BU Crucis
{{Short description|Star in the constellation Crux}}
{{Starbox begin
| name=BU Crucis
}}
{{Starbox image
| image = 260px
| caption = The star cluster NGC 4755. BU Crucis is the bright blue star just above and to the right of the centre.
| credit = ESO/Y. Beletsky
}}
{{Starbox observe
| epoch=J2000
| constell=Crux
}}
{{Starbox character
| variable=Eclipsing?
}}
{{Starbox astrometry
| parallax=0.4441
| p_error=0.0330
| dist_ly=
| dist_pc=
}}
{{Starbox detail
| source=
| metal_fe=
}}
{{Starbox catalog
| names= BU Cru, CD−59°4458, HD 111934, HIP 62913, 2MASS J12533761-6021254
}}
{{Starbox reference
|Simbad = BU+Crucis
}}
{{Starbox end}}
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
File:Trishanku Shir (Beta Crucis).png 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. 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.
Variability
File:BUCruLightCurve.png for BU Crucis, adapted from Lefèvre et al. (2009)]]
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, but the International Variable Star Index classifies it as an α Cygni variable with a visual magnitude range of 6.82 - 7.01.
References
{{reflist|refs=
{{cite web |url =https://www.aavso.org/vsx/index.php?view=detail.top&oid=10866 |title = BU Crucis |publisher = American Association of Variable Star Observers |work = International Variable Star Index |accessdate = 2016-09-30 |date = 4 January 2010}}
| first=F. | last=van Leeuwen
| title=Validation of the new Hipparcos reduction
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664
| date=November 2007 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357
| arxiv=0708.1752
| s2cid=18759600
| postscript=.
}}
| display-authors=1
| last1=Dufton | first1=P. L.
| last2=Smartt | first2=S. J.
| last3=Lee | first3=J. K.
| last4=Ryans | first4=R. S. I.
| last5=Hunter | first5=I.
| last6=Evans | first6=C. J.
| last7=Herrero | first7=A.
| last8=Trundle | first8=C.
| last9=Lennon | first9=D. J.
| last10=Irwin | first10=M. J.
| last11=Kaufer | first11=A.
| title=The VLT-FLAMES survey of massive stars: Stellar parameters and rotational velocities in NGC 3293, NGC 4755 and NGC 6611
| journal=Astronomy and Astrophysics
| volume=457 | pages=265–280 | year=2006
| issue=1 | doi=10.1051/0004-6361:20065392
| bibcode=2006A&A...457..265D
| arxiv=astro-ph/0606409
| s2cid=15874925 | postscript=.
}}
| last1=Dachs | first1=J.
| last2=Kaiser | first2=D.
| title=UBV photometry of the southern galactic cluster NGC 4755 = Kappa Crucis
| journal=Astronomy and Astrophysics Supplement Series
| volume=58 | date=November 1984 | pages=411–429
| bibcode=1984A&AS...58..411D
| postscript=.
}}
| last1=Lefèvre |first1=L.
| last2=Marchenko | first2=S. V.
| last3=Moffat | first3=A. F. J.
| last4=Acker | first4=A.
| title=A systematic study of variability among OB-stars based on HIPPARCOS photometry
| journal=Astronomy & Astrophysics
| date=November 2009
| volume=507
| issue=2
| pages=1141–1201
| doi=10.1051/0004-6361/200912304
|bibcode=2009A&A...507.1141L
| doi-access=free
| url=https://hal.science/hal-03742152/file/aa12304-09.pdf
}}
| bibcode= 2004AN....325..740K
| title= Astrophysical supplements to the ASCC-2.5. II. Membership probabilities in 520 Galactic open cluster sky areas
| journal= Astronomische Nachrichten
| volume= 325
| issue= 9
| pages= 740–748
| last1= Kharchenko
| first1= N. V.
| last2= Piskunov
| first2= A. E.
| last3= Röser
| first3= S.
| last4= Schilbach
| first4= E.
| last5= Scholz
| first5= R.-D.
| year= 2004
| doi= 10.1002/asna.200410256
}}
{{cite DR2|6056407605465867392}}
}}
External links
- {{APOD |date=17 August 2010 |title=NGC 4755: A Jewel Box of Stars}}
{{Stars of Crux}}
{{DEFAULTSORT:BU Crucis}}