 θ Boötis in optical light | |
Location of θ Boötis (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 14 25 11.79695 |
| Declination | +51° 51′ 02.6772″ |
| Apparent magnitude (V) | 4.05 + 13.23 |
| Characteristics | |
| Spectral type | F7 V + M2.5V |
| U−B color index | −0.02 |
| B−V color index | +0.50 |
| Astrometry | |
| Radial velocity (Rv) | −10.627±0.0065 km/s |
| Proper motion (μ) | RA: −235.97 mas/yr Dec.: −399.696 mas/yr |
| Parallax (π) | 69.0686 ± 0.1579 mas |
| Distance | 47.2 ± 0.1 ly (14.48 ± 0.03 pc) |
| Absolute magnitude (MV) | 3.25 |
| Details | |
| A | |
| Mass | 1.41 1.24 M☉ |
| Radius | 1.4±0.15 R☉ |
| Luminosity | 4.131±0.096 L☉ |
| Surface gravity (log g) | 4.07 cgs |
| Temperature | 6,294±40 K |
| Metallicity | 0.03 dex |
| Rotational velocity (v sin i) | 29.2 km/s |
| Age | 3.1 Gyr 3.83 Gyr |
| B | |
| Mass | 0.4–0.48 M☉ |
| Radius | 0.4013±0.012 R☉ |
| Other designations | |
| Asellus Primus, θ Boo, 23 Boötis, NSV 6669, BD+52° 1804, FK5 531, GJ 549, HD 126660, HIP 70497, HR 5404, SAO 29137, WDS J14252+5151A, LTT 14245 | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Theta Boötis, Latinized from θ Boötis, is a star in the northern constellation of Boötes the herdsman, forming a corner of the upraised left hand of this asterism. It has the traditional name Asellus Primus (/əˈsɛləs ˈpraɪməs/; Latin for "first donkey colt") and the Flamsteed designation 23 Boötis. Faintly visible to the naked eye, this star has a yellow-white hue with an apparent visual magnitude of 4.05. It is located at a distance of 47.2 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −10.6 km/s.
Properties
The stellar classification of Theta Boötis is F7 V, matching an F-type main-sequence star. It is a solar-type star that may be near the end of its main sequence lifetime based on a high luminosity for a star of its type. Theta Boötis is a suspected variable star and a source of X-ray emission. There is evidence for low amplitude radial velocity variation of about 5 km/s. The star has a 24/41% greater mass and a 40% larger radius than the Sun. It is about 3–4 billion years old and is spinning with a projected rotational velocity of 29 km/s. The star is radiating 4.1 times the luminosity of the Sun from its photosphere at an effective temperature of 6,294 K.
There is a nearby 11th magnitude optical companion star about 70 arcseconds away. This is a class M2.5 red dwarf that is separated by a minimum of 1,000 AUs. It is uncertain whether they are gravitationally bound, but they do have a common motion through space and so the two stars probably share a common origin.
Nomenclature
θ Boötis, along with the other Aselli (ι Boo and κ Boo) and λ Boo, were Aulād al Dhiʼbah (أولاد الضّباع - awlād al-ḍibā‘), "the Whelps of the Hyenas".
In Chinese, 天枪 (Tiān Qiāng), meaning Celestial Spear, refers to an asterism consisting of θ Boötis, κ Boötis and ι Boötis. Consequently, the Chinese name for θ Boötis itself is 天枪三 (Tiān Qiāng sān, English: the Third Star of Celestial Spear.)
References
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{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101, S2CID 18993744.. See Table 10.
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