Stars and Stellar Astrophysics with ngCFHT...• large statistical samples of planet hosting stars - ﬁrst isolate the relevant chemical signatures (or varieties) - then exploit a

ngCFHT Workshop, 27-29 March 2013

Stars and Stellar Astrophysicswith ngCFHT

Kim VennU. Victoria

Stellar SWG:Katia Cunha (NOAO), Rolf-Peter Kudritzki (IfA), Else Starkenburg (U. Victoria)

and especially Pat Cote for scientific input and post-processing

Patrick Dufour (U.Montreal)Zhanwen Han (Yunnan Obs.)

Chiaki Kobayashi (ANU)

Monday, April 1, 13

Stellar astrophysics forms the backbone of modern astronomy

• stellar evolution theory underpins models of galaxy evolution and cosmology• formation of planetary systems closely connected to that of the stellar host

SDSS has shown the impact of large surveys of stellarastrophysics

• can be used to map the Galaxy, especially outer halo that requires large fraction of the sky to be covered.• higher resolution deepens our understanding of

- planet formation processes, - effect of environment on star formation, - chronology of Galactic disk and halo formation, - end stages of low mass stars- precision stellar parameters


Monday, April 1, 13


The Galactic Archaeology survey can be complemented by smaller targeted programs, even time domain studies

ngCFHT Stellar Astrophysics Science Drivers:SWG focused on what a Large and/or HR survey could do (wrt ESO-VLT-LP, Keck-HIRES/DEIMOS, Subaru-PFS/HDS, SDSS-Apogee, etc)

Examples:

• Exoplanet hosts and Solar Twins• Blue supergiants beyond the Local Group• White dwarfs as probes of Galactic formation & evolution• Time Domain stellar spectroscopy

Monday, April 1, 13


Exoplanet Hosts and Solar Twins

The metallicity of the stellar host correlates with the mass of the planet. Relationship seen to terrestrial sizes as well from Kepler discoveries.

Monday, April 1, 13



Melendez et al. (2009) and Ramirez et al. (2009) have examined 33 solar twins and 10 solar analogues within 75 pc of the Sun.

• very few have abundances exactly like the Sun.

• discussed various options- Galactic chemical evolution, yet all solar twin ages are similar (4-5 Gyr)- Sun migrating from inner disk, yet [O/Fe] gradients not large enough- Proto-solar neighbourhood only polluted by SN II, yet all are nearby.- Dust separation during the time of terrestrial planet formation.

- inner solar system meteorites enriched in refractories- role of giant planets since all solar analogues with giant planets resemble the solar twins chemically, not the Sun.

- Cleansed of dust by radiation of nearby hot luminous stars early on.

• also, the effect is very subtle - is it real? - Chromospheric activity, First Ionization potential effect, ...

Monday, April 1, 13



The Sun has a peculiar chemistry compared to solar twins, Δ[X/Fe] < 0.06 dex

The mass of refractory elements in Mercury, Venus, Earth, and Mars is equal to the amount of dust depleted gas required to explain the difference.

• Only 1 solar twin was known in 2002,• ~ 40 are known in 2012.

This is a field that improves with better statistics.

Monday, April 1, 13



The prospect of finding terrestrial planets from the detailed chemistry of their host star is incredible. Requirements:

• high resolution spectroscopy R~20,000 - precision stellar parameters - abundances for a wide variety of elements covering all nucleosynthetic origins.

- also determining the site of the r-process - and a priori modelling of (all) metal poor SN

• large statistical samples of planet hosting stars- first isolate the relevant chemical signatures (or varieties)- then exploit a large database to reduce systematic errors

ngCFHT could provide >100,000 solar analogues, <1000 solar twins.

Monday, April 1, 13


Blue Supergiants beyond the Local Group

Stellar winds of blue supergiants reveal intrinsic parameters : e.g., stellar parametersfrom Keck/LRIS R~2000 using the Balmer jump, Balmer profiles, spectral templates.

Can map disk structures, metallicities, reddening; e.g., M81 is at 3.5 Mpc.

