J/ApJS/96/303 J/ApJS/96/303 Calibrating Broad Band X-ray Telescope K A Weaver K A Arnaud E A Boldt D Christian M Corcoran S S Holt K Jahoda R Kelley F E Marshall R F Mushotzky R Petre G Rawley P J Serlemitsos E M Schlegel A P Smale J H Swank A E Szymkowiak Astrophys. J. Suppl. Ser. 96 303 1995 1995ApJS...96..303W X-ray sources instrumentation: detectors space vehicles X-rays: general This paper describes the calibration of the two solid-state Si(Li) X-ray detectors and the X-ray telescopes that flew as part of Goddard Space Flight Center's Broad Band X-Ray Telescope (BBXRT) experiment on board the space shuttle Columbia in 1990 December. During the 9 day shuttle mission, BBXRT performed ~150 observations of 82 celestial sources. The content of the archive is summarised here. Although BBXRT had a relatively short life, it stands as a milestone in X-ray astronomy as being the first instrument to offer moderate spectral resolution over a wide bandpass (0.3-12.0keV). Among other things, this paper discusses the effective area calibration of the instrument, the flux calibration and flux corrections for off-axis observations, the detector background, and optimal background subtraction techniques. The on-axis effective area calibration for the central detector elements was performed using data from the Crab Nebula, while other carefully selected targets were used for calibration of the outer detector elements. The remaining systematic uncertainties in the effective area calibration for point sources observed both on and off axis are generally less than 5%-10%. The energy scale is known to better than 0.5% at 6.0 keV for both detectors. The results presented here have an impact on the calibration of other medium resolution X-ray experiments such as the CCDs on board ASCA (Astro-D) as well as the Advanced X-Ray Astrophysics Facility detectors.

Source Source name --- RAdeg Nominal right ascension (1950.0) deg DEdeg Nominal declination (1950.0) deg DRA Offset in right ascension number=1 Offset of the pointing direction of the A-system telescope from the nominal RA and DE (epoch 1950.0), given as RAnom - RAaspect, and DEnom - DEaspect. Numbers are supplied only if there exists an aspect solution derived from data taken with the aspect camera. Specific details about aspect solutions can be obtained through the HEASARC at GSFC. deg DDE Offset in declination number=1 Offset of the pointing direction of the A-system telescope from the nominal RA and DE (epoch 1950.0), given as RAnom - RAaspect, and DEnom - DEaspect. Numbers are supplied only if there exists an aspect solution derived from data taken with the aspect camera. Specific details about aspect solutions can be obtained through the HEASARC at GSFC. deg Roll Roll angle of the A-system telescope (phi) number=2 If no aspect solution exists, the roll angle is only an approximate value. deg Start Start time of MET measured from 1990 December 2, 06:49:01 UT d ExpTime Exposure time s D/N Indicator of shuttle day or night number=3 N = night D = day MN = mostly night (>75%) MD = mostly day (>75%) B = both, mixed --- GR Mean detector guard rate number=4 Parameter that measures the rate of particle interactions with the guard. --- Angle Average off-axis angle number=5 Average off-axis angle (THETA) as derived rom the nominal and aspect RA.s and DE.s (cols. [2]-[5]). When an angle but no RA or DE offset is given, that angle is derived from ray tracing. A value of -1 indicates that the angle has not yet been calculated. A ray-tracing program is available from the HEASARC that allows observers to determine their own off-axis angles and to confirm our aspect solutions. arcmin Rate Total count rate in all 10 pixels. ct/s Class Type of object. --- James Marcout, Patricia Bauer CDS 1997Aug28 UNKNOWN UNKNOWN Prepared via OCR at CDS. J_ApJS_96_303.xml