Tc trends and terrestrial planet formation The case of Zeta Reticuli

Transcription

1 Tc trends and terrestrial planet formation The case of Zeta Reticuli Vardan Adibekyan Institute of Astrophysics and Space Sciences E. Delgado-Mena, P. Figueira, S.G. Sousa, N.C. Santos, J.P. Faria, J.I. González Hernández, G. Israelian, G. Harutyunyan, L. Suárez-Andrés, A.A. Hakobyan

2 Planet occurrence Planets and metallicity Metallicity

3 Why are giant planet hosts metal-rich? Self enrichment (Gonzalez 1997) Primordial cloud (Santos et al 2001) (This is the commonly accepted scenario)

4 Self enrichment and the abundance trends with condensation temperature The Sun, and other giant-planet hosts accreted H- and He-poor material during planet formation (Gonzalez 1997). If some fractionation in the disk occurred, then an abundance trend with Tc is expected (Gonzalez 1997). Gonzalez 1997

5 Abundance trends with condensation temperature. Observations Melendez et al 2009 Anomalous volatile-to-refractory ratio of the Sun when compared to solar twins. Refractories remained in rocky planets (Ramirez et al 2009,2010).

6 Tc-trend and terrestrial planet formation Chambers 2010 If the Tc-trend is only due to rocky-planet formation, then the Tc-slope can be used to detect and characterize terrestrial planets.

7 Abundance trends with condensation temperature. Observations Gonzalez Hernandez et al 2013 No clear evidence of relation between volatile-to-refractory abundance ratio and presence of rocky planets (Gonzalez Hernandez et al 2010,2013).

8 Tc-trend: Possible explanations. Galactic chemical evolution Adibekyan et al 2014 Tc slope strongly correlates with the stellar age! Older stars show lower refractory-to-volatile ratio independently of the presence of planets.

9 Tc-trend: Possible explanations. Environmental effect Onehag et al 2014 The Sun was formed in a dense stellar environment! The gas of the proto-cluster was depleted by formation and cleansing of dust before the stars formed.

10 Abundance trends with condensation temperature. Observations: binary stars XO-2S/N Biazzo et al 2015 signature of the ingestion of material (several tens of M ) by XO-2N or depletion in XO-2S due to locking of heavy elements by the planetary companions HAT-P-1a/b Liu et al 2014 This is in line with the expectation that the presence of close-in giant planets preventing the formation or survival of terrestrial planets Contradictory results Liu et al 2014; Saffe et al 2015; Mack et al 2016; Biazzo et al 2015; Teske et al 2015, 2016; Ramırez et al 2015; Tucci Maia et al. 2014

11 Tc-trend: Possible explanations. Gas-dust segregation The trend with condensation temperature mirrors the pattern of depletion of elements in ISM gas. There is evidence (also theoretical predictions) for dust-gas segregation in the ISM. The dust-gas segregation will induce a variation in element abundances which will show correlation with the Tc. Gaidos 2015

12 Tc-trend: Possible explanations Terrestrial planet formation Galactic chemical evolution Large-scale environmental effect Gas-to-dust segregation in the protoplanetary disk 'Spectroscopic analysis' effect

13 Tc-trend: Possible explanations Terrestrial planet formation Galactic chemical evolution Large-scale environmental effect Gas-to-dust segregation in the protoplanetary disk 'Spectroscopic analysis' effect About these and more you can hear on Thursday at our splinter session Sun-like Stars Unlike the Sun

14 The case of Zeta Reticuli system

15 THE ZETA RETICULI INCIDENT HOME SYSTEM OF THE GREYS

16 THE ZETA RETICULI INCIDENT HOME SYSTEM OF THE GREYS

17 The Zeta Reticuli system Zet1 Ret Teff = 5720 ± 13 K Logg = 4.52 ± 0.03 dex [Fe/H] = ± dex Zet2 Ret Teff = 5833 ± 15 K Logg = 4.48 ± 0.03 dex [Fe/H] = ± dex Hosts a debris disk

18 The Zeta Reticuli system: Saffe et al HARPS spectra observed during the same night: S/N ~ 250 Following Chambers (2010) : Mrock 3 M depleted material Saffe et al 2016

19 The Zeta Reticuli system with higher-quality data Combined HARPS spectra S/N ~ 1300 (Zet1 Ret) S/N ~ 3000 (Zet2 Ret) Adibekyan et al 2016

20 The Zeta Reticuli system with careful spectroscopic analysis σ(2 lines) usually σ(real) Use [X/H] instead of [X/Fe] if possible Fe abundance is not free of errors!

21 Tc-trend in Zeta Reticuli Adibekyan et al 2016

22 Does the trend have an astrophysical origin? An extra test Three individual spectra for each star with S/N ~

23 Tc-trend from individual spectra: WLS Adibekyan et al 2016

24 Tc-trend from individual spectra: OLS Adibekyan et al 2016

25 The Zeta Reticuli system Is the Tc-trend has an astrophysical origin? A clear Tc-trend in the system with still unclear origin

26 Conclusions There are several phenomena, both of astrophysical and non-astrophysical origin, that can produce a trend with condensation temperature. Should be very careful with interpretations when dealing with extremely high-precision spectroscopy. Thank you!