Spectroscopic Survey of Solar Twins

The planet – stellar chemical composition connection

Jorge Meléndez Departamento de Astronomia IAG - Univ. São Paulo Ivan Ramirez (Austin), J. Bean (Chicago), P. Baumann, M. Bergemann, K. Lind (MPA), B. Gustafsson (Uppsala), D. Yong, A. Karakas, M. Asplund, A. Alves Brito (Stromlo), T. Monroe, M. Tucci Maia (IAG/USP), M. Castro, J.D. do Nascimento (UFRN) Outline

• Metallicity – giant planet connection • Lithium: is there a link to planets ? • Signatures of terrestrial planets • Signatures of giant planets • Solar twin planet survey with HARPS at ESO

Sunset in Paracas, Peru (c) www.flickr.com/photos/rodrigocampos/ Metallicity – giant planet connection Metallicity – giant planet connection Stars with Comparison giant planets sample Metallicity – giant planet connection

1040 FGK-type stars

metallicity Lithium: is there a planet connection?

Orgueil meteorite CI carbonaceous chondrite • Li is severely depleted in the Sun • The Sun is a planet host ... • Is the solar Li abundance typical of other Suns ?

0 1 2 3 4 5

Meléndez et al. 2010 Ap&SS 328, 193 Lithium: is there a planet connection? Is the Sun peculiar in Li? Sun vs. Stars with Planets (SWP) and without Planets ʘ Gonzalez et al (2010): Sun has a Li abundance 0.7 dex lower than 50 comparison stars Lithium: is there a planet connection? Open cluster with solar age (~ 4 Gyr) and slightly higher [Fe/H] = +0.03 Solar twins in M67 (Pasquini et al. 2008)

Randich et al. 2006, Pace et al. 2008)

Sun seems normal in Li with respect to solar twins in M67. Using solar twins to learn more on the solar Li abundance and Li-depletion High resolution (R=65,000) high S/N (200-450) spectra

McDonald 2.7m

Magellan 6.5m

- Meléndez et al. 2010, Ap&SS, 328, 193

- Baumann, Ramirez, Melendez, Asplund & Lind 2010, A&A, 519, A87 Lithium in solar twins (Meléndez et al. 2010 Ap&SS 328, 193)

The solar Li is “normal” for a 1-solar- mass of solar metallicity at 4.6 Gyr Yonsei-Yale isochrones Solar twins in Coma Benerices open Hyades NGC762 cluster and field stars M67 The solar Li is normal for a 1-solar-mass star at 4.6 Gyr

(Meléndez et al. 2010 Ap&SS 328, 193) Non- standard solar models roughly fit data Montalban & Schatzmann: mixing by internal waves Xiong & Deng: Convective overshooting + gravitational settling Do Nascimento et al: Difussion + grav settling + rotation-induced mixing (Meléndez et al. 2010 Ap&SS 328, 193)

Conclusion: the Sun has a normal Li abundance (for a solar-metallicity solar- age one-solar-mass star)

What about lithium in stars with giant planets ? Planet hosts Comparison Planet-host stars around

solar Teff seem depleted in Li You cannot compare apples and oranges ...

comparer des pommes avec des oranges comparer des pommes et des poires comparar peras con manzanas

You cannot add pears and apples … No puedes sumar peras con manzanas

Comparing Luminosity apples & apples Li depletion is not enhanced in planet hosts ! Comparing apples & apples (only stars with similar stellar parameters within 2-sigma) Planet hosts Comparison

Baumann, Ramírez, Meléndez, & Asplund 2010, A&A, 519, A87 Li depletion is not enhanced in planet hosts ! Apples & oranges Israelian et al. 2009, Nature

Planet hosts Comparison Apples & apples Baumann, Ramírez, Meléndez, & Asplund 2010, A&A, 519, A87 Conclusion on lithium: there is no difference in Li abundance between stars with and without planets

Li-7 : no planet connection The Sun has a normal Li abundance, but what about other chemical elements ?

