We present optical and infrared observations of Roque Praesepe 1 (RPr 1), a faint ( I=21.01 ) and very red object ( I-K=4.57 ) discovered in a deep CCD survey, covering an area of 800 arcmin2 of the Praesepe open cluster. A low-resolution spectrum shows that RPr 1 is a very late object, the latest object in Praesepe for which a spectrum has been

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In the paper "Third-Order Perturbative Approach to Gravitational Instability: Evolution of Isolated Structures and Environmental Effects" by L. J. Goicoechea and J. Buitrago (ApJ, 483, 541 [1997]), there is a typographical error in equations (4), (5), (8), and (21). In these equations, the volume integrals must include both numerator and

This paper presents observations made at intermediate spectral and spatial resolutions along the major and minor axes of the starburst galaxy NGC 253. The spectral ranges analyzed are in the region of the stellar Mg I b (~5175 Angstroms) line, in the near-IR Ca II triplet (~8550 Angstroms) absorption features, and in the region of the H alpha

We present a one-dimensional numerical scheme that allows for the simultaneous solution of the hydrodynamic equations coupled with energy and ionization equations. The code accounts for the time-dependent ionization of H, He, and He(+) and for radiative cooling derived from collisional excitation of C, N, O and Ne, whose ionization structures with

In a previous paper, we presented an atlas containing 59 low-resolution spectra that correspond to 27 Type Ia supernovae, covering about 1 year of Type Ia supernova evolution. This paper is a continuation, with the aim of performing a standard spectral evolution for ``normal'' Type Ia supernovae from the homogeneous set of data compiled in the