Lambda Coronae Borealis

λ Coronae Borealis
Location of λ Coronae Borealis (circled)
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]
Distance135.5 ± 0.5 ly
(41.6 ± 0.2 pc)
Absolute magnitude (MV)+2.34[6]
Details[7]
Mass1.60±0.02 M☉
Radius2.13+0.13
−0.02[1] R☉
Luminosity9.382±0.046[1] L☉
Surface gravity (log g)4.05±0.02 cgs
Temperature6,991±63 K
Metallicity [Fe/H]0.00±0.05 dex
Rotational velocity (v sin i)75.7±3.8[8] km/s
Age1.42+0.08
−0.20 Gyr
Other designations
λ CrB, 12 Coronae Borealis, FK5 3259, GJ 9531, HD 142908, HIP 78012, HR 5936, WDS J15558+3757A[9]
Database references
SIMBADdata

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]

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]

  1. ^ a b c d e f g h i j Cite error: The named reference dr2 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference gray was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference EgUBV was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference holmberg was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference AguileraGómez_et_al_2018 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference AmmlerVonEiff_Reiners_2012 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Eggleton_Tokovinin_2008 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Cotten_Song_2016 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Mason_et_al_2014 was invoked but never defined (see the help page).