Are the solar abundances typical of other Suns ? Magellan ultra high Observations of the solar twin 18 Sco precision study of solar twins - Magellan 6.5m Clay Telescope & Mike spectrometer - R = 65,000 - S/N = 450 per pixel - coverage 340 – 1000 nm - Solar spectrum: Vesta - 3 nights of observations

BLUE frame RED frame Example of Magellan spectra (total spectral coverage 3400 A -1um)

Small part (597-603nm) of solar twin & Sun’s spectra Meléndez et al. 2009, ApJ, 704, L66 Δ abundance: Sun - 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. 2009 Sun’s anomalies are strongly correlated to dust condensation temperature of the elements! Correlation is highly significant ~ 0.08 dex ~ 20% probability ~10-9 to happen by chance

It’s most likely to win Dust condensation temperature (K) the lottery Meléndez et al. 2009 Condensation in the solar nebula

Mercury

Venus

Condensation

The late accreted gas in the

convection zone Meléndez 2009 et al. Meléndez was deficient in refractories The missing refractories were used to form dust, planetesimals & terrestrial planets Relation with terrestrial planet formation:

Tcond trend in meteorites Alexander et al. (2001)

The abundance pattern seen in meteorites is a mirror-image of the Sun’s chemical composition Relation with terrestrial planet formation: Amount of dust removed from the Sun is enough to form terrestrial planets

How much dust-cleansed gas is required to affect the Sun in this way?

Assume gas accretion until solar convection zone reached

~ present size (~0.02 Msun):

Refractories depleted in the 28 Sun: ~2*10 g ≈ 4 M

Refractories locked-up in terrestrial planets: 27 ~8*10 g ≈ 1.3 M

SUN

Earth-like material SUN

Meteorite-like material SUN

Earth-like material

Meteorite-like material Are there other solutions besides rocky planets? Could it be a problem in the abundance analysis ?

Is the effect confirmed by other samples ?

Can you really get this unprecedented precision ?

Any problems with the asteroids used ?

Could it be just pollution by a supernova or AGB ?

Perhaps it is just galactic chemical evolution ?

What about random line-of-sight effects ?

Could it be an age effect?

No matter what, I don’t believe it Results are almost independent of adopted model atmospheres As the stars are solar twins, the results do not depend much on the adopted models.

Effect of using different sets of models is only ~0,001 dex

Meléndez et al. 2012, A&A, 543, A29 Yes, the abundance trend is real The abundance signature is also seen in other samples and using different instruments and different asteroids

Our Sun is indeed anomalous in its chemical makeup Meléndez et al. 2012, A&A, 543, A29 High precision (0,005 dex) is possible !

Analysis of solar spectra using two different asteroids shows that it is possible to achieve a precision of about 0,005 dex !

Meléndez et al. 2012, A&A, 543, A29 Asteroids are suitable for high precision high resolution spectroscopy Comparison of asteroids of different spectral types shows no meaningful trend with condensation temperature

Juno

Ceres

Chapman, Morrison & Zellner (1975) Meléndez et al. 2012, A&A, 543, A29 There is no line-of-sight (inclination) effect

There are no changes in the abundances obtained at different latitudes in the Sun for both volatile (to within 0.005 dex) and refractory (to within 0.002 dex) elements. Pollution by AGB stars, supernova type II, supernova type Ia, or hypernova, are not responsible for the abundance signature

Meléndez et al. 2012, A&A, 543, A29 Also, the abundance signature cannot be explained by age by galactic chemical evolution effects

The most likely explanation for the abundance signature seems to be the formation of terrestrial planets HIP 56948 : the most ScienceNews, 30/8/2012, Star's missing elements could signal lurking likely candidate for small planets: solar chemistry suggests best places to hunt. hosting other Earths ? Meléndez et al. 2012 Rádio USP - Revista FAPESP, 6/7/2012, Um outro Sol.

Revista FAPESP, 6/2012, Um segundo sol.

Veja, 4/5/2012, Astrônomo da USP revela estrela 'gêmea' do Sol.

