Li Be B Si O Fe Dy Ce Ru Y Pb C a Ti L V b Y Eu Al N Pr d Sr Mo Ba P Ca K Cr S N Sm Gd U Ag Pd Mg Ni Galac%c Archaeology @ Unprecedented Precision (0.01 dex) @DrJorgeMelendez Dep. Astronomia, Univ. São Paulo
- Is the observed star-to-star abundance scaver just due to errors in the analyses? - Can we find evidences of real cosmic scaver? What are the causes? - Analyses based on small samples (>=2) #SolarTwins #Binaries #OpenClusters #GlobularClusters #MetalPoorStars
Thick disk Star-to-star scatter due to errors or true cosmic scatter? Thin disk 714 stars Bensby et al. 2014
Chemical homogeneity in open clusters: 0.03 dex Bovy 2016 Ness et al. 2017
Reaching a 0.01 dex precision using stellar twins (T eff ±100K) Very high S/N (> 400) High spectral resolu%on (R > 50 000) Careful selec%on of lines Strictly differen-al approach using stars similar between them ( stellar twins ): - precise rela-ve efec-ve temperartures - line-by-line cancel errors in gf-values - weak dependence on model atmospheres
Differen%al abundances A X (element X) log (W/λ) = cte + A X + log (g f ) + log λ - θ χ exc - log k cont,λ Precise differential EW measurements are key to precise differential abundances Bedell, Meléndez, Bean et al. 2014
Solar Twins: Defined Solar type stars late F, G, early K Solar analogs about G2V and factor of 2 in chemical composi%on Solar twins very rare stars with similar T eff (within 100 K), gravity & composi%on (0.1 dex) to the Sun's values Implies: [Fe/H] = 0.0±0.1, mass = 1.00±0.05 M & ages = 0 10 Gyr
Experiment on precision abundances using solar twins - Magellan 6.5m Telescope & Mike spectrometer - R = 65,000 - S/N = 450 per pixel - coverage 340 1000 nm - Solar spectrum: Vesta - 3 nights of observa%ons Observa-ons of the solar twin 18 Sco BLUE frame RED frame
Example of Magellan spectra of 11 solar twins and the Sun (total spectral coverage 3350 A -1µm) Small part (597-603nm) of solar twin & Sun s spectra Meléndez, Asplund, Gustafsson, Yong 2009
[Cr/Fe] distribu%on in 11 solar twins Star-to-star scaver of only 0.009 dex
Δ abundance: Sun - <twins> vs. atomic number Z Sun typical: Δ = 0 Sun weird: Δ 0 Our solar system is not host by a typical Sun Meléndez et al. 200 Meléndez, Asplund, Gustafsson, Yong 2009
Sun s anomalies are strongly correlated to the dust condensa%on temperature of the elements! Correla%on is highly significant. Probability ~10-9 to happen by chance Volatile elements ~ 0.08 dex ~ 20% Dust condensation temperature (K) Meléndez, Asplund, Gustafsson, Yong 2009
Meléndez et al. 2009 The missing refractories were used to form dust, planetesimals & terrestrial planets The late accreted gas in the convec%on zone was deficient in refractories
Planet effects in binary system with twins 16 Cyg: widely separated pair of solar analogs 16 Cyg A : no planets 16 Cyg B : giant planet (~ 2 M J )
Signatures of giant planet forma%on: 16 Cyg binary 16 Cyg A: no planet B: hosts a giant planet
Another binary system: XO-2 Both components host planets 0.6 M J >0.3 M J + > 1.4 M J Ramírez et al. 2015. See also Teske et al. 2015; Biazzo et al. 2015
Binary pair ζ Ret with debris disk in one component (ζ 2 ) Saffe et al. (2016) Trend with T cond confirmed by Adibekyan et al. 2016
Teske et al. 2016
Chemical inhomogeneity in open clusters: solar twins in M67 Liu et al. 2016
