Lambda Crucis

λ Crucis, Latinized as Lambda Crucis, is a single,[10] variable star in the southern constellation Crux, near the constellation border with Centaurus. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.62.[2] The star is located approximately 384 light-years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s.[5] It is a proper motion member of the Lower Centaurus–Crux sub-group in the Scorpius–Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.[6]

A light curve for Lambda Crucis, plotted from Hipparcos data[11]
λ Crucis
Location of λ Crucis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension 12h 54m 39.18258s[1]
Declination −59° 08′ 48.1229″[1]
Apparent magnitude (V) 4.62[2]
Characteristics
Evolutionary stage main sequence
Spectral type B4 Vne[3]
U−B color index −0.60[4]
B−V color index −0.15[4]
Variable type β Cep?[2]
Astrometry
Radial velocity (Rv)+12.0±4.2[5] km/s
Proper motion (μ) RA: −32.92[1] mas/yr
Dec.: −14.60[1] mas/yr
Parallax (π)8.50 ± 0.21 mas[1]
Distance384 ± 9 ly
(118 ± 3 pc)
Absolute magnitude (MV)−1.2[6]
Details
Mass5.0±0.1[7] M☉
Radius3.00[8] R☉
Luminosity790[6] L☉
Surface gravity (log g)3.01[8] cgs
Temperature16,500[8] K
Rotational velocity (v sin i)290[8] km/s
Age53.3±8.1[7] Myr
Other designations
λ Cru, Lambda Cru, CD−58°4794, HD 112078, HIP 63007, HR 4897, SAO 240368[9]
Database references
SIMBADdata

λ Crucis is listed in the General Catalogue of Variable Stars as a possible β Cephei-type variable. Its brightness varies with an amplitude of 0m.02 over a period of 0.3951 days.[2] However, it is currently thought more likely to be a different type of variable,[12] possibly a λ Eridani variable or rotating ellipsoidal variable.[13][14]

This object is a B-type main-sequence star with a stellar classification of B4 Vne,[3] where the suffix notation indicates "nebulous" (broad) lines due to rapid rotation, along with emission lines from circumstellar material, making it a Be star.[13] It is around 53[7] million years old and is spinning rapidly with a projected rotational velocity of 341 km/s.[15] The star has five[7] times the mass of the Sun and about 3.0[8] times the Sun's radius. It is radiating 790[6] times the luminosity of the Sun from its photosphere at an effective temperature of 16,500 K.[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.
  2. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869. Retrieved 2019-09-16.
  3. Levenhagen, R. S.; Leister, N. V. (2006). "Spectroscopic analysis of southern B and Be stars". Monthly Notices of the Royal Astronomical Society. 371 (1): 252–262. arXiv:astro-ph/0606149. Bibcode:2006MNRAS.371..252L. doi:10.1111/j.1365-2966.2006.10655.x. S2CID 16492030.
  4. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  5. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  6. de Geus, E. J.; et al. (June 1989). "Physical parameters of stars in the Scorpio-Centaurus OB association". Astronomy and Astrophysics. 216 (1–2): 44–61. Bibcode:1989A&A...216...44D.
  7. Tetzlaff, N.; et al. (January 2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
  8. Arcos, C.; Kanaan, S.; Chávez, J.; Vanzi, L.; Araya, I.; Curé, M. (2018). "Stellar parameters and H α line profile variability of be stars in the BeSOS survey". Monthly Notices of the Royal Astronomical Society. 474 (4): 5287–5299. arXiv:1711.08675. Bibcode:2018MNRAS.474.5287A. doi:10.1093/mnras/stx3075.
  9. "lam Cru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-16.
  10. Rizzuto, A. C.; et al. (December 2013). "Long-baseline interferometric multiplicity survey of the Sco-Cen OB association". Monthly Notices of the Royal Astronomical Society. 436 (2): 1694–1707. arXiv:1309.3811. Bibcode:2013MNRAS.436.1694R. doi:10.1093/mnras/stt1690.
  11. "Light Curve". Hipparcos ESA. ESA. Retrieved 18 August 2022.
  12. Stankov, Anamarija; Handler, Gerald (2005). "Catalog of Galactic β Cephei Stars". The Astrophysical Journal Supplement Series. 158 (2): 193–216. arXiv:astro-ph/0506495. Bibcode:2005ApJS..158..193S. doi:10.1086/429408. S2CID 119526948.
  13. Balona, L. A. (1995). "Tests of the pulsation and starspot models for the periodic be stars". Monthly Notices of the Royal Astronomical Society. 277 (4): 1547–1554. Bibcode:1995MNRAS.277.1547B. doi:10.1093/mnras/277.4.1547.
  14. Morris, S. L. (1985). "The ellipsoidal variable stars". The Astrophysical Journal. 295: 143. Bibcode:1985ApJ...295..143M. doi:10.1086/163359.
  15. Uesugi, Akira; Fukuda, Ichiro (1970). "Catalogue of rotational velocities of the stars". Contributions from the Institute of Astrophysics and Kwasan Observatory. University of Kyoto. Bibcode:1970crvs.book.....U.
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