HEAsoft 5.0, Patch 4

February 20, 2001

Summary of changes in the fourth patch to HEAsoft 5.0.  This patch is
intended primarily for people using the tools in the XTE subpackage to
analyze RXTE data. (Patch 3 was never publicly released).

For more information check the fhelp documentation after installing the
update or write to XTEHELP (xtehelp@athena.gsfc.nasa.gov)
---------------------------------------------------------------------

**New Tools**

faxbary / axBary:

  An alternative to fxbary (which fails for dates after 31 December,
  2000). For observations through the end of 2000 either program may
  be used. faxbary is a Perl script which calls a standalone program,
  axBary, (also provided with this update) and gives it functionality
  very similar to that of fxbary.  Users are strongly encouraged to use
  the faxbary script rather than calling axBary directly.  The parameter
  list for faxbary differs from its predecessor as follows:

                         FXBARY           FAXBARY
                         ------           -------
                         in_file           infile
                        out_file          outfile
                      orbit_file       orbitfiles
                          ra_str               ra
                         dec_str              dec
                         timecol       *NOT USED*
                      start_time       *NOT USED*
                        end_time       *NOT USED*
                       sensecase       *NOT USED*
                      *NOT USED*         refframe

Beyond the changes listed above, the biggest difference in usage is that
the ra/dec parameters in faxbary must be given numerically as decimal
degrees. Also the refframe parameter may be used to control whether
the JPLEPH.200 (default) or JPLEPH.405 ephemeris file is used. 

The behavior of faxbary has been designed to match fxbary as much as
possible.  As with fxbary, the value of the TIMEZERO keyword applies
to the BARYTIME column in the output file, thus the barycentric
correction can be derived by simply taking the difference between the
TIME and BARYTIME columns. Note also that because axBary applies the
fine clock corrections (derived from the file tdc.dat located in the
$LHEASOFT/refdata directory) and also accounts for instrumental delay
(both of these effects are ignored by fxbary) the more precise barycentric
corrections computed by faxbary/axBary may differ from fxbary by as much
as +/- 50 microseconds.

An input list of orbit files is also handled slightly differently by
faxbary than by fxbary. To use more than one orbit file one can either
just enter them directly at the orbitfiles parameter prompt (as a
whitespace separated list) or use the typical ftools @filelist syntax,
where the named file lists the orbit files one per line. Like fxbary,
faxbary will first examine all of the orbit files and reject any which
do not overlap with the times in the datafile to be corrected.  Note,
however, that any list of orbit files MUST be continuous and not contain
any gaps! If this criterion is not satisfied the faxbary script will
print an explanatory error message and exit.


**Updated Tools**

pcarmf / pcarsp (version 7.10):

These tools now calculate appropriate response matrices for PCU0 following 
the loss of the propane veto layer on May 12, 2000.   The date May 13, 2000
marks the start of calibration Epoch 5.   No overall gain adjustment was
made to the PCA: Epoch 5 simply refers to the dates following the loss
of propane in PCU0.

New energy-to-channel file, pca_e2c_e05v01.fits,
includes several new columns used in the improved
energy-to-channel algorithm for all PCUs, namely:

 channel = A + B * (E/W(E))+ C * (E/W(E))^2  + D * (E/W(E))^3

 where:

    E = energy,
    W(E) = the energy required to create one thermal electron.
           (taken from T.H.V.T. Dias et al. Phys Rev A, 48,
            2887 (1993) and personal communication.)
    (factor of 22 makes the apparent X-axis in XSPEC ~= energy)

    Day_Offset = (Day - Ref_Day) [Ref_Day from parameter file]

and: 

    A = PARM1 + PARM5 * Day_Offset + PARM7 * Day_Offset^2
    B = PARM2 + (PARM6 * Day_Offset + PARM8 * Day_Offset^2) * PARM4
    C = PARM3
    D = PARM9

    PARM4 = PARM2(current epoch) / PARM2(epoch 3)

    Currently, the value of PARM9 is zero everywhere.

    The model assumes that gain drift can be fit (in epoch 3 space)
as the sum of a linear plus a quadratic term. The entire shift
is corrected by the relative channel/keV term (PARM4).

Additional improvements:

PCARMF v7.10 also includes a fix to a bug found in v7.01 and all
previous versions of the code, which resulted erroneous low energy
responses when choosing  "all" layers.  The patched PCARSP/PCARMF 
included a work-around for this bug.  The corrected code is more
efficient and noticeably quicker.

Known features in the response matrices at 5 and 35 keV have reduced
equivalent widths with the new tools.

The spectral index for the Crab pulsar is closer to the canonical value
of 2.1 (the degree of improvement depends on your PCU/layer combination).
For all PCUs, all layers, the Crab pulsar spectral index is now 2.16
(down from 2.2 in the previous version).

PCARSP checks to make sure the appropriate energy-to-channel file is
being requested.  It includes warnings for data taken on May 12, 2000
as the propane was venting PCU0.

Web page maintained by: Bryan K. Irby