The aperture photometry package "vaphot" was developed to perform reliable and precise time-series photometry of uncrowded fields. This package works within the Image Reduction and Analysis Facility (IRAF) environment and is built upon the standard aperture photometry task "phot" from IRAF. The design goal of vaphot was a simple-to-use photometry

We study the large-scale spatial distribution of low-redshift quasars and Seyfert 1 galaxies using a sample of 106 luminous emission-line objects (MB~-23) selected by their Hα emission lines in a far-red objective prism survey (0.2

The effects of seeing on the parameters of the Sèrsic profile are studied in an analytical form using a Gaussian point spread function. The surface brightness of Sèrsic profiles is proportional (in magnitudes) to r1/n. The parameter n serves to classify the type of profile and is related to the central luminosity concentration. It is the parameter

We use an inversion technique to derive the luminosity functions of the Galactic bulge from point source counts extracted from the Midcourse Space Experiment's Point Source Catalog (version 1.2).

The possible occurence of highly deformed configurations is investigated in the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si + $^{12}$C and $^{28}$Si + $^{28}$Si reactions, respectively, by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments (A $geq$ 6) and

We explain the Hα emission of the cometary knots in the Helix Nebula (NGC 7293) with an analytical model that describes the emission of the head of the globules as a photoevaporated flow produced by the incident ionizing radiation of the central star. We compare these models with the Hα emission obtained from the Hubble Space Telescope (HST)