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]
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][8] Some observers have found BO Car not to be variable,[9] but more extensive studies find small amplitude variations with a possible period of 145 days.[10]
Multiple star catalogues list an 11th-magnitude star as a companion to BO Car. The separation was 14.2″ in 2015, and slowly increasing.[11] The companion is a distant blue giant.[12]
^ abcdSamus, 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.
^ abJosselin, 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.
^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. S2CID182952598.
^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. ISSN0035-872X.
^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.