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„Mixed chemistry” phenomena during late stages of stellar evolution of low- & intermediate mass stars. Ryszard Szczerba N. Copernicus Astronomical Center Toruń, Poland NCAC TORUN OVERVIEW •1) Silicate carbon stars :IRAS/ISO/Spitzer •2) Crystalline silicates in C-rich planetary nebulae :ISO/Spitzer •3) Fullerenes in H-rich environment :Spitzer •4) Water in envelopes of C-rich stars :Herschel • Concluding remarks Introduction 3 (F.Herwig, 2005 – Mi = 2 Mo, Z=0.02) 4 NCAC TORUN -because of mass loss (for star of given parameteres we still cannot predict what will be mass loss rate on AGB) NCAC TORUN -bacause of unknown nebula shaping mechanism(s) Planetary nebulae • SBS 1998: Gagik Tovmassian SOLE – Star Obvious Low-level Elonated (Siódmiak et al 2008) RL – Richardson-Lucy deconvolution algorithm Post-AGB objects DUPLEX – DUst Prominent Longitudinally EXtended (Siódmiak et al 2008) RL – Richardson-Lucy deconvolution algorithm NCAC TORUN -bacause we observe unexpected „chemistry” in stellar ejecta. NCAC TORUN A „standard” model Equillibrium chemical models predict that chemical processes depend on the ratio C/O: molecules: n(C)/n(O)>1 => CO, HCN, C2H2, ... n(O)/n(C)>1 => CO, SiO, H2O, ... dust: n(C)/n(O)>1 => C-based: AC, graphite, PAH, C60, ... n(O)/n(C)>1 => O-based, silicates (amorphous and crystalline) NCAC TORUN Therefore it was (and still is, in some cases) surprising to observe O-based dust (silicates) and O-rich molecules (like OH and H2O) from envelopes around C-stars. 1. Silicate carbon stars IRAS/ISO/Spitzer „normal” O- and C-rich stars & „silicate C-stars” 14 amorphous silicate features 9.7 mm Si-O stretching mode 18 mm O-Si-O bending mode ISO observations (Yamamura et al. 2000) 16 The proposed model of the V778 system (Yamamura+ 2000) 17 Only then high and low excitation water lines can be observed 22 GHz Merlin interferometer 19 MERLIN observations of H2O (Szczerba et al. 2006) 20 Disc model - Babkovskaia et al. (2006) 21 MERLIN vs. Tycho-2 (Szczerba et al. 2006) m cos( Dec ) ; m (8.2 2.3 ; 3.9 8.4) 22 MERLIN vs. Tycho-2 (Szczerba et al. 2006) m cos( Dec ) ; m (8.2 2.3 ; 3.9 8.4) 23 1. Silicate carbon stars: are binary systems! Warning! IRAS 04496-6958 Trams et al. (1999) IRAS 04496-6958 Speck et al. (2006) Warning! Question: why silicate C-stars are known in our Galaxy only? 2. Crystalline silicates in C-rich planetary nebulae (ISO/Spitzer) (probably due to NOT binary systems) (F.Herwig, 2005 – Mi = 2 Mo, Z=0.02) 31 NCAC TORUN Historical overwiev: „How PNe are formed” • Shklovsky (1956): ... immediate predecessors of the PNe may be red giants of high luminosity.... 32 NCAC TORUN Historical overwiev: „How PNe are formed” • Paczyński & Ziólkowski (1968): ... PNe may be formed due to dynamical instabilities in convective envelopes of supergiants when they have sufficiently large luminosity.... 33 NCAC TORUN Historical overwiev: „How PNe are formed” • Paczyński (1970): ... PNe are ionized envelopes of supergiants, which were lost during the double shell burning phase .... 34 Structure of AGB star in mass coordinate (F.Herwig) 35 NCAC TORUN Historical overwiev: „How PNe are formed” (Paczyński, 1970) 36 NCAC TORUN Historical overwiev: „How PNe are formed” (Iben, 1982) 37 NCAC TORUN Historical overwiev: „How PNe are formed” (Iben, 1982) 38 NCAC TORUN Carbon stars formation (Herwig 2005) PDCZ – Pulse Driven Convection Zone 39 (Piovan et al. 2003) MminDUP(Z) – from analysis of model atmospheres and callibration with C-star LF in LMC & SMC Torun, May 2009 40 [WR] PNe are emission-line stars, which are H-poor & C-rich Cohen et al. 1999 The detection by ISO of crystalline silicates marks begining of: ASTROCRYSTALOGRAPHY dust emission versus blackbody 42 Crystalline Amorphous O-Si-O O-Si-O (18 μm) Si-O Wavelength (μm) III OSSA, Toruń 2006 Si-O (9.7 μm) Wavelength (μm) Mg2+ SiO4 ISO: PAHs & Crystalline silicates in [WR] PNe - MIXED CHEMISTRY Waters et al. 1998 [WR] PNe are emission-line stars, which are H-poor & C-rich Waters et al. 1998 PAHs: aromatic rings + H Leger & Puget (1984) Allamandola et al. (1989) •C-H „stretch” @ 3.3 mm •C-C „stretch” @ 6.2 mm •C-C „stretch” @ 7.7 mm •C-H in-plane „bend” @ 8.6 mm •C-H out of plane „bend” @ 11.3 mm for