相关论文: Physical and Chemical Properties of Planetary Nebu…

We have undertaken a near-IR spectral survey of stars associated with compact nebulae recently revealed by the Spitzer and WISE imaging surveys. These circumstellar nebulae, produced by massive evolved stars, display a variety of symmetries…

Neon abundances are derived in four Galactic WC stars -- gamma Vel (WR11, WC8+O7.5III), HD156385 (WR90, WC7), HD192103 (WR135, WC8), and WR146 (WC5+O8) - using mid-infrared fine structure lines obtained with ISO/SWS. Stellar parameters for…

In this paper we discuss some results concerning the abundance discrepancy problem in the context of H II regions. We discuss the behavior of the abundance discrepancy factor (ADF) for different objects and ions. There are evidences that…

We present chemical abundances for planetary nebulae and H II regions in the Local Group dwarf irregular galaxy NGC 6822 based upon spectroscopy obtained at the Canada-France-Hawaii Telescope using the Multi-Object Spectrograph. From these…

We have spectroscopically discovered a pair of twin, nitrogen-type, hydrogen-rich, Wolf-Rayet stars (WN8-9h) that are both surrounded by circular, mid-infrared-bright nebulae detected with the Spitzer Space Telescope and MIPS instrument.…

The spectra of the planetary nebula NGC2392 is reanalysed using spectral measurements made in the mid-infrared with the Spitzer Space Telescope. The aim is to determine the chemical composition of this object. We also make use of IUE and…

Planetary Nebulae (PNe) abundance patterns have long been used to note signatures of nuclear processing and to trace the distribution of metals throughout galaxies. We present abundance gradients and heavy element ratios based upon newly…

According to previous spectral analyses of Wolf-Rayet type central stars, late [WC] subtypes show systematically higher carbon-to-helium abundance ratios than early [WC] subtypes. If this were true, it would rule out that these stars form…

We present a morphological study of nebulae around Wolf-Rayet (WR) stars using archival narrow-band optical and Wide-field Infrared Survey Explorer (WISE) infrared images. The comparison among WISE images in different bands and optical…

In this contribution, we present the results of a study on the high abundance discrepancy factor (ADF $\sim$ 10) planetary nebula (PN) NGC 6153 with MUSE. We have constructed flux maps for dozens of emission lines, that allowed us to build…

A summary is given of planetary nebulae abundances from ISO measurements. It is shown that these nebulae show abundance gradients (with galactocentric distance), which in the case of neon, argon, sulfur and oxygen (with four exceptions) are…

Diagnostic diagrams of electron density - excitation for a sample of 613 planetary nebulae are presented. The present extensive sample allows the definition of new statistical limits for the distribution of planetary nebulae in the log…

Electron temperatures derived from the \ion{He}{1} recombination line ratios, designated $T_{\rm e}$(\ion{He}{1}), are presented for 48 planetary nebulae (PNe). We study the effect that temperature fluctuations inside nebulae have on the…

We present new optical spectra of the nearby, bright, planetary nebula NGC 6778. The nebula has been known to emit strong recombination lines for more than 40 years but this is the first detailed study of its abundances. Heavy element…

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…

(shortened) We investigate the properties of Galactic WR stars and their environment to identify evolutionary channels that may lead to the formation of LGRBs. To this purpose we compile available information on the spectropolarimetric…

The ultraviolet spectra of all "weak emission line central stars of planetary nebulae" (WELS) with available IUE data is analyzed. We found that the WELS can be divided in three different groups regarding their UV: (1) Strong P-Cygni…

The study of planetary nebulae in the inner-disk and bulge gives important information on the chemical abundances of elements such as He, N, O, Ar, Ne, and on the evolution of these abundances, which is associated with the evolution of…

Many binary companions to the central stars of planetary nebulae (PNe) are found to be inflated, perhaps indicating that accretion onto the central star might occur during the PN phase. The discovery of a handful of nova eruptions and…

Echelle spectrophotometry of the 30 Doradus nebula in the LMC is presented. The data consists of VLT UVES observations in the 3100 to 10350 A range. The intensities of 366 emission lines have been measured, including 269 identified…