National Aeronautics and Space Administration

The OSO-8 Archive

Experiment	Lightcurves	Raw Data
GCXSE	FITS, GIF	FITS

There are four OSO-8 databases from which data can be retrieved. OSO8BCLC is a collection of lightcurves from the GCXSE B and C detectors. OSO8ALC is a collection of lightcurves from the GCXSE A detectors. OSO8RTRAW accesses the raw rate data files and OSO8PHARAW the raw pha data files (defined below). All of these databases are available via Browse. The data are also available in the OSO-8 FTP area of the HEASARC archive.

The GCXSE High level Products: the lightcurves The FITS lightcurves were extracted from the raw rate data (see below) for the B (2-20 keV) and C (2-60 keV) GCXS detectors only, which were located in opposite directions parallel and antiparallel to the spin axis. The lightcurves were accumulated based on positions from an input catalog which merges the following catalogs: the HEAO-1 A3 MC LASS Catalog, the HEAO-1 A2 Piccinotti Catalog, and the X-ray binaries catalog.
The B and C fields of view were 3 and 5 degrees respectively with an area of 76 cm² and 237 cm², respectively. Data were kept in the lightcurves only for off-axis angles corresponding to effective areas greater than 5 or 10 cm2 for the B and C detectors, respectively. Constant values of 1 and 10 count/s for the B and C detector, respectively, were used to background subtract the lightcurves. The time resolution of the lightcurves is 160 ms. Multiple lightcurves were accumulated for the same sky position, if this was viewed by the same detector in time intervals separated by more than a week. The maximum number of lightcurves per source is 3 and the total number for all sources is 608. Not all of the lightcurves contain a significant source detection and many are affected by source confusion.

Raw data: The raw OSO-8 data consists of 4 data sets: the rates data, binned counts with a time resolution of 160 ms and no spectral information, the pha data containing the 63 channel spectra, the superimposed data and the orbit . All the data have been reformatted by the HEASARC in FITS format using bintable extensions with different layouts.

The FITS files of the rates data consists of two extensions. The first extension contains the spin vector coordinates and various flags, which indicate if the data are usable, updated every spin revolution (about 10 sec). The second extension contains the 160 ms resolution data for the A, B and C detectors. Each file contains data for 1 day. Data from 79 days could not be recovered from the original storage media (9 track tapes). The missing data correspond to the following mission days: 453-462 (10), 465-478 (14), 488-499 (12), 509-511 (3), 513-521 (9), 529-530 (2), 533-554 (22), 559-562 (4),565-567 (3). Using the spin axis position, which is included in the rate data, we constructed a series of plots (available as either ps or ascii files) each containing satellite positions for about 40 days.

The FITS files for the pha data have two extensions. The first extension contains the scientific data with a layout identical to the original data, e.g. one 63 channel spectrum per integration (or one spectrum per FITS row). The integration time is 40.96 sec for the detector B and C and a quarter of a rotation period (2.56 sec) for the detector A. The original available pha data were already clean for SAA passages and earth occulation. A Good Time Interval (GTI) extension was added to facilitate exposure calculation, taking advantage of existing software. For the A detector each FITS file contains approximately 2 weeks of data. For the B and C detectors, approximately 200 days of data have been stored in each FITS file. There are in total 94 files containing the A, B and C spectral data convering the 1194 mission days: 82 files are for the A detector, each containing about 2 week of data, and 6 files each for the B and C detectors, each containing about 200 days of data.

The superimposed data were obtained by averaging over several spin periods the rates data from the detector A. This data set was created to facilitate the usage of data for the A scanning detector.