Discovery of IRC10216 Eric Becklin

Offscale

IRC+10216

Old carbon rich red giant with a dusty expanding shell at 10-20 km

s-1

Harry Kroto 2004

Harry Kroto 2004

Central warm core

T~ 1000K

Diameter ~ Earth orbit

Outer shell T~ 100K

Diameter ~ 1ly

Optical image of IRC+10216 in Milky Way . VLT. Izan Leao (Universidade Federal do Rio Grande do Norte, Brazil).

2 mm molecular line survey of IRC+10216 m Cernicharo et al

HC3N emission

36 GHz imaging of SiS and HC3N line emission from the AGB star IRC+10216 for the synthesis imaging summer school data reduction tutorials

http://www.ynao.ac.cn/~jinhuahe/know_base/catalogues/agb/irc+10216/irc10216.htm

Recent radio emission from .C≡C–C≡C–H

in the circumstellar envelope of the Red Giant IRC+10216

http://bima.astro.umd.edu/images/astronomy/irc10216.gif.html

ca 1 ly diameter

Discovery of IRC10216 Eric Becklin

Offscale

Abstract References

We report a spectral-line survey of the extreme carbon star IRC+10216 carried out between 293.9 and 354.8 GHz with the Submillimeter Array. A total of 442 lines were detected, more than 200 for the first time; 149 are unassigned. Maps at an angular resolution of ~3'' were obtained for each line. A substantial new population of narrow lines with an expansion velocity of ~4 km s–1 (i.e., 30% of the terminal velocity) was detected. Most of these are attributed to rotational transitions within vibrationally excited states, emitted from energy levels above the v = 0, J = 0 ground state with excitation energy of 1000-3000 K. Emission from these lines appears to be centered on the star with an angular extent of <1''. We use multiple transitions detected in several molecules to derive physical conditions in this inner envelope of IRC+10216.

Keywords astrochemistry; line: identification; stars: AGB and post-AGB; stars: individual (IRC+10216, CW Leo); surveys

PACS 95.80.+p Astronomical catalogs, atlases, sky surveys, databases, retrieval systems, archives, etc. 97.10.Fy Circumstellar shells, clouds, and expanding envelopes; circumstellar masers 95.85.Fm Submillimeter (300 &mgr;m–1 mm) 97.30.Hk Carbon stars, S stars, and related types (C, S, R, and N) 97.10.Tk Abundances, chemical composition Subjects Astrophysics and astroparticles Dates Issue 1 (2011 March) Received 2010 July 13 , accepted for publication 2010 December 22 Published 2011 March 3

Weekly Science Update Friday, March 11, 2011The Rich Chemistry Around an Evolved StarOver 170 molecules have been detected in space, from simple diatomic molecules like CO to complex organic molecules with over 70 atoms, like fullerene. These molecules play a critical role in the development of molecular clouds as they form new stars and planetary systems, and of course in the chemistry that later develops on the surfaces of planets. One of the major issues in modern astronomy is figuring out exactly where all these molecules and associated dust grains came from. The variable star CW Leo, also known as IRC+10216, is one of the brightest objects in the sky as seen from Earth; it is about 450 light-years away. It shines mostly in the infrared (not optical) because the central star is surrounded by a dense cloud of dust and gas that it ejected in a late stage of its evolution; that dust blocks the optical light. The material is known to be rich in carbon-bearing molecules. CfA astronomers Nimesh Patel, Ken Young, Carl Gottlieb, Pat Thaddeus, Bob Wilson, Mark Reid, Mike McCarthy, and Eric Keto, together with five colleagues, used the Submillimeter Array (SMA) to study the spectrum of IRC+10216 across a wavelength band, in an effort to detect and characterize as many molecules in the star's envelope as possible. The scientists report finding an amazing 442 spectral lines in their survey, more than 200 of them detected for the first time in any astronomical source. All but 149 can be identified as arising from specific molecules. In addition to measuring the strengths of the lines and the motions of the molecules responsible, the SMA survey also obtained images of the nebula around in the star in the light of each of these species. The unidentified features, for example, tend to arise from compact regions around the star and probably correspond to hotter states of the known molecules; future work is needed to confirm this conclusion. The new results provide a remarkable view of the rich chemistry around this nearby star, and help to strengthen the conclusion that many complex molecules trace their origin to the envelopes of evolved stars.

http://www.cfa.harvard.edu/news/2011/su201110.html

A deep optical image of the carbon star IRC+10216, showing traces of its surrounding envelope. New SMA observations study the rich chemistry of the envelope, and find 442 spectral lines from over fifty molecules. Credit: Izan Leao; the Very Large TelescopeLow Resolution Image (jpg)

http://www.cfa.harvard.edu/news/2011/su201110_images.html

IRC+10216

Old carbon rich red giant with a dusty expanding shell

(at 10-20 km s-1)

Central warm core

ca 300 - 700K

diam ca 1AU = 10-5 ly

Harry Kroto 2004

IRC+10216

Old carbon rich red giant with a dusty expanding shell

(at 10-20 km s-1)

Central warm core

ca 300 - 700K

diam ca 1AU = 10-5 ly

More tenuous cooler (150-250K) outer

expanding envelope ca 1ly diam

Harry Kroto 2004

1ly

image at: bima.astro.umd.edu/.../irc10216.gif.html

HCN

C4H

image at: www.ifa.hawaii.edu/%7Ejpw/classes/ast622/

Maps from the Plateau de Bure interferometer showing the molecular distributions in the envelope of IRC+10216 MgNC, C2H, HC5N, and C4H all exist in the outer shell, whereas NaCl is an inner envelope species. SiC2 is present in the intermediate regions.

