GQ Leonis
Star in the constellation Leo
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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.
 | |
| Observation data Epoch J2000.0[1] Equinox 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 mas[1] |
| Distance | 200 ± 2 ly (61.2 ± 0.6 pc) |
| Orbit[8] | |
| Primary | MET 57Aa |
| Name | MET 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 |
| Temperature | 4364±113 K |
| Metallicity [Fe/H] | −0.171±0.036 dex |
| Rotation | 4.45±0.20 d[11] |
| Rotational velocity (v sin i) | 7.2±1.6[12] km/s |
| Age | 126[3] or 12±4[12] Myr |
| Other designations | |
| GQ Leo, BPM 87617, TIC 14722732, TYC 870-798-1, GSC 00870-00798, 2MASS J11474574+1254033, Gaia DR3 3922763029242716032[13] | |
| Database references | |
| SIMBAD | data |
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
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]