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G. Gaspar

Publications and source records attributed to G. Gaspar.

2 recordsLinked to original sources

Catalogue of central stars of planetary nebulae: Expanded edition

Planetary nebulae represent a potential late stage of stellar evolution, however the central stars (CSPNe) are relatively faint and therefore pertinent information is merely available for <20% of the Galactic sample. Consequently, the literature was surveyed to construct a new catalogue of 620 CSPNe featuring important spectral classifications and information. The catalogue supersedes the existing iteration by 25%, and includes physical parameters such as luminosity, surface gravity, temperature, magnitude estimates, and references for published spectra. The marked statistical improvement enabled the following pertinent conclusions to be determined: the H-rich/H-poor ratio is 2:1, there is a deficiency of CSPNe with types [WC 5-6], and nearly 80% of binary central stars belong to the H-rich group. The last finding suggests that evolutionary scenarios leading to the formation of binary central stars interfere with the conditions required for the formation of H-poor CSPN. Approximately 50% of the sample with derived values of log L, log Teff, and log g, exhibit masses and ages consistent with single stellar evolutionary models. The implication is that single stars are indeed able to form planetary nebulae. Moreover, it is shown that H-poor CSPNe are formed by higher mass progenitors. The catalogue is available through the Vizier database.

astro-ph.GA

Circumnuclear rings and Lindblad resonances in spiral galaxies

In order to study the location of circumnuclear rings (CNR) and their possible relation with the inner Lindblad resonances (ILR), we investigate a sample of spiral galaxies. For this purpose, we have obtained and analyzed medium resolution spectra of 5 spiral galaxies in the range 6200 Å\ to 6900 Å.\, Through the H$α$ emission line, we constructed the radial velocity curves, and then the rotation curves. By fitting them, considering two or three components of an axisymetric Miyamoto$-$Nagai gravitational potential, we constructed the angular velocity and Lindblad curves. In addition, we determined the CNR radius by using the 2D spectra and generating the H$α$ spatial emission radial profiles. We determined the position of the resonances and we calculated the angular velocity pattern, which are in the range of 26 $-$ 47 km s$^{-1}$ kpc$^{-1}$ for the galaxies of the sample. According to our results, the CNRs are located between the inner ILR (iILR) and the outer ILR (oILR), or between the center of the galaxy and the ILR, when the object has only one of such resonance; in agreement with previous results. In addition, we calculated the dimensionless parameter defined as $\mathcal{R}=$ R$_{CR}$ / R$_{bar}$, being in the range 1.1 $-$ 1.6, in agreement with previous results found in the literature.

astro-ph.GA