Walter Weidmann

Central stars of planetary nebulae: New spectral classifications and catalogue

Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. Aims. We undertook a spectroscopic survey of central stars of PNe at low resolution and compiled a large list of central stars for which information was dispersed in the literature. Methods. We observed 45 PNs using the 2.15 m telescope at Casleo, Argentina. Results. We present a catalogue of 492 confirmed and probable CSPN and provide a preliminary spectral classification for 45 central star of PNe. This revises previous values of the proportion of CSPN with atmospheres poor in hydrogen in at least 30% of cases and provide statistical information that allows us to infer the origin of H-poor stars.

Central stars of planetary nebulae - II. New OB-type and emission-line stars

Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae, but central star spectroscopic information is available for only 13% of them. Aims. We undertook a spectroscopic survey of central stars of PNe to identify their spectral types. Methods. We performed spectroscopic observations, at low resolution, with the 2-m telescope at CASLEO, Argentina. Results. We present the spectra of 46 central stars of PNe, most of them are OB-type and emission-line stars.

Improved spectral descriptions of planetary nebulae central stars

Context. At least 492 central stars of Galactic planetary nebulae (CSPNs) have been assigned spectral types. Since many CSPNs are faint, these classification e fforts are frequently made at low spectral resolution. However, the stellar Balmer absorption lines are contaminated with nebular emission; therefore in many cases a low-resolution spectrum does not enable the determination of the H abundance in the CSPN photosphere. Whether or not the photosphere is H deficient is arguably the most important fact we sho uld expect to extract from the CSPN spectrum, and should be the basis for an adequate spectral classification system. Aims. Our purpose is to provide accurate spectral classifications and contribute to the knowledge of central stars of planetary nebulae and stellar evolution. Methods. We have obtained and studied higher quality spectra of CSPNs described in the literature as weak emission-line star (WELS). We provide descriptions of 19 CSPN spectra. These stars had been previously classified at low spectral resolutio n. We used medium-resolution spectra taken with the Gemini Multi-Object Spectrograph (GMOS). We provide spectral types in the MorganKeenan (MK) system whenever possible. Results. Twelve stars in our sample appear to have normal H rich photospheric abundances, and five stars remain unclassified. The rest (two) are most probably H deficient. Of all central stars described by other authors as WELS, we find that at least 26% of them are, in fact, H rich O stars, and at least 3% are H deficient. Thi s supports the suggestion that the denomination WELS should not be taken as a spectral type, because, as a WELS based on low-resolution spectra, it cannot provide enough information about the photospheric H abundance.

The interstellar medium and the massive stellar content towards the SNR G18.1−0.1 and neighbouring H ii regions

Fil: Paron, Sergio Ariel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio(i); Argentina;

Discovery of a [WO] central star in the planetary nebula Th 2-A (Research Note)

Context. About 2500 planetary nebulae are known in our Galaxy but only 224 have central stars with reported spectral types in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al. 1992; Acker et al. 1996). Aims. We have started an observational program aiming to increase the number of PN central stars with spectral classification. Methods. By means of spectroscopy and high resolution imaging, we identify the position and true nature of the central star. We carried out low resolution spectroscopic observations at CASLEO telescope, complemented with medium resolution spectroscopy performed at Gemini South and Magellan telescopes. Results. As a first outcome of this survey, we present for the first time the spectra of the central star of the PN Th 2-A. These spectra show emission lines of ionized C and O, typical in Wolf-Rayet stars. Conclusions. We identify the position of that central star, which is not the brightest one of the visual central pair. We classify it as of type [WO 3]pec, which is consistent with the high excitation and dynamical age of the nebula.

Near-infrared photometry of Galactic planetary nebulae with the VVV Survey

Fil: Weidmann, Walter Alfredo. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

The Ap 2-1 nebula and the surrounding molecular cloud G35.2 − 0.74: an active star-forming region

ABSTRACT Usingdatafromlarge-scalesurveys:2MASS,GLIMPSE,MIPSGAL,VGPS,GRS,and IPHAS, we performed a multiwavelength study of the ISM in a region of about20 0 20 0 towardsthe molecularcloudG35.2-0.74.Additionally, theAp2-1nebula,thatis seen in projection over the molecular cloud, was studied using optical data obtainedwith the 2.15 m telescope at CASLEO, Argentina. From the HI absorption study weestimate a distance of ˘ 2 kpc for Ap 2-1 con rming that the nebula is embedded inthe south portion of the molecular cloud G35.2-0.74. Performing a photometric studyand analysing the spectral energy distributions of the sources likely embedded in thecloud, we con rm that this region is very active in star formation, mainly towardsthe north, where we discover a cluster of young stellar objects. From the H and[NII] lines we obtain a radial velocity of v LSR ˘ 31 km s 1 for the Ap 2-1 nebula, incoincidence with the velocity of the molecular cloud. Finally, we conclude that Ap 2-1is an HII region probably excited by an early B-type star.Key words: ISM: clouds - (ISM:) HII regions - Stars: formation

Asymmetric emission of the [OIII]λ5007 profile in narrow-line Seyfert 1 galaxies

Many active galactic nuclei (AGN) and particularly narrow-line Seyfert 1 (NLS1) galaxies, usually exhibit blueshifts and blue wings in several emission lines, which are mainly associated with outflows and strong winds. In order to study the radial velocity difference between the narrow component of H

Atlas of monochromatic images of planetary nebulae

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VISTA Variables in the Vía Láctea (VVV): Current Status and First Results

and the core component of [OIII]