BU Crucis

BU Crucis

NGC 4755, with BU Crucis in the centre
Credit: ESO/Y. Beletsky
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension 12h 53m 37.62181s[1]
Declination −60° 21′ 25.3912″[1]
Apparent magnitude (V) 6.80 - 6.90[2]
Characteristics
Spectral type B2 Ia[3]
U−B color index −0.67[4]
B−V color index +0.20[4]
Variable type Eclipsing?[2]
Astrometry
Radial velocity (Rv)−17.00[5] km/s
Proper motion (μ) RA: −2.10[1] mas/yr
Dec.: +1.95[1] mas/yr
Parallax (π)0.62 ± 0.30[6] mas
Distance2,600[3] pc
Absolute magnitude (MV)−7.00[3]
Details
Mass29.2[3] M☉
Radius41.6[3] R☉
Luminosity275,000[3] L☉
Surface gravity (log g)2.65[3] cgs
Temperature20,600[3] K
Rotational velocity (v sin i)75[7] km/s
Age5.6[3] Myr
Other designations
BU Cru, CD−59°4458, HD 111934, HIP 62913, 2MASS J12533761-6021254
Database references
SIMBADdata

BU Crucis (HD 111934) is a variable star in the open cluster NGC 4755, which is also known as the Kappa Crucis Cluster or Jewel Box Cluster.

Location

NGC 4755 to the SE of β Crucis (Credit: ESO, ESA/Hubble and Digitized Sky Survey 2. Acknowledgment: Davide De Martin)

BU Cru is one of the brightest members of the NGC 4775 open cluster, better known as the Jewel Box Cluster.[8] It forms the right end of the bar of the prominent letter "A" asterism at the centre of the cluster. The cluster is part of the larger Centaurus OB1 association and lies about 8,500 light years away.

The cluster, and BU Crucis itself, is just to the south-east of β Crucis, the lefthand star of the famous Southern Cross.

Properties

BU Crucis is a B2 bright supergiant (luminosity class Ia). It is 275,000 times the luminosity of the sun, partly due to its higher temperature over 20,000 K, and partly to being forty times larger than the sun. The κ Crucis cluster has a calculated age of 11.2 million years, and BU Crucis itself around five million years.[3]

Variability

BU Crucis is a variable star with a brightness range of about 0.1 magnitudes. It is listed as a probable eclipsing binary in the General Catalogue of Variable Stars,[2] but the International Variable Star Index classifies it as an α Cygni variable with a visual magnitude range of 6.82 - 7.01.[9]

References

  1. 1 2 3 4 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. 1 2 3 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. 1 2 3 4 5 6 7 8 9 10 Aidelman, Y.; Cidale, L. S.; Zorec, J.; Arias, M. L. (2012). "Open clusters. I. Fundamental parameters of B stars in NGC 3766 and NGC 4755". Astronomy & Astrophysics. 544: A64. Bibcode:2012A&A...544A..64A. doi:10.1051/0004-6361/201219069.
  4. 1 2 Dachs, J.; Kaiser, D. (November 1984), "UBV photometry of the southern galactic cluster NGC 4755 = Kappa Crucis", Astronomy and Astrophysics Supplement Series, 58: 411−429, Bibcode:1984A&AS...58..411D.
  5. ↑ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (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. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776.
  6. ↑ Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G.
  7. ↑ Dufton, P. L.; et al. (2006), "The VLT-FLAMES survey of massive stars: Stellar parameters and rotational velocities in NGC 3293, NGC 4755 and NGC 6611", Astronomy and Astrophysics, 457: 265, arXiv:astro-ph/0606409Freely accessible, Bibcode:2006A&A...457..265D, doi:10.1051/0004-6361:20065392.
  8. ↑ Kharchenko, N. V.; Piskunov, A. E.; Röser, S.; Schilbach, E.; Scholz, R.-D. (2004). "Astrophysical supplements to the ASCC-2.5. II. Membership probabilities in 520 Galactic open cluster sky areas". Astronomische Nachrichten. 325 (9): 740. Bibcode:2004AN....325..740K. doi:10.1002/asna.200410256.
  9. ↑ "BU Crucis". International Variable Star Index. American Association of Variable Star Observers. 4 January 2010. Retrieved 2016-09-30.

External links

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