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CW Leonis or IRC +10216 is a carbon star that is embedded in a thick dust envelope. It was first discovered in 1969 by a group of astronomers led by Eric Becklin, based upon infrared observations made with the 62 inches (1.6 m) Caltech Infrared Telescope at Mount Wilson Observatory. Its energy is emitted mostly at infrared wavelengths. At a wavelength of 5 μm, it was found to have the highest flux of any object outside the Solar System.[9]

CW Leonis

CW Leonis in ultraviolet showing the bowshock
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 09h 47m 57.406s[1]
Declination +13° 16′ 43.56″[1]
Characteristics
Spectral type C9,5e[2]
Apparent magnitude (R) 10.96[1]
Apparent magnitude (J) 7.34[1]
Apparent magnitude (H) 4.04[1]
Apparent magnitude (K) 1.19[1]
Variable type Mira[3]
Astrometry
Proper motion (μ) RA: 35±1 mas/yr
Dec.: 12±1[4] mas/yr
Parallax (π)10.56 ± 2.02 mas[5]
Distanceapprox. 310 ly
(approx. 90 pc)
Details
Mass0.7 - 0.9[4] M☉
Radius560[6] R☉
Luminosity8,500 (average), 11,850 (maximum)[6] L☉
Temperature2,300[6] (1,915 - 2,105)[7] K
Other designations
CW Leo, Peanut Nebula, IRC+10216, IRAS 09452+1330, PK 221+45 1, Zel 0945+135, RAFGL 1381, 2MASS J09475740+1316435, SCM 50[8]
Database references
SIMBADdata

Properties


A LINEAR (white-light) light curve for CW Leonis, adapted from Palaversa et al. (2013)[10]
A LINEAR (white-light) light curve for CW Leonis, adapted from Palaversa et al. (2013)[10]

CW Leonis is believed to be in a late stage of its life, blowing off its own sooty atmosphere to form a white dwarf. Based upon isotope ratios of magnesium, the initial mass of this star has been constrained to lie between 3–5 solar masses. The mass of the star's core, and the final mass of the star once it becomes a white dwarf, is about 0.7–0.9 solar masses.[11] Its bolometric luminosity varies over the course of a 649-day pulsation cycle, ranging from a minimum of about 6,250 times the Sun's luminosity up to a peak of around 15,800 times. The overall output of the star is best represented by a luminosity of 11,300 L☉.[12]

The carbon-rich gaseous envelope surrounding this star is at least 69,000 years old and the star is losing about (1–4) × 10−5 solar masses per year.[12] The extended envelope contains at least 1.4 solar masses of material.[13] Speckle observations from 1999 show a complex structure to this dust envelope, including partial arcs and unfinished shells. This clumpiness may be caused by a magnetic cycle in the star that is comparable to the solar cycle in the Sun and results in periodic increases in mass loss.[14]

Various chemical elements and about 50 molecules have been detected in the outflows from CW Leonis, among others nitrogen, oxygen and water, silicon and iron. One theory was that the star was once surrounded by comets which melted once the star started expanding,[15] but water is now thought to form naturally in the atmospheres of all carbon stars.[16]


Distance


CW Leonis glows from deep within a thick shroud of dust in this image from the NASA/ESA Hubble Space Telescope.
CW Leonis glows from deep within a thick shroud of dust in this image from the NASA/ESA Hubble Space Telescope.

If the distance to this star is assumed to be at the lower end of the estimate range, 120 pc, then the astrosphere surrounding the star spans a radius of about 84,000 AU. The star and its surrounding envelope are advancing at a velocity of more than 91 km/s through the surrounding interstellar medium.[13] It is moving with a space velocity of [U, V, W] = [21.6 ± 3.9, 12.6 ± 3.5, 1.8 ± 3.3] km s−1.[11]


Companion


Several papers have suggested that CW Leonis has a close binary companion. ALMA and astrometric measurements may show orbital motion. The astrometric measurements, combined with a model including the companion, provide a parallax measurement showing that CW Leonis is the closest carbon star to the Earth.[5]


