Astronomy:GQ Leonis

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Short description: Star in the constellation Leo
GQ Leonis
Location of GQ Leonis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Leo
Right ascension  11h 47m 45.72617s
Declination +12° 54′ 03.3509″
Apparent magnitude (V) 10.8[2]
Characteristics
Spectral type K5Ve[3]
B−V color index 1.020[4]
J−H color index 0.608[5]
J−K color index 0.782[5]
Variable type BY Dra?[6]
Astrometry
Radial velocity (Rv)−12.121±0.0020[7] km/s
Proper motion (μ) RA: −73.229[1] mas/yr
Dec.: 7.648[1] mas/yr
Parallax (π)16.3363 ± 0.1721[1] mas
Distance200 ± 2 ly
(61.2 ± 0.6 pc)
Orbit[8]
PrimaryMET 57Aa
CompanionMET 57Ab
Period (P)~45 yr
Semi-major axis (a)0.25″
Details[9]
Radius~0.8[10] R☉
Surface gravity (log g)4.345±0.096 cgs
Temperature4364±113 K
Metallicity [Fe/H]−0.171±0.036 dex
Rotation4.45±0.20 d[11]
Rotational velocity (v sin i)7.2±1.6[12] km/s
Age126[3] or 12±4[12] Myr
Other designations
GQ Leo, BPM 87617, TYC 870-798-1, GSC 00870-00798, 2MASS J11474574+1254033[13]
Database references
SIMBADdata

GQ Leonis (GSC 00870-00798) is a variable star located in the zodiac constellation of Leo, close to the second-magnitude star Denebola. With an apparent magnitude of 10.8, it is too faint to be seen by the naked eye but observable using a telescope with an aperture of 35 mm (1.4 in) or larger. It is situated at a distance of 200 light-years (61 parsecs) according to Gaia EDR3 parallax measurements, and is advancing towards the Solar System at a heliocentric radial velocity of −12.121 km/s.

Physical properties

This is a K-type main-sequence star with the spectral type K5Ve, where the "e" suffix denotes the presence of emission lines. It is considered to be a field star, not part of any star cluster.[3] It is expected to have a radius of about 0.8 R☉, and shines at an effective temperature of 4,364 K (7,396 °F), giving it an orange hue. It is poorer in heavy elements than the Sun with a metallicity of −0.171, meaning it has 10−0.171 ≈ 67% the Sun's iron content. Age estimates vary between publications, but the consensus is that it is young and very active, as evidenced by strong emission in the calcium H and K lines and the Balmer series.[14] The star is also a source of X-rays and extreme ultraviolet (EUV) radiation.[11]

Variability

File:GQLeoLightCurve.png
Light curves for GQ Leonis. The upper panel shows the short term variability as seen by TESS,[15] and the lower panel shows the brightness over a much longer time interval as seen by ASASSN.[16]

In 2001, the star was reported to show low-amplitude photometric variations with a period of 4.45 days. It was suspected that the star was a BY Draconis variable due to the period paired with the X-ray and EUV emissions.[11] This was confirmed in 2004 in a paper which also newly classified HD 77191 and V573 Puppis as BY Dra variables.[14] The star received its variable-star designation GQ Leonis in 2003.[17]

Stellar companions

Slow fluctuations are known to occur in the star's radial velocity. In a 2019 study, a 572-day (1.57 a) period was mentioned to fit the observed variations, but other periods remain possible. This object is also a visual binary, designated MET 57Aa/Ab in the Washington Double Star Catalog, with a separation of 0.25 arcseconds and a period of roughly 45 years. Additionally, an optical component (MET 57B) exists 9.5 arcseconds away.[8]

