HR Carinae

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HR Car
HR Carinae ESO MUSE (H-alpha).png
HR Carinae and its nebula in Hydrogen-Alpha with MUSE
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Carina
Right ascension 10h 22m 53.84074s [1]
Declination −59° 37′ 28.3774″ [1]
Apparent magnitude  (V)8.42 [2] (6.95–8.80 [3] )
Characteristics
Spectral type LBV [4] + RSG [5]
U−B color index −0.22 [2]
B−V color index +0.92 [2]
Variable type LBV [3]
Astrometry
Proper motion (μ)RA: –6.161 [6]   mas/yr
Dec.: +2.163 [6]   mas/yr
Parallax (π)0.1708 ± 0.0326  mas [6]
Distance 4,370 [7]   pc
Absolute magnitude  (MV)−9.4 [4]
Orbit [5]
Period (P)4557.5 ± 21.0 days
Semi-major axis (a)3.324 ± 0.026"
(18 AU)
Eccentricity (e)0.4 ± 0.2
Inclination (i)119.2 ± 0.7°
Details
HR CarLBV
Mass 25 [8] –40 [9]   M☉
Radius 220±60 [5] (100 [4] –350 [9] )  R☉
Luminosity 416,000–790,000 [10]   L☉
Temperature 7,900–21,900 [10]   K
Rotational velocity (v sin i)150 [8]  km/s
HR CarRSG
Mass 9–20 [5]   M☉
Radius 500±150 [5]   R☉
Temperature 3,600–4,000 [5]   K
Other designations
HR  Car, HD  90177, HIP  50843, SAO  238005, CD-59 3044, GC  14276, MWC  202, AAVSO  1019-59
Database references
SIMBAD data

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.

Contents

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. [11] It was catalogued in 1933 as a Be star [12] and was discovered to be variable in 1940. [13] 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. [14]

By 1970, HR Carinae and the similar variable AG Carinae were recognised as being related to the P Cygni variables, unstable hot supergiants. [15] [16] The group was formally recognised as S Doradus variables to avoid confusion with the P Cygni spectral features shared with other types of star. [17] 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. [18] [19]

Brightness variation

An I band (near infrared) light curve for HR Carinae, plotted from ASAS data HRCarLightCurve.png
An I band (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. [8]

Characteristics

HR Carinae has a temperature around 21,000  K when quiescent and the spectrum is of an early B hypergiant, [21] but in outburst it cools to below 8,000 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. [22] 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). [23]

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. [5]

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 0.85±0.20 mas, translating to a radius about 500±150 R☉, and also with a mass of 9–20 M☉ and a temperature of 3,600–4,000 K. The diameter of the primary star was also measured directly at 0.38±0.08 mas, corresponding to a radius of 220±60 R☉ at 5.4 kpc. [5]

Related Research Articles

<span class="mw-page-title-main">Blue supergiant</span> Hot, luminous star with a spectral type of A9 or earlier

A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants.

<span class="mw-page-title-main">S Doradus</span> Star in the Large Magellanic Cloud

S Doradus is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, located roughly 160,000 light-years away. The star is a luminous blue variable, and one of the most luminous stars known, having a luminosity varying widely above and below 1,000,000 times the luminosity of the Sun, although it is too far away to be seen with the naked eye.

<span class="mw-page-title-main">Luminous blue variable</span> Type of star that is luminous, blue, and variable in brightness

Luminous blue variables (LBVs) are rare, massive and evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud.

<span class="mw-page-title-main">LBV 1806−20</span> Likely binary star in the constellation Sagittarius

LBV 1806−20 is a candidate luminous blue variable (LBV) and likely binary star located around 28,000 light-years (8,700 pc) from the Sun, towards the center of the Milky Way. It has an estimated mass of around 36 solar masses and an estimated variable luminosity of around two million times that of the Sun. It is highly luminous but is invisible from the Solar System at visual wavelengths because less than one billionth of its visible light reaches us.

<span class="mw-page-title-main">P Cygni</span> Variable star in the constellation Cygnus

P Cygni is a variable star in the constellation Cygnus. The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova. Located about 5,300 light-years from Earth, it is a hypergiant luminous blue variable (LBV) star of spectral type B1-2 Ia-0ep that is one of the most luminous stars in the Milky Way.

Alpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time other parts expand. They are supergiant stars of spectral types B or A. Variations in brightness on the order of 0.1 magnitudes are associated with the pulsations, which often seem irregular, due to beating of multiple pulsation periods. The pulsations typically have periods of several days to several weeks.

