the physics of crystallization in a dense coulomb plasma from globular cluster white dwarf stars don...
TRANSCRIPT
![Page 1: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/1.jpg)
![Page 2: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/2.jpg)
The Physics of Crystallization in a Dense Coulomb Plasma
from Globular Cluster White Dwarf Stars
Don WingetDepartment of Astronomy and McDonald Observatory
University of Texasand
Department of Physcis UFRGS Brasil
S.O. Kepler, Pierre Bergeron, Mike Montgomery, Fabi Campos, Leo Girardi, Kurtis Williams
![Page 3: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/3.jpg)
OUTLINE
I. Historical & Astrophysical Context Quantum mechanics, cosmochronology and the equation of state (EoS) of matter
II. What We Can Learn From the DiskObstacles remain, even after 20 years
III. White Dwarf Physics from Globular Clusters Overcoming obstacles with globular clusters
![Page 4: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/4.jpg)
OUTLINE
I. Historical & Astrophysical Context Quantum mechanics, cosmochronology and the equation of state (EoS) of matter
II. What We Can Learn From the DiskObstacles remain, even after 20 years
III. White Dwarf Physics from Globular Clusters Overcoming obstacles with globular clusters
![Page 5: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/5.jpg)
White Dwarf Stars: Eddington’s “Impossible” Star
Sirius B
•1844: Bessel notices “wobble” in Sirius’ position
•1862: Alvan Clark directly observes a faint companion
![Page 6: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/6.jpg)
White Dwarf Stars: Eddington’s “Impossible” Star
•Dark companion is hot and compact, roughly the size of Earth and the mass of the Sun•Interior, even if made of the smallest atoms, must be ionized•“ … to cool the star must expand and do work against gravity …” Eddington.•Heisenberg uncertainty principle and Pauli exclustion principle to the rescue – Fowler 1926
•Chandrasekhar (1931) limit •Mestel (1952) Theory: develops understanding of decoupled mechanical and thermal properties:
ions electrons
![Page 7: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/7.jpg)
White Dwarf Flavors
![Page 8: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/8.jpg)
•Endpoint of evolution for most stars•Homogeneous
–Narrow mass distribution–Chemically pure layers
•Uncomplicated–Structure–Composition–Evolution dominated by cooling: (oldest=coldest)
They Shed Their Complexity!
White Dwarf Stars:
![Page 9: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/9.jpg)
… and why are they interesting?
• Representative (and personal)– 98% of all stars, including our sun, will become one– Archeological history of star formation in our galaxy
=> White Dwarf Cosmochronology
• A way to find Solar Systems dynamically like ours
• Exploration of Extreme physics– Matter at extreme densities and temperatures
• 60% of the mass of the Sun compressed into star the size of the Earth
– Chance to study important and exotic physical processes: plasmon neutrinos, search for dark matter in the form of axions , and study the physics of crystallization …
![Page 10: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/10.jpg)
![Page 11: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/11.jpg)
Observations of Coolest WDs
•Observations: finding the coolest white dwarf stars in a population
–Thin disk
–Open clusters
–Thick disk
–Halo
–Globular clusters
White Dwarf Cosmoshronology
![Page 12: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/12.jpg)
Calculate the ages of the coolest white dwarf stars:
White dwarf cosmochronology• Critical theoretical uncertainties for
dating the coolest WDs– Outer layers
• Convection, degeneracy, and radiative opacity control throttle
– Interiors• Neutrino emission in the hot stars
• Crystallization and phase separation in coolest
• Compare with observed distribution, and repeat the cycle…
![Page 13: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/13.jpg)
(log P, log T) plane
Hot pre-white dwarfmodel
cool white dwarfmodel
![Page 14: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/14.jpg)
Various physical processes thought to occur in WDs as they cool
The DB“Gap”
![Page 15: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/15.jpg)
OUTLINE
I. Historical & Astrophysical Context Quantum mechanics, cosmochronology and the equation of state (EoS) of matter
II. What We Can Learn From the DiskObstacles remain, even after 20 years
III. White Dwarf Physics from Globular Clusters Overcoming obstacles with globular clusters
![Page 16: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/16.jpg)
The Disk Luminosity Function
Fontaine, Brassard, & Bergeron (2001)
![Page 17: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/17.jpg)
DeGennaro et al. (2008) Disk LF 3358 new SDSS WDs (with spectra)
![Page 18: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/18.jpg)
shows the lower left portion of the reduced proper motion diagram from SDSS Data
Release 2.
Going after the cool WDs: Mukremin Kilic ….
![Page 19: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/19.jpg)
HET Spectra of Cool White Dwarf Stars
![Page 20: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/20.jpg)
The Disk vs M4: Globular clusters are older than the disk ….
