We present early-time infrared (IR) and optical spectroscopy, and optical photometry, of the Type Ia supernova 1994D. These observations provide the most complete optical-IR spectral coverage ever achieved for a Type Ia at this phase. Optical and IR spectra were obtained as early as 9d before maximum light. The combined optical and IR spectra of SN

In this paper we propose a new method to prevent the saturation of any set of hidden units of a multilayer neural network. This method is implemented by adding a regularization term to the standard quadratic error function, which is based on a repulsive action between pairs of patterns.

This is a study of the UV variability of the galaxy Fairall-9 between 1978 and 1991. Table 1 shows the UV continuum fluxes measured in three "line-free" windows centered at 1171, 1400 and 1910 A (observed wavelengths), and corrected for E(B-V)=0.035 extinction. The IUE Fine Error Sensor (FES) counts (optical photometry) are also given in this table

We present long-slit spectra of the Seyfert 2 galaxy NGC 5252, covering the nucleus and part of the extranuclear emission-line region. All the regions sampled by our spectra have emission-line ratios characteristic of photoionization by an active galactic nucleus-like (AGN-like) continuum source. The spectrum of the nucleus differs from those

New spectroscopic observations, including the optical and near-infrared ranges, have been obtained for a sample of HII regions located towards the Galactic anticentre. The sample includes HII regions with known galactocentric distances, their ionizing stars having been clearly identified from previous work. The spectra correspond to low-to

Here we describe a method that can be used to derive, with a high degree of confidence, the direction of the rotation axis of a galaxy. The method is based on the deformation, caused by differential galactic rotation, of the remnants produced by multi-supernova explosions. We consider two realistic extreme sets of galactic boundary conditions, and