Rolling in their graves: White dwarf rotation and the endpoints of angular momentum evolution

Conference presentation, 20 min. March 2017: Hubble Fellows Symposium, STScI, Baltimore, MD, USA.

Transcript

1. http://jjherm.es J.J. Hermes Hubble Fellow University of North Carolina at Chapel Hill Rolling in their Graves: White Dwarf Rotation and the Endpoints of Angular Momentum Evolution
2. U. North Carolina: Stephen Fanale, Erik Dennihy, Josh Fuchs, Bart Dunlap, Chris Clemens U. Warwick: Boris Gaensicke, Tom Marsh, Pier-Emmanuel Tremblay, Mark Hollands, Roberto Raddi U. Texas: Keaton Bell, Mike Montgomery, Don Winget + Steve Kawaler, S.O. Kepler, Alejandra Romero, Agnes Bischoff-Kim, Judi Provencal Rolling in their Graves: White Dwarf Rotation and the Endpoints of Angular Momentum Evolution
3. Solar Dynamics Observatory
4. BiSON; Thompson et al. 2003 25 d 30 d 35 d tachocline surface core 5 min 4 min 6 min The Sun rotates as a solid body in its radiative interior
5. Main Sequence Subgiant First Ascent Red Giant Red Clump (Core He-Burning) The Pulsational Evolution of a ~1 M¤ Star as Observed with Kepler 14 hr 3 hr 30 min 4 min Chaplin & Miglio 2013
6. Mosser et al. 2012 Pulsations of red giants probe deeply, below 0.01 Rstar Kepler showed: Cores of first-ascent red giants (shell H burning) are rotating ~10 times faster than surface But the cores are spinning up as they contract! Surface
7. There is a missing angular momentum transport process that couples contracting red giant cores to their surface Cantiello et al. 2014 observed (Mosser+ 2012) plus Taylor-Spruit (magnetic torques from dynamo-driven fields in radiative regions) with hydrodynamic rotational instabilities (e.g. Eddington- Sweet; Heger+ 2000) Internal gravity waves also insufficient (e.g., Fuller+ 2014)
8. How fast to white dwarfs rotate? Are they still differentially rotating? White dwarfs serve as empirical final boundary conditions
9. g-modes—remarkably similar to the large-amplitude DAV pulsators (Winget et al. 19 The observed pulsating white dwarf stars lie in three strips in the H-R diagram, in Figure 3. The pulsating pre-white dwarf PG 1159 stars, the DOVs, around 7 170,000 K have the highest number of detected modes. The first class of pulsating 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 obs Annu. Rev. Astro. Astrophys. 2008.46:157-199. Downloaded fr by University of Texas - Austin on 01/28/09. For Winget & Kepler 2008 H He C/O Pulsating white dwarfs can address these questions, but first we have to find them
10. K2 observes a new field every 75-80 days Kp = 15.7 mag
11. Original Kepler Mission (4 years): 20 white dwarfs observed, 6 pulsating WDs (just two >3 months) K2 through Campaign 10: >1100 WDs observed 43 pulsating WDs K2 through Campaign 16: >2000 WDs (If our last GO proposal is ), >90 pulsating WDs (~280 known today) K1 K2, today K2, by mid-2018
12. Mike Montgomery White dwarf pulsations: Periodic brightness changes, caused by surface temperature variations Nonradial g-modes Spherical star: spherical harmonics! hotter cooler
13. 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 Fourier transform, 75-d of K2 data from Campaign 1
14. 100 101 102 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 N Asteroseismic Giammichele et al. 2015 1 hr 0.5 d 2 d Ground-based rotation rates of isolated white dwarfs are hard: 1-day (11.57 µHz) aliasing Still, 15 WDs well-constrained: 5 hr to 2.4 d (18.9 hr over 5 nights on a 3.6-m telescope) V = 14.2 mag Actual signal Kawaler 2015
15. Used to Be, Getting Data Required Going to the Telescope
16. *PG 1159 star = hot pre-white-dwarf (aka DOV)
17. Vauclair et al. 2002 Maidanak Observatory, Uzbekistan 2-week coordinated, global (14-site) Whole Earth Telescope run in 1994
18. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
