MASSIVE compact objects in the Galactic halo, known as MACHOs, have been postulated as the origin of a substantial fraction of the 'dark matter' known to exist in the haloes of galaxies1,2. Paczyn acuteski3 has suggested that it might be possible to detect these low-luminosity objects by their potential to act as gravitational lenses, causing a

We have observed a number of the most luminous A and B supergiants in the galaxies M 31 and M 33 at intermediate dispersion obtaining both blue and red spectrograms. We have determined spectral types and luminosity classifications from these data, in a few cases revising previous evaluations. From comparison with galactic analogues we estimate

We present the spectral evolution, from about one to six months after optical maximum, of two type Ic supernovae, 1990U in NGC 7479 and 1991A in IC 2973 (UGC 6872). We analyze and compare the SN 1990U and SN 1991A spectral sequences. We looked for differences, at similar phases, between the more characteristic spectral features and their evolution

EN ESTA TESIS SE HA UTILIZADO LA RED DE DETECTORES DE CENTELLEO HEGRA-KIEL INSTALADO EN EL OBSERVATORIO DEL ROQUE DE LOS MUCHACHOS PARA ESTUDIAR LA EMISION DE RADIACION GAMMA PROCEDENTE DE FUENTES PUNTUALES A ENERGIAS MAYORES QUE 1014 EV. EN PRIMER LUGAR, SE HA REALIZADO UNA BUSQUEDA DE EMISION CONTINUA PROCEDENTE DE 27 OBJETOS GALACTICOS Y 3

IAUC 6023 available at Central Bureau for Astronomical Telegrams.

We present optical spectrophotometric observations for 50 blazars obtained in 13 different campaigns over a 7 year period. The spectral flux distribution is studied in terms of a power-law (fnu varies as nu exp alpha) and, when relevant, the contribution of a host galaxy. We give spectral indices and fluxes of the nonthermal component and, when