References

  1. ↑ 1.0 1.1 1.2 1.3 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.
  2. ↑ Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (2013-01-14). "The Fourth Us Naval Observatory CCD Astrograph Catalog (Ucac4)". The Astronomical Journal 145 (2): 44. doi:10.1088/0004-6256/145/2/44. ISSN 0004-6256. Bibcode: 2013AJ....145...44Z. 
  3. ↑ 3.0 3.1 3.2 Launhardt, Ralf; Loinard, Laurent; Dzib, Sergio A.; Forbrich, Jan; Bower, Geoffrey C.; Henning, Thomas K.; Mioduszewski, Amy J.; Reffert, Sabine (2022-05-01). "Nonthermal Radio Continuum Emission from Young Nearby Stars". The Astrophysical Journal 931 (1): 43. doi:10.3847/1538-4357/ac5b09. ISSN 0004-637X. Bibcode: 2022ApJ...931...43L. 
  4. ↑ Patel, Manoj K.; Pandey, Jeewan C.; Karmakar, Subhajeet; Srivastava, D. C.; Savanov, Igor S. (2016-04-11). "Broad-band linear polarization in late-type active dwarfs". Monthly Notices of the Royal Astronomical Society 457 (3): 3178–3190. doi:10.1093/mnras/stw195. ISSN 0035-8711. https://academic.oup.com/mnras/article-pdf/457/3/3178/8002202/stw195.pdf. Retrieved 2025-02-08. 
  5. ↑ 5.0 5.1 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E. et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues 2246: II/246. Bibcode: 2003yCat.2246....0C. 
  6. ↑ 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. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  7. ↑ Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  8. ↑ 8.0 8.1 Sperauskas, J.; Deveikis, V.; Tokovinin, A. (2019). "Spectroscopic orbits of nearby stars". Astronomy & Astrophysics 626: A31. doi:10.1051/0004-6361/201935346. ISSN 0004-6361. Bibcode: 2019A&A...626A..31S. https://www.aanda.org/articles/aa/pdf/2019/06/aa35346-19.pdf. Retrieved 2025-02-08. 
  9. ↑ Zhang, Li-yun; Su, Tianhao; Misra, Prabhakar; Han, Xianming L.; Meng, Gang; Pi, Qingfeng; Yang, Jiawei (2023-01-01). "Stellar Parameters and Spectroscopic Properties of TESS Objects Observed in the LAMOST Low- and Medium-resolution Spectral Survey". The Astrophysical Journal Supplement Series 264 (1): 17. doi:10.3847/1538-4365/ac9b28. ISSN 0067-0049. Bibcode: 2023ApJS..264...17Z.  Record for this source at VizieR.
  10. ↑ Griffin, R. F. (October 2005). "The BY Dra Star HD 77191 Is a Spectroscopic Binary, but GQ Leo May Not Be". The Observatory 125: 323–325. Bibcode: 2005Obs...125..323G. 
  11. ↑ 11.0 11.1 11.2 Robb, R. M.; Wagg, J.; Berndsen, A. (24 May 2001). "The Discovery of Brightness Variations of GSC 0870-0798". Information Bulletin on Variable Stars (Konkoly Observatory, Budapest: International Astronomical Union) 5088 (1). Bibcode: 2001IBVS.5088....1R. 
  12. ↑ 12.0 12.1 Weise, P.; Launhardt, R.; Setiawan, J.; Henning, T. (2010). "Rotational velocities of nearby young stars". Astronomy and Astrophysics 517: A88. doi:10.1051/0004-6361/201014453. ISSN 0004-6361. Bibcode: 2010A&A...517A..88W. https://www.aanda.org/articles/aa/pdf/2010/09/aa14453-10.pdf. Retrieved 2025-02-11. 
  13. ↑ "GQ Leo". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=GQ+Leo. 
  14. ↑ 14.0 14.1 Dall, T. H. (9 December 2004). "Spectroscopic Confirmation of Three Suspected BY Dra Variables". Information Bulletin on Variable Stars (Konkoly Observatory, Budapest: International Astronomical Union) 5581 (1). Bibcode: 2004IBVS.5581....1D. 
  15. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  16. ↑ "ASAS-SN Variable Stars Database". ASAS-SN. https://asas-sn.osu.edu/variables/lookup. 
  17. ↑ Kazarovets, E. V.; Kireeva, N. N.; Samus, N. N.; Durlevich, O. V. (27 May 2003). "The 77th Name-List of Variable Stars". Information Bulletin on Variable Stars 5422: 1–56. Bibcode: 2003IBVS.5422....1K. 



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