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
Rolling in their Graves: White Dwarf Rotation and the Endpoints of Angular Momentum Evolution U. North Carolina: Chris Clemens, Bart Dunlap, Erik Dennihy, Josh Fuchs, Stephen Fanale U. Warwick: Boris Gaensicke, Roberto Raddi, N. P. Gentile Fusillo, P.-E. Tremblay, Paul Chote U. Texas: Keaton J. Bell, Mike Montgomery, Don Winget, Zach Vanderbosch + Steve Kawaler, Judi Provencal, Agnes Bischoff-Kim, S.O. Kepler, Alejandra Romero
J ∝ MR2 Prot M = 1.0 M¤ R = 1.0 R¤ Prot ~ 27 d Sun White dwarf M = 0.55 M¤ R = 0.01 R¤ Expect Prot ~min If the Sun perfectly conserved its angular momentum…
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 are only found in narrow instability strips set by temperature
Mike Montgomery White dwarfs pulsate: periodic brightness changes, caused by surface temperature variations Nonradial g-modes with periods of 100-1400 s Spherical star: spherical harmonics! hotter cooler
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 Data from a “typical” pulsating white dwarf
Giammichele et al. 2015 The view from one telescope on the ground 18.9 hr over 5 nights on 3.6-m CFHT on Mauna Kea: 1.57-d rotation in the star Ross 548 V = 14.2 mag Actual signal
Original Kepler Mission (4 years): Just 20 white dwarfs observed, 6 pulsating WDs (just two >3 months) K2 through Campaign 13: >1200 white dwarf candidates observed 53 more pulsating WDs now >55 pulsating WDs with space data! K2 has given us hundreds of candidate pulsating white dwarfs to observe
K2 is helping us answer big questions about white dwarfs: • How thick are the outer H/He layers? • What’s the carbon/oxygen ratio in the core? • How can the pulsations help us understand convection? 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]
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 Hermes et al. 2017d: k2wd.org None of the stars are currently in binaries: Representative of single-star evolution Mode Identification -> Rotation Falls Readily from K2 Data 0.5 d 1 d 2 d 4 d
Mosser et al. 2012 Pulsations of red giants probe deeply – below 0.01 Rstar The cores of first-ascent red giants are rotating ~10 times faster than surface But the cores are slowing down as they contract!
There is a missing angular momentum transport process that couples contracting red giant cores to their surface – i.e., missing physics Cantiello et al. 2014 observed (Mosser+ 2012) plus Taylor-Spruit (magnetic torques from dynamo-driven fields in radiative regions) with hydrodynamic rotational instabilities (Heger+ 2000) R-2 Internal gravity waves also insufficient (Fuller+ 2014)
Isolated core He-burning giants (2-3 M¤ ) have cores rotating slightly faster than their envelopes Deheuvels et al. 2015 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. Jamie Tayar et al. 2017, in prep. Red clump core rotation rates range from ~30-180 days towards core towards surface slower faster
1 WD R 0.4 0.5 0.6 0.7 0.8 0.9 WD Mass (M⊙ ) 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N Kepler & K2 Kawaler (2015) WD cavity ~0.005-0.013 R¤ 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. Clump RGB cavity ~0.02-0.10 R¤ White dwarfs rotate within a factor of two of expected conserving internal rotation of core He-burning giants Prot : 30-180 d Prot : 0.2-5 d
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 Hermes et al. 2017d: k2wd.org Hard upper limit of 4.5 d (sensitive up to 40 d Prot ) Mode Identification -> Rotation Falls Readily from K2 Data 0.5 d 1 d 2 d 4 d
The most rapidly rotating pulsating WD is massive 500 s 200 s 118 s Hermes et al. 2017c Ground-based time-series photometry breaks Nyquist ambiguity EPIC 211914185
The most rapidly rotating pulsating WD is massive 500 s 200 s 118 s Prot : 1.13 ± 0.02 hr Hermes et al. 2017c Ground-based time-series photometry breaks Nyquist ambiguity EPIC 211914185
The most rapidly rotating pulsating WD is massive SDSS Hermes et al. 2017c SOAR spectroscopy yields WD mass Teff : 13,590± 340 K log(g) = 8.434 ± 0.052 MWD : 0.87 ± 0.03 M¤ Using cluster-calibrated initial-to-final mass relation: MProg. : 4.0 ± 0.5 M¤ The fastest-rotating pulsating white dwarf is also the most massive
