BO Carinae

{{Short description|Star in the constellation Carina}}

{{Starbox begin

| name = BO Carinae

}}

{{Starbox image

| image=280px

| caption=BO Carinae is the brightest red star, towards upper left, in this image of the Carina Nebula.

| credit=ESO

}}

{{Starbox observe

| epoch=J2000

| ra={{RA|10|46|00.53}}

| dec={{DEC|59|29|19.5}}

| appmag_v=7.18 - 8.50

| constell=Carina

}}

{{Starbox character

| class=M4 Ib

| b-v=

| u-b=

| variable=Lc

}}

{{Starbox astrometry

| radial_v=

| prop_mo_ra={{val|-7.334|0.027}}

| prop_mo_dec={{val|-1.420|0.028}}

| parallax=0.6020

| p_error=0.0259

| parallax_footnote={{cite Gaia EDR3|5350343775447416704}}

| dist_pc=

| dist_ly=

| absmag_v=–5.53{{cite journal |title=The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought |author1-link=Emily Levesque|last1=Levesque|first1=Emily M.|last2=Massey|first2=Philip|last3=Olsen|first3=K. A. G.|first4=Bertrand|last4=Plez|first5=Eric|last5=Josselin|first6=Andre|last6=Maeder|first7=Georges|last7=Meynet |journal=The Astrophysical Journal |volume=628 |issue=2 |date=August 2005 |pages=973–985 |doi=10.1086/430901 |bibcode=2005ApJ...628..973L|arxiv = astro-ph/0504337 |s2cid=15109583}}

}}

{{Starbox detail

| mass=

| radius=790

| luminosity=78,000

| temperature=3,525

| metal=

| rotation=

| gravity=

| age=

}}

{{Starbox catalog

| names=BO Car, IDS 10419-5858, IRAS 10438-5913, 2MASS J10455065-5929193, AAVSO 1042-58, SAO 238447, CD-58 3547, HD 93420

}}

{{ Starbox reference

| Simbad = BO+Carinae

}}

{{Starbox end}}

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 {{val|2,500|ul=parsecs|fmt=commas}} ({{val|8,150|ul=light-years|fmt=commas}}).{{cite journal

|author1=Tapia, Mauricio |author2=Roth, Miguel |author3=Vázquez, Rubén A. |author4=Feinstein, Alejandro

| title = Imaging study of NGC 3372, the Carina nebula - I. UBVRIJHK photometry of Tr 14, Tr 15, Tr 16 and Car I

| date = 2003

| journal = Monthly Notices of the Royal Astronomical Society

| volume = 339

| number = 1

| pages = 44–62

| doi = 10.1046/j.1365-8711.2003.06186.x

| bibcode = 2003MNRAS.339...44T

| doi-access = free

| hdl = 11336/36798

| hdl-access = free

}} The Gaia Data Release 2 parallax of {{val|0.73|0.08|ul=mas}} suggests a closer distance, but the value is considered unreliable due to excess astrometric noise.{{cite DR2|5350343775447416704}}

BO Car is a red supergiant of spectral type M4Ib with an effective temperature of {{val|3,525|ul=K|fmt=commas}}, a radius of {{val|790|ul=solar radii}}. Its bolometric luminosity is {{solar luminosity|78,000}}. Mass-loss is on the order of {{val|0.3|e=−9|ul=solar masses}} per year.{{cite journal

| title = Observational investigation of mass loss of M supergiants

| date = 2000

| journal = Astronomy and Astrophysics

| volume = 357

| number =

| pages = 225–232

| bibcode = 2000A&A...357..225J

| last1 = Josselin

| first1 = E.

| last2 = Blommaert

| first2 = J. A. D. L.

| last3 = Groenewegen

| first3 = M. A. T.

| last4 = Omont

| first4 = A.

| last5 = Li

| first5 = F. L.

}}

File:BOCarLightCurve.png (near infrared) light curve for BO Carinae, plotted from ASAS data]] In 1919, William Matthew Worssell of the Union Observatory announced that the star, then known as CPD-58 2683, is a variable star. It was given its variable star designation, BO Carinae, in 1921. 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.{{cite journal |bibcode=2019MNRAS.487.4832C |title=The period-luminosity relation of red supergiants with Gaia DR2 |last1=Chatys |first1=Filip W. |last2=Bedding |first2=Timothy R. |last3=Murphy |first3=Simon J. |last4=Kiss |first4=László L. |last5=Dobie |first5=Dougal |last6=Grindlay |first6=Jonathan E. |journal=Monthly Notices of the Royal Astronomical Society |year=2019 |volume=487 |issue=4 |page=4832 |doi=10.1093/mnras/stz1584 |doi-access=free |arxiv=1906.03879 |s2cid=182952598 }} Some observers have found BO Car not to be variable,{{Cite journal|last1=Percy|first1=John R.|last2=Sato|first2=Hiromitsu|date=2009-02-01|title=Long Secondary Periods in Pulsating Red Supergiant Stars|journal=Journal of the Royal Astronomical Society of Canada|volume=103|issue=1|pages=11|bibcode=2009JRASC.103...11P|issn=0035-872X}} but more extensive studies find small amplitude variations with a possible period of 145 days.{{cite journal |bibcode=2020JAVSO..48...50P |title=Period Analysis of All-Sky Automated Survey for Supernovae (ASAS-SN) Data on a Sample of "Irregular" Pulsating Red Giants |last1=Percy |first1=J. R. |journal=Journal of the American Association of Variable Star Observers (Jaavso) |year=2020 |volume=48 |issue=1 |page=50 }}

Multiple star catalogues list an 11th-magnitude star as a companion to BO Car. The separation was {{val|14.2|ul="}} in 2015, and slowly increasing.{{cite journal | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | title=The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog | journal=The Astronomical Journal | volume=122 | issue=6 | pages=3466 | year=2001 | last1=Mason | first1=Brian D. | last2=Wycoff | first2=Gary L. | last3=Hartkopf | first3=William I. | last4=Douglass | first4=Geoffrey G. | last5=Worley | first5=Charles E. | doi-access=free }} The companion is a distant blue giant.{{cite DR2|5350343775447422080}}