5. Scientific program

5.1. Scientific objectives

Given the instrument capabilities over the wide energy range described in the previous sections, BeppoSAX can provide an important contribution in several areas of X-ray astronomy (Perola 1990) such as:

• Compact galactic sources: Shape and variability of the various continuum components and of the narrow spectral features (e.g. iron line, cyclotron lines); phase resolved spectroscopy. Discovery and study of X-ray transients.
• Active Galactic Nuclei: spectral shape and variability of the continuum and of the narrow and broad features from 0.1 to 200 keV in bright objects (soft excess, warm and cold absorption and related O and Fe edges, iron line and high energy bump, high energy cut-off); spectral shape and variability of different classes of AGN down to 1/20 of 3C 273 up to 100-200 keV; spectra of weak AGN (e.g. high redshift objects) up to 10 keV.
• Clusters of galaxies: spatially resolved spectra of nearby objects and the study of temperature gradients; chemical composition and temperature of more distant clusters.
• Supernova remnants: spatially resolved spectra of extended remnants; spectra of Magellanic Cloud remnants.
• Normal Galaxies: spectra from 0.1 to 10 keV of the extended emission.
• Stars: multi-temperature spectra of stellar coronae from 0.1 to 10 keV; temperature/spatial structure of coronae by observation of eclipsing binary systems; evolution of flares.
• Gamma-ray bursts: temporal profile with 1 msec resolution from 60 to 600 keV. X-ray counterparts of a subset with positional accuracy of 5'.

5.2. Strategy and operations

Due to the constraint on the solar panel orientation (Sect. 2.2), the sky region accessible to the NFI at any time is a band wide (50% of the sky, slightly larger for the WFC) in the direction perpendicular to the sun vector. In six months all the sky will be therefore accessible. Depending on target position, the observing efficiency will be limited to 50% on average by Earth eclipses (the Earth subtends an angle of about at 600 km) and by passages skirting the edge of the South Atlantic Anomaly.

With a lifetime of two - four years, BeppoSAX will be able to perform 1000-2000 pointings with durations from to . The NFI will be the prime instruments most of the time. When the NFI perform their sequence of pointed observations, the WFC will be operated in parallel (secondary mode) to point preferentially towards the galactic plane, to catch X-ray transients, or to monitor selected regions of the sky. We expect to detect about 10-20 bright X-ray transients per year during the WFC observations. The observing program will be held flexible in order to accommodate these TOO for follow-up observations with the NFI, and the operational capability of BeppoSAX will allow an unexpected new target to be acquired within half a day of its discovery.

Thanks to their large field of view and the distribution of the NFI targets in the sky we expect that, in addition to the Galactic plane, a large fraction of the high Galactic latitude sky will also be covered by the WFC with a sensitivity of a few mCrabs.

The observing time of BeppoSAX is allocated on the basis of proposals submitted in responce to announcements of opportunity and selected by a Time Allocation Committee (TAC) under the auspices of the BeppoSAX Scientific Steering Committee. The observing time is divided in two parts. The first part is devoted to a Core Program amounting to 80% in the first round of 12 months, to 60% the second round of 12 months and 50% in the following. The Core Program will result from the selection of those proposals explicitely submitted for consideration as a part of it and that should be primarily devoted to systematic studies with particular regard to scientific objectives that exploit BeppoSAX capabilities. The Core Program observing time is reserved for competition only to proposals led by Principal Investigators (PI) belonging to Italian or Dutch institutions, to SSD or to the Max Planck Institute for Extraterrestrial Physics in Garching. The second part of the observing time, the Guest Observers Program, is open for competition to proposals led by PI from any country worldwide.

More details on the observing program as well as a detailed technical description of the mission can be found in the BeppoSAX Observers' Handbook (Piro et al. 1995) and via network (Sect. 1).

Acknowledgements

The BeppoSAX program is the result of the efforts of many entusiastic people and it is impossible to thank them all here. A particular tribute to the memory of the project manager Massimo Casciola, who gave so much to the mission, not only with his professional contributions and competence but also with his humanity. We acknowledge the key contribution to the mission by G. Di Cocco, B. Taylor, by the ASI team G. Manarini and B. Negri and R. Ibba, by NIVR, in particular A. Hoeke, by M. Palenzona of ESTEC, and by all the scientists and technical staff of the Consortium institutes and SDC, in particular L. Chiappetti, G. Conti, E. Costa, D. Dal Fiume, F. Favata, M. Feroci, F. Fiore, F. Frontera, S. Giarrusso, P. Giommi, P. Grandi, M. Guainazzi, J. Heise, R. Jager, M.C. Maccarone, G. Manzo, G. Matt, T. Mineo, S. Molendi, L. Nicastro, M. Orlandini, A. Parmar, S. Re, B. Sacco, A. Santangelo, M. Trifoglio. We would like to thank the teams in Alenia Spazio, in particular B. Strim, G. Finocchiaro, P. Santoro, P. Attina', W. Cugno, A. Martelli, in Nuova Telespazio, in particular M. Manca, L. Bruca, L. Cicali, L. Salotti, A. Coletta, G. Tarchini, C. De Libero and in Laben, in particular M. Iacopini, F. Volpi, A. Lenti, E. Alippi, F. Monzani, G. Falcetti, for their professional job on the satellite, the ground segment, the payload. Thanks are due to the team of the Lockheed Martin, in particular B. Sherwood, for the succesful launch. The key role of O. Citterio in the optics design is acknowledged.