Lambda Coronae Borealis, its name Latinised from λ Coronae Borealis, is a single[10] star in the northern constellation of Corona Borealis. In publications it is also identified as HR 5936 and HD 142908. It has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.43.[2] The star is located at a distance of 136 light years based on parallax,[1] but is drifting closer with a radial velocity of −12 km/s.[5]
Observation data Epoch J2000 Equinox | |
---|---|
Constellation | Corona Borealis |
Right ascension | 15h 55m 47.58774s[1] |
Declination | +37° 56′ 49.0397″[1] |
Apparent magnitude (V) | 5.43[2] |
Characteristics | |
Spectral type | F2 IV-V[3] |
U−B color index | +0.01[4] |
B−V color index | +0.352±0.004[2] |
Astrometry | |
Radial velocity (Rv) | −11.6±0.8[5] km/s |
Proper motion (μ) | RA: 29.099[1] mas/yr Dec.: 79.528[1] mas/yr |
Parallax (π) | 24.0631 ± 0.0890 mas[1] |
Distance | 135.5 ± 0.5 ly (41.6 ± 0.2 pc) |
Absolute magnitude (MV) | +2.34[6] |
Details[7] | |
Mass | 1.60±0.02 M☉ |
Radius | 2.13+0.13 −0.02[1] R☉ |
Luminosity | 9.382±0.046[1] L☉ |
Surface gravity (log g) | 4.05±0.02 cgs |
Temperature | 6,991±63 K |
Metallicity [Fe/H] | 0.00±0.05 dex |
Rotational velocity (v sin i) | 75.7±3.8[8] km/s |
Age | 1.42+0.08 −0.20 Gyr |
Other designations | |
Database references | |
SIMBAD | data |
The stellar classification of Lambda Coronae Borealis is F2 IV-V,[3] which means it is somewhat hotter than the sun and shows spectral features intermediate between a main sequence and subgiant star. It has an estimated age of 1.4 billion years with a relatively high projected rotational velocity of 76 km/s.[8] The star has 1.6[7] times the mass of the Sun and 2.1[1] times the Sun's radius. Based on the amount of iron in the atmosphere, the elemental abundances are similar to those in the Sun.[7] It is radiating 9.4[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,991 K.[7]
The star displays an infrared excess with a signature that indicates a pair of circumstellar disks of dusty debris are orbiting the star. A blackbody fit to the higher temperature signal gives a temperature of 320 K with an orbital distance of 2.20 AU. The cooler outer disk is orbiting 144.07 AU from the star with a temperature of 40 K.[11]
A magnitude 11.44 visual companion was discovered by W. Herschel in 1782. As of 2015, it was located at an angular separation of 90.6″ from the brighter component, along a position angle of 68°.[12]