ABC - corrects the arrival times of the rosat photon at the barycenter.
abc infile bcfile outfile ra dec
This task corrects the arrival times of the photons, in the EVENT extension and the times in the GTI extension, for the spacecraft clock to UTC relation (SCC-UTC) and uses the correction table created from the task BCT to correct the arrival time to the barycenter. The Barycenter correction is computed by a linear interpolation between the corrected orbit times (output from BCT). If a photon falls outside of the orbit interval a warning is issued together with the photon time.
This task takes as input:
1. A photon event list data file (in FITS) in either RDF/REV2 format or older US REV0 format (the German REV0 formatted data is not supported). To minimize the amount of time needed for ABC to run, we recommend that the event data be spatially screened so that it only contains photons from the source for which the correction is required.
2. A correction table. This table, created by the task 'BCT', contains the corrected and uncorrected orbit times. The table is in FITS format. It consists of 4 columns, containing the integer and the fractional part of the uncorrected and corrected times. The times are written as JD. See also help on BCT.
3.the equatorial coordinates of the source (epoch 2000.0) given either as hh mm ss.s, dd mm ss.s (separated by a blank space) or in degrees. The coordinates are not used for computation but they are requested in order to test the compatability with the input correction table (from 'BCT').
This task generates:
1. An output event file with the arrival times of the photon corrected at the barycenter.
Correction of photon times to UTC:
The ROSAT spacecraft clock was calibrated to UTC by dividing the ROSAT mission into 10 time intervals and fitting the SCC - UTC relation with a fifth order polynomial. The start and stop times of the intervals, and the fit coefficients, are stored in a file called scc_to_utc2.fits, available either from the REFDATA area ($LHEASOFT/../refdata) For each photon, the correction of the spacecraft clock times (SCC) to UTC is computed according to the following formula :
UTC = JDref(I) + (A(i,1)/86400.0 + (A(i,2)*(SCC-SCCo(i))/86400.0 + (A(i,3)*(SCC-SCCo(i))**2/86400.0 + (A(i,4)*(SCC-SCCo(i))**3/86400.0 + (A(i,5)*(SCC-SCCo(i))**4/86400.0
where
i= the appropriate mission interval containing the SCC time of arrival for that photon A(i,j)= the coefficient of the jth polynomial in the ith time interval SCCo = an offset time for the ith interval JDRef(i) = an offset time for the ith interval
% bct Name of input file [orbit file][] rp900176a01_anc.fits Name of output file[] bct.out RA in hh mm ss.s or degrees -- epoch 2000[] 10 45 13 DEC in dd mm ss.s or degrees -- epoch 2000[] -59 44 20 WARNING: Defaulting to first FITS extension Extensions: HDU type HDU name Rows Columns ____________________________________________________________ 2 Binary Table EPHEM 422 19 % abc Name of input events file[] rp900176a01_bas.fits Name of barycenter correction table[] bct.out Name of output file[] abc.out RA in hh mm ss.s or degrees -- epoch 2000[] 10 45 13 DEC in dd mm ss.s or degrees -- epoch 2000[] -59 44 20 Copying to output file... ...done Extensions: HDU type HDU name Rows Columns ____________________________________________________________ 2 Binary Table STDEVT 283394 8 1 Binary Table STDGTI 17 3 Extensions: HDU type HDU name Rows Columns ____________________________________________________________ 1 Binary Table TIMEREF 422 4
For LHEASOFT version 5.1 and earlier, this tool will fail if the input photon events file is compressed.
rosbary, bct