Related papers: CNO Abundances of BA-Type Supergiants
Star clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases, during which the classical Be stars occur, which unlike HAe/Be stars, are not…
Context: In recent years mid- and far infrared spectra of planetary nebulae have been analysed and lead to more accurate abundances. It may be expected that these better abundances lead to a better understanding of the evolution of these…
The S-type stars are believed to have a C/O-ratio close to unity (within a few percent). They are considered to represent an intermediate evolutionary stage as AGB stars evolve from oxygen-rich M-type stars into carbon stars. As possible…
In this work we present the main atmospheric parameters, carbon, nitrogen and oxygen abundances, and 12C/13C ratios determined in a sample of 28 Galactic clump stars. Abundances of carbon were studied using the C2 band at 5086.2 {\AA}. The…
Chemical elements in the hot medium permeating early-type galaxies, groups, and clusters make them an excellent laboratory for studying metal enrichment and cycling processes in the largest scales of the universe. Here, we report the…
Red Supergiants (RSGs) are cool (~4000K), highly luminous stars (L - 10^5 Lsun), and are among the brightest near-infrared (NIR) sources in star-forming galaxies. This makes them powerful probes of the properties of their host galaxies,…
We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0 - B5 supergiants of luminosity classes Ia, Ib, Iab and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical…
Using spectroscopic data presented in Magrini et al. (2003), we have analyzed with the photoionization code CLOUDY 94.00 (Ferland et al. 1998) 11 Planetary Nebulae belonging to the spiral galaxy M 33. Central star temperatures and nebular…
B[e] Supergiants are luminous evolved massive stars. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dusty regions usually found in rings or disk-like structures. For a better…
B[e] stars are massive B type emission line stars in different evolutionary stages ranging from pre-main sequence to post-main sequence. Due to their mass loss and ejection events these objects deposit huge amounts of mass and energy into…
Supermassive primordial stars in hot, atomically-cooling haloes at $z \sim$ 15 - 20 may have given birth to the first quasars in the universe. Most simulations of these rapidly accreting stars suggest that they are red, cool hypergiants,…
Active galactic nuclei (AGN) with relativistic jets are the most powerful persistent astrophysical sources of electromagnetic radiation in the Universe. Blazars are the most extreme subclass of AGN with jets directed along the line of sight…
We present elemental abundance patterns (C, N, Mg, Si, Ca, Ti, V, Cr, Fe, Co, and Ni) for a population of 135 massive quiescent galaxies at $z\sim0.7$ with ultra-deep rest-frame optical spectroscopy drawn from the LEGA-C survey. We derive…
Because of their enormous intrinsic brightness blue supergiants are ideal stellar objects to be studied spectroscopically as individuals in galaxies far beyond the Local Group. Quantitative spectroscopy by means of efficient multi-object…
We present observations and analyses of seven Galactic O stars of type O6 and earlier. Analyses are carried out using NLTE plane-parallel, hydrostatic models as well as NLTE spherical models with mass-loss. With detailed calculations for…
Recent JWST observations of the z=10.6 galaxy GN-z11 have revealed a very high gas-phase nitrogen abundance (higher than four times the solar value), a very small half-light radius(~ 60 pc), and a large stellar mass (M_s ~ 10^9 M_sun) for…
We used the UVES spectrograph (VLT-UT2 telescope) to obtain high-resolution spectra of 6 stars hosting transiting planets, namely for OGLE-TR-10, 56, 111, 113, 132 and TrES-1. The spectra are now used to derive and discuss the chemical…
The Balmer lines of four A Ia - supergiants (spectral type A0 to A3) and fourteen B Ia and Ib - supergiants (spectral type B0 to B3) in the solar neighbourhood are analyzed by means of NLTE unified model atmospheres to determine the…
We have studied four complex organic molecules (COMs), methyl formate ($CH_3OCHO$), dimethyl ether ($CH_3OCH_3$), formamide ($NH_2CHO$), and ethyl cyanide ($C_2H_5CN$), towards a large sample of 39 high-mass star-forming regions…
(Abridged) New boron abundances for seven main-sequence B-type stars are determined from HST STIS spectroscopy around the BIII 2066A line. Boron abundances provide a unique and critical test of stellar evolution models that include…