Lambda Cassiopeiae

Lambda Cassiopeiae, Latinized from λ Cassiopeiae, is a binary star system, in the northern constellation of Cassiopeia. The system has a combined apparent magnitude of +4.74, making it faintly visible to the naked eye. With an annual parallax shift of 8.64 mass,[1] it is approximately 380 light years from Earth. The system is moving closer to the Sun with a radial velocity of −12 km/s.[6]

λ Cassiopeiae

Map of the Bayer-designated stars in Cassiopeia. Lambda Cassiopeiae is circled.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 00h 31m 46.35935s[1]
Declination +54° 31′ 20.2257″[1]
Apparent magnitude (V) 4.772[2]
(5.33 / 5.62)[3]
Characteristics
Spectral type B8 Vnn[4]
U−B color index −0.35[5]
B−V color index −0.10[5]
Astrometry
Radial velocity (Rv)−12.20±1.3[6] km/s
Proper motion (μ) RA: +41.20±0.29[1] mas/yr
Dec.: −16.54±0.35[1] mas/yr
Parallax (π)8.64 ± 0.43 mas[1]
Distance380 ± 20 ly
(116 ± 6 pc)
Absolute magnitude (MV)−0.57[4]
Orbit[3]
Period (P)245.70±35.96 yr
Semi-major axis (a)0.448±0.028″
Eccentricity (e)0.689±0.119
Inclination (i)53.6±5.2°
Longitude of the node (Ω)17.6±9.6°
Periastron epoch (T)2025.54±4.56
Argument of periastron (ω)
(secondary)		301.0±2.6°
Details
λ Cas A
Mass2.9+0.45
−0.40[7] M☉
Radius3.50[8] R☉
Luminosity255[4] L☉
Surface gravity (log g)4.0±0.25[7] cgs
Temperature12,000±1,000[7] K
Rotational velocity (v sin i)253[9] km/s
Age58+104
−48[7] Myr
Other designations
λ Cas, 14 Cassiopeiae, BD+53°82, HD 2772, HIP 2505, HR 123, SAO 21489, ADS 434, CCDM J00318+5431
Database references
SIMBADλ Cas
λ Cas A
λ Cas B
λ Cassiopeiae in optical light

Both components are blue-white B-type main-sequence stars. The brighter member, component A, has an apparent magnitude of +5.5, while its companion, component B, has an apparent magnitude of +5.8. The two stars are separated by 0.6 arcseconds and complete one orbit around their common centre of mass about once every 250 years.[3] The primary displays an infrared excess, possibly due to a debris disk or other orbiting material.[8]

References
  1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.Vizier catalog entry
  2. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 16 May 2017.
  4. 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.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  7. Gullikson, Kevin; et al. (August 2016). "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars". The Astronomical Journal. 152 (2): 13. arXiv:1604.06456. Bibcode:2016AJ....152...40G. doi:10.3847/0004-6256/152/2/40. S2CID 119179065. 40.
  8. 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
  9. Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
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