mono H @ 12.0 mm for duo H @ 12.7 mm for trio H @ 13.6 mm for quartet H •aliphatic (chain-like) C-H „strech” @ 3.4 mm Inventory of mixed chemistry in [WR]PNe – after ISO Mixed chemistry seen only in 16 [WR] PNe About 100 PNe were observed Szczerba et al. 2001 Perea-Calderon et al. (2009) – observations of GB PNe with SST Gutenkunst et al. 2008: 5 O-rich dust 6 mixed chemistry ...No surprise: more [WC] PNe in the GB (Górny et al 2004) => more PNe with mixed chemistry ... Perea-Calderón et al. 2009: 5 O-rich dust 21 mixed chemistry 5 [WC] 3 VL 5 WELS 7 “none” 1 unknown Gutenkunst et al. 2008: 5 O-rich dust 6 mixed chemistry 1 [WC] 1 WELS Perea-Calderón et al. 2009: 2 “none” 2 unknown 5 O-rich dust 21 mixed chemistry 5 [WC] 3 VL 5 WELS 7 “none” 1 unknown 50 Perea-Calderón et al. 2009 Galactic Bulge • Is composed (mostly) of old stellar population (older than 10 Gyr) => low mass stars (~1.5 Mo) • Metallicity is (rather) larger than (or comparable to) the solar metallicity • In such environment (i.e. low stellar mass & large metallicity) theory predicts: no efficient dredge-up (of carbon) to the stellar surface during AGB (no production of C-stars) (Piovan et al. 2003) Torun, May 2009 52 NCAC TORUN SOLUTION • There is no C-stars toward GB • crystalline silicates are seen only in OH/IR stars from GB • Close binary companions are known for only 10-20% of GB PNe •Galactic Bulge PNe are formed simultaneously with mixing of C-rich material to the surface at the end of AGB evolution from OH/IR stars: THE FATAL THERMAL PULSE! which not always mixed Hydrogen out! Gutenkunst et al. 2008: 5 O-rich dust 6 mixed chemistry 1 [WC] 1 WELS Perea-Calderón et al. 2009: 2 “none” 2 unknown 5 O-rich dust 21 mixed chemistry 5 [WC] 3 VL 5 WELS 7 “none” 1 unknown Guzman-Ramirez+ 2015 Other properties of GB PNe Gorny et al. 2010 59 AMORPHOUS SILICATES & CRYSTALLINE SILICATES & PAH’s (mixed chemistry) AMORPHOUS SILICATES weak CRYSTALLINE SILICATES, BUT ... NO PAH’s 61 * Spitzer allowed IR investigation of PNe from the GB. * Most of the observed GBPNe show mixed chemistry and (almost?) all show crystalline silicates, while there are no Cstars in the GB and „normal”AGB stars do not show crystalline silicates. •Thus, we may expect violent „end of AGB evolution in OH/IR stars” due to the last thermal pulse which (can) mixe carbon to the surface. * Mass & metallicity play an important role in formation of PNe 62 3. Fullerenes in H-rich environment (Spitzer) C60 - „Buckyballs” or „Fullernes” – were found in PNe and ISM Jul./Sep.:Cami et.al. (2010, Sci. 329, 180) Jun./Oct.:Sellgren et al. (2010, ApJLet. 722, L54) Oct./Nov.:Garcia-Hernandez et al. (2010, ApJLet. 724, L39) C60: 20 - hexagons & 12 pentagons: H-poor Allotropes of carbon. ubiquitous PNe/ISM PNe/ISM P Ehrenfreund, B H Foing Science 2010;329:1159-1160 Published by AAAS meteorites laboratory CSE/ISM meteorites Perea-Calderon et al. (2009) – observations of GB PNe with SST - On June 1st, 2010, Kris Seelgren gave a talk: 16:00-16:25 Confirmation of C60 in the Reflection Nebula NGC 7023 -On June 14-18, 2010 I have visited ESAC to discuss progress made on „hidden post-AGB evolution” - I met there Anibal Garcia-Hernandez, who was a post-doc of David Lambert and worked with him on search of fullerenes in environments where they should be, i.e. in H-poor R CrB stars - When, I demonstrated him our IDL code for continua subtraction, I used as an example spectrum of Tc1 .... SFB 956 Colloquium, 16 Jan. 2012 - Show me the short-wavelength range, please!!! SFB 956 Colloquium, 16 Jan. 2012 WOOOW …. We have found fullerenes!!! Peeters et al. (2004) „PAHs in the 15-21 micron region” S106 - HII region, ISO CD-42 11721 – YSO, ISO NGC 7023 – RN, SST !!! LKHa 234 – YSO SFB 956 Colloquium, 16 Jan. 2012 S106 - HII region, ISO CD-42 11721 – YSO, ISO NGC 7023 – not modeled! Peeters et al. (2004) „PAHs in the 15-21 micron region” Plans in June 2010 • Letizia Stanghellini observed about 160 Galactic (mostly disk) PNe & 40 in SMC/LMC: she was also at that time in ESAC • 3 additional PNe in her samples showed signatures of C60 – 2 from MW and 1 from SMC • We have decided to prepare paper to Science or Nature ....... after summer holidays But .... Cami et al. 2010, Science 329, 1180 (Jul/Sep) : Tc 1 – must