Stars science questions Origin of the Elements Mass Loss, Enrichment High Mass Stars Binary Stars.
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Transcript of Stars science questions Origin of the Elements Mass Loss, Enrichment High Mass Stars Binary Stars.
Stars science questions
•Origin of the Elements•Mass Loss, Enrichment•High Mass Stars•Binary Stars
Origin of the Elements
Key questionsWhat is the composition of the earliest generation of stars?
What do abundance patterns tell us about nucleosynthesis?
What causes mass loss, and how does it enrich the ISM?
What is the current abundance distribution of high mass stars?
Origin of the Elements
Earliest generation of stars Measure elemental
abundances at very low metallicity
[Fe/H] = -5.3 (VLT spectrum)
[R=50-100K; NUV, optical, NIR; high S/N]
Christlieb et al. 2002
Origin of the Elements
Nucleosynthesis Need alpha elements, rare elements,
isotopic abundances [R=50-100K; NUV, optical, NIR; high
S/N]NIR spectrum of aBulge M giant(IRTF/CSHELL)showing Fe, Mg, Ca
Figure fromS. Balachandran
Isotopic 16O/17O measurement in a metal poor giant(Keck/NIRSPEC)
Implications for stellar structure, mixing, galactic chemical evolution
Figure from S. Balachandran
Origin of the Elements
Mass loss and enrichment
Old stars -- RGB, AGBMassive stars -- Wolf-RayetYoung stars -- TTs, Herbig AeBe
Image outflows in H2, H3+ [2-4 mu, 1e-6 contrast]
Image scattered light from dust [1-2.5 mu, 1e-6 contrast, dual polarization]
Spectroscopy of outflows [R=150K, optical/NIR]
mid-IR spectroscopy of dust emission features Complements ALMA
Mass Loss from Evolved Stars - 1
•Broad Scientific Goals & Key Objectives• Measure outflow characteristics for evolved stars
• Temperature, density, velocity, and composition• Radial dependence for resolved sources
• Understand molecular and dust chemistry in outflows• Nonequilibrium gas chemistry• Dust formation mechanisms and rates
• Understand dynamical mechanisms driving outflows• Radiative acceleration beyond a few stellar radii• Adams & MacCormack (1935), Spitzer (1938)
• Predictive model of mass loss from evolved stars• Function of stellar age and initial stellar mass• Feedback on interstellar structure and composition
• Test stellar evolution models for evolved stars• Nuclear reaction pathways• Internal mixing mechanisms
Mass Loss from Evolved Stars - 2
•Key Measurements• Molecular lines at infrared and millimeter wavelengths
• Over 50 species detected in IRC+10216• Line ratios constrain temperature and density• Line shifts and widths constrain velocity fields• Isotopic abundance ratios constrain stellar models
• Infrared dust features• A few dust families (silicates, graphites, ices, etc.)• Band strengths constrain dust chemistry
• Angular resolution (10 mas)• Resolves radial dependence of outflow characteristics• Directly image clumps and general asymmetry• Measure proper motion of clumps in nearest sources
• Spectral energy distribution constrains unresolved sources
High mass stars
Abundances of high mass stars in the Galaxy Measure abundance patterns vs. location,
age, understand recent enrichment history [1-5 mu, R=20-50K]
Measure terminal velocity of outflows, constrain mass and luminosity [He 10830, 1-2.5 mu, R=50K]
Complements SIRTF/GLIMPSE survey IR is important because sources are usually highly embedded
Fundamental Stellar Physics
Binary stars - 1Measure masses of low mass PMS stars and young brown dwarfs in binaries, calibrate mass-luminosity relations (also for field main sequence low mass stars!)
In open clusters (age) constrain evolutionary models.
[velocities -- R=10-50K, 1-2.5 mu needed]
Masses of PMS binaries
Measure:
V, SpT
Mass, age
L, Teff
PMS tracks
Mass, Radius
Measure:
InteriorsAtmospheres
Treatment of convection
Molecules
Initial conditions
Birthline (t=0)
Rotation, Accretion
?
B.C.
SpT-Teff
Surface gravities of PMS stars?
Distance
Determining Mass and Age of a Young Star
Figure from K. Stassun
Masses of PMS binaries
M1 = 1.01 +/- 0.015 Msun
M2 = 0.72 +/- 0.008 Msun
Stassun et al. (2003)
Need velocities and light curves (opt/NIR)
Masses of PMS binaries
Stassun et al. (2003)
M1 = 1.01 MsunM2 = 0.73 Msun
Constrain PMS evolutionary models
Masses of PMS binaries
Each point represents the primary star in an
eclipsing binary
Current status – 4 systems in progress
Figure from K. Stassun
Fundamental Stellar Physics
Binary stars - 2Understand evolution of secondary stars in cataclysmic variables, origin of period gap
Origin of type I SN populationExtreme case - mass loss turns the secondary star effectively into a brown dwarf.
Measure velocities, abundances [need NIR spectra for sensitivity, contrast] [R=10-50K]
IR spectrum of SS Cyg
SS Cyg secondary C, Mg depleted
Figure from T. Harrison
IR spectrum of U Gem
U Gem secondary again C depleted lower mass, very faint and red
Figure from T. Harrison
IR spectrum of EF Eri
Secondary is anirradiated “browndwarf’’?
Harrison et al.(2003)
Instrumentation Summary
High resolution [R=10-20-50-100-150K] spectroscopyNUV, optical, NIR, MIRHigh sensitivity (faint sources)Good wavelength coverage
High contrast imaging [1.e-6]1-5 mu, polarization capability
Chick – 1
Chick - 2