HD 84810

HD 84810, also known as l Carinae (l Car), is a star in the southern constellation of Carina. Its apparent magnitude varies from about 3.4 to 4.1, making it readily visible to the naked eye and one of the brighter members of Carina. Based upon parallax measurements, it is approximately 1,600 light-years (490 parsecs) from Earth.[1]

This article is about ℓ Carinae. For L Carinae, see HD 90264. For I Carinae, see HD 90589. For i Carinae, see HD 79447.
ℓ Carinae
Location of l Carinae (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension  09h 45m 14.81122s[1]
Declination –62° 30′ 28.4519″[1]
Apparent magnitude (V) 3.35 - 4.06[2]
Characteristics
Spectral type F6Ib-K0Ib[2]
U−B color index +0.76[3]
B−V color index +1.03[3]
Variable type Classical Cepheid[2]
Astrometry
Radial velocity (Rv)+3.3[4] km/s
Proper motion (μ) RA: –12.88[1] mas/yr
Dec.: +8.19[1] mas/yr
Parallax (π)2.09 ± 0.29[1] mas
Distance498+55
−45[5] pc
Absolute magnitude (MV)–5.22[6]
Details
Mass8.4[7] to 13[8] M☉
Radius169±8[9] R☉
Luminosity11,482[5] L☉
Surface gravity (log g)1.5[10] cgs
Temperature5,091[10] K
Metallicity [Fe/H]0.30[10] dex
Age31.25[5] Myr
Other designations
l Carinae, 2MASS J09451481-6230284, CD–61 2349, FK5 1254, HD 84810, HIP 47854, HR 3884, IRAS 09438-6216, SAO 250683.
Database references
SIMBADdata
ESO - Model Image of Cepheid l Carinae

From the characteristics of its spectrum, l Carinae has a stellar classification of G5 Iab/Ib.[7] This indicates the star has reached a stage in its evolution where it has expanded to become a supergiant with 169 times the radius of the Sun.[9] As this is a massive star with 8[7]–13[8] times the mass of the Sun, it rapidly burns through its supply of nuclear fuel and has become a supergiant in roughly 17-19 million years, after spending 15–17 million years as a main sequence star.[8]

l Carinae is classified as a Cepheid variable star and its brightness varies over an amplitude range of 0.725 in magnitude with a long period of 35.560 days. The radial velocity of the star likewise varies by 39 km/s during each pulsation cycle.[11] Its radius varies by about 40 R☉ as it pulsates, reaching maximum size as its brightness is decreasing towards minimum.[5]

It has a compact circumstellar envelope that can be discerned using interferometry. The envelope has been resolved at an infrared wavelength of 10μm, showing a radius of 10–100 AU at a mean temperature of 100 K. The material for this envelope was supplied by mass ejected from the central star.[8]

The period of l Carinae is calculated to be slowly increasing and it is thought to be crossing the instability strip for the third time, cooling as it evolves towards a red supergiant after a blue loop.[5]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  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: B/gcvs. Bibcode:2009yCat....102025S.
  3. Madore, B. F. (June 1975), "Photoelectric UBV photometry of Cepheids in the Magellanic Clouds and in the southern Milky Way", Astrophysical Journal Supplement Series, 29: 219–284, Bibcode:1975ApJS...29..219M, doi:10.1086/190342.
  4. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and their Applications. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
  5. Neilson, Hilding R; Engle, Scott G; Guinan, Edward F; Bisol, Alexandra C; Butterworth, Neil (2016). "The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid". The Astrophysical Journal. 824 (1): 1. arXiv:1604.03128. Bibcode:2016ApJ...824....1N. doi:10.3847/0004-637X/824/1/1.
  6. Fouqué, P.; Arriagada, P.; Storm, J.; Barnes, T. G.; Nardetto, N.; Mérand, A.; Kervella, P.; Gieren, W.; Bersier, D.; Benedict, G. F.; McArthur, B. E. (2007). "A new calibration of Galactic Cepheid period-luminosity relations from B to K bands, and a comparison to LMC relations". Astronomy and Astrophysics. 476 (1): 73–81. arXiv:0709.3255. Bibcode:2007A&A...476...73F. doi:10.1051/0004-6361:20078187.
  7. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  8. Kervella, P.; Mérand, A.; Gallenne, A. (2009), "The circumstellar envelopes of the Cepheids ℓ Carinae and RS Puppis. Comparative study in the infrared with Spitzer, VLT/VISIR, and VLTI/MIDI", Astronomy and Astrophysics, 498 (2): 425–443, arXiv:0902.1588, Bibcode:2009A&A...498..425K, doi:10.1051/0004-6361/200811307.
  9. Davis, J.; et al. (April 2009), "Observations of the pulsation of the Cepheid l Car with the Sydney University Stellar Interferometer", Monthly Notices of the Royal Astronomical Society, 394 (3): 1620–1630, arXiv:0812.4791, Bibcode:2009MNRAS.394.1620D, doi:10.1111/j.1365-2966.2009.14433.x.
  10. Luck, R. E. (September 1979), "The chemical compositions of nine southern supergiant stars", Astrophysical Journal, Part 1, 232: 797–806, Bibcode:1979ApJ...232..797L, doi:10.1086/157340.
  11. Klagyivik, P.; Szabados, L. (September 2009), "Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes", Astronomy and Astrophysics, 504 (3): 959–972, arXiv:0908.3561, Bibcode:2009A&A...504..959K, doi:10.1051/0004-6361/200811464.
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