19. Jul 27th Uzbeks introduced new rules for the visas ... spent long 8 night hours in the old stinking Russian bus, which, using longest possible route and stopping more than ten times for the repairs, after which passengers were supposed to push the bus to start the engine, brought us to Shakhrisabz. Jul 28th Old military jeep, which exhaust went more inside than via its pipes, after 5 hours brought us to Maidanak [Observatory]. ... Some windows of our living house were broken, no clean sheets ... no butter, meat, sugar. Running water system was not working anymore, not to mention hot water. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
20. Jul 29th I checked telescope; tracking and positioning were working, but telescope mirrors needed cleaning... Jul 30th Managed to repair distiller and to get 3 L of water late in the evening only. Decided to wash mirrors next day. Still lots of yellow Afghanistan dust in the sky. Jul 31st Washed mirrors, cleaned telescope inner surfaces from thick dust layer. Started the full scale system test. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
21. Aug 1st All day no clouds, but wind increasing to the evening. Worked all night. Aug 3rd All day clear sky with some clouds. Quite strong wind in day time but diminished before the night. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
22. Aug 5th It was first night there on the mountain without me. I was at that time in Kitab Hospital severely injured by the Tashkent Astrophysical Institute Director son Iskander Yuldashbaev, apparently mentally ill young man of about 21. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
23. Aug 5th It was first night there on the mountain without me. I was at that time in Kitab Hospital severely injured by the Tashkent Astrophysical Institute Director son Iskander Yuldashbaev, apparently mentally ill young man of about 21. He did some cleaning ... suddenly saying no words grabbed my hair with his left hand and hit my throat with a broken knife from our kitchen. I ran in horror, but he managed to hit me twice into my back. I ran to the Russian house for the help all in the blood. It was no phone connection with outside world and two of them had to run all the way to Maidanak to soldiers, and in three hours at last I was delivered to Kitab hospital in rather weak condition. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev
24. THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev Aug 5th It was first night there on the mountain without me. I was at that time in Kitab Hospital severely injured by the Tashkent Astrophysical Institute Director son Iskander Yuldashbaev, apparently mentally ill young man of about 21. He did some cleaning ... suddenly saying no words grabbed my hair with his left hand and hit my throat with a broken knife from our kitchen. I ran in horror, but he managed to hit me twice into my back. I ran to the Russian house for the help all in the blood. It was no phone connection with outside world and two of them had to run all the way to Maidanak to soldiers, and in three hours at last I was delivered to Kitab hospital in rather weak condition. ... He is in a custody now and cannot say the reason either, says he did not like the way I looked at him. But he was smart enough to steal before that event good sum of my money ... Until helicopter arrived I explained the basics of the work with the quilt program to Alexey -- my assistant. Luckily I trained him on almost everything...
25. Aug 10th Alexey arrived from the Maidanak in the afternoon. Everything seems OK. Aug 11th Aug 12th I lived in the Russian hotel in Kitab ... working with data: writing logs, marking bad points. Tomorrow night Uzbeks promised to bring me to the Samarkand airport. My throat is swollen, still hurts and ugly. END OF CAMPAIGN HERE IN THE UZBEKISTAN ------------------------------------------------------------------------ THE MAIN LOG Observations at Maidanak observatory in Uzbekistan. Aug 1994 Observers: E. Meistas, and local assistant Alexey V. Chernyshev Aug 8th I ... practically defected from Kitab hospital, where black bugs were running on the walls at night even in the patient's beds, over the face too. Throat is badly swollen and hurts.
