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

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What can we learn from What can we learn from CEMP?CEMP?

Constraints on nucleosynthesis at low Z

Constraints on the IMF

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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!

•

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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

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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

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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!!

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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

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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

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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

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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

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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

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Work in progressWork in progress

7 UVES spectra

5 Keck spectra

4 TNG spectra

Abundance analysis Vrad monitoring

2-4 spectra for ~30 objects