Theta Lyrae
Theta Lyrae (θ Lyr) is a star in a trinary star system, in the constellation Lyra, approximately 770 light years away from Earth. Theta Lyrae is an orange bright giant star of the spectral type K0II, which means that it possesses a surface temperature of about 5,000 kelvins, and is many times bigger and brighter, yet cooler, than the Sun.[3]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 16m 22.0951s / 19h 16m 30.069s / 19h 16m 28.7s |
| Declination | +38° 8' 1.431" / +38° 8' 35.80" / +38° 7' 1" |
| Apparent magnitude (V) | 4.347 / 9.5 / 11.0 |
| Characteristics | |
| Spectral type | K0II[1] + K2III + ? |
| U−B color index | +1.23 |
| B−V color index | +1.25 |
| Astrometry | |
| Radial velocity (Rv) | -30.9 km/s |
| Proper motion (μ) | RA: -0.49 mas/yr Dec.: 1.23 / 14.0 mas/yr |
| Parallax (π) | 4.24 ± 0.49 mas |
| Distance | approx. 770 ly (approx. 240 pc) |
| Absolute magnitude (MV) | −2.76+0.27 −0.24[1] |
| Details | |
| θ Lyr | |
| Radius | 57±7[2] R☉ |
| Surface gravity (log g) | 1.93[1] cgs |
| Temperature | 4500[1] K |
| Metallicity [Fe/H] | −0.01[1] dex |
| Rotational velocity (v sin i) | 3.6±1.4[1] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
It is orbited by a subsystem composed of BD+37° 3399 and BD+37° 3399B. 10th magnitude BD+37° 3399 is a giant star with a spectral type of K2III. It is therefore almost the same temperature as Theta Lyrae, but smaller and dimmer.[4] BD+37° 3399B is an 11th magnitude star of an unknown spectral type.[5]
References
- Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892
- Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114
- "* tet Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.
- "BD+37 3399". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.
- "Simbad Query Result". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.
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