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A large class of stellar systems (e.g., planetary nebulae (PNe), supernova envelopes, LBV stars, young stars in formation) shows structures in their accretion/ejection phase that have similar characteristics. In particular, one currently…
We argue that relative to non-spherical planetary nebulae (PNs), spherical PNs are about an order of magnitude less likely to be detected, at distances of several kiloparsecs. Noting the structure similarity of halos around non-spherical…
We have performed integral field spectroscopy of the planetary nebulae Hen 3-1333 (PNG332.9-09.9) and Hen 2-113 (PNG321.0+03.9), which are unusual in exhibiting dual-dust chemistry and multipolar lobes but also ionized by late-type [WC 10]…
The shaping of the nebula is currently one of the outstanding unsolved problems in planetary nebula (PN) research. Several mechanisms have been proposed, most of which require a binary companion. However, direct evidence for a binary…
We present the ultraviolet (UV) imaging observation of planetary nebulae (PNe) using archival data of Galaxy Evolution Explorer (GALEX). We found 358 PNe detected by GALEX in near-UV (NUV). We have compiled a catalogue of 108 extended PNe…
The structure of the dusty circumstellar envelopes (CSEs) of proto-planetary nebulae (PPNs) reveals the mass-loss history of these sources and how such histories may differ for elliptical (SOLE) and bipolar (DUPLEX) PPNs. To study the PPN…
We report a multi-wavelength study of two evolved planetary nebulae (PNs) M 2-55 and Abell 2. Deep optical narrow-band images ([O III], H?, and [N II]) of M 2-55 reveal two pairs of bipolar lobes and a new faint arc-like structure. This…
We study the oxygen abundance in five H II regions and seven planetary nebulae (PNe) located within 2 kpc from the Sun that have available spectra of high quality. Our analysis uses a similar procedure and the same atomic data to derive…
Most of the planetary nebulae (PN) have bipolar or other non-spherically symmetric shapes. The presence of a magnetic field in the central star may be the reason for this lack of symmetry, but observational works published in the literature…
Planetary nebulae (PNe) constitute an important tool to study the chemical evolution of the Milky Way and other galaxies, probing the nucleosynthesis processes, abundance gradients and the chemical enrichment of the interstellar medium. In…
We present new planetary nebulae (PNe) positions, radial velocities, and magnitudes for 6 early-type galaxies obtained with the Planetary Nebulae Spectrograph, their two-dimensional velocity and velocity dispersion fields. We extend this…
In this paper we report new observations and derive chemical abundances for a sample of 26 planetary nebulae (PN) located in the anticenter direction. Most of these nebulae are far away objects, located at galactocentric distances greater…
Here we present initial results of our search for extensive halos around the planetary nebulae (PNe) in our Galaxy based on imaging data from the Southern H-Alpha Sky Survey Atlas (SHASSA). A threshold surface brightness in H$\alpha$…
The results of an adaptive optics survey of exoplanet host stars for stellar companions is presented. We used the AEOS Telescope and its adaptive optics system to collect deep images of the stars in $I$-band. Sixty-two exoplanet host stars…
Recent spectropolarimetric observations of Herbig AeBe stellar systems show linear polarization variability with wavelength and epoch near their obscured H-alpha emission. Surprisingly, this polarization is not coincident with the H-alpha…
We analyse the distribution of position angles of 1 million galaxies from the Hyperleda catalogue, a sample that presents the galaxies coordinates in the celestial sphere, information that allows us to look for a possible privileged…
We present narrow-band optical and near-IR imaging and optical long-slit spectroscopic observations of Hu1-2, a Galactic planetary nebula (PN) with a pair of [N II]-bright, fast-moving (> 340 km/s) bipolar knots. Intermediate-dispersion…
Planetary nebulae (PNe) represent the near endpoints of evolution for stars of initial mass $\sim$1-8 $M_\odot$, wherein the envelope of an asymptotic giant branch (AGB) star becomes photodissociated and ionized by high-energy radiation…
We have obtained H$\alpha$ CCD images of 21 compact planetary nebulae in the galactic bulge. All objects are resolved and, after deconvolving the seeing disk, we find diameters of 1--2$''$ with typical uncertainties of 20\%. The values are…
We present near-IR K-band intermediate-dispersion spatially-resolved spectroscopic observations of a limited sample of bipolar planetary nebulae (PNe). The spectra have been used to determine the excitation mechanism of the H2 molecule…