Molecules in stellar atmospheres

Thomas Masseron ULB

In collaboration with P. Neyskens, A. Jorissen, S. Van Eck, B.Plez,

M. Godefroid, P.F. Coheur, R. Colin

OutlineMolecules in stellar atmospheresMaking molecular linelistsApplicationsConclusions

Molecules in stellar spectra

electronic transitions:Optical

rotational transitions:mm

vibrational transitions:IR

OutlineMolecules in stellar atmospheresMaking molecular linelistsApplicationsConclusions

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

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)

OutlineMolecules in stellar atmospheresMaking molecular linelistsApplicationsConclusions

CHCEMP star

CH: predissociation lines

Transition lifetimes need to be included !

Definition: transition involving a level above the dissociation limit or perturbed by an unbound state

C2

In collaboration with Bertrand Plez

LaO-YO in S-stars…

In collaboration with Pieter Neyskens

Without YO

With YO

… CeO in Mira (?) and “?”

In collaboration with Pieter Neyskens

In collaboration with Pieter Neyskens

Conclusions and perspectivesDetermine 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 astronomicalobjects 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)