1. HYDEF07 Tuebingen Hot DO and DB White Dwarfs From the Sloan Digital Sky Survey James Liebert University of Arizona with Jurek Krzesinski Mt. Suhora Observatory, Krakow, Poland Simon Hugelmeyer and Stefan Dreizler Inst. f. Astrophysik, Georg-August Universitaet Gottingen

2. Sloan Digital Sky Survey 2.5-meter o Catalog of 9,000+ White Dwarfs oMost are Hot DA,DB.. o Eisenstein et al. 2006 o Catalog of 9,000+ White Dwarfs oMost are Hot DA,DB.. o Eisenstein et al. 2006 Apache Peak, near Sunspot, NM

3. Daniel Eisenstein -- Cosmologist and Cataloguer of 9,316 White Dwarfs

4. HYDEF07 Tuebingen DO and DB Stars with no Balmer jump hug blackbody curve SDSS two color Diagram Solid curves Hydrogen models (log g = 9,8,7) and a blackbody Dashed curves Helium models

5. HYDEF07 Tuebingen 50,000 K 25,000 K 17,000 K 12,000 K 8,000 K DA Harris et al.

6. HYDEF07 Tuebingen 60,000 K 48,000 K 28,000 K 11,000 K DO DB Harris et al.

7. HYDEF07 Tuebingen DB-DO Stars: 1. The Mass Distribution 2. Filling the “DB Gap” 3. A preliminary luminosity function of DO-DB white dwarfs

8. HYDEF07 Tuebingen Liebert, Bergeron, Holberg 348 DA White Dwarfs From the Palomar Green Survey Koester and Weidemann (1979) first showed from fitting colors that the mean mass of DA white dwarfs was near 0.6M 

9. HYDEF07 Tuebingen Eisenstein et al. 2006, ApJS, 167, 40 Ttemperature Index Subtype -- 50,400 / Teff -- easier than plotting Teff

10. HYDEF07 Tuebingen A. Beauchamp PhD dissertation Univ. Montreal DB white dwarfs have same mean mass as the DA’s But very few low and high mass outliers

11. DA Mass Distribution Corrected to Fixed Volume of Space Search volume to m lim ~ R(wd) 3 = (distance) 3 3% ( 0.8)

12. HYDEF07 Tuebingen Mysore, India 1985 -- HYDEF85 J. Liebert reports in talk on DB-DO stars: Up to now, no non-DA with an analyzed spectrum has a T eff between 30,000 and 45,000K came to be called the “DB gap” 1990s come and go More DB / DO stars analyzed from different samples A. Beauchamp completes PhD thesis on DB star models, fits spectra Still.. No DB / DO found between 30,000 and 45,000 K. Then comes the Sloan Digital Sky Survey..

13. HYDEF07 Tuebingen Model Synthetic Spectra From Detlev Koester All lines He I (of course)

14. HYDEF07 Tuebingen He II 4686Å starts appearing at 38,000K (super S/N ratio) or 40,000K Little change of Spectra with T eff From 18-20,000K Till 38,000K

15. HYDEF07 Tuebingen Some fits to possible “DB gappers”

16. HYDEF07 Tuebingen SDSS Stars in our near the “DB gap” region 30,000 - 45,000 K T phot estimated from SDSS u g r I z mags with an assumption about extinction T spect from fitting He I line spectrum Open squares: from 6.5-m MMT spectra Filled squares: SDSS spectra

17. HYDEF07 Tuebingen  DB “gap”  Ratio DA/non-DA appears lower above 50,000K and below 20,000K than inbetween

18. HYDEF07 Tuebingen DA LF overestimated for T eff > 50,000K for several reasons ------------------------------ -------------------- PG incomplete