TY  - JOUR
A1  - Ramos-Larios, Gerardo
A1  - Toala, Jesús Alberto
A1  - Rodriguez-Gonzalez, Janis B.
A1  - Guerrero, Martin A.
A1  - Gomez-Gonzalez, Víctor Mauricio Alfonso
T1  - Rings and arcs around evolved stars - III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present the analysis of Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least five ring-like structures north and south of the main nebula of IC4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (n(e)), and temperature (T-e). The rings are found to have similar T-e as the rim of the main nebula, but smaller n(e). Ratios between different ionic species suggest that the rings of IC4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC 6543, the Cat's Eye Nebula.
KW  - stars: evolution
KW  - stars: winds, outflows
KW  - planetary nebulae: general;
KW  - planetary nebulae: individual: IC4406
Y1  - 2022
U6  - https://doi.org/10.1093/mnras/stac605
SN  - 0035-8711
SN  - 1365-2966
VL  - 513
IS  - 2
SP  - 2862
EP  - 2868
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aguilera-Dena, David R.
A1  - Langer, Norbert
A1  - Antoniadis, John
A1  - Pauli, Daniel
A1  - Dessart, Luc
A1  - Vigna-Gómez, Alejandro
A1  - Gräfener, Götz
A1  - Yoon, Sung-Chul
T1  - Stripped-envelope stars in different metallicity environments: I. Evolutionary phases, classification, and populations
JF  - Astronomy and astrophysics
N2  - Massive stars that become stripped of their hydrogen envelope through binary interaction or winds can be observed either as Wolf-Rayet stars, if they have optically thick winds, or as transparent-wind stripped-envelope stars. We approximate their evolution through evolutionary models of single helium stars, and compute detailed model grids in the initial mass range 1.5-70 M. for metallicities between 0.01 and 0.04, from core helium ignition until core collapse. Throughout their lifetimes some stellar models expose the ash of helium burning. We propose that models that have nitrogen-rich envelopes are candidate WN stars, while models with a carbon-rich surface are candidate WC stars during core helium burning, and WO stars afterwards. We measure the metallicity dependence of the total lifetimes of our models and the duration of their evolutionary phases. We propose an analytic estimate of the wind's optical depth to distinguish models of Wolf-Rayet stars from transparent-wind stripped-envelope stars, and find that the luminosity ranges at which WN-, WC-, and WO-type stars can exist is a strong function of metallicity. We find that all carbon-rich models produced in our grids have optically thick winds and match the luminosity distribution of observed populations. We construct population models and predict the numbers of transparent-wind stripped-envelope stars and Wolf-Rayet stars, and derive their number ratios at different metallicities. We find that as metallicity increases, the number of transparent-wind stripped-envelope stars decreases and the number of Wolf-Rayet stars increases. At high metallicities WC- and WO-type stars become more common. We apply our population models to nearby galaxies, and find that populations are more sensitive to the transition luminosity between Wolf-Rayet stars and transparent-wind helium stars than to the metallicity-dependent mass loss rates.
KW  - stars: massive
KW  - stars: Wolf-Rayet
KW  - stars: winds, outflows
KW  - binaries: general
KW  - supernovae: general
Y1  - 2022
U6  - https://doi.org/10.1051/0004-6361/202142895
SN  - 0004-6361
SN  - 1432-0746
VL  - 661
PB  - EDP Sciences
CY  - Les Ulis
ER  -