sara lucatello
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Sara LucatelloSara Lucatello
Extremely metal poor CH stars:Extremely metal poor CH stars:
a window on the first generationa window on the first generation
of intermediate mass starsof intermediate mass stars
INAF-Osservatorio Astronomico di PadovaDipartimento di Astronomia, Università di Padova
Bologna, June 13th 2003 2
TeamTeam
Timothy Beers - Michigan State UniversityTimothy Beers - Michigan State UniversityEugenio Carretta - Osservatorio Astronomico di PadovaEugenio Carretta - Osservatorio Astronomico di PadovaNorbert Chriestlieb – Hamburger SternewarteNorbert Chriestlieb – Hamburger SternewarteJudith Cohen – California Institute of TechnologyJudith Cohen – California Institute of TechnologyRaffaele Gratton - Osservatorio Astronomico di PadovaRaffaele Gratton - Osservatorio Astronomico di PadovaJennifer Johnson – DAOJennifer Johnson – DAOSolange Ramirez - California Institute of TechnologySolange Ramirez - California Institute of Technology
Bologna, June 13th 2003 3
Metal poor CH starsMetal poor CH stars
IIIs-process elementsrich
Three kinds of CH stars?Three kinds of CH stars?
IIr-process elementsrich
INormal n-captureelements
Surveys of metal-deficient stars find a large number of stars with strong CH bands
Explanation analogous to classical CH starsExplanation analogous to classical CH stars
Bologna, June 13th 2003 5
What can we learn from What can we learn from CEMP?CEMP?
Constraints on nucleosynthesis at low Z
Constraints on the IMF
Bologna, June 13th 2003 6
Constraints on the IMFConstraints on the IMF
Surveys find ~30% CEMP at [Fe/H]<-2.5 dex
~30% IMS
Almost flat IMF at low Z?
CNO and ¹²C/¹³C
Binary fraction ~60%
~50% of CH stars s-process binaries
IMF works forBa and classicalCH stars!
•
Bologna, June 13th 2003 8
NucleosynthesisNucleosynthesis
s and r-process at low Z
Early galactic chemical evolution
Measuring C and N abundanceMeasuring C and N abundance Broadened linesBroadened lines
[C/Fe]=2.6[C/Fe]=2.6±0.1dex±0.1dex
[N/Fe]=2.1±0.1dex[N/Fe]=2.1±0.1dex
Bologna, June 13th 2003 18
Radial velocity curveRadial velocity curve
Hires & Uves dataHires & Uves dataPalomar DataPalomar Data
Orbital ParametersOrbital ParametersP=(3.413P=(3.413±0.001)d±0.001)dTo(MJD)=(52066.921±0.006)d To(MJD)=(52066.921±0.006)d G=(-178.7±0.5) km/sG=(-178.7±0.5) km/sK=(52.0±0.6) km/sK=(52.0±0.6) km/see=0=0aasinsinii=(2.442±0.029)10e6 km=(2.442±0.029)10e6 kmf(m)=(0.0498±0.002) Mf(m)=(0.0498±0.002) Msunsun
Bologna, June 13th 2003 19
Rotational velocityRotational velocity
vsinvsini=i=(9.7(9.7±1.5) km/s measured from our spectra±1.5) km/s measured from our spectra
From orbital parameters + few assumptions expected synchrone velocity:
Vsinisyn=<(13.5±3.9)km/s
Compatible!!Compatible!!
Bologna, June 13th 2003 21
What do we infer from this What do we infer from this information?information?
P<<PP<<Pchch~100d~100d
Circular orbit Circular orbit
Synchrone orbitSynchrone orbit
Common envelopephase
Bologna, June 13th 2003 23
s s and and rr process elements process elements
[Ba/Fe]=1.4±0.2
[Eu/Fe]<1.1 dex
If Ba r-process:
[Eu/Fe]=2.2
[Pb/Fe]=3.3[Pb/Fe]=3.3±0.2 dex±0.2 dex
Bologna, June 13th 2003 27
Abundances summary
Teff=6625Klog(g)=4.3 [Fe/H]=-2.7 vt=1.4 km/s
[Fe/H] -2.70 0.10 32 a[C/Fe] 2.6 0.1 syn[N/Fe] 2.1 0.1 syn[O/Fe] 0.4 1 a[Mg/Fe] 0.7 0.1 3 a[Al/Fe] 0.3 .. 1 a[Si/Fe] 0.3 .. 1 a[Ca/Fe] 0.6 0.2 3 a[ScII/Fe] 0.4 0.1 3 a[Ti/Fe] 0.36 0.05 14 a[Cr/Fe] -0.5 0.2 2 a[Mn/Fe] -0.2 0.1 2 a[SrII/Fe] 0.3 0.2 2 a[BaII/Fe] 1.4 0.2 3 a[EuII/Fe] <1.1 syn[Pb/Fe] 3.3 0.1 syn
C/O 100 syn
N/O 8 syn
¹²C/¹³C 6 1 syn
Bologna, June 13th 2003 28
Is theory able to explain these values?Is theory able to explain these values?A preliminary model Gallino et al. (private communication)
Dilution factor 10
Standard pocketM(¹³C)=4 10e-6 Msun
at top of He intershell
Model for [Fe/H]=-2.6
M=1.5Msun
Mass of the evolved companion
Existing sampleExisting sample
10 stars 10 stars
Vr variablesVr variables
Vr constantVr constant
No info on VrNo info on Vr
UpdatedUpdated
Bologna, June 13th 2003 31
ConclusionsConclusions
Sample too limited to draw conclusions
Abundance analysis and radial velocity infos Abundance analysis and radial velocity infos are both crucial are both crucial
This object is clearly a case of s-process rich, binary This object is clearly a case of s-process rich, binary star: enrichment through mass transfer from an star: enrichment through mass transfer from an
AGB companionAGB companion
Bologna, June 13th 2003 32
Work in progressWork in progress
7 UVES spectra
5 Keck spectra
4 TNG spectra
Abundance analysis Vrad monitoring
2-4 spectra for ~30 objects
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