Uwe Lammers

Early Results from the Low-Energy Concentrator Spectrometer On-Board Bepposax

SAX, an acronym for “Satellite Italiano per Astronomia a raggi X”, now renamed “BeppoSAX” in honor of Giuseppe Occhialini, is the first X-ray mission sensitive in the very broad energy range between 0.1 and 300 keV (Boella et al. 1997a). The Narrow Field Instruments (NFI) have approximately 1° fields of view and consist of the imaging low- and medium-energy concentrator spectrometers (LEGS, 0.1-10 keV, Parmar et al. 1997; and MECS, 1-10 keV, Boella et al. 1997b), and the non-imaging high pressure gas scintillation proportional counter (HPGSPC, 3-120 keV, Manzo et al. 1997) and Phoswich detector system (PDS, 15-300 keV, Prontera et al. 1997). All the NFI are coaligned and are normally operated simultaneously. In addition, the payload includes two wide field cameras (WFC, 2-30 keV; Jager et al. 1997) which observe in directions perpendicular to the NFI. These allow the detection of X-ray transient phenomena, as well as long-term variability studies.

Low-energy line emission from Cygnus X-2 observed by the BeppoSAX LECS

We present a 0.2–10 keV spectrum of the low-mass X-ray binary Cygnus X-2 obtained using the Low Energy Concentrator Spectrometer on-board BeppoSAX. The spectrum can be described by a cut-off power-law model with absorption of (2.28±0.07)×1021u2009atomsu2009cm−2, a power-law index of 0.78±0.02 and a cut-off energy of 4.30±0.08u2009keV (68% confidence errors), except at energies near ∼1 keV where excess emission is present. This can be modeled by a broad Gaussian line feature with an energy of 1.02±0.04u2009keV, a full width half-maximum of 0.47±0.07u2009keV and an equivalent width of 74±1125u2009eV. This result confirms earlier reports of line emission near 1 keV and shows the intensity and structure of the feature to be variable. For a more detailed account of these observations we refer to Kuulkers et al. [4].

BeppoSAX LECS X-ray observations of Hercules X-1

Abstract We present 0.1–10 keV observations of Her X-1 obtained with the Low-Energy Spectrometer Concentrator instrument onboard the BeppoSAX satellite during the main on-state of the 35 day cycle. We confirm the existence of an intense 0.093 keV blackbody component and a broad emission feature at 0.94 keV. The pulse phase dependence of these components is similar, suggesting a common origin. This is most likely fluorescent excitation of moderately ionized (ξ ∼ 10–100) material located at the inner edge of the accretion disk.