<span class="mw-page-title-main">Yellow hypergiant</span> Class of massive star with a spectral type of A to K

A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (MV) around −9, but also one of the rarest, with just 20 known in the Milky Way and six of those in just a single cluster. They are sometimes referred to as cool hypergiants in comparison with O- and B-type stars, and sometimes as warm hypergiants in comparison with red supergiants.

<span class="mw-page-title-main">AG Carinae</span> Luminous variable star in the constellation Carina

AG Carinae is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.

<span class="mw-page-title-main">Hypergiant</span> Rare star with tremendous luminosity and high rates of mass loss by stellar winds

A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae. Notable examples of hypergiants include the Pistol Star, a blue hypergiant located close to the Galactic Center and one of the most luminous stars known; Rho Cassiopeiae, a yellow hypergiant that is one of the brightest to the naked eye; and Mu Cephei (Herschel's "Garnet Star"), one of the largest and brightest stars known.

<span class="mw-page-title-main">HD 168607</span> Star in the constellation Sagittarius

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<span class="mw-page-title-main">NGC 2363-V1</span> Luminous blue variable star in the constellation Camelopardalis

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<span class="mw-page-title-main">AFGL 2298</span> Star in the constellation Aquila

AFGL 2298, also known as IRAS 18576+0341, is a luminous blue variable star (LBV) located in the constellation Aquila, very close to the galactic plane. Its distance is not well known; it may be anywhere between 23,000 and 42,000 light years away from the Earth. Despite being extremely luminous, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands; in fact, in visual wavelengths it is completely undetectable.

R99 is a star in the Large Magellanic Cloud in the constellation Dorado. It is classified as a possible luminous blue variable and is one of the most luminous stars known.

<span class="mw-page-title-main">HD 316285</span> Star in the constellation Sagittarius

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<span class="mw-page-title-main">WR 31a</span> Wolf Rayet star in the constellation Carina

WR 31a, commonly referred to as Hen 3-519, is a Wolf–Rayet (WR) star in the southern constellation of Carina that is surrounded by an expanding Wolf–Rayet nebula. It is not a classical old stripped-envelope WR star, but a young massive star which still has some hydrogen left in its atmosphere.

<span class="mw-page-title-main">V1936 Aquilae</span> Blue supergiant star in the constellation Aquila

V1936 Aquilae is a blue supergiant and candidate Luminous blue variable located in the nebula Westerhout 51, in the constellation Aquila, about 20,000 light years away. The star was originally identified as a massive star in 2000, and was thought to be an O-type supergiant. However, subsequent analyses have shown it to be not O but B-type, as well as being possibly an LBV.

<span class="mw-page-title-main">AF Andromedae</span> Luminous blue variable star in the constellation Andromeda

AF Andromedae is a luminous blue variable (LBV), a type of variable star. The star is one of the most luminous variables in M31, the Andromeda Galaxy.

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<span class="mw-page-title-main">B324</span> Star in the Triangulum Galaxy

