40 Eri, S. Smith Star Trek writer James Blish put planet Vulcan in orbit around 40 Eri A 40 Eri B: coeval white dwarf with total age ~1.8 Gyr I have evolved telepathy in less than 2 billion years… ~35 au ~400 au Bond, Bergeron & Bédard 2017
WD Teff /Mass à WD Cooling Age WD Initial-Final Mass Relation à Main-Sequence Mass/Age Total System Age(~30%) How Do We Get Coeval Ages from White Dwarfs? + = - Cooling ages come from WD evolution models - Calibrated by WDs in clusters with known turnoff ages WD Teff /log(g)
see also Cummings et al. 2016 How do we build an Mi /Mf relation? E.g.: 0.77(0.03) M¤ WD in NGC 2527(630 Myr) 185 Myr WD cooling age tprog = 441 Myr -> Mprog = 3.1 M¤ Raddi et al. 2016
Bond, Bergeron & Bédard 2017 0.573±0.018 M¤ 17,200±110 K WD Cooling Age: ~122 Myr + Cluster-Calibrated Initial-to-Final Mass Relation (Cummings et al. 2016): 1.8 M¤ Progenitor: ~1.7 Gyr MS age 40 Eri, S. Smith ~35 AU ~400 AU 40 Eri B Total Age ~1.8 Gyr
A handful of composite WD+dM in K2 with likely dM rotation periods - All M1−M3 - No radial-velocity variations in SDSS subspectra - Spatially unresolved (all >200 pc away) Jennifer van Saders 0.3 < M/M¤ < 0.4 −0.4 < [Z/H] < +0.4 Fast and slow initial rotation rates
WD Teff /Mass à WD Cooling Age WD Initial-Final Mass Relation à Main-Sequence Mass/Age Total System Age How Do We Improve Coeval Ages from White Dwarfs? + = - Core C/O Ratio (where heat stored) - Envelope Masses (opacities, how fast heat escapes) - Improved MS Ages - More WDs in Clusters for IFMR - More Wide WD+WD Binaries WD Teff /log(g)
WD Teff /Mass à WD Cooling Age WD Initial-Final Mass Relation à Main-Sequence Mass/Age Total System Age (~10%) How Do We Improve Coeval Ages from White Dwarfs? - Core C/O Ratio (where heat stored) - Envelope Masses (opacities, how fast heat escapes) - Improved MS Ages - More WDs in Clusters for IFMR - More Wide WD+WD Binaries WD Teff /log(g) White Dwarf Asteroseismology with K2/TESS Gaia
Coeval Degerates: Clusters of Two Calibrate gyrochronology, age-activity, & age-flaring continuously out to 8-10 Gyr in the solar neighborhood Gaia will uncover orders more wide WD+MS binaries
A ‘typical’ white dwarf electron degenerate C/O core (r = 8500 km) non-degenerate He layer (260 km) non-degenerate H layer (30 km) [thermal reservoir] [insulating blanket]