HR Carinae
{{Short description|Star in the constellation Carina}}
{{Starbox begin
| name = HR Car
}}
{{Starbox image
| image = 250px
| caption = HR Carinae and its nebula in Hydrogen-Alpha with MUSE
}}
{{Starbox observe
| epoch = J2000.0
| constell = Carina
| ra = {{nowrap|{{RA|10|22|53.84074}}{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}}}
| dec = {{DEC|−59|37|28.3774}}
| appmag_v = 8.42 ({{nowrap|6.95–8.80}})
}}
{{Starbox character
}}
{{Starbox astrometry
| radial_v =
| parallax = 0.1708
| p_error = 0.0326
| parallax_footnote = {{cite DR2|5255045082580350080}}
| absmag_v = −9.4{{cite journal|title=HR Carinae – A luminous blue variable surrounded by an arc-shaped nebula|journal=Astronomy and Astrophysics|date=1991|volume=281|pages=141–149|last1=Hutsemekers|first1=D|last2=van Drom|first2=E.|bibcode=1991A&A...248..141H}}
}}
{{Starbox orbit
| period_unitless = 4557.5 ± 21.0 days
| axis = 3.324 ± 0.026
| axis_unitless = 18 AU
| eccentricity = 0.4 ± 0.2
| inclination = 119.2 ± 0.7
}}
{{Starbox detail
| component1=HR CarLBV
| age =
| metal_fe =
| mass = 25{{cite journal|doi=10.1088/0004-637X/705/1/L25|title=Bona Fide, Strong-Variable Galactic Luminous Blue Variable Stars Are Fast Rotators: Detection of a High Rotational Velocity in Hr Carinae|journal=The Astrophysical Journal|volume=705|pages=L25–L30|year=2009|last1=Groh|first1=J. H.|last2=Damineli|first2=A.|last3=Hillier|first3=D. J.|last4=Barbá|first4=R.|last5=Fernández-Lajús|first5=E.|last6=Gamen|first6=R. C.|last7=Moisés|first7=A. P.|last8=Solivella|first8=G.|last9=Teodoro|first9=M.|issue=1|bibcode=2009ApJ...705L..25G|arxiv = 0909.4459 |s2cid=16609230}}–40{{cite journal
| last1= Machado |first1= M. A. D.|last2=de Araújo|first2=F. X.|last3=Pereira|first3=C. B.|last4=Fernandes|first4=M. B.
| title = HR Carinae: New spectroscopic data and physical parameters
| year = 2002
| journal = Astronomy and Astrophysics
| volume = 387
| pages = 151–161| number =
| id = pp. 151–161
| bibcode = 2002A&A...387..151M
| doi = 10.1051/0004-6361:20020295|doi-access = free}}
| radius = {{val|220|60}} {{nowrap|(100–350)}}
| luminosity = {{nowrap|416,000–790,000}}
| gravity =
| component2=HR CarRSG
| luminosity2=
| metal_fe2=
| gravity2=
| rotational_velocity2=
| rotation2=
| age_gyr2=
}}
{{Starbox catalog
| names = HR Car, HD 90177, HIP 50843, SAO 238005, CD-59 3044, GC 14276, MWC 202, AAVSO 1019-59
}}
{{Starbox reference
| Simbad = HR+Car
}}
{{Starbox end}}
HR Carinae is a luminous blue variable star located in the constellation Carina. It is surrounded by a vast nebula of ejected nuclear-processed material because this star has a multiple shell expanding atmosphere. This star is among the most luminous stars in the Milky Way. It has very broad emission wings on the Balmer lines, reminiscent from the broad lines observed in the spectra of O and Wolf–Rayet stars. A distance of 5 kpc and a bolometric magnitude of −9.4 put HR Car among the most luminous stars of the galaxy.
Discovery
HR Carinae was first noticed at the start of the 20th century because of its Hβ emission. It was placed in Secchi class I, corresponding to modern A and F-type stars.{{cite journal|last1=Pickering|first1=E. C.|last2=Fleming|first2=W. P.|title=Objects having peculiar spectra|journal=The Astrophysical Journal|volume=14|year=1901|pages=144|issn=0004-637X|doi=10.1086/140844|bibcode=1901ApJ....14..144P|url=https://zenodo.org/record/2421319}} It was catalogued in 1933 as a Be star{{cite journal|last1=Merrill|first1=Paul W.|last2=Burwell|first2=Cora G.|title=Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines|journal=The Astrophysical Journal|volume=78|year=1933|pages=87|issn=0004-637X|doi=10.1086/143490|bibcode=1933ApJ....78...87M|doi-access=free}} and was discovered to be variable in 1940.{{cite journal|bibcode=1940BHarO.913....4H|title=A New Variable Star with Be Spectrum|journal=Harvard College Observatory Bulletin|volume=913|pages=4|last1=Hoffleit|first1=Dorrit|year=1940}} A more detailed spectroscopic study gave it the type B2eq with emission line of hydrogen, helium, and ionised iron and P Cygni profiles on some lines.{{cite journal|last1=Henize|first1=Karl G.|title=Six Peculiar Hα-EMISSION Stars|journal=The Astrophysical Journal|volume=115|year=1952|pages=133|issn=0004-637X|doi=10.1086/145522|bibcode=1952ApJ...115..133H|doi-access=free}}
