C. Jordi, E. Solano Universitat de Barcelona LAEFF, Madrid

1. Progress report on the determination of absolute magnitudes using Strömgren photometry. C. Jordi, E. Solano Universitat de Barcelona LAEFF, Madrid COROT week 9: Dec-2005

2. Contents of COROTSKY: seismology programme • Stars brighter than V=9, centre & anticentre directions. • 12000 stars. 6820 stars later than A5. • Hierarchical criteria for assigning Mv to a target. •  The criteria was reviewed in COROT week 7 (see Jordi, • Solano & Ribas). •  Already adopted in COROTSKY (see Charpinet’s • presentation in CW8.

4. (5) Absolute magnitude from Strömgren / Physpar • “Stars with Strömgren photometry in the Physpar windows not having / < 0.1”. • 12 stars of “region1” (O-B) • 3 stars of “region 2” (A0-A2) • 249 stars of “region 3” (late A) post-Hipp. calib (CW7) Mv = 1.88 + 5.2 (b-y) o– 9.1co++ 4.9 mo + 2.7 10-6 vsini2 • 278 stars of “region 4” (F0-G2) post-Hipp. calib (CW7) • Mv = Mv(ZAMS,) - 0.13 + 1.57 b- (8.9+29.6 ) co+ 0.22 [Fe/H] • Stars of “region 5” (from G2) PENDING • 50 stars of “regions 6-8” (B0-G5 supergiants)

5. G2-K type stars: Mv calibration

6. Complete uvby- photometry in Hauch & Mermilliod (1998) • Classified as “region 5” with PHYSPAR • V in Hipparcos and Hauck & Mermilliod (1998) in agreement • At least 2 measurements in Hauck & Mermilliod (1998) • Spectral type in Hipparcos in agreement with photometry • Not anomalous location in colour-colour diagrams • Not supergiants according to photometry • Not luminosity classes I & II according to spectral type in Hipparcos • Not peculiar, variable or belonging in multiple systems (HIP flags) • Not variable or joint photometry in Hauck & Mermilliod (1998) • Not variable or belonging in multiple systems according to SIMBAD 303 stars: 272 with /<0.15 104 with /<0.1 Definition of a well-controlled stellar sample

7. How do the pre-Hipparcos calibrations behave?

8. A trend with metallicity A slight trend with evolution Olsen(1984)

9. What’s happening here? COROTSKY

10. Let’s see an example • HD46241. Δ(Mv)=-6.809. Classified by Physpar as K0V. • π : 6.3 • σ(π)/ π: 0.149  d= 159 pc.  Av = 0 • V= 5.83  Mv(π) = -0.18 •  It cannot be a MS star

11. What’s happening here? COROTSKY T T T T T t • GKM giants have Mv in the range [0.0, -0.5] • GKM MS have Mv > 5 • Stars having ΔMv < -5 are giants wrongly classified.

12. Why so many giants? COROTSKY T T T T T t • GKM Main Sequence stars with V < 9.5 are nearby stars  they have good parallaxes  classified in group (2): σ(π)/π<0.1 • Stars with V < 9.5 not having good parallaxes must be far  they must be giants.

13. Building the new calibration ...

14. largest dependency

15. Same approach as for F0-G2 calibration 1) stars with / < 5 % (104 stars, small bias, unreddened) least-squares fit with 3-sigma clipping Mv()-Mv(ZAMS, (b-y) o)= 0.238–[ 5.49 + 18.89(b-y)o]co 2) stars with / < 15 % (272 stars, unreddened) least-squares fit with 3-sigma clipping Mv()- Mv = +0.08 – 6.78 mo

17. The new calibration ... Mv = Mv(ZAMS,) + 0.238–[ 5.49 + 18.89(b-y)o]co– 6.78 mo ± 0.018 0.587.36 0.40 Valid for -0.10 < co< 0.25 = 0.11 mag -0.05 < mo< 0.11 0.36 < (b-y)o< 0.60

18. =0.40 =0.28 Trends have been removed COROTSKY 24 stars; /<6%

19. Conclusions • A new Strömgren calibration has been derived for the G Main Sequence stars. • Both systematic and random errors have been reduced. • 249 late-A + 278 F0-G2 + 30 G2-K0 MS stars with Mv derived from Strömgren photometry using post-Hipparcos calibrations ready to be delivered to COROTSKY. • … BUT still too many stars without information on Mv… • New method: Spectral type & luminosity: σ(Mv) = 1 subtype • - SIMBAD has been explored but VizieR has not. • - To explore all the catalogues contained in VizieR using VO-like tools (e.g. vizquery).