1. The Search for the Shortest Period Binary WDs: The Latest Results from the ELM Survey Alexandros Gianninas EUROWD14 Université de Montréal August 15 th, 2014

2. The ELM Survey Extremely Low-Mass WDsExtremely Low-Mass WDs –M < 0.30 M  (5 < log g < 7) –He-core WDs –Found in P < 1 d binary systems The ELM Survey is an ongoing, targeted search for ELM WDsThe ELM Survey is an ongoing, targeted search for ELM WDs Papers I – V + VI : 61 + 12 ELM WDs Brown et al. (2010, 2012, 2013), Kilic et al. (2011, 2012) + Gianninas et al. (2014, in prep)Papers I – V + VI : 61 + 12 ELM WDs Brown et al. (2010, 2012, 2013), Kilic et al. (2011, 2012) + Gianninas et al. (2014, in prep) EUROWD142

3. SDSS colors work well for choosing ELM WD candidates EUROWD143 Brown et al. (2012, ApJ, 744, 142)Gianninas et al. (2014, in prep)

4. Radial Velocity Follow-Up EUROWD144 FLWO 1.5m MMT 6.5m KPNO 4m

5. ELM VI: 12 new ELM WDs EUROWD145 Gianninas et al. (2014, in prep)

6. Standard Spectroscopic Technique EUROWD146 Gianninas et al. (2014, in prep)

7. Many ELM WDs have Ca lines… EUROWD147 Gianninas et al. (2014, arXiv:1408.3118)

8. … some have Mg lines… EUROWD148 Gianninas et al. (2014, arXiv:1408.3118)

9. … others have a lot more! EUROWD149 Gianninas et al. (2014, ApJ, 781, 104) J0745+1949 See also GALEX J1717+6757 Hermes et al. (2014) + poster Vennes et al. (2011) PSR J1816+4510 Kaplan et al. (2013)

10. Some even have Helium EUROWD1410 Gianninas et al. (2014, arXiv:1408.3118) a lot of it!

11. EUROWD1411 Gianninas et al. (2014, arXiv:1408.3118) Althaus et al. (2013) Dorman et al. (1998) with Ca with Ca & He

12. Where do the metals come from? Accretion from circumbinary disk?Accretion from circumbinary disk? –Typical Roche radius for WDs ≈ 1 - 1.5 R  –Stable orbits around a binary ~2x the orbital separation (a) (Holman et al. 1999) –All metal-rich ELMs (except J0745) have a > 1 R  H-shell flash?H-shell flash? –Kaplan et al. (2013) –Diffusion times too short EUROWD1412 Gianninas et al. (2014, arXiv:1408.3118)

13. EUROWD1413 with Ca with Ca & He Gianninas et al. (2014, arXiv:1408.3118)

14. WD 0931+444: a new 20 minute ELM WD C. A. Prieto: SDSS DR10 selectionC. A. Prieto: SDSS DR10 selection W. Brown: end of the night “shot in the dark”W. Brown: end of the night “shot in the dark” EUROWD1414 Kilic et al. (2014, MNRAS, 441, L1 )

15. WD 0931+444: a new 20 minute ELM WD EUROWD1415 Kilic et al. (2014, MNRAS, 441, L1 ) MMT 6.5m SDSS DA+dM1 : Silvestri et al. (2006) Rebassa-Mansergas et al. (2007,2010) Rebassa-Mansergas et al. (2007,2010) Heller et al. (2009) Heller et al. (2009)

16. WD 0931+444: a new 20 minute ELM WD EUROWD1416 Kilic et al. (2014, MNRAS, 441, L1 ) GMOS-North time resolved spectroscopy Na I HHHH

17. Gravitational Wave Verification Sources EUROWD1417 Kilic et al. (2014, ASSP, in press) Average Galactic Foreground Nelemans et al. (2001) eLISA after 2 years Amaro-Seoane et al. (2013)

18. Two populations are emerging EUROWD1418 Gianninas et al. (2014, in prep)

19. Updated Instability Strip: ML2/  =0.8 EUROWD1419 Gianninas et al. (2014, arXiv:1408.3118)

20. Magenta: New ELM Pulsator (see Keaton Bell’s poster C1) EUROWD1420

21. Blue: ELM VI sample EUROWD1421

22. Red: …stay tuned! EUROWD1422

23. CONCLUSIONS ELM Survey: 74 new ELM WDs and more to comeELM Survey: 74 new ELM WDs and more to come –Starting to be able to do some statistics Helium might be the ‘smoking gun’ for a recent H-shell flash, not metalsHelium might be the ‘smoking gun’ for a recent H-shell flash, not metals ELMs are important sources of gravitational waves (two verification sources)ELMs are important sources of gravitational waves (two verification sources) Mapping out the instability strip from within (7 known pulsators) and withoutMapping out the instability strip from within (7 known pulsators) and without Wish list:Wish list: –Expand survey to the southern hemisphere –Constrain parameters of the secondaries EUROWD1423

24. Collaborators EUROWD1424 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 University of Texas: Keaton Bell, Samuel Harrold Instituto de Astrofisica de Canarias: Carlos Allende Prieto

25. The ‘high log g problem’ at low log g EUROWD1425 Gianninas et al. (2014, arXiv:1408.3118)

26. How precise is ‘precise’? EUROWD1426 Gianninas et al. (2014, arXiv:1408.3118)