Rolling in their Graves: White Dwarf Rotation as a Function of Mass

Conference presentation, 13 min. July 2018: 21st European Workshop on White Dwarfs, Austin, TX, USA.

Transcript

1. J.J. Hermes Hubble Fellow University of North Carolina at Chapel Hill Rolling in their Graves: White Dwarf Rotation as a Function of Mass Boris Gänsicke, Steve Kawaler, Sandra Greiss, Pier- Emmanuel Tremblay, Nicola Pietro Gentile Fusillo, Roberto Raddi, Stephen Fanale, Keaton Bell, Erik Dennihy, Josh Fuchs, Joshua Reding, Ben Kaiser, Bart Dunlap, Chris Clemens, Mike Montgomery, Don Winget, Paul Chote, Tom Marsh, and Seth Redfield Isolated, canonical-mass white dwarfs rotate between 0.5-2.0 days
2. Tremblay et al. 2011 Karl et al. 2005 SDSS Keck/HIRES solid: v sin i = 11 km/s dashed: v sin i = 0 km/s White dwarfs typically have unmeasurable v sin i (<15 km/s) (Prot > hours) Broad Balmer lines NLTE Hα core
3. m = +1 m = -1 m = 0 1000 s 200 s 500 s 125 s 316.8 s 345.3 s n = Number of radial nodes l = Number of vertical nodes m = Number of horizontal + vertical nodes n l = 1 n = 5 l = 1 n = 6 Prot = 0.9 ± 0.2 day Asteroseismology gives us our clearest insight into white dwarf rotation Data from a typical pulsating white dwarf observed by Kepler (g = 18.2 mag)
4. Original Kepler Mission (4 years): Just 20 white dwarfs observed, 6 pulsating WDs (just two >3 months) K2 through Campaign 16: >2100 white dwarfs observed 71 more pulsating WDs K2 has given us hundreds of candidate pulsating white dwarfs to observe
5. Model-Independent Rotation Falls Readily from K2 Data Hermes et al. 2017d k2wd.org Assume Ck,l =0.47 in all cases for modes l=1
6. 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N Kepler & K2 Kawaler (2015) Most isolated white dwarfs rotate between 0.5-2.2 days None of the stars are currently in binaries: Representative of single-star evolution of mostly 1-3 M¤ stars Model-Independent Rotation Falls Readily from K2 Data 0.5 d 1 d 2 d 4 d Hermes et al. 2017d: k2wd.org
7. SDSS SOAR spectroscopy yields WD mass We have obtained SOAR spectra of 62/65 DAVs observed so far by Kepler/K2 Hermes et al. 2017d: k2wd.org
8. The DAV Instability Strip Observed by K2, To Date Blue: Observed by Kepler Open: Ground-based first 27 from Hermes et al. 2017d: k2wd.org 3D-corrected fits carried out by Pier-Emmanuel Tremblay
9. 1 10 100 WD Rotation Period (hr) 0.4 0.5 0.6 0.7 0.8 0.9 WD Mass (M ) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 ZAMS Progenitor Mass (M ) 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 12 14 N K2 C8-14 Hermes+ (2017d) Kawaler (2015) 1 d 2 d 4 d We Can Now Probe WD Rotation as a Function of Mass The fastest-rotating pulsating white dwarf (1.13 hr) is also the most massive (0.87 M¤ ) – descended from a single 4.0 M¤ ZAMS progenitor (Hermes et al. 2017c) Hermes et al. 2017d: k2wd.org
10. Most white dwarfs evolve from 1-3 M¤ ZAMS stars, and rotate at 0.5-2.2 days Possible link emerging between higher white dwarf mass and faster rotation 1 10 100 0 1 2 3 4 5 6 7 N 0.52 0.56 M WD Prot = 1.48 ± 0.99 d 1 10 100 0 1 2 3 4 5 6 7 N 0.57 0.64 M WD Prot = 1.29 ± 0.69 d 1 10 100 0 1 2 3 4 5 6 7 N 0.65 0.71 M WD Prot = 1.33 ± 1.03 d 1 10 100 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 6 7 N 0.78 0.88 M WD Prot = 0.17 ± 0.15 d We Can Now Probe WD Rotation as a Function of Mass Hermes et al. 2017d: k2wd.org (1.0-2.0 M ¤ ZAMS) (2.0-2.5 M ¤ ZAMS) (2.5-3.0 M ¤ ZAMS) (3.5-4.0 M ¤ ZAMS)
11. in Figure 3. The pulsating pre-white dwarf PG 1159 stars, the DOVs, around 75,000 K to 170,000 K have the highest number of detected modes. The first class of pulsating stars to be 5.5 5.0 4.5 Planetary Nebula Main sequence DOV DBV DAV 4.0 3.5 3.0 log [T eff (K)] 4 2 0 –2 –4 log (L/L ) Figure 3 A 13-Gyr isochrone with z = 0.019 from Marigo et al. (2007), on which we have drawn the observed locations of the instability strips, following the nonadiabatic calculations of C´ orsico, Althaus & Miller Bertolami (2006) for the DOVs, the pure He fits to the observations of Beauchamp et al. (1999) for the DBVs, and the observations of Gianninas, Bergeron & Fontaine (2006) and Castanheira et al. (2007, and references therein) for the DAVs. 172 Winget ·Kepler 2.5 M¤ A star: Prot,ZAMS ~ 10 hr Core-He RGB: modes ~0.02-0.10 R¤ Prot : 30-180 d White dwarf: ~0.005-0.013 R¤ Prot : 0.5-2.2 d 10 100 Secondary Clump Rotation Period (d) 0 1 2 3 4 5 6 7 8 N Deheuvels et al. 2015 Tayar et al., in prep. Kepler has mapped internal rotation evolution all the way from MS to WD 1 10 100 WD Rotation Period (hr) 0.4 0.5 0.6 0.7 0.8 0.9 WD Mass (M ) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 ZAMS Progenitor Mass (M ) 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 12 14 N K2 C8-14 Hermes+ (2017d) Kawaler (2015)
12. Where are We Going with White Dwarf Rotation? Coming Soon: NASA TESS will observe all bright WDs every 2 min for ~27 d 815 white dwarfs brighter than I < 16 mag accepted in Cycle 1 target list (Ecliptic South): dozens of new pulsators and rotation rates Exploring v sin i of UVES spectra of massive (>0.8 M¤ ) DAs with T eff > 15,000 K (ESO 0101.D-0295)
13. k2wd.org
14. 1 10 100 0 1 2 3 4 5 6 7 N 0.52 0.56 M WD Prot = 1.48 ± 0.99 d 1 10 100 0 1 2 3 4 5 6 7 N 0.57 0.64 M WD Prot = 1.29 ± 0.69 d 1 10 100 0 1 2 3 4 5 6 7 N 0.65 0.71 M WD Prot = 1.33 ± 1.03 d 1 10 100 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 6 7 N 0.78 0.88 M WD Prot = 0.17 ± 0.15 d White Dwarf Rotation as Function of Mass Revealed by K2 k2wd.org 1-3 M¤ on ZAMS evolve into WDs rotating at 0.5-2.2 d (35 hr w/ std. dev. 28 hr) - Kepler suggests that most core angular momentum lost on first ascent up RGB Evidence is emerging that more massive WDs rotate faster - More massive ZAMS stars rotate faster - More massive ZAMS spend less time on first-ascent RGB (1.0-2.0 M ¤ ZAMS) (2.0-2.5 M ¤ ZAMS) (2.5-3.0 M ¤ ZAMS) (3.5-4.0 M ¤ ZAMS)