Theta Lyrae

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Theta Lyrae
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
Theta Lyrae, 21 Lyrae, HR 7314, BD+37°3398, HD 180809, SAO 68065, HIP 94713, GC 26585, IDS 19129+3757, GSC 03121-02287, BD +37°3399, BD +37°3399B[3][4][5]

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, meaning it possesses a surface temperature of about 5,000 kelvins, and is many times bigger and brighter, yet cooler, than our Sun.[3]

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[edit]

  1. ^ a b c d e f 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 
  2. ^ 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 
  3. ^ a b "Simbad Query Result". Simbad. Retrieved October 15, 2007. 
  4. ^ a b "Simbad Query Result". Simbad. Retrieved October 15, 2007. 
  5. ^ a b "Simbad Query Result". Simbad. Retrieved October 15, 2007.