Hunting down the subdwarf populations Peter Nemeth Roy Østensen and Joris Vos KU Leuven, Belgium; In collaboration with Stephane Vennes and Adela Kawka Astronomical Institute of the Czech Republic SDOB6; Tucson AZ, USA; May 20, 2013

SDOB6 - Tucson - May 20, A GALEX sample

SDOB6 - Tucson - May 20, How it got started Classical nova X-ray spectra New model atoms from Topbase and NIST Chi-by-eye fitting

SDOB6 - Tucson - May 20, The sample ~700 UV-excess objects, N UV -V < observing runs at KPNO and ESO, Low-resolution, optical spectroscopy ~200 targets, 6 new WDs Modeling with TLUSTY/SYNSPEC Paper I: 52 stars, interpolation in 3 grids, H, He Paper II: 180 stars, steepest-descent with a constant level structure, H, He, CNO

SDOB6 - Tucson - May 20, The fitting method Green: Model, T = K, log g = 5.6, log He = -1, log CNO = -2 Red: J , T = K, log g = 4.5, log He = -0.4 log C = -2.8, log N = -2.9, log O < -2.6

SDOB6 - Tucson - May 20, The fitting method Green: Model, T = K, log g = 5.6, log He = -1, log CNO = -2 Red: J , T = K, log g = 4.5, log He = -0.4 log C = -2.8, log N = -2.9, log O < -2.6

SDOB6 - Tucson - May 20, Composite spectra Must be addressed, ~20 % of the sample shows a significant IR excess.

SDOB6 - Tucson - May 20, Composite spectra Must be addressed, ~20 % of the sample shows a significant IR excess.

SDOB6 - Tucson - May 20, Temperature – gravity

SDOB6 - Tucson - May 20, Temperature – gravity

SDOB6 - Tucson - May 20, He abundance H. Edelmann, U. Heber, H.-J. Hagen et al.; 2003, A&A, 400, 939

SDOB6 - Tucson - May 20, Abundances Abundances Multiple dichotomies Can abundance patterns indicate the evolution or other properties, like pulsations of these stars? HST STIS shows high abundances of iron-peak elements, but not much Fe. (O’Toole & Heber, 2006) Slow, rapid and hybrid pulsators are well separated, but not preictable Are C&N class sdB and He- sdO stars related?

SDOB6 - Tucson - May 20, Abundances Abundances Multiple dichotomies Can abundance patterns indicate the evolution or other properties, like pulsations, of these stars? HST STIS shows high abundances of iron-peak elements, but not much Fe. (O’Toole & Heber, 2006) Slow, rapid and hybrid pulsators are well separated, but not preictable Are C&N class sdB and He- sdO stars related? C. Binary: 4% Nitrogen: 70% C. Binary: 30% Nitrogen: 22% S. Charpinet, E. M. Green, A. Baglin et al.; 2010; A&A 516 L6

SDOB6 - Tucson - May 20, Abundances Abundances Multiple dichotomies Can abundance patterns indicate the evolution or other properties, like pulsations of these stars? HST STIS shows high abundances of iron-peak elements, but not much Fe. (O’Toole & Heber, 2006) Slow, rapid and hybrid pulsators are well separated, but not preictable Are C&N class sdB and He- sdO stars related?

SDOB6 - Tucson - May 20, Luminosity distribution * * before GAIA Correlates with observed mass distribution, eg. SPY (Lisker et al. 2005)

SDOB6 - Tucson - May 20, Abundance evolution? Speculations... CanonicalHot-flasher e.g.: Miller Bertolami M. M. et al., 2008, A&A, 491, 253e.g.: Zhang X., Jeffery S. C., 2012, MNRAS, 419, 452

SDOB6 - Tucson - May 20, Abundance evolution? Complicated... UV flux induces convection, turbulence, mixing, wind... lots of complications. eg.: Unglaub, 2008

SDOB6 - Tucson - May 20, Puzzling questions How do subdwarfs form? Which formation scenarios are viable and what are their contributions to the observed SD distribution? What drives the mass-loss on the RGB? He-sdO  ?  sdB How clean is the observed population from ELM WD, post-AGB, CSPN stars? These questions remain and need more attention.

SDOB6 - Tucson - May 20, The SD1000 Collaboration Spectroscopy for the largest possible sample for a better statistics and distribution. Homogeneous analysis to find subtle trends and correlations among surface parameters. ERC: From inhomogeneous data? Find connections to RGs and WDs Provide a statistically significant sample for GAIA and derive absolute luminosities and masses. Find binary fractions and correlations between surface and binary parameters. Collaborators needed...

SDOB6 - Tucson - May 20, New improvements in XTGRID Rotational broadening; first application for CD : v sin(i) ~170 km/s Vennes et al. (2012); Geier et al. (2013) Simultaneous fit and radial velocity correction for multiple datasets Efforts to speed-up model calulations with Iron-peak elements by adjusting opacity sampling parameters “ICHANG”; examine the ionization balance... and numerous bug fixes New directions: Abundance stratification Resolve lower mass MS companions in the IR Radial velocities from composite spectra

SDOB6 - Tucson - May 20, Highlight from Paper III: GALEX J is a short-period eccentric binary Kawka et al.; in prep.