1. Hot subdwarfs from the SDSS/BOSS
One month in Bamberg
Peter Nemeth et al.
March

2. SEGUE and BOSS targets in DR10
1159 spectra of 860 stars, 238 SEGUE BOSS
Average magnitude: g = ± 2
90% over ∣b∣ = 30°

3. Some challenges with SDSS spectra
Continuum normalization near the Balmer jump, always a question
Spectral resolution, in particular R(λ) is important for a precise analysis
Further challenges:
SNR
flux calibration
fiber loss
R(λ, fiber)
BOSS
SDSS
Spectral range
Resolution

4. Spectrostatistics
We are not (yet) after the fine details, just look for a reasonable distribution of stars in the T-g and T-He diagrams
TLUSTY/SYNSPEC NLTE models in sampling mode
XTGRID fits, steepest descent method with statistical error determination
Simple analysis assuming:
H and He composition
vmicro = ξ = 0 ; vmacro = 0
vr sin(i) = 0 ; E(B-V) = 0 (determined from the fit)
Done on a single node of the MAIDS cluster
8 cores, x4 GHz
~20 days, 3 hrs/spectrum

5. GALEX sample (Nemeth et al. 2012, Vennes et al. 2011)
166 bright subdwarfs from the disk
Consistent results with the SPY survey (Stroer et al. 2007)
Clumpings and trends were observed
Abundance extremes at K
sdB: gravity too low
Some He-sdO: gravity too high

6. SDSS sample
1158 spectra
Dive and Giraffe diagrams

7. SDSS sample 860 stars sdB: gravity even lower
He-sdO: for some gravity is still high
Next steps:
Evaluate results
Go for CNO models with all the three MAIDS nodes

8. He-sdO gravity One possible explanation: Magnetic fields + rotation
Requires better data and appropriate models

9. Radial velocity variations
All combined spectra have been modeled and shifted to the lab wavelength
RV variations are “estimated” for 6038 individual spectra of the 860 stars
Monte Carlo method: resampling the original data and do a χ2 minimization
Mean velocity from 13 trials
Correlates with SNR
Eccentric orbits?