Solar twins in M67 are chemically inhomogeneous Two solar twins in M67 differ in ~0.05±0.01 dex Liu et al. 2016
Galac%c chemical evolufon: precise stellar ages can be obtained using solar twins We can study [X/Fe] vs. age rather than only [X/Fe] vs. [Fe/H]
Solar twin HIP 56948 σ (LTE) = 0.0096 dex σ (NLTE) = 0.0093 dex
Differen%al method is also useful to obtain high precision stellar parameters (Δ Teff 10 K, Δ log g 0.02 dex) à good stellar masses and ages
Diverse abundance signatures unveiled in the solar twin 18 Sco a solar twin younger than the Sun and rich in refractories, s-process and r-process elements Using UV spectra obtained at the VLT / ESO
18 Sco (brightest solar twin, V = 5.5) UVES+VLT R = 110 000 (red) R = 65 000 (blue) Rich in silver and other n-capture elements Rich in refractory elements Age = 2.9 Gyr Meléndez et al. 2014, ApJ 791, 14 August 10, 2014
18 Sco (brightest solar twin, V = 5.5) UVES+VLT R = 110 000 S/N = 800 Subtrac%ng T cond trend Sr observations Ru Mo Y Zr Pd Ag Ba Eu Sm Nd La Ce Pr Gd Dy Yb AGB model (Amanda Karakas) Meléndez et al. 2014, ApJ
Perfect agreement between residual abundances and predic%ons from the SS r-process frac%ons Meléndez et al. 2014, ApJ
Abundance ra%os as a func%on of age
Spina et al. 2016
Spina et al. (2016): chemical clocks
Tucci-Maia et al. 2016 [Y/Mg] can also tell us about mass transfer in binaries
Schirbel et al. 2015
Schirbel et al. 2015 Dust from AGB star?
Schirbel et al. 2015 Signatures of former AGB star
Peculiar solar twin Condensa%on temperature of the elements Meléndez et al. 2017, in prep. Why the scaver is so high?
Enhanced odd-even effect detected in a solar twin using precise (0.01 dex) abundances, likely due to a peculiar supernova Solar twin - Sun C O Mg Na Al Si S Z Ca Sc Ti V Cr Fe Ni Mn Co Cu Zn Meléndez et al. 2017, in prep. <odd - even> ~ 0.035 dex
Cosmic scaver in metal-poor stars? Cayrel et al. 2004 True scaver (0.15 dex)?
High precision in very metal-poor stars requires high S/N G 64-12, G64-37: Extremely metal-poor twins 6463 K, 6570 K; log g = 4.26, 4.40, [Fe/H] = -3.2, -3.0 HIRES @ Keck, R ~ 95 000, S/N ~ 700
Distinct abundances in twins G64-12 & G64-37 EMP stars [Fe/H] < -3 Reggiani et al. 2016
High Precision in Metal-Poor Stars SAGA, T eff = 6250±250K, log g = 4.0±0.5 dex UVES@VLT R ~ 50 000 S/N ~ 200 Abundance error = 0.06 dex Star-to-scatter = 0.06 dex Reggiani et al. 2017, to be submived
High Precision in Metal-Poor Stars UVES@VLT R ~ 50 000 S/N ~ 200 Abundance error = 0.05 dex Star-to-scatter = 0.05 dex Reggiani et al. 2017, to be submived
High precision in metal-rich halo stars
UVES@VLT FIES@NOT R ~ 50 000 S/N ~ 200-500 Nissen & Schuster 2010
Field stars born in a globular cluster
Differen%al techniques applied to cool metalpoor giants in cluster NGC 6752 ([Fe/H] = -1.6) Yong, D., Meléndez, J., Grundahl, F., et al. 2013
Differen%al techniques applied to cool metalpoor giants in NGC 6752 [Fe/H] = -1.6 At high precision (0.01-0.02 dex) all elements show abundance variafons Yong, D., Meléndez, J., Grundahl, F., et al. 2013
Conclusions - Precision Spectroscopy of solar (& stellar) twins is a powerful tool for Galac%c archaeology - A precision of about 0.01 dex may be needed to disentangle effects of planets and nucleosynthe%c signatures of SN + AGB stars