1. Thomas Masseron ULB In collaboration with P. Neyskens, A. Jorissen, S. Van Eck, B.Plez, M. Godefroid, P.F. Coheur, R. Colin

2. Outline Molecules in stellar atmospheres Making molecular linelists Applications Conclusions

3. Molecules in stellar spectra

4. electronic transitions: Optical rotational transitions: mm vibrational transitions: IR

5. Outline Molecules in stellar atmospheres Making molecular linelists Applications Conclusions

6. Coupling dedicated codes & lab+astro observations Making molecular linelists I simulate rotational structure to determine the line positions from molecular constants (Pgopher) Calculate transition moment (LEVEL) Compute stellar spectrum with stellar radiative transfer code (MARCS+Turbospectrum) Derive new molecular constants (Pgopher) Identify new lines and merge with laboratory’s

7. Making molecular linelists II Many more lines are observed in stellar spectra. Stellar spectra can be used to improve the molecular laboratory data a from faboratory data Zachwieja et al. (1995)

8. Outline Molecules in stellar atmospheres Making molecular linelists Applications Conclusions

9. CH CEMP star

10. CH: predissociation lines Transition lifetimes need to be included ! Definition: transition involving a level above the dissociation limit or perturbed by an unbound state

11. C2 In collaboration with Bertrand Plez

12. LaO-YO in S-stars… In collaboration with Pieter Neyskens Without YO With YO

13. … CeO in Mira (?) and “?” In collaboration with Pieter Neyskens

14. Conclusions and perspectives Determine abundances (C-rich stars, S-stars…) Include other molecules (HCl, NH, MgH, TiH, SH, TiS, CS …) Mine spectroscopic archives (ESO-POP, HERMES…) Include Landé factors (spectropolarimetry) Molecules are present in many other astronomical objects such as ISM, DLA or QSOs, blend planet spectra. The information on molecules we can get from stellar spectra can be used for those (and reciprocally)