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References

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  3. 1 2 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.
  4. 1 2 3 Hutsemekers, D; van Drom, E. (1991). "HR Carinae – A luminous blue variable surrounded by an arc-shaped nebula". Astronomy and Astrophysics . 281: 141–149. Bibcode:1991A&A...248..141H.
  5. 1 2 3 4 5 6 7 8 Boffin, Henri M. J.; Rivinius, Thomas; Merand, Antoine; Mehner, Andrea; Lebouquin, Jean-Baptiste; Pourbaix, Dimitri; De Wit, Willem-Jan; Martayan, Christophe; Guieu, Sylvain (2016). "The LBV HR Car has a partner: Discovery of a companion with the VLTI". Astronomy & Astrophysics. 593: A90. arXiv: 1607.07724 . Bibcode:2016A&A...593A..90B. doi:10.1051/0004-6361/201629127. hdl:2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/239364. S2CID   118399536.
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  7. ↑ Groh, Jose H.; Stassun, Keivan G.; Drout, Maria R.; Murphy, Jeremiah W.; Aghakhanloo, Mojgan; Smith, Nathan (2019). "On the Gaia DR2 distances for Galactic luminous blue variables". Monthly Notices of the Royal Astronomical Society. 488 (2): 1760–1778. arXiv: 1805.03298 . Bibcode:2019MNRAS.488.1760S. doi: 10.1093/mnras/stz1712 . S2CID   119267371.
  8. 1 2 3 Groh, J. H.; Damineli, A.; Hillier, D. J.; Barbá, R.; Fernández-Lajús, E.; Gamen, R. C.; Moisés, A. P.; Solivella, G.; Teodoro, M. (2009). "Bona Fide, Strong-Variable Galactic Luminous Blue Variable Stars Are Fast Rotators: Detection of a High Rotational Velocity in Hr Carinae". The Astrophysical Journal. 705 (1): L25–L30. arXiv: 0909.4459 . Bibcode:2009ApJ...705L..25G. doi:10.1088/0004-637X/705/1/L25. S2CID   16609230.
  9. 1 2 Machado, M. A. D.; de Araújo, F. X.; Pereira, C. B.; Fernandes, M. B. (2002). "HR Carinae: New spectroscopic data and physical parameters". Astronomy and Astrophysics . 387: 151–161. Bibcode:2002A&A...387..151M. doi: 10.1051/0004-6361:20020295 . pp. 151–161.
  10. 1 2 Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics. 538: A47. arXiv: 1111.6375 . Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040. S2CID   43688343.
  11. ↑ Pickering, E. C.; Fleming, W. P. (1901). "Objects having peculiar spectra". The Astrophysical Journal. 14: 144. Bibcode:1901ApJ....14..144P. doi:10.1086/140844. ISSN   0004-637X.
  12. ↑ Merrill, Paul W.; Burwell, Cora G. (1933). "Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines". The Astrophysical Journal. 78: 87. Bibcode:1933ApJ....78...87M. doi: 10.1086/143490 . ISSN   0004-637X.
  13. ↑ Hoffleit, Dorrit (1940). "A New Variable Star with Be Spectrum". Harvard College Observatory Bulletin. 913: 4. Bibcode:1940BHarO.913....4H.
  14. ↑ Henize, Karl G. (1952). "Six Peculiar Hα-EMISSION Stars". The Astrophysical Journal. 115: 133. Bibcode:1952ApJ...115..133H. doi: 10.1086/145522 . ISSN   0004-637X.
  15. ↑ Bond, Howard E.; Landolt, Arlo U. (1970). "Photometric and Spectroscopic Observations of AG and HR Carinae". Publications of the Astronomical Society of the Pacific. 82 (485): 313. Bibcode:1970PASP...82..313B. doi:10.1086/128910. S2CID   120611422.
  16. ↑ Viotti, R. (1971). "Note on the Spectrum and Luminosity of AG and HR Carinae". Publications of the Astronomical Society of the Pacific. 83 (492): 170. Bibcode:1971PASP...83..170V. doi: 10.1086/129095 .
  17. ↑ Sharov, A. S. (1975). "S Dor-Type Variables in Other Galaxies". In Vicki E. Sherwood; Lukas Plaut (eds.). Variable Stars and Stellar Evolution. Proceedings of the International Astronomical Union Symposium No.67 held in Moscow, USSR July 29 to August 4, 1974. pp. 275–284. Bibcode:1975IAUS...67..275S. doi:10.1017/S007418090001038X. ISBN   978-90-277-0579-2.
  18. ↑ Van Genderen, A. M. (1989). "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". Astronomy and Astrophysics. 208: 135. Bibcode:1989A&A...208..135V.
  19. ↑ Stothers, Richard B.; Chin, Chao-Wen (1994). "Luminous blue variables at quiescence: The zone of avoidance in the Hertzsprung-Russell diagram". The Astrophysical Journal. 426: L43. Bibcode:1994ApJ...426L..43S. doi:10.1086/187335. ISSN   0004-637X.
  20. ↑ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  21. ↑ Clampin, M.; Schulte-Ladbeck, R. E.; Nota, A.; Robberto, M.; Paresce, F.; Clayton, G. C. (1995). "High Resolution Coronographic Imaging and Spectropolarimetry of the HR Carinae Nebula". The Astronomical Journal. 110: 251. Bibcode:1995AJ....110..251C. doi:10.1086/117514.
  22. ↑ Rivinius, Th.; Boffin, H. M. J.; De Wit, W. J.; Mehner, A.; Martayan, Ch.; Guieu, S.; Le Bouquin, J.-B. (2015). "Binarity of the LBV HR Car". New Windows on Massive Stars: Asteroseismology. 307: 295–296. arXiv: 1408.0511 . Bibcode:2015IAUS..307..295R. doi:10.1017/S174392131400698X. S2CID   118591807.
  23. ↑ Groh, J. H.; Meynet, G.; Ekström, S. (2013). "Massive star evolution: luminous blue variables as unexpected supernova progenitors". Astronomy & Astrophysics. 550: 4. arXiv: 1301.1519 . Bibcode:2013A&A...550L...7G. doi:10.1051/0004-6361/201220741. S2CID   119227339. L7.
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