Lucy M. Ziurys

Issue A&A Suppl. Ser. Volume 142, Number 2, March I 2000 Page(s) 181 - 215DOI10.1051/aas:2000147DOI: 10.1051/aas:2000147

Astron. Astrophys. Suppl. Ser. 142, 181-215 A 2 mm molecular line survey of the C-star envelope IRC+10216 J. Cernicharo1 - M. Guélin2 - C. Kahane3

The chemistry in circumstellar envelopes of evolved stars: Following the origin of the elements to the origin of life

Lucy M. Ziurys†

Fig. 2. Maps from the Plateau de Bure interferometer showing the molecular distributions of various species in the envelope of IRC+10216 (17, 18). MgNC, C2H, HC5N, and C4H all exist in the outer shell, whereas NaCl is an inner envelope species. SiC2 is present in the intermediate regions.

Structure and physical properties of the rapidly evolving dusty envelope of IRC+10216 reconstructed by detailed two-dimensional radiative transfer modelling A. Men'shchikov, Y. Balega, T. Blöcker, R. Osterbart, and G. Weigelt Astronomy & Astrophysics 368, 497-526 (2001) Abstract. We present the first detailed, two-dimensional radiative transfer model of the dusty envelope around the carbon star IRC+10216. Our goal was to find a self-consistent model of the star and its envelope which takes into account as many observational constraints as possible. The model reproduces very well the entire beam-matched spectral energy distribution of IRC+10216. from optical to centimeter wavelengths (at several phases of stellar luminosity), observed intensity profiles of the object at 1.25, 2.2, 10.5, 50, 100µm, and 1.3mm, a 10.5µm lunar occultation intensity profile, our high-resolution J, H, K, and H-K bispectrum speckle-interferometry images, and visibilities in J, H, K, L, M, and N bands. For the adopted distance of 130pc, the model of IRC+10216 implies that the object changes its luminosity between 13000 and 5200Lsun, its effective temperature between 2800 and 2500K, and its radius between 500 and 390Rsun. There is a dense non-spherical dust shell around the star, with outflow cavities at position angle PA~20°. The southern cavity with a full opening angle of 36° is tilted toward us by 40° from the plane of sky, causing the observed bipolar appearance of the object on a subarcsecond scale. If the envelope's outflow velocity of 15km/s applies to the material making up the dense core, then just ~15 years ago the star was losing mass at a rate of 9x10^{-5} Msun/yr. Dust exists in the envelope of IRC+10216 everywhere from the stellar photosphere up to a distance of 3pc from the star. The total mass of the envelope lost by the central star is 3Msun and the dust-to-gas mass ratio is 0.004. The total optical depth tau_{V} toward the star in the visual is 40, in the polar cavities it is 10. The innermost parts of the envelope are optically thick even at 10.7µm due to a strong resonance absorption of silicon carbide grains at that wavelength. In addition to SiC dust, the model contains inhomogeneous grains made of a mixture of SiC and incompletely amorphous carbon with thin MgFeS mantles. This is the simplest dust mixture required to fit all observations ofIRC+10216 and to correctly interpret the well-known 11.3µm and 27µm emission bands. The dust model found in this study can also be successfully applied to many other carbon stars exhibiting broad emission features in the 10.3-12.6µm and 25-37µm wavelength regions. An important and firm result of our modeling is that the brightest compact peak observed in IRC+10216 not the direct light from the underlying central star. In contrast to previous suggestions, the brightest southern component, labeled A in our high-resolution near-infrared images (Weigelt et al. 1998a,b; Osterbart et al. 2000) is only the radiation emitted and scattered in the optically thinner southern cavity of the bipolar dense shell moving away from the central star. The carbon star is at the position of the fainter component B in our H and K images, which is 0.21" away from A along the symmetry axis. Direct stellar light (component B) is not seen at all in the Hubble Space Telescope 0.8µm and 1.1µm images, being absorbed by the dense dusty material. The even fainter components C and D in the H and K images are probably due to smaller deviations of the dense shell from the spherical shape. IRC+10216 seems to have entered a phase immediately before moving off the asymptotic giant branch and started developing asymmetries in its envelope

Channel maps of cyanopolyyne emission in contours superposed on optical V-band image (Leão et al. 2006) of IRC+10216 in false color. HC3N emission is shown in the top frame, HC5N in the middle frame, and HC5N in the bottom frame, respectively. Channel velocities are indicated in the upper left corner. The synthesized beams are shown in the lower left corner. Contour levels are 3, 5, 7, 9, 11, 13 σ for HC3N ( mJy beam–1) and HC5N ( mJy beam–1). Contour levels are 2, 3, 4, 5, 6, 7, 9, 11 σ for HC5N ( mJy beam–1).

http://iopscience.iop.org/0004-637X/678/1/303/fulltext

image at: www.aanda.org/.../aa4577-05/aa4577-05.right.html