be H-poor (fatal thermal pulse), so fullerenes can form. SFB 956 Colloquium, 16 Jan. 2012 Sellgren et al. 2010, ApJL 722, L54 (Oct) : fullerenes in RNe Garcia-Hernandez et al. (2010, ApJLet 724, L39) (Nov) „Formation of fullerenes in H-containing PNe” Garcia-Hernandez et al. (2010, ApJLet 724, L39) (Nov) „Formation of fullerenes in H-containing PNe” 3 PNe show PAHs – C & H containing molecules and fullerenes All stars show Hydrogen in their optical spectra!!! SFB 956 Colloquium, 16 Jan. 2012 Scott, Duley & Pinho (1997) ABSTRACT: The gaseous products evolved from solid hydrogenated amorphous carbon (HAC) under UV irradiation have been sampled using time of flight (TOF) mass spectrometry. A notable feature is the appearance of … fullerenes such as C50 , C60 , and C70 . There is also evidence in these mass spectra for the ejection of small dehydrogenated polycyclic aromatic hydrocarbon (PAH) molecules….., which ….show absorption and emission features at 3.3, 3.4, and 6.2 mm and other wavelengths characteristic of PAH molecules. These experiment show that the decomposition of HAC in circumstellar or interstellar shocks may be a source of large PAH and fullerene molecules! Vibrational modes of C60 18.9 mm vibr. mode SFB 956 Colloquium, 16 Jan. 2012 17.4 mm vibr. mode SFB 956 Colloquium, 16 Jan. 2012 8.5 mm vibr. mode SFB 956 Colloquium, 16 Jan. 2012 7.0 mm vibr. mode SFB 956 Colloquium, 16 Jan. 2012 Some facts 1970: C60 was predicted by E. Osawa 1985: C60 and other fullerenes were created in laboratory by H. Kroto, R. Curl, & R. Smalley (Nobel Prize in chemistry – 1996) Named after Richard Buckminster Fuller – a noted architect of geodesic domes (seen from lab in Dallas): „Buckyballs”, „Buckminsterfullerenes”, „Fullerenes” Some facts 1991: Donald Huffman & Wolfgang Krätschmer showed easy way to form fullerenes: Burning of graphite in H-poor (He-rich) environment Nice article – interview of Donald Huffman http://azstarnet.com/news/science/article_57d08830-a127-5bbb-b57ef4262017e887.html Interview of Huffman Now, 25 years after the discovery, Huffman is excited that astronomers using the Spitzer Space Telescope have found evidence for the complex carbon molecule in near and distant galaxies. The discoveries in space and the award of the Nobel Prize in physics this year for another carbon form, graphene, made the subject much more topical, he said. Huffman said it's enough to send him back to the lab with some new ideas 10 years after his retirement from the University of Arizona. 88 Some facts 1992: C60 found on Earth in shungite mineral (Buseck et al.) 2003: C60 in meteorites (Harris et al.) 2009: possible C60+ in ISM (Misawa et al.) 2010: ... 4.Water in envelopes of C-rich stars (Herschel) Water is an axisymmetric rotator: something in-between: oblate top (disc-like) and prolate top (cigar-like) NCAC TORUN Equillibrium chemical models predict that almost no water is formed in C-rich stars: n(C)/n(O)>1 => CO, HCN, C2H2, ... n(O)/n(C)>1 => CO, H2O, ... 2001: Water (ortho-ground level transition @ 557 GHz) was detected in C-rich star: IRC+10216 by SWAS – Melnick et al. (2001, Nature, 412, 160) Estimated amount of water relative to H2 was 424 x 10-7 Only then high and low excitation water lines can be observed 557 GHz NCAC TORUN Different models predict different water location: Inner envelope shocks -> water present close to the star Kuiper belt vaporization -> no water within ~100 AU Fischer-Tropsch catalysis -> no water within ~100 AU Outer envelope chemistry -> no water within 1000 AU. Water vapour is present in another C-rich star: V Cyg HIFI – broken on Aug rd 3 , 2009 HIFI – replaced by the redundant one on Jan 15, 2010 Water vapour is seen in (almost) ALL observed C-rich stars! ortho- para- ortho- para- Rotational transitions of water from C-rich star: IRC+10 216 7 transitions 3 transitions IRC+10216 transitions with E/k < 160 K Models of water rotational transitions (IRC+10 216) Water in C-rich stars: the 1st Herschel paper in Nature – Leen Decin et al. (2010, 467, 2nd September) Blue - PACS 160 mm. Green – SPIRE 250 mm. Red – SPIRE 350 mm. IRC+10 216 – clumpy envelope of dust Only then high and low excitation water lines can be observed Only then high and low excitation water lines can be observed