The existence of systematic spectral-fit residuals in ROSAT PSPC spectra, and their dependence on time, is by now a well established fact. This paper describes how those residuals may be related to second order variations of the gain of the PSPC as a function of energy and time. As a result, the energy scale used for the interpretation of PSPC

This paper presents an atlas containing 59 low-resolution supernova spectra which correspond to 27 type Ia supernovae. These 59 spectra spectra which correspond to 27 type Ia supernovae. These 59 spectra refer to different ages along the postmaximum type Ia evolution, covering from the photospheric to the old (~>300 days) nebular phases. These

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P Cygni is one of the most luminous variable stars in our Galaxy. It is the only luminous blue variable which does not show photometric variability on a scale of 1 - 2m. In this paper a possible interpretation of the small-scale photometric variability of ΔV ≍ 0.2m for this peculiar supergiant is discussed.

This paper reports on the fifth STEPHI multi-site photometric campaign in 1993 devoted to the δ Scuti star BDS 1269A (VW Ari). The observation yielded a data set of 150.7 hours. Our analysis has resulted in 7 identified frequencies. These frequencies exhibit three couple-frequency character, and also fit the previous investigations quite well. An

The authors examine the evolution of inhomogeneities (fragments) of supernova ejecta in compact supernova remnants by means of hydrodynamical modelling and simplified analytical calculations. Under the influence of intense post-shock cooling the fragments become strongly compressed as they traverse the hot shocked region between the reverse and