Alex Gianninas December 3 rd 2013 UNT Physics

Alex Gianninas December 3 rd, 2013 UNT Physics Colloquium

Collaborators � University of Oklahoma �Mukremin Kilic, Sara Barber, Paul Canton � Smithsonian Astrophysical Observatory �Warren Brown, Scott Kenyon � University of Warwick �JJ Hermes � Université de Montréal �Patrick Dufour, Pierre Bergeron 11/29/2020 UNT Colloquium 2

White Dwarf Properties � M ~ 0. 6 M� � R ~ 0. 01 R�~ 1 R � ~ 106 � � log g ~ 8. 0 (log g�= 4. 4) � Teff ~ 150, 000 3000 K � No H burning WDs cool over several Gyrs 11/29/2020 UNT Colloquium 3

Internal Structure of WDs H He He C/O Non-DA (DO, DB, DQ, DZ) C/O DA 11/29/2020 Hot DQ UNT Colloquium 4

Gianninas et al. (2011) Binary Evolution 11/29/2020 UNT Colloquium 5

These “friends” are binary companions that stripped a significant amount of material from the progenitor, preventing the ignition of He burning, giving birth to an extremely low mass (ELM) WD � ELM WDs are found almost exclusively in shortperiod binaries (P < 1 day) � Many will merge in less than a Hubble time! � 11/29/2020 UNT Colloquium 6

Internal Structure of WDs H He He C/O DA 11/29/2020 H ELM DA UNT Colloquium 7

ELM Survey � Targeted search for Extremely Low Mass WDs � M < 0. 25 M� � Motivation: �Progenitors of Type Ia supernovae �Progenitors of underluminous supernovae (. Ia, Bildsten et al. 2007) �Progenitors of AM CVn systems (Kilic et al. , 2013) �Pulsar companions �Nearest systems are important sources of gravitational waves 11/29/2020 UNT Colloquium 8

ELM Survey: Target Selection � Hypervelocity Survey (Warren Brown, SAO): search for B type stars leaving the Galaxy, colors similar to ELM WDs 15% of targets are in fact ELM WDs � Spectroscopy from the Sloan Digital Sky Survey (SDSS) � SDSS colors (u-g, g-r) 11/29/2020 UNT Colloquium 9

ELM Survey: Target Selection Brown et al. (2010) 11/29/2020 UNT Colloquium 10

ELM Survey: Target Selection Brown et al. (2012) 11/29/2020 UNT Colloquium 11

ELM Survey: Observations � MMT (6. 5 m), FLWO (1. 5 m), KPNO 4 m � Radial velocity follow-up to confirm the binary nature of each candidate � Once confirmed, we seek to improve our orbital solution by better sampling all phases of the orbit 11/29/2020 UNT Colloquium 12

ELM Survey: Success Rate 11/29/2020 Paper ELM WD Merger Systems Brown et al. (2010) I 12 6 Kilic et al. (2011) II 4 2 Brown et al. (2012) III 7 6 Kilic et al. (2012) IV 7 5 Brown et al. (2013) V 17 6 • Before ELM Survey: • Only 6 known merger systems • Shortest known period is P = 1. 5 hr • ELM Survey has found 8 systems with P < 1. 5 hr and 3 UNTwith P < 1 hr Colloquium 13

Orbital Solutions Orbital solutions provide period (P) and velocity semi-amplitude (K) 11/29/2020 UNT Colloquium Brown et al. (2013) 14

Orbital Parameters � Mass Function Lower limit on M 2 � Merger time Upper limit on 11/29/2020 UNT Colloquium 15

ELM Survey: Results � � Super. Chandrasekhar mass systems not necessarily Type Ia progenitors Mass ratio is important 0. 2 + 1. 2 M systems → Stable mass transfer system (AM CVn, . Ia SN) Can be WD+NS binaries Brown et al. (2013) 11/29/2020 UNT Colloquium 16

Progenitors of AM CVn (cataclysmic variables, novae) � Massive Companion � Pulsars? No detections with Chandra � Will undergo stable mass transfer � Result: AM CVn 11/29/2020 Kilic et al. (2013) UNT Colloquium 17

Masses & Radii � Model dependent and model independent measurements � Model dependent: two ingredients �Precise measurements of the atmospheric parameters (Teff and log g) �Evolutionary models � Model independent: �Eclipses �Ellipsoidal variations (tidal distortion) 11/29/2020 UNT Colloquium 18

Hydrogen Balmer lines (model spectra) 11/29/2020 UNT Colloquium 19

Spectroscopic Fits 11/29/2020 UNT Colloquium 20

New Model Atmospheres � New regime in surface gravity (log g < 7. 0) � New grid of models (down to log g = 4. 5) computed with the atmosphere code of P. Bergeron (Ude. M) � Need to include higher Balmer lines (up to H 12) in the fits since lines are still present in WDs with log g < 7. 0 11/29/2020 UNT Colloquium 21

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Latest Evolutionary Models H-shell flash Althaus et al. (2013) 11/29/2020 UNT Colloquium 23

Evolutionary Models � Statistical approach to calculate masses and ages � Mean weighted by the time spent at each point in Teff log g plane � Still much uncertainty 11/29/2020 UNT Colloquium Althaus et al. (2013) 24