See also



References


  1. Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  2. Cohen, M. (1979). "Circumstellar envelopes and the evolution of carbon stars". Monthly Notices of the Royal Astronomical Society. 186 (4): 837–852. Bibcode:1979MNRAS.186..837C. doi:10.1093/mnras/186.4.837.
  3. 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. Matthews, L. D.; Gérard, E.; Le Bertre, T. (2015). "Discovery of a shell of neutral atomic hydrogen surrounding the carbon star IRC+10216". Monthly Notices of the Royal Astronomical Society. 449 (1): 220–233. arXiv:1502.02050. Bibcode:2015MNRAS.449..220M. doi:10.1093/mnras/stv263. S2CID 96460867.
  5. Sozzetti, A.; Smart, R. L.; Drimmel, R.; Giacobbe, P.; Lattanzi, M. G. (2017). "Evidence for orbital motion of CW Leonis from ground-based astrometry". Monthly Notices of the Royal Astronomical Society: Letters. 471 (1): L1–L5. arXiv:1706.04391. Bibcode:2017MNRAS.471L...1S. doi:10.1093/mnrasl/slx082. S2CID 119070871.
  6. Schmidt, M. R.; He, J. H.; Szczerba, R.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Decin, L.; Justtanont, K.; Teyssier, D.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Marston, A. P.; Sobolev, A. M.; De Koter, A.; Schöier, F. L. (2016). "Herschel/HIFI observations of the circumstellar ammonia lines in IRC+10216". Astronomy & Astrophysics. 592: A131. arXiv:1606.01878. Bibcode:2016A&A...592A.131S. doi:10.1051/0004-6361/201527290. PMC 5217166. PMID 28065983.
  7. Bergeat, J.; Knapik, A.; Rutily, B. (2001). "The effective temperatures of carbon-rich stars". Astronomy and Astrophysics. 369: 178–209. Bibcode:2001A&A...369..178B. doi:10.1051/0004-6361:20010106.
  8. "V* CW Leo -- Variable Star of Mira Cet type". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2011-05-09.
  9. Becklin, E. E.; et al. (December 1969). "The Unusual Infrared Object IRC+10216" (PDF). Astrophysical Journal. 158: L133. Bibcode:1969ApJ...158L.133B. doi:10.1086/180450.
  10. Palaversa, Lovro; Ivezić, Željko; Eyer, Laurent; Ruždjak, Domagoj; Sudar, Davor; Galin, Mario; Kroflin, Andrea; Mesarić, Martina; Munk, Petra; Vrbanec, Dijana; Božić, Hrvoje; Loebman, Sarah; Sesar, Branimir; Rimoldini, Lorenzo; Hunt-Walker, Nicholas; VanderPlas, Jacob; Westman, David; Stuart, J. Scott; Becker, Andrew C.; Srdoč, Gregor; Wozniak, Przemyslaw; Oluseyi, Hakeem (October 2013). "Exploring the Variable Sky with LINEAR. III. Classification of Periodic Light Curves". The Astronomical Journal. 146 (4). doi:10.1088/0004-6256/146/4/101.
  11. Ladjal, D.; et al. (July 2010). "Herschel PACS and SPIRE imaging of CW Leonis". Astronomy and Astrophysics. 518: L141. arXiv:1005.1433. Bibcode:2010A&A...518L.141L. doi:10.1051/0004-6361/201014658. S2CID 14279789.
  12. De Beck, E.; et al. (January 10, 2012). "On the physical structure of IRC+10216". Astronomy & Astrophysics. 539: A108. arXiv:1201.1850. Bibcode:2012A&A...539A.108D. doi:10.1051/0004-6361/201117635. S2CID 56163906.
  13. Sahai, Raghvendra; Chronopoulos, Christopher K. (March 2010). "The Astrosphere of the Asymptotic Giant Branch Star IRC+10216". The Astrophysical Journal Letters. 711 (2): L53–L56. arXiv:1001.4997. Bibcode:2010ApJ...711L..53S. doi:10.1088/2041-8205/711/2/L53. S2CID 118705396.
  14. Dinh-V-Trung, Jeremy; Lim (May 2008). "Molecular Shells in IRC+10216: Evidence for Nonisotropic and Episodic Mass-Loss Enhancement". The Astrophysical Journal. 678 (1): 303–308. arXiv:0712.1714. Bibcode:2008ApJ...678..303D. doi:10.1086/527669. S2CID 16389370.
  15. Ford, K. E. Saavik; Neufeld, David A.; Goldsmith, Paul F.; Melnick, Gary J. (2003). "Detection of OH toward the Extreme Carbon Star IRC +10216". The Astrophysical Journal. 589 (1): 430–438. arXiv:astro-ph/0302103. Bibcode:2003ApJ...589..430F. doi:10.1086/374552. S2CID 16682238.
  16. Lombaert, R.; Decin, L.; Royer, P.; De Koter, A.; Cox, N. L. J.; González-Alfonso, E.; Neufeld, D.; De Ridder, J.; Agúndez, M.; Blommaert, J. A. D. L.; Khouri, T.; Groenewegen, M. A. T.; Kerschbaum, F.; Cernicharo, J.; Vandenbussche, B.; Waelkens, C. (2016). "Constraints on the H2O formation mechanism in the wind of carbon-rich AGB stars". Astronomy & Astrophysics. 588: A124. arXiv:1601.07017. Bibcode:2016A&A...588A.124L. doi:10.1051/0004-6361/201527049. S2CID 62787287.



На других языках

[de] CW Leonis

CW Leonis oder IRC +10216 ist ein Kohlensstoffstern im Sternbild Löwe, etwa 310 Lichtjahre entfernt. Er wurde im Jahr 1969 von einer Gruppe Astronomen unter der Leitung von Eric Becklin entdeckt, anhand von Infrarotbeobachtungen mithilfe des Caltech Infrared Telescope am Mount Wilson Observatory. Er ist von einer dicken Staubhülle umgeben, und strahlt seine Energie überwiegen im Infrarot-Spektrum ab. Bei einer Wellenlänge von 5 μm ist es das hellste Objekt außerhalb des Sonnensystems.
- [en] CW Leonis

[es] CW Leonis

CW Leonis (IRC +10216 / CGCS 2619)[1] es el nombre de la estrella de carbono más conocida y estudiada, que se encuentra en la constelación de Leo. Aunque visualmente es una estrella muy tenue, es, después de Eta Carinae, el objeto extrasolar más brillante del cielo en longitud de onda de 10 μm,[2] ya que emite la mayor parte de su energía como radiación infrarroja. Se encuentra aproximadamente a 490 años luz del Sistema Solar.[3]

[ru] IRC +10216

CW Льва или IRC +10216 является наиболее изученной углеродной звездой, которая находится на расстоянии 650 световых лет от Земли в созвездии Льва. Несмотря на исполинские размеры (её радиус более чем втрое превышает расстояние от Земли до Солнца), в оптическом диапазоне она светит очень тускло и потому видна только в большие телескопы. Звезда окружена толстой пылевой оболочкой. В результате этого основная излучаемая энергия приходится на инфракрасный диапазон: IRC +10216 является самым ярким объектом в небе на длине волны 10 мкм[5].


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