Discovery News, 26/4/2012, Sun's Object: the star HIP 56948 twin discovered ? the perfect seti Size: same as the Sun target ? Temperature: same as the Sun Composition: same as the Sun New Scientist, 20/4/2012, Astrophile: Planets: same as the Sun? an alien sunrise just like Earth's. Meléndez et al. 2012, A&A, 543, A29 HIP 56948: best solar twin

Comparison of HIP56948 (red circles) and the Sun (solid line)

HIRES spectra R ~ 95,000, S/N=600 Meléndez et al. 2012, A&A, 543, A29 HIP 56948 is very similar to the Sun in physical parameters and chemical abundances

Meléndez et al. 2012, A&A, 543, A29 Abundance pattern of HIP 56948 is compatible with 1,5 Earth masses of Earth-like material (using Earth’s composition from Chambers 2010)

Meléndez et al. 2012, A&A, 543, A29 Planet search for HIP 56948 No giant planets in the terrestrial planet region around HIP 56948 !

Looks promising for hosting Earth-like planets in the habitable zone

Meléndez et al. 2012, A&A, 543, A29 What about the effect of giant planet formation?

16 Cyg: pair of solar analogs

16 Cyg A : no planets

16 Cyg B : giant planet 16 Cyg B (planet-host) is 0,04 dex more metal-poor in all elements (photospheric abundances)!

Was the missing material used to form the giant planet around the solar analog 16 Cyg B ? Large Programme: 88 nights at La Silla 3.6m telescope + HARPS spectrograph Brasil no ESO: primeiros resultados 3af, 14:30 (Salão Pentágono)

Planets around solar twins PI: Jorge Meléndez (IAG/USP) Collaborators: T. Monroe (IAG/USP) Australia: Alan Alves Brito, M. Asplund, L. Casagrande USA: I. Ramírez, J. Bean Germany: P. Baumann, S. Dreizler, K. Lind

© Ana M. Molina at La Silla Our Large Programme explores the planet – star connection using precise chemical abundances (0,01 dex) and precise radial velocities (1m/s) obtained with HARPS @ 3,6m telescope. 88 nights from Oct 2011 – Oct 2015 Large Programme: 88 nights at La Silla 3.6m telescope + HARPS spectrograph Current Status - Whole sample observed with VLT and Magellan for high precision (0,01 dex) abundance analysis - About 70 solar twins being observed for planets using HARPS at 1m/s precision - Visitor observing runs in Oct 2011, Feb 2012, April 2012, August 2012, January 2013, …, 2015

O estudo se viabilizou graças ao acesso recém-obtido pelo Brasil às instalações do ESO (Observatório Europeu do Sul). O governo assinou no fim do ano passado o acordo que torna o país o mais novo membro do consórcio. Embora o acerto ainda careça de aprovação do Congresso para entrar em vigor, o ESO já trata o Brasil como parceiro, concedendo o direito de solicitar tempo de observação nos telescópios da organização.

Foi por conta disso que a equipe de Jorge Meléndez, peruano que trabalha no IAG (Instituto de Astronomia, Geofísica e Ciências Atmosféricas) da Help USP, conseguiu aprovação num projeto que pode finalmente revelar alguns dos segredos mais bem guardados most sobre os exoplanetas. welcome Pesquisa sobre procura de planetas com o HARPS é destaque na mídia internacional

Melendez and his colleagues are currently looking for small planets around roughly 75 solar twins, using the super-sensitive HARPS instrument at the La Silla Observatory in Chile. Treinamento de estudantes da disciplina de Astrofísica Observacional no ESO (La Silla) Palestra da Andressa Ferreira 3af, 16:45 (Salão Turquesa) Conclusions • Metallicity is related to frequency of giant planets • Lithium is not related to planets • Trend with condensation temperature may be related to the formation of terrestrial planets • Abundances at the 0,01 dex level can give us important information on planets • Ongoing solar twin planet survey at ESO should allow better studies of the planet-stellar chemical composition connection