Stars and Stellar Astrophysics. Kim Venn U. Victoria

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1 Stars and Stellar Astrophysics with ngcfht Kim Venn U. Victoria Stellar SWG: Katia Cunha (NOAO), Rolf-Peter Kudritzki (IfA), Else Starkenburg (U. Victoria) Patrick Dufour (U.Montreal) Zhanwen Han (Yunnan Obs.) Chiaki Kobayashi (ANU) and especially Pat Cote for scientific input and post-processing

2 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 stellar astrophysics 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

3 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

4 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.

5 Exoplanet Hosts and Solar Twins 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,...

6 Exoplanet Hosts and Solar Twins 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 This is a field that improves with better statistics.

7 Exoplanet Hosts and Solar Twins 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.

8 Blue Supergiants beyond the Local Group Stellar winds of blue supergiants reveal intrinsic parameters : e.g., stellar parameters from 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.

9 Blue Supergiants : M81 and Sculptor groups Comparison of abundances by Kudritzki et al. (2012) Planetary Nebulae vs Blue Supergiants vs H II Regions Suggests 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.

10 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

11 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.

12 White Dwarfs as Probes of Galactic Formation & Evolution 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) pc volume-limited sample. - About 8 per ngcfht field.

13 White Dwarfs as Probes of Galactic Formation & Evolution Finding white dwarfs in binaries: Steele et al UKIDSS DR 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

14 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.

15 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).

16 Possible Kepler Field Spectroscopy Survey Imagine an ngcfht targeted project for the spectral follow-up to the Kepler field: 115 deg 2 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.

17 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)