096.x, Bibcode: 1999MNRAS.302..457D. 
  • 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 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 26: pp. 255–258, Bibcode: 1992ASPC...26..255S. 



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