Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member states and the USA (NASA). Also based on observations collected with the VLA, an instrument of the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated by Associated Universities, Inc. Optical data were collected at the European Southern Observatory (La Silla, Chile), and at the Observatorio Astronómico Nacional of San Pedro Mártir (Mexico).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

Research Associate FNRS (Belgium).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...1,

Research Fellow FNRS (Belgium).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...%

We do not consider flux values above 5.0 keV for two reasons: firstly only a few photons are detected in that region of the spectrum, and secondly this energy band is the most strongly affected by the soft proton flare which occurred during the April observation.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... (GTIs)

Even if no flare contaminated time interval was rejected, standard GTIs are anyway always applied to XMM-Newton data, and must be taken into account in every timing analysis.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... star

$\zeta$ Pup was observed with the ASCA satellite in October 1993 during about 30 ks (P.I.: Dr. T. G. Tsuru). Screened event files were retrieved from the ARNIE database at Leicester University and reduced using the XSELECT software (version 1.4b).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.