Ian M George: RXTE Software & Analysis Crib Sheets

These pages are unofficial in all respects. They are primarily simply notes to myself regarding the installation on lancelot. The information is not guaranteed to be correct or up-to-date.

Rate-Selected Obsids

After running rex to make light curves, one can use these light-curves to make a new obsid.lis file containing only those observations for which the mean count rate lies which a given range.

This is achived using the find_lc_rex_ratecut.csh script.

As an example, lets assume you want a list of obsids for which the the mean count rate in a previously constructed set of light curves std_layer1_ch8-27_net.lc lies in the range 13.5 to 14.5 counts per second.
- Assuming you ran rex from the {wherever}/ngc999/work/ directory (as suggested), then the files required (ie the std_layer1_ch8-27_net.lcs) will be in directories {wherever}/ngc999/work/12345-xx-yy-zz/.

In the directory {wherever}/work/

Make sure the obsid.lis is correct. For instance, using the examle from earlier
```
cp obsid_P12345_epoch4.lis obsid.lis
```
Then simply
```
./find_lc_rex_ratecut.csh std_layer1_ch8-27_net 14.0 1.0
```
- The value 14.0 on the command line refers to the centre of the range of count rates wanted.
- The value 1.0 on the command line refers to the full width of the range of count rates wanted.
Assuming at least dataset is found within the requested range, and output file called rex_ratecut.out will be written.
- Obviously you probably want to rename this to something descriptive for future use (& to stop it being over written)
```
mv rex_ratecut.out std_layer1_ch8-27_net_ratecut_14.0_1.0_obsid.lis
```

The next step is probably to use this new list of obsids to construct a mean Spectrum for this Rate-level.

More Sophisticated Rate-Selected Datasets

After running rex to make light curves, one can use this light-curve as a basis for further rate-selected analysis.

This is achived in several steps

First make a new gti file based on the desired rate criteria using the ftool maketime
- For example, say one wants to make the new gti for times when the count rate in the file std_layer1_ch8-27_net_16.lc_snip was in the range 7 to 8 counts/s/PCU:
  - ```
  maketime infile=std_layer1_ch8-27_net_16.lc_snip outfile=rate_0708.gti expr="(RATE1.GE.7).AND.(RATE1.LT.8)" name=NAME value=VALUE time=TIME compact=no clobber=yes           
```
This is what we want, however I'm afraid there is a bit of messing around we have to do associated with zeropoint of the above gti and that which we'll need later....

Find the required values & fix the zeropoint in our new gti using a few ftools

Note some of the header keywords in our gti file (1st extension)

fdump rate_0708.gti+1

Should see something like this:

TIMEUNIT= 'd       '           / Units for header timing keywords
TIMEZERI=                10405 / Zero-point offset for TIME column
TIMEZERF=   0.6860134540711442 / Zero-point offset for TIME column
COMMENT TIMESYS keyword is not currently set. If the input lightcurve
COMMENT contains the header keyword MJDREF, the time in the xronos
COMMENT  output is in TJD (JD-2440000.5)

We're going to be combining our gti file with another ("standard") gti (made by hackedrex_v2 below). The latter files will have a zeropoint given by

TSTART  = 9.095198900000000E+07 / As in the "Time" column
TSTOP   = 9.098014900000000E+07 / As in the "Time" column
MJDREFI =                49353 / 1994.0(UTC) expressed in TT (integer part)
MJDREFF =   6.965740740000E-04 / 1994.0(UTC) expressed in TT (fractional part)
COMMENT   MJD = JD - 2400000.5
TIMESYS = 'TT      '           / XTE time will be TT (Terrestrial Time)
TIMEZERO=       3.37843167E+00 / Clock correction
TIMEUNIT= 's       '           /

So we need to calculate and fix the zeropoint in our gti file to be compatible with the latter.
- In the above example, our gti is specified in seconds from the Julian day
```
2440000.5 + 10405.6860134540711442
```
- The "standard" gti will be specified in seconds from the Julian Day
```
2400000.5 + 49353.0006965740740000
```
- ie Our gti has a zeropoint which is LATER by
```
1052.6856199 days = 9.0952036e7 s
```
Thus we can use the ftool fmodhead to add an appropriate offset to our gti
- Make an ASCII file (say fix_gti.txt) containing the following lines
```
TZERO1 = + 9.0952036e7
TZERO2 = + 9.0952036e7
TIMEZERO = 3.37843167E+00 / Clock correction 
```
- Run
```
fmodhead rate_0708.gti+1 fix_gti.txt
```

Now run hackedrex_v2. This is basically the same as the regular ftool rex, except that one is prompted for gti, which (internally) is merged (using the ftool mgtime) with the "standard" gti that rex makes for each obsid (called "basic.gti"). This merged gti is of course then used for the extraction of the spectral data.
Example:
```
./hackedrex_v2 -d ../P40151  -l 1 -c 7-23 on these 
      Target [all]:
      Printmode, l (ligh curve), s (spectra) [both]:s
      Our rate-selected GTI file: rate_0708.gti
      Root name for products []: rate0708
```
which will (should) produce source & background spectral files rateo708_layer1_*.pha

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