2. Data reduction
3C 390.3 was observed on Jan. 9-10, 1997, with the Narrow Field Instruments (NFI) of the BeppoSAX satellite (Parmar et al. 1997, Boella et al. 1997, Manzo et al. 1997 and Frontera et al. 1997). The data reduction followed the standard procedure. LECS and MECS cleaned photon lists and PDS background-subtracted products (spectrum and light curve) were obtained using SAXDAS 1.3.0 , included in the Ftools package.
The LECS and the MECS (3 units) spectra were accumulated over circular regions of radius and the background spectra were extracted from blank field observations, using extraction regions on the detector equal to those of the source. The observed background-subtracted count rates are 0.18, 0.37 and 0.49 with a net exposure time of 35 ksec, 100 ksec and 46 Ksec in the LECS (0.12-10 keV), MECS (1.5-10 keV) and PDS (13-100 keV), respectively.
The grouping files available at the BeppoSAX Scientific Data Center (http://www.sdc.asi.it/software/) were used to re-bin the data with the ftool GRPPHA. The data were rebinned so as to allow the use of the statistic and, at the same time, to sample the spectral resolution of the instruments ( for the LECS and the MECS; for the PDS). Publicly available matrices (September 1997 release) were used for all the instruments.
The LECS, MECS and PDS light curves were inspected to search for possible time variability, using the XRONOS package. A standard test was applied to the average count rate in each light curve. We could not detect any flux variation in the whole 0.1-100 keV range during our observation. The probability that the source was not constant is smaller than in each instrument, independently of the temporal bin size used. This result confirms observations done with older X-ray missions, which never detected short time variability on time scales day (Shafer, Ward & Barr 1985; Ghosh & Soundararajaperumal 1991; Inda et al. 1994; Leighly et al. 1997).
© European Southern Observatory (ESO) 1999
Online publication: March 1, 1999