Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extra-solar planets. This paper presents a new line database Toto for the main isotopologues of titanium oxide (TiO): 46 Ti 16 O, 47 Ti 16 O, 48 Ti 16 O, 49 Ti 16 O and 50 Ti 16 O. The 48 Ti 16 O line list contains transitions with wave-numbers up to 30,000 cm −1 ie long-wards of 0.33 µm.The Toto line list includes all dipole-allowed transitions between 13 low-lying electronic states (X Σ + ). Ab initio potential energy curves (PECs) are computed at the icMRCI level and combined with spin-orbit and other coupling curves. These PECs and couplings are iteratively refined to match known empirical energy levels. Accurate line intensities are generated using ab initio dipole moment curves. The Toto line lists are appropriate for temperatures below 5000 K and contain 30 million transitions for 48 Ti 16 O; it is made available in electronic form via the CDS data centre and via www.exomol.com. Tests of the line lists show greatly improved agreement with observed spectra for objects such as M-dwarfs GJ876 and GL581.

We determine the radial abundance gradient of Cl in the Milky Way from H ii regions spectra. For the first time, the Cl/H ratios are computed by simply adding ionic abundances and not using an ionization correction factor (ICF ). We use a collection of published very deep spectra of Galactic H ii regions. We have re-calculated the physical conditions, ionic and total abundances of Cl and O using the same methodology and updated atomic data for all the objects. We find that the slopes of the radial gradients of Cl and O are identical within the uncertainties: −0.043 dex kpc −1 . This is consistent with a lockstep evolution of both elements. We obtain that the mean value of the Cl/O ratio across the Galactic disc is log(Cl/O) = −3.42 ± 0.06. We compare our Cl/H ratios with those determined from Cl 2+ abundances and using some available ICF schemes of the literature. We find that our total Cl abundances are always lower than the values determined using ICF s, indicating that those correction schemes systematically overestimate the contribution of Cl + and Cl 3+ species to the total Cl abundance. Finally, we propose an empirical ICF (Cl 2+ ) to estimate the Cl/H ratio in H ii regions.

Context. Luminous Galactic OH/IR stars have been identified as massive (> 4-5 M ) asymptotic giant branch (AGB) stars experiencing hot bottom burning and Li production. Their Rb abundances and [Rb/Zr] ratios, as derived from classical hydrostatic model atmospheres, are significantly higher than predictions from AGB nucleosynthesis models, posing a problem to our understanding of AGB evolution and nucleosynthesis. Aims. We report new Rb and Zr abundances in the full sample (21) of massive Galactic AGB stars, previously studied with hydrostatic models, by using more realistic extended model atmospheres. Methods. For this, we use a modified version of the spectral synthesis code Turbospectrum and consider the presence of a circumstellar envelope and radial wind in the modelling of the optical spectra of these massive AGB stars. The Rb and Zr abundances are determined from the 7800 Å Rb I resonant line and the 6474 Å ZrO bandhead, respectively, and we explore the sensitivity of the derived abundances to variations of the stellar (T e f f ) and wind (Ṁ, β and v exp ) parameters in the pseudo-dynamical models. The Rb and Zr abundances derived from the best spectral fits are compared with the most recent AGB nucleosynthesis theoretical predictions. Results. The Rb abundances derived with the pseudo-dynamical models are much lower (in the most extreme stars even by ∼1-2 dex) than those derived with the hydrostatic models, while the Zr abundances are similar. The Rb I line profile and Rb abundance are very sensitive to the wind mass-loss rateṀ (especially forṀ ≥ 10 −8 M yr −1 ) but much less sensitive to variations of the wind velocity-law (β parameter) and the expansion velocity v exp (OH). Conclusions. We confirm the earlier preliminary results based on a smaller sample of massive O-rich AGB stars, that the use of extended atmosphere models can solve the discrepancy between the AGB nucleosynthesis theoretical models and the observations of Galactic massive AGB stars. The Rb abundances, however, are still strongly dependent of the wind mass-lossṀ, which, unfortunately, is unknown in these AGB stars. Accurate mass-loss ratesṀ (e.g., from rotationally excited lines of the CO isotopologues in the radio domain) in these massive Galactic AGB stars are needed in order to break the models degeneracy and get reliable (no modeldependent) Rb abundances in these stars.