28. Today We Are Spoiled with Telescopes in Space
29. 100 101 102 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 6 7 N K2 Asteroseismic Asteroseismic 1 hr 0.5 d 2 d 4 d K2 delivers 70+ days of nearly continuous data, every 58.8 s, on dozens of pulsating WDs With K2 we have already more than doubled the number of rotation rates of isolated WDs Window
30. 100 101 102 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 6 7 N K2 Asteroseismic Asteroseismic 1 hr 0.5 d 2 d 4 d K2 delivers 70+ days of nearly continuous data, every 58.8 s, on dozens of pulsating WDs With K2 we have already more than doubled the number of rotation rates of isolated WDs Window My throat is swollen, still hurts and ugly. END OF CAMPAIGN HERE IN THE UZBEKISTAN ----------------------------------------------------------
31. 100 101 102 White Dwarf Rotation Period (hr) 0.5 0.6 0.7 0.8 0.9 WD Mass (M ) 100 101 102 White Dwarf Rotation Period (hr) 0 1 2 3 4 5 6 7 N K2 Asteroseismic Asteroseismic 1 hr 0.5 d 2 d 1.5 M¤ 2.5 M¤ 3.5 M¤ 4.5 M¤ 4 d Progenitor: Spectroscopy yields WD mass
32. SOAR spectrum shows it is massive: 0.90 ± 0.04 M¤ The most rapidly rotating pulsating WD is massive 1000 s 200 s 100 s Nyquist ν of 58.8 s exposures SDSS
33. The most rapidly rotating pulsating WD is massive 1000 s 200 s 100 s Ground-based time-series photometry breaks Nyquist ambiguity Prot : 1.1±0.1 hr Is this 1.1-hr rotating, 0.90 M¤ the descendent of an isolated ~4.5 M¤ B star, or the product of a binary merger? 190.45 s 109.15 s
34. Hermes et al. 2017a l=1 modes l=2 modes With K2 we can test radial differential rotationin WDs PG 0112+104 is a 31,000 K pulsating He-atmosphere WD
35. With K2 we can test radial differential rotationin WDs Hermes et al. 2017a l=1 modes n (n) n=2 n=3 n=4 n=5 n=6 Frequency splittings and overtone spacings behave in concert: Modes trapped to different depths Early hints: rigid rotation Period spacing difference (s)
36. We also see a surface spot Surface: 10.17404 hr Towards core: 10.1±0.9hr Hermes et al. 2017a 10.17404 hr surface spot rotation period With K2 we can test radial differential rotationin WDs Using l=1 and l=2 modes we measure a rotation period of 10.1±0.9 hr in PG 0112+104 (better asteroseismic modeling will improve this uncertainty)
37. 100 101 102 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic J1136+0409 K2 Magnetic Magnetic 5.0 d 2.0 d 0.5 d 5 hr 1 hr 10 min The long stare of K2 is helping us find many new spotted magnetic white dwarfs
38. 100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 100 101 102 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic J1136+0409 K2 Magnetic Magnetic 1 hr 0.5 d 5 d 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: v sin i lower limits 10 min This is the first bulk ensemble of white dwarf rotation rates, especially delineated by mass (v sin i unreliable for cool WDs with convective surfaces)
39. 100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 100 101 102 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic J1136+0409 K2 Magnetic Magnetic 1 hr 0.5 d 5 d 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: 10 min Asteroseismic targets should be representative of single star evolution Tremblay et al. 2016
40. 100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 100 101 102 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic J1136+0409 K2 Magnetic Magnetic 1 hr 0.5 d 5 d 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: 10 min The fastest rotating isolated white dwarf (727.5 s) is both massive and strongly magnetic (>200 MG) Very likely a merger byproduct Burleigh et al. 1999 HST far UV
41. 100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 100 101 102 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic J1136+0409 K2 Magnetic Magnetic 1 hr 0.5 d 5 d 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: 10 min Asteroseismic targets should be representative of single star evolution Is the spread in magnetic spot rotation rates telling us something about history (i.e., mergers)? What is their evolution with temperature (spin down?) K2 & Gaia will give us even more numbers soon!
42. How fast to white dwarfs rotate? Most 0.5-2.0 d, but notable exceptions. Are they still differentially rotating? Likely not. White dwarfs: final boundary conditions on angular momentum evolution