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Home > Data Analysis > BAT > Energy conversion

BAT energy conversion

The command bateconvert ensures that the PHA to PI energy conversion is quadratic (rather than linear) and gives more correct results. By default, this is now run by the ground software; to determine whether an older file has been correctly processed, certain keywords should be checked:

>fkeyprint sw00377487000bevshsp_uf.evt GAIN

Look for the GAINAPP and GAINMETH keywords; these should be set to T(rue) and FIXEDDAC respectively, if bateconvert has already been run. I.e.:

GAINAPP =               T / Gain correction has been applied
GAINMETH= 'FIXEDDAC'      / Cubic ground gain/offset correction using DAC-b

If these keywords do not exist, or have different values, then bateconvert should be run. This should be done as follows. Note that the event file must be unzipped, since the file, itself, is modified.

>bateconvert
> Input file name [ ]: sw00377487000bevshsp_uf.evt
> Flight calibration (gain/offset) file name [ ]: sw00377487000bgocb.hk.gz
> Quadratic pulser residuals calibration file name [ ]: CALDB
> Ground pulser DAC to keV calibration file name [ ]: CALDB
> Flight pulser DAC to keV calibration file name [ ]: CALDB

The gain/offset file (sw*bgocb.hk.gz) should be in the [obsid]/bat/hk directory; if it is missing, the next earliest should be obtained from the trend data on the HEASARC ftp site (heasarc.gsfc.nasa.gov; use anonymous as the user name, and your e-mail address as the password). Trend data are sorted by months, so look in /swift/data/trend/YYYY_MM/bat/bgainoffs. See GSFC's BAT analysis threads for more details.