Results for ELM sample ∆ □ 11/29/2020 Pulsating Non-pulsating UNT Colloquium 25

ZZ Ceti Instability Strip • • 11/29/2020 Non-Pulsating UNT Colloquium 26

Results for ELM sample ∆ □ 11/29/2020 Pulsating Non-pulsating UNT Colloquium 27

1 st Pulsating ELM WD: J 1840 Hermes et al. (2012) 11/29/2020 UNT Colloquium 28

J 1112 et J 1518 Hermes et al. (2012) 11/29/2020 UNT Colloquium 29

J 1614 et J 2228 Hermes et al. (2013) 11/29/2020 UNT Colloquium 30

Pulsating ELM WDs � Currently 5 known pulsating ELM WDs � Van Grootel et al. (2013): first exploration of pulsations models appropriate for ELM WDs � Equivalent properties to ZZ Ceti stars at lower mass � Additional evidence that these are indeed bona fide WDs 11/29/2020 UNT Colloquium 31

Extended Instability Strip Van Grootel et al. (2013) 11/29/2020 UNT Colloquium 32

Results for ELM sample ∆ □ • • 11/29/2020 Pulsating Non-pulsating Ca lines He lines UNT Colloquium 33

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ALL ELM WDs with log g < 6. 0 have Ca lines! 11/29/2020 UNT Colloquium 35

Ca abundances 11/29/2020 UNT Colloquium 36

He abundances 11/29/2020 UNT Colloquium 37

J 074511. 56+194926. 5 (J 0745) 11/29/2020 UNT Colloquium 38

J 0745 : A whole lot of metals! Gianninas et al. (2013, submitted) 11/29/2020 UNT Colloquium 39

J 0745: An Extreme DAZ ELM WD � Teff = 8380 K � log g = 6. 21 � Abundances log Ca/H = -5. 8 log Mg/H = -3. 9 log Cr/H = -6. 1 log Ti/H = -5. 6 log Fe/H = -4. 5 All nearly solar! Gianninas et al. (2013, submitted) 11/29/2020 UNT Colloquium 40

Origin of metals � For more massive DAZ WDs circumstellar debris disks… circumbinary disks for ELM WDs? Optically thick Dotted i = 30° Dashed-dotted i = 60° Rin = 1. 3 R� Rout = 1. 4 – 5. 0 R� � Radiative levitation? � Recent H-shell flash? 11/29/2020 UNT Colloquium 41

PSR J 1816+4510 � � � 11/29/2020 UNT Colloquium Kaplan et al. (2013) ELM WD pulsar companion Teff = 16, 000 K log g = 4. 90 Hypothesis: result of a recent H-shell flash 42

HST (COS) Yes! 10 orbits Keck (HIRES) TBD… 11/29/2020 UNT Colloquium 43

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J 065133. 34+284423. 4 (J 0651) ‘‘Poster child” for ELM WDs � Shortest period ELM WD binary P = 12. 75 min! � Eclipsing! � After initial discovery, photometric followup at Mc. Donald, APO, Gemini North and GTC � 11/29/2020 UNT Colloquium 45

Light Curves Direct detection of orbital decay! 11/29/2020 UNT Colloquium Hermes et al. (2013) 46

O-C Diagram 11/29/2020 UNT Colloquium Hermes et al. (2013) 47

J 0651: Rotation Rate � Isolated WDs : slow rotators ( < 10’s of km/s), measured with Ca line profile � Evolution in compact binaries and interactions with companions could ELM WDs be fast rotators? � Tidal forces synchronized orbits � For J 0651 = 200 km/s Berger et al. (2005) 11/29/2020 UNT Colloquium 48

Rossiter-Mc. Laughlin Effect Winn et al. (2005) 11/29/2020 UNT Colloquium 49

Prediction � Follow recipe from Winn et al. (2005) � 1. Rotationally broaden line profile of primary to simulate integrated spectrum (S ) � 2. Unbroadened line profile, Doppler shifted to the red/blue (Sp) � 3. Str = S - Sp 11/29/2020 UNT Colloquium 50

Prediction Magnitude of R -M Effect ~ 40 km/s 11/29/2020 UNT Colloquium 51

Keck Observations � Awarded ½ night on Keck I with LRIS � Only telescope where we could obtain necessary S/N � 5 - 7 spectra (t ~ 25 s) per exposure to reduce number of times we read the CCD and ensure the best possible temporal sampling � Needed to synchronize blue and red sides of instruments (different read times) � 6 hours of observing = 313 spectra 11/29/2020 UNT Colloquium 52

Observations Keck : J 0651 11/29/2020 UNT Colloquium 53

Observations Keck : J 0651 11/29/2020 UNT Colloquium 54

Conclusions � ELM Survey: targeted search for extremely low-mass WDs � Success: ~60 systems avec P < 1 day � Observed Phenomena: �Pulsations �Metals �Eclipses �Orbital Decay �Ellipsoidal Variations 11/29/2020 UNT Colloquium 55

More to come… � ELM Survey � Upcoming observing runs: MMT, KPNO 4 m � LAMOST? � Southern Hemisphere? � Spectroscopic Analysis � Abundances � � Spitzer J 0745 � HST: December 6 and 7 � Keck: TBD � J 0651 � Finish data reduction and analysis 11/29/2020 UNT Colloquium 56

Fate of J 0651? 11/29/2020 UNT Colloquium 57