By 1970, HR Carinae and the similar variable AG Carinae were recognised as being related to the P Cygni variables, unstable hot supergiants.{{cite journal|last1=Bond|first1=Howard E.|last2=Landolt|first2=Arlo U.|title=Photometric and Spectroscopic Observations of AG and HR Carinae|journal=Publications of the Astronomical Society of the Pacific|volume=82|year=1970|issue=485|pages=313|doi=10.1086/128910|bibcode=1970PASP...82..313B|s2cid=120611422 }}{{cite journal|last1=Viotti|first1=R.|title=Note on the Spectrum and Luminosity of AG and HR Carinae|journal=Publications of the Astronomical Society of the Pacific|volume=83|year=1971|issue=492|pages=170|doi=10.1086/129095|bibcode=1971PASP...83..170V|doi-access=free}} The group was formally recognised as S Doradus variables to avoid confusion with the P Cygni spectral features shared with other types of star.{{cite conference |bibcode=1975IAUS...67..275S|title=Variable Stars and Stellar Evolution|conference= Proceedings of the International Astronomical Union Symposium No.67 held in Moscow, USSR July 29 to August 4, 1974 |editor1= Vicki E. Sherwood |editor2= Lukas Plaut |pages=275–284|last1=Sharov|first1=A. S.|chapter=S Dor-Type Variables in Other Galaxies |year=1975|doi=10.1017/S007418090001038X |isbn=978-90-277-0579-2}} HR Carinae became one of the best-studied examples of the class, clearly showing the brightness and spectral variations that came to characterise the stars known as luminous blue variables.{{cite journal|bibcode=1989A&A...208..135V|title=The maximum amplitude of the optical micro-variations of massive O-F type stars (or Alpha Cygni variables, including LBV's or S DOR variables) across the HR diagram|journal=Astronomy and Astrophysics|volume=208|pages=135|last1=Van Genderen|first1=A. M.|year=1989}}{{cite journal|last1=Stothers|first1=Richard B.|last2=Chin|first2=Chao-Wen|title=Luminous blue variables at quiescence: The zone of avoidance in the Hertzsprung-Russell diagram|journal=The Astrophysical Journal|volume=426|year=1994|pages=L43|issn=0004-637X|doi=10.1086/187335|bibcode=1994ApJ...426L..43S}}
Brightness variation
File:HRCarLightCurve.png (near infrared) light curve for HR Carinae, plotted from ASAS data]]
HR Carinae undergoes spectral variations apparently correlated with the light variations similarly to other luminous blue variables. It has undergone several outbursts during which the visual brightness increases and the temperature drops, but the bolometric luminosity remains approximately constant. The visual brightness increased erratically but consistently during the later decades of the 20th century to a record peak of mag 6.8, then dropped straight to a record minimum of mag 8.8 by 2010.
Characteristics
HR Carinae has a temperature around {{val|21,000|fmt=commas|ul=K}} when quiescent and the spectrum is of an early B hypergiant,{{cite journal|doi=10.1086/117514|title=High Resolution Coronographic Imaging and Spectropolarimetry of the HR Carinae Nebula|journal=The Astronomical Journal|volume=110|pages=251|year=1995|last1=Clampin|first1=M.|last2=Schulte-Ladbeck|first2=R. E.|last3=Nota|first3=A.|author3-link=Antonella Nota|last4=Robberto|first4=M.|last5=Paresce|first5=F.|last6=Clayton|first6=G. C.|bibcode=1995AJ....110..251C}} but in outburst it cools to below {{val|8,000|fmt=commas|u=K}}.
HR Carinae is a lot like Eta Carinae, both luminous blue variables, and both surrounded by ejected material. HR Carinae is also likely to be a binary system with a similar separation, period, and ratio of component sizes to Eta Carinae.{{cite journal|bibcode=2015IAUS..307..295R|title=Binarity of the LBV HR Car|journal=New Windows on Massive Stars: Asteroseismology|volume=307|pages=295–296|last1=Rivinius|first1=Th.|last2=Boffin|first2=H. M. J.|last3=De Wit|first3=W. J.|last4=Mehner|first4=A.|last5=Martayan|first5=Ch.|last6=Guieu|first6=S.|last7=Le Bouquin|first7=J.-B.|year=2015|doi=10.1017/S174392131400698X|arxiv = 1408.0511 |s2cid=118591807}} However, the Eta Carinae system is more massive and more luminous.
It has been identified as a possible type IIb supernova candidate in modelling of the fate of stars 20 to 25 times the mass of the Sun (with LBV status as the predicted final stage beforehand).{{cite journal|author1=Groh, J. H. |author2=Meynet, G. |author3=Ekström, S. |date=2013|title=Massive star evolution: luminous blue variables as unexpected supernova progenitors |journal=Astronomy & Astrophysics|volume=550|id=L7|pages=4|doi=10.1051/0004-6361/201220741 | bibcode=2013A&A...550L...7G|arxiv = 1301.1519 |s2cid=119227339 }}
Binary system
AMBER and PIONIER interferometry has shown that HR Carinae is a binary star system. The orbit is only weakly constrained but the most likely orbit has a semi-major axis of 3.3 mas, eccentricity of 0.4, and a period of 12.5 years. The possible orbits vary from nearly circular orbits of just a few years to highly eccentric orbits of several hundred years, all with the closest separation of the two stars at about 2 mas.
The companion appears to be larger than the primary LBV star, but much less bright. It is most likely a red supergiant with an angular diameter of {{val|0.85|0.20|u=mas}}, translating to a radius about {{val|500|150|u={{solar radius}}}}, and also with a mass of {{solar mass|9–20}} and a temperature of 3,600–{{val|4,000|fmt=commas|u=K}}. The diameter of the primary star was also measured directly at {{val|0.38|0.08|u=mas}}, corresponding to a radius of {{val|220|60|u={{solar radius}}}} at {{val|5.4|u=kpc}}.
References
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{{Stars of Carina}}
{{DEFAULTSORT:HR Carinae}}
Category:Luminous blue variables
Category:Carina (constellation)