Earth Occultation FITS Histories: These fits files consist of a primary header and 3 extensions. These files contain 20-100 keV flux light curves and daily 16-channel count rate spectra that can be used with the FTOOLS bod2rmf and bod2pha to generate response and pha files for spectral fitting in XSPEC. General Definitions: Truncated Julian Date (TJD) = Julian Date - 2,440,0000.5 BATSE - Burst and Transient Source Experiment CGRO - Compton Gamma Ray Observatory Occultation step: An instance of the astronomical source of interest either setting behind or rising above the limb of the Earth. Extension 1: BATSE_E_CALIB Description: This extension contains channel to energy conversion calibration information used to compute the photon fluxes in extension 3. Columns: CAL_DET: BATSE Large area detector number (0-7) CAL_STRT/CAL_STOP: Beginning and end times in Truncated Julian Dates for a particular calibration. ENERGY_EDGES: Energy in keV for the lower boundary of each of 16 channels (plus the upper bound of the last channel.) For each channel, the upper bound is equal to the lower bound of the next energy channel. CAL_NAME: Program and version of calibration record. IMPORTANT NOTES/CAVEATS: For most of the BATSE mission, the channel to energy conversion was standard. However, for a few intervals, the on-board programmable look-up table was changed to optimize particular observations (TJDs 8361-8406, 8807-8809, 8812, 9400-9419, 10062-10178, 10465-10504, 10983-11053, 11055-11085, see FITS files for exact times). Data from these intervals should not be used with the FTOOLs bod2rmf and bod2pha for spectral analysis. Changes to the calibration information are not fully implemented in these tools. Extension 2: BATSE_FIT_HIS Description: This extension specifies the spectral model used to derive photon fluxes in extension 3. Columns: FITID: Brief description of the spectral model used. FIT_HIS: Bit code for the spectral model identified in FITID. Bit codes are defined in the header to extension 2. FITPARM: Name of a spectral model parameter which was held fixed (constant). FITVAL: Value of FITPARM DSELECT: String denoting which detectors were available for use. 'YYYYYYY' is the default, meaning all 8 detectors were available, although the source of interest was only viewed by 1-4 detectors in any given CGRO pointing. NUM_SUM: Maximum number of occultation steps included in a particular row in extension 3. CHANNELS: Lowest and highest energy channels used in spectral fitting (keV). ENERGIES: Energy range used to compute the photon flux in extension 3 (keV). IMPORTANT NOTES/CAVEATS: If the FITS file name contains "his" instead of "nhis", this extension will be present, but all values will be zero or null, indicating that the FITS file contains only detector count rates, not photon fluxes. Extension 3: BATSE_SRC_HIS Description: This extension contains all of the information corresponding to each measurement of an astronomical source. Columns: STRT-DAY/STRT-TIM: Beginning day (TJD) and seconds of day (s) of the measurement. END-DAY/END-TIM: Ending day (TJD) and seconds of day (s) of the measurement. FLUX/FLUX-ERR: Model dependent flux measurement in units of either photons/cm^2/s or keV/cm^2/s, depending on FIT_ID in extension 2. Usually in photons/cm^2/s. Energy range for this flux measurement is denoted in extension 2: ENERGIES. Note, since detectors are fit simultaneously this value may be repeated in up to 4 consecutive rows of the fits file to allow full inclusion of the count spectra for each detector. PARM1/PARM1-ER,etc.: Fitting parameter values, depending on FIT_ID in extension 2. If PARM_ERR = 0, the parameter was fixed (constant) when the spectral fitting was performed. The normalization is generally not included as a parameter because the fitting software returned an integrated flux directly. RCHISQ: Reduced Chi-square of the spectral fit with degrees of freedom equal to the number of energy channels used (see extension 2: CHANNELS and extension 1: ENERGY_EDGES to determine which channels were used) minus the number of free parameters in the spectral model. RATES/RATES_ER: Source count rate and associated errors for the detector denoted in OPT_SET. (cts/s) TOT_DET: The total number of detectors included in the measurement. OPT_SET: Detector bit code. OPT_SET Detector 1 0 2 1 4 2 8 3 16 4 32 5 64 6 128 7 N_INT: Number of occultation steps included in the measurement. PROG-VER: Program that created the file. CR_DATE: Original creation date. FLAGS: A bit code with the following definitions: BIT Description 0-15 Reduced chi-square > 1.5 in channel 0-15 16 Manual rejection of record (set by BATSE team.) 17 Not used. 18 Set in record for second, third, etc. in a subset of detectors fitted simultaneously to produce one flux measurement. 19 Not used. 20 Rising occultation if set (N_INT, NUM_SUM=1 only) or measurement contains only rising occultations if NUM_SUM>1. 21 Setting occultation if set (N_INT, NUM_SUM=1 only) or measurement contains only setting occultations if NUM_SUM>1. 22 Fit failure. IMPORTANT NOTES/CAVEATS: 1. Flux values for most sources assume a fixed power-law with index -3.0. The validity of the flux measurements depends upon how close this model is to the correct energy spectrum for a particular source. This model is used primarily to remove detector response effects, i.e. different viewing angles and different detector combinations when CGRO was re-pointed, allowing for variability studies. 2. To properly use the flux values, any rows with FLAGS=262144 (bit 18 set) must be excluded from any analysis. This bit denotes repeated flux values. Flux values were repeated to allow inclusion of the count rate information when multiple detectors were simultaneously fitted. 3. Caution must be used when interpreting results especially for faint sources in crowded regions, e.g the Galactic center region, or near bright sources. Sources undergoing Earth occultation at approximately the same time that are not properly accounted for can result in source confusion and spuriously positive or negative fluxes. 4. The CGRO satellite had an orbital precession period of about 52 days. As a result of this, the same sources were in the same positions relative to the Earth's limb every ~52 days. If not all sources were properly accounted for, this could result in an apparent ~52 day signal in the Earth occultation data. Any ~52 day signals in BATSE Earth occultation data should be treated as spurious unless independently confirmed.