Hansen & Liebert (2003)
![Page 21: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/21.jpg)
OUTLINE
I. Historical & Astrophysical Context Quantum mechanics, cosmochronology and the equation of state (EoS) of matter
II. What We Can Learn From the DiskObstacles remain, even after 20 years
III. White Dwarf Physics from Globular Clusters Overcoming obstacles with globular clusters
![Page 22: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/22.jpg)
White Dwarf Stars in Clusters
• Explore white dwarf cooling ages as compared to main sequence isochrone ages
• Open clusters help in establishing constraints on disk age
• Older open clusters sample critical physics of white dwarf cooling
• Minimize problems with birthrates
• Globular Clusters: Finally, we can isolate masses and explore the physics!
![Page 23: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/23.jpg)
NGC 6397
![Page 24: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/24.jpg)
![Page 25: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/25.jpg)
NGC 6397 with HST AC
![Page 26: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/26.jpg)
ComparingTheoretical
models:new(er)
opacities, interior EOS and
atmospheric boundary conditions
Hansen & Liebert (2003)
![Page 27: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/27.jpg)
Fontaine 2001 models and Winget et al. 2008 models 0.5 Msun
![Page 28: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/28.jpg)
Conclusions from model comparisons• Mass – radius is consistent for all groups
– EoS improvements ( Chabrier et al. 2000 over Lamb & Van Horn 1975 for interiors and Saumon Chabrier & Van Horn 1993 over Fontaine , Graboske & Van Horn 1977 for the envelope) do not produce (presently) observable differences in the models.
– Improved atmospheric surface boundary condition is not as important as has been claimed in the literature … it produces no observable differences until bolometric luminosities below the largest magnitude globular cluster stars
![Page 29: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/29.jpg)
HST ObservationsHansen et al.
2007point sources
only
![Page 30: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/30.jpg)
Data: proper motion screened sample from Richer et al. 2008, AJ, 135,2131
Fixing the WD evolutionary tracks in the
CMD by simultaneously
fitting the main sequence
and the WDsgives Z, (m-M)
and E
![Page 31: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/31.jpg)
![Page 32: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/32.jpg)
![Page 33: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/33.jpg)
What advantages do we have over the disk population?
• The cooling sequences are “pinned” to the CMD by the main sequence and white dwarfs fitted together – sliding is not allowed.
• If we ignore the observational errors, the CMD location of a star uniquely determines its mass and radius: setting the mechanical properties of the white dwarf determined independently of the thermal.
• The mass range is very narrow.
• Ages provide some independent information … The terminus white dwarfs aren’t as old as you think!
![Page 34: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/34.jpg)
![Page 35: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/35.jpg)
Oops … the CIA hook is in the wrong place!
![Page 36: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/36.jpg)
![Page 37: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/37.jpg)
![Page 38: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/38.jpg)
Luminosity Function for NGC 6397 proper motion screened WD sample
![Page 39: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/39.jpg)
Richer et al. 2008 (proper motion)
Hansen et. Al. 2007
![Page 40: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/40.jpg)
Richer et al. 2008 completeness
![Page 41: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/41.jpg)
What physics might be relevant near the peak of theLuminosity Function
(the “clump” in the CMD)?
• Convective Coupling: The surface convection zone reaches the degeneracy boundary, reducing the insulation of the envelope
• Crystallization: Ions crystallize with attendant latent heat and phase separation expected from theory
![Page 42: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/42.jpg)
Fontaine, Brassard & Bergeron (2001)
![Page 43: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/43.jpg)
Crystallization Visuallization a cartoon by M.H. Montgomery
![Page 44: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/44.jpg)
Ratio of Coulomb Energy to Ion Thermal Energy
What is the expected value of Gamma at crystallization?
(OCP) = 176 (Potekhin & Chabrier 2000, DeWitt et al. 2001, Horowitz, Berry & Brown 2007)
(MIX)= 230 - 260 (Horowitz, Berry & Brown 2007)
This is at the frontier of (brute force) molecular dynamics
![Page 45: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/45.jpg)
Ratio of Coulomb Energy to Ion Thermal Energy
What is the value of Gamma at and near the “clump” in the observed CMD, or equivalently, the value of Gamma at and before (rise) the peak of the Luminosity Function?
log rho = 6.32 log T = 6.40 … nearly independent of composition!
(peak) = 194 (carbon) = 313 (oxygen)
(rise) = 182 (carbon) = 291 (oxygen)
![Page 46: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/46.jpg)
Richer et al. 2008 completeness
![Page 47: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/47.jpg)
![Page 48: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/48.jpg)
![Page 49: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/49.jpg)
Conclusions from NGC 6397• Confirm that crystallization occurs• Confirm that Debye cooling occurs• We can measure the Gamma of crystallization• Low metallicity clusters may not produce significant
O in cores of some of the 0.5Msun stars … or Brown and collaborators are right and Gamma = 230 - 260
• We find the first empirical evidence that Van Horn’s 1968 prediction is correct: Crystallization is a first order phase transition
![Page 50: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/50.jpg)
The End
Thank you
![Page 51: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/51.jpg)
![Page 52: The Physics of Crystallization in a Dense Coulomb Plasma from Globular Cluster White Dwarf Stars Don Winget Department of Astronomy and McDonald Observatory](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649c9b5503460f9495a0eb/html5/thumbnails/52.jpg)