1. Getting Precise Stellar Parameters in PLATO’s first field PLATO science conference 24/25 th Feb 2011 T. Granzer, K.G. Strassmeier, & M. Weber

2. Dedicated photometric characterization survey in Strömgren uvby  n  w and H  Deliverables: (b-y), c1, m1,   Teff, [M/H], log g; Flux F(H  ) down to 13mag. Constraints: bright limit 9.5, faint 16mag First field (fixed) in southern hemisphere Challenge: 2000 □ 2 A dedicated input catalog?

3. Challenge: 2000 sq-deg Super Wasp-South (SAAO), 8x11.1cm lens optics, FoV 7.8x7.8º,~35 pointings, filters ‘on demand’ (?) OmegaCam@VST (Paranal): 2.6m Ritchey- Crétien, FoV 1x1º,~2000 pointings, ugriz&H  RoboTel (C. Armazones): 80cm, Cassegrain, 33.5 arcmin, ~7500 pts., full Strömgren and H  set (plus UBVRI, ugriz).

4. Robotel

5. NGC 891 LBT Mt.Graham 5min, seeing 0.8“ B-band RoboTel in Potsdam 20min, seeing 3.3“ V-band

6. Identical Instrument on STELLA-1, 1.2m, Izaña 40 sec, on 5.8.2010 1.3´´ seeing 10´´ 1´´

7. Bochum-University/Antofagasta Observatory at base of Cerro Armazones ~350 clear nights ~50% seeing < 1” Image: R. Chini

8. Strömgren indices (b-y)for eff. Temperature m1=(v-b)-(b-y)for line blanketing c1=(u-v)-(v-b)for Balmer discontinuity For late-type (FGKM) stars (dwarfs), m1 is a good proxy for metallicity, c1 for log(g) Holmberg et al., A&A 475, 519 Ramirez & Melendez, ApJ 626, 446 Árnadóttir et al., A&A 521, A40 The calibrations used for error analysis are from:

9. 3-year survey? 1300h/year h>30 85% clear nights Moon: 3-5 days around full moon Downtime <20% (STELLA) Standards? (~20min/night) 11-17min/pointing

10. Photometric precision Including slewing/read-out overhead, effective exposure times in y are 10.3-23.7 sec. (8 filters) 20.1-40.7 sec. (6 filters) 52.6-97.2 sec. (4 filters) STELLA-1 (1.2m)! translates to 13.3-15.8  ybv = 3.5-15 mmag,  u = 8-30 mmag

11. …but only in the standard system Transformation to account for different filter curves (  i,  i ) and atmospheric conditions (k’ i,  i ) …determined by observation of standard fields, with errors  k,  ,  ,  . nightly varies slowly

12. Observe at high and low X 0.030.0150.009 0.0240.0120.007 0.220.05- 0.120.080.015   k’   c1m1(b-y) On STELLA-1, two observations in one night, each 20min at X=1.5 and X=1.05 …errors hold only for the standard field!

13. Reddening? Stromgren indices only in de-reddened form, but Plato field at moderate galactic latitude... Use ß–index, independent of reddening (same ). According to Crawford (AJ 80, 955) …again one notch on your error budget

14. Results  Error budget dominated by filter transformations ( ,  ) because only two fields measured. Alleviated by slow variation in these coefficients.  Redding only significant in (b-y)

15. T eff (b-y)  ,  =0,  inst =10 mmag  std =11. 7mmag  red =18. 8mmag Sample data from Olsen, A&AS 57, 443

16. Metallicity (b-y,m1,c1)  ,  =0,  inst =17.1 mmag  std =19.6 mmag  red =5.6 mmag Sample data from Olsen, A&AS 57, 443

17. log(g)  ,  =0,  inst =21.7 mmag  std =39.2 mmag  red =3.8 mmag Sample data from Olsen, A&AS 57, 443

18. Conclusions  Extremely ambitious task.  Success depends on good filter transformation.  Are there enough standards (in the field)?  log(g) at best to distinguish dwarfs and giants.  Sacrifice filters/fields?