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]

References

  1. ^ a b c d e f g h i j Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. ^ a b Gray, R. O.; et al. (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence". The Astronomical Journal. 121 (4): 2159. Bibcode:2001AJ....121.2159G. doi:10.1086/319957.
  4. ^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. ^ a b Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  6. ^ Holmberg, J.; et al. (2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics. 501 (3): 941. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511.
  7. ^ a b c d Aguilera-Gómez, Claudia; et al. (June 2018). "Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert". Astronomy & Astrophysics. 614: 15. arXiv:1803.05922. Bibcode:2018A&A...614A..55A. doi:10.1051/0004-6361/201732209. S2CID 62799777. A55.
  8. ^ a b Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  9. ^ "lam CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-31.
  10. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  11. ^ Cotten, Tara H.; Song, Inseok (July 2016). "A Comprehensive Census of Nearby Infrared Excess Stars". The Astrophysical Journal Supplement Series. 225 (1): 24. arXiv:1606.01134. Bibcode:2016ApJS..225...15C. doi:10.3847/0067-0049/225/1/15. S2CID 118438871. 15.
  12. ^ Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
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