Transcript MIXED CHEMISTRY

„Mixed chemistry” phenomena
during late stages of stellar evolution
of low- & intermediate mass stars.
Ryszard Szczerba
N. Copernicus Astronomical Center
Toruń, Poland
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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
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(F.Herwig, 2005 – Mi = 2 Mo, Z=0.02)
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-because of mass loss (for star of given
parameteres we still cannot predict what
will be mass loss rate on AGB)
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-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
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-bacause we observe unexpected
„chemistry” in stellar ejecta.
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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)
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 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”
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amorphous silicate features
9.7 mm Si-O
stretching mode
18 mm O-Si-O
bending mode
ISO observations (Yamamura et al. 2000)
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The proposed model of the V778 system (Yamamura+ 2000)
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Only then high and low excitation water lines can be observed
22 GHz
Merlin interferometer
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MERLIN observations of H2O (Szczerba et al. 2006)
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Disc model - Babkovskaia et al. (2006)
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MERLIN vs. Tycho-2 (Szczerba et al. 2006)
m  cos( Dec ) ; m  
(8.2  2.3 ;  3.9  8.4)
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MERLIN vs. Tycho-2 (Szczerba et al. 2006)
m  cos( Dec ) ; m  
(8.2  2.3 ;  3.9  8.4)
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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)
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Historical overwiev: „How PNe are formed”
• Shklovsky (1956): ... immediate predecessors of
the PNe may be red giants of high luminosity....
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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....
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Historical overwiev: „How PNe are formed”
• Paczyński (1970): ... PNe are ionized envelopes of
supergiants, which were lost during the double shell
burning phase ....
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Structure of AGB star in mass coordinate
(F.Herwig)
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Historical overwiev: „How PNe are formed”
(Paczyński, 1970)
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Historical overwiev: „How PNe are formed”
(Iben, 1982)
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Historical overwiev: „How PNe are formed”
(Iben, 1982)
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Carbon stars formation
(Herwig
2005)
PDCZ –
Pulse
Driven
Convection
Zone
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(Piovan et al. 2003)
MminDUP(Z) – from
analysis of model
atmospheres and
callibration with C-star LF
in LMC & SMC
Torun, May 2009
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[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
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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
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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)
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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
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AMORPHOUS SILICATES & CRYSTALLINE SILICATES & PAH’s (mixed chemistry)
AMORPHOUS SILICATES weak CRYSTALLINE SILICATES, BUT ... NO PAH’s
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* 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
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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.
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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)
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 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
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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