| Autor: |
Yarovova, Anastasiya D, Egorov, Oleg V, Moiseev, Alexei V, Maryeva, Olga V |
| Předmět: |
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| Zdroj: |
Monthly Notices of the Royal Astronomical Society; Jan2023, Vol. 518 Issue 2, p2256-2272, 17p |
| Abstrakt: |
We report the identification of the unusual emission-line stellar-like object in the nearby low-metallicity (|$Z \sim 0.1 \, \mathrm{Z_{\odot }}$|) dwarf galaxy NGC 4068. Our observations performed with long-slit spectrograph and Fabry–Perot interferometer demonstrate high velocity dispersion in H α line, presence of He ii λ4686Å line and peculiarly low [S ii ]/[N ii ] fluxes ratio for this object. From observational data, we derived that the object represents a single star of high bolometric luminosity (L * ∼ 1.5 × 106 L⊙) surrounded by an expanding nebula with kinematical age of t ∼ 0.5 Myr. The nebula exhibits significant nitrogen overabundance [log (N/O) ∼ −0.05, that is by ∼1.4 dex higher than expected for low-metallicity galaxies]. We suggested that this is a massive blue supergiant (BSG) or Wolf–Rayet (WR) star surrounded by its ejecta interacting with the interstellar medium. We calculated the models of the nebula using cloudy photoionization code, applying cmfgen -modelled BSG and WR stars as ionization sources. We found a best agreement between the modelled and observed spectra for the model assuming ionization by low-metallicity WR star of mass |$M_*\approx 80\, \rm M_\odot$| , ionizing the nebula through the strong wind and enriching the interstellar medium with nitrogen. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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