Estimation of photometric distances for NOMAD stars

1. Mathematics & Mechanics dept., SPbSU, 2009. { } Estimation of photometric distances for NOMAD stars Supervisor: PhD, Alexander S. Tsvetkov Alexey A. Smirnov ] [

2. NOMAD — superiority NOMAD (Naval Observatory Merged Astrometric Dataset), contains1 117 612 732 stars, from catalogues: — Hipparcos — UCAC2 (>10m) — Tycho-2 — USNO-B — 2MASS. Total volume — 92 Gb! Catalogue includes: — positions, proper motions and their errors; — six-band photometry; — cross-identity data.

3. NOMAD — photometry About 243 millions of stars have photometry in all bands.

4. NOMAD — number of stars against visual mag.

5. NOMAD — disadvantages • Not good proper motions 2. Artifacts are about 2.3% of all catalogue. 3. No distances!

6. Conception of Distance determination Six-band photometry Spectral classification Photometric distances

7. Auto classification of stars by multiband photometry 1962—1965 —Vilnius multiband photometry system (UPXYZVH) with a goal to provide full auto spectral classification.(StrajysV. et. al.) BVRJHK system doesn’t allow 100% classify any star (temperature and luminosity classes). The main goalis to establish classification of stars of NOMAD that have six band photometry.

8. Normal color indexes “Normal” index means that the stars we use are in 100 pc radius where the interstellar extinction is small (all but). NOMAD photometry allows to compute the next color indexes for 243 millions of stars: —B–V — V–R — V–J — V–H — V–K And we can compare this color indexes with normal color indexes.

9. Computing normal color indexes We compiled next catalogue: base—Hipparcos + Sp. classification fromTycho-2 Spectral Type + BVRJHK bands fromNOMAD Distances limit 100 pc. B2—M8 stars,III andV luminosity classes.

10. “Normal color index — temperature class” diagrams

11. B-V – T_class

12. V-R – T_class

13. V-J – T_class

14. V-H – T_class

15. V-Ks – T_class

16. Temperature class detection We have no big difference between dwarfs and giants branches. Average it! Now, we can detect temperature class (simple bijective mapping).

17. Luminosity class detection

18. Spectral classifications accuracies Accuracies checking of the catalogue: HIPPARCOS + Tycho-2 Sp.t.+NOMAD—photometry. Accuracy of: temperature class: ~ < 0.3temp. class; luminosity class:depends on star reddening.

19. Tycho-2 Sp.t. stars distribution

20. NOMAD six-band photometry stars distribution

21. Detection of luminosity class from temperature class

22. Distance computing 2d spectral classification Photometric distances Interstellar extinction: If rsp > 1 kpc: Av =0

23. NOMAD —distances Distances for 243 000 000 stars!

24. NOMAD, G stars

25. NOMAD, M stars

26. In result The catalogue of spectral classifications and photometric distances for 243 millions of NOMAD stars is constructed.

27. Conclusion • We have no facilities to compute some excellent distances for NOMAD objects. • But we can do estimations of spectral classification: • Good detecting of temperature class (accuracy is about 0.3temperature class); • Satisfactorily detection of luminosity class.

28. Applications Detection of stellar clusters spectral consistence, this is very important for: history of cluster evolution; kinematics; and… distances.

29. Thank you You can contact with me by e-mail: alsmirn@gmail.com