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 N Kepler & K2 Kawaler (2015) 1 d 2 d 4 d We Can Finally Probe WD Rotation as a Function of Mass Hermes et al. 2017d: k2wd.org SOAR spectroscopy gets us WD masses
WDs from 1-3 M¤ progenitors rotate at 0.5-2.2 d (WD Prot : 35 ± 28 hr) Link emerging between higher WD mass and faster rotation Hard upper limit at 4.5 d (sensitive up to 40 d Prot ) 1 10 100 0 1 2 3 4 N 1.7 2.0 M ZAMS WD Prot = 1.48 ± 0.94 d 1 10 100 0 1 2 3 4 N 2.0 2.5 M ZAMS WD Prot = 1.35 ± 0.74 d 1 10 100 0 1 2 3 4 N 2.5 3.0 M ZAMS WD Prot = 1.32 ± 1.04 d 1 10 100 White Dwarf Rotation Period (hr) 0 1 2 3 4 N 3.5 4.0 M ZAMS WD Prot = 0.17 ± 0.15 d We Can Finally Probe WD Rotation as a Function of Mass Hermes et al. 2017d: k2wd.org
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
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
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
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
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
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...
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.
PG 0112+104: Hermes et al. 2017a l=1 modes l=2 modes The Most Evolved Test of Radial Differential Rotation PG 0112+104 is a ~31,000 K pulsating He-atmosphere WD (DBV)
The Most Evolved Test of Radial Differential Rotation l=1 l=2 PG 0112+104: Hermes et al. 2017a Splittings of l=1 and l=2 modes both indicate rotation period of 10.1±0.9 hr in PG 0112+104 Each pulsation mode is trapped to different depths in such a stratified star
We also see a surface spot Surface: 10.17404 hr Towards core: 10.18±0.27 hr The Most Evolved Test of Radial Differential Rotation Using l=1 and l=2 modes we measure a rotation period of Prot = 10.18 ± 0.27 hr l=1 l=2 PG 0112+104: Hermes et al. 2017a Giammichele et al. 2017, in prep.
1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic K2 Magnetic Magnetic 10.0 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, even low-magnetic-field white dwarfs
100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic K2 Magnetic Magnetic 1 hr 0.5 d 10 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
100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic K2 Magnetic Magnetic 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: 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 1 hr 0.5 d 10 d 10 min
100 101 102 White Dwarf Rotation Period (hr) 0.6 0.8 1.0 1.2 1.4 WD Mass (M ) 2.5 M¤ 6.5 M¤ 4.5 M¤ Progenitor: Is the wider spread in magnetic WD rotation rates telling us something about their histories? Asteroseismic targets should be representative of single star evolution Gaia kinematics will illuminate merger histories 1 hr 0.5 d 10 d 10 min 1 10 100 White Dwarf Rotation Period (hr) 0 2 4 6 8 10 N K2 Asteroseismic Asteroseismic K2 Magnetic Magnetic
This outburst phenomenon never seen before in 40+ years of pulsating white dwarf studies A surprising discovery with Kepler: Aperiodic Outbursts Quiescent pulsations (1151.9 s, 1160.8 s, …) In Outburst (999.9 s, 896.6 s, …) PG 1149+057: Hermes et al. 2015b
• White dwarf Teff = 11,060 K • é 14% mean flux = é 750 K • é >25% flux = é >1500 K Black line is 30-min running mean Event 1 Event 7 Quiescence Pulsations Persist in Outburst, But Surface >700 K Hotter
A surprising discovery with Kepler: Aperiodic Outbursts Keaton Bell et al. 2017 None of the outbursts in pulsating WDs are periodic; appear chaotic Outburst recurrence times can be as short as a few hours and as long as 45 days
(3-day sliding window) Of order 1033-1034 erg per outburst At least 1033 erg kinetic energy in a single pulsation mode Outbursts seen in 9 pulsating WDs so far (not rare) Possibly rapid energy transfer via parametric resonance PG 1149+057: Hermes et al. 2015b A surprising discovery with Kepler: Aperiodic Outbursts
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