Lambda Coronae Borealis
Yellow-white hued star in the constellation Corona Borealis
From Wikipedia, the free encyclopedia
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. The star is located at a distance of 137 light years based on parallax, but is drifting closer with a radial velocity of â12 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 55m 47.58728s[1] |
| Declination | +37° 56â² 49.0449â³[1] |
| Apparent magnitude (V) | 5.43[2] |
| Characteristics | |
| Evolutionary stage | main sequence[1] |
| Spectral type | F2 IV-V[3] |
| UâB color index | +0.01[4] |
| BâV color index | +0.352±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | â11.6±0.8[5] km/s |
| Proper motion (μ) | RA: +29.460[1] mas/yr Dec.: +79.199[1] mas/yr |
| Parallax (Ï) | 23.7741±0.0530 mas[1] |
| Distance | 137.2 ± 0.3 ly (42.06 ± 0.09 pc) |
| Absolute magnitude (MV) | +2.34[6] |
| Details | |
| Mass | 1.60±0.02[7] Mâ |
| Radius | 2.23±0.04[1] Râ |
| Luminosity | 9.53±0.04[1] Lâ |
| Surface gravity (log g) | 4.05±0.02[7] cgs |
| Temperature | 6,991±63[7] K |
| Metallicity [Fe/H] | 0.00±0.05[7] dex |
| Rotational velocity (v sin i) | 75.7±3.8[8] km/s |
| Age | 1.42+0.08 â0.20[7] Gyr |
| Other designations | |
| λ CrB, 12 Coronae Borealis, FK5 3259, GJ 9531, HD 142908, HIP 78012, HR 5936, WDS J15558+3757A[9] | |
| Database references | |
| SIMBAD | data |
The stellar classification of Lambda Coronae Borealis is F2 IV-V, 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. The star has 1.6 times the mass of the Sun and 2.2 times the Sun's radius. Based on the amount of iron in the atmosphere, the elemental abundances are similar to those in the Sun. It is radiating 9.5 times the luminosity of the Sun from its photosphere at an effective temperature of 6,991 K.
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 90.6Ⳡfrom the brighter component, along a position angle of 68°.[12]