Monday, April 1, 13


Blue Supergiants : M81 and Sculptor groups

Comparison of abundances by Kudritzki et al. (2012)

Planetary Nebulae vs Blue Supergiants vs H II RegionsSuggests oxygen-gradient in M81 has evolved over the past 5 Gyr (steeper PN): - radial gas flows,

- stellar radial migration - effects/causes of radial disk breaks - effects of turbulent disk at early times.

Monday, April 1, 13


Blue Supergiants : Stars and Rotation

Ekstrom et al. (2011) - effects of rotation on the HRD (Li not shown) - due to vsini, rotational effects examined statistically

Monday, April 1, 13


White Dwarfs as Probes of Galactic Formation & Evolution

White dwarfs are excellent age indicators of their host stellar population:

For example, the Galactic halo - Kalirai et al. (2012)

• selected recently formed WDs (top of the cooling curve) in M4• compared ages for 4 kinematically confirmed inner Galactic halo WDs• heavier inner halo WDs formed from heavier progenitors ~1 Gyr after M4

(M4 is 12.5 Gyr, with old GC age distribution in the grey box).• Also compares with WDs in the disk, but other effects to consider.

Clearly another field that improves with increased statistics.

Monday, April 1, 13



• Prior to SDSS, only 2500 white dwarfs were known.• After SDSS DR7, >20,000 spectroscopically confirmed candidates expected

- 20 pc volume limited sample (80% complete)

• ngCFHT could produce ~170,000 brighter than g~21 i.e., the Galactic Archeaology survey faint limits (with R~6500). - 100 pc volume-limited sample. - About 8 per ngCFHT field.

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Finding white dwarfs in binaries:Steele et al. 2011 UKIDSS DR8

• 14-16 WD + low mass companion systems• 9-11 WD + brown dwarf systems• 3 candidate WD + debris disk systems

Clearly WDs in binary systems rare,yet precursors to CVs, XRB, and SN Ia

- long term spectral monitoring with ngCFHT- new candidates- precision parameters

Time Domain Astronomy

Monday, April 1, 13


Time Domain Spectroscopy

A large number of imaging surveys over the next decade (LSST, PanStarrs, HSC-SSS, DEC, Euclid, Skymapper, etc.)will have explored and characterized the transient sky.

Spectroscopic follow up/ long term spectral monitoring applications include :

- progenitor properties for CVs, XRB, SN Ia.- stellar multiplicity- precision parameters for pulsating and/or eclipsing variables - comparative planetary atmospheres

Note: minimum ngCFHT radial velocity accuracies are ~150 m/s, thus not meant to compete with VLT ESPRESSO’s ~10 cm/s

instead, ngCFHT provides wide field and long term monitoring.

Monday, April 1, 13


Time Domain Spectroscopy : Variable star monitoring

Distribution of 2500 Cepheids in M31 from CFHT POMME survey (Fliri & Vals-Gabaud 2012)

Spectral monitoring can improve direct determinations of stellar parameters (radius, temperature, e.g., Baade-Wesselink method for Cepheids, thus distances).

Monday, April 1, 13


Possible Kepler Field Spectroscopy Survey

Imagine an ngCFHT targeted project forthe spectral follow-up to the Kepler field:

• 115 deg2 Kepler survey area covered in 84 ngCFHT pointings• To date, ~2000 planetary candidates await verification.• Kepler mission extended to 2016

Now imagine long term ngCFHT monitoring (10 years, ~50 epochs)

• RVs at R=20,000 for exoplanet candidates• determine stellar multiplicity • determine precision stellar parameters• also rotational velocities, ages, orbits, Galactocentric orbits too, etc.

Monday, April 1, 13


ngCFHT will significantly impact Stellar Astrophysics

Exoplanet hosts and Solar Twins

Blue supergiants beyond the Local Group

White dwarfs as probes of Galactic formation & evolution

Time Domain stellar spectroscopy (multiples, progenitors, hosts)

Monday, April 1, 13

Documents

Stars and Stellar Astrophysics with ngCFHT...• large statistical samples of planet hosting stars - ﬁrst isolate the relevant chemical signatures (or varieties) - then exploit a