BO Carinae

BO Carinae

BO Carinae is the brightest red star, towards upper left, in this image of the Carina Nebula. Credit: ESO
Observation data Epoch J2000      Equinox J2000
Constellation	Carina
Right ascension	10^h 46^m 00.53^s
Declination	59° 29′ 19.5″
Apparent magnitude (V)	7.18 - 8.50[1]
Characteristics
Spectral type	M4 Ib[1]
Variable type	Lc[1]
Astrometry
Proper motion (μ)	RA: −7.334±0.027[2] mas/yr Dec.: −1.420±0.028[2] mas/yr
Parallax (π)	0.6020 ± 0.0259 mas[2]
Distance	5,400 ± 200 ly (1,660 ± 70 pc)
Absolute magnitude (MV)	–5.53[3]
Details
Radius	790[3] R☉
Luminosity	78,000[3] L☉
Temperature	3,525[3] K
Other designations
BO Car, IDS 10419-5858, IRAS 10438-5913, 2MASS J10455065-5929193, AAVSO 1042-58, SAO 238447, CD-58 3547, HD 93420
Database references
SIMBAD	data

BO Carinae, also known as HD 93420, is an irregular variable star in the constellation Carina.

BO Car has a maximum apparent magnitude of +7.18. Its distance and membership is uncertain, but its possible membership to the star cluster Trumpler 15 allows a distance estimate of approximately 2,500 parsecs (8,150 light-years).[4][5] The Gaia Data Release 2 parallax of 0.73±0.08 mas suggests a closer distance, but the value is considered unreliable due to excess astrometric noise.[6]

BO Car is a red supergiant of spectral type M4Ib with an effective temperature of 3,525 K, a radius of 790 solar radii. Its bolometric luminosity is 78,000 L_☉.[3] Mass-loss is on the order of 0.3×10^−9 solar masses per year.[5]

An I band (near infrared) light curve for BO Carinae, plotted from ASAS data[7]

In 1919, William Matthew Worssell of the Union Observatory announced that the star, then known as CPD-58 2683, is a variable star.[8] It was given its variable star designation, BO Carinae, in 1921.[9] Billed as an irregular variable like TZ Cassiopeiae or V528 Carinae; its apparent brightness fluctuates between magnitude +7.18 and +8.50 without clear periodicity.[1][10] Some observers have found BO Car not to be variable,[11] but more extensive studies find small amplitude variations with a possible period of 145 days.[12]

Multiple star catalogues list an 11th-magnitude star as a companion to BO Car. The separation was 14.2″ in 2015, and slowly increasing.[13] The companion is a distant blue giant.[14]

See also

• RT Carinae
• V528 Carinae
• EV Carinae
• List of largest known stars

References

1. 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.
2. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
3. Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (August 2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. S2CID 15109583.
4. Tapia, Mauricio; Roth, Miguel; Vázquez, Rubén A.; Feinstein, Alejandro (2003). "Imaging study of NGC 3372, the Carina nebula - I. UBVRIJHK photometry of Tr 14, Tr 15, Tr 16 and Car I". Monthly Notices of the Royal Astronomical Society. 339 (1): 44–62. Bibcode:2003MNRAS.339...44T. doi:10.1046/j.1365-8711.2003.06186.x. hdl:11336/36798.
5. Josselin, E.; Blommaert, J. A. D. L.; Groenewegen, M. A. T.; Omont, A.; Li, F. L. (2000). "Observational investigation of mass loss of M supergiants". Astronomy and Astrophysics. 357: 225–232. Bibcode:2000A&A...357..225J.
6. 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.
7. "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
8. Worssell, M. W. (1919). "Variable Stars". Circular of the Union Observatory Johannesburg. 46: 17. Retrieved 7 January 2025.
9. Hartwig; Müller (January 1921). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten. 212 (19): 353–374. doi:10.1002/asna.19202121902. Retrieved 7 January 2025.
10. Chatys, Filip W.; Bedding, Timothy R.; Murphy, Simon J.; Kiss, László L.; Dobie, Dougal; Grindlay, Jonathan E. (2019). "The period-luminosity relation of red supergiants with Gaia DR2". Monthly Notices of the Royal Astronomical Society. 487 (4): 4832. arXiv:1906.03879. Bibcode:2019MNRAS.487.4832C. doi:10.1093/mnras/stz1584. S2CID 182952598.
11. Percy, John R.; Sato, Hiromitsu (2009-02-01). "Long Secondary Periods in Pulsating Red Supergiant Stars". Journal of the Royal Astronomical Society of Canada. 103 (1): 11. Bibcode:2009JRASC.103...11P. ISSN 0035-872X.
12. Percy, J. R. (2020). "Period Analysis of All-Sky Automated Survey for Supernovae (ASAS-SN) Data on a Sample of "Irregular" Pulsating Red Giants". Journal of the American Association of Variable Star Observers (Jaavso). 48 (1): 50. Bibcode:2020JAVSO..48...50P.
13. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
14. 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.