HEXTE Configurations: Event List
- General Description
- Detailed Description
- Time and energy resolution
- Reduction requirements and options
Event List mode data configurations are designated with a character
string beginning with E, e.g. E_8us_256_DX1F.
Files containing Event data are in science event format. The science data occupy the XTE_SE extension in the form of individual time-stamped binary event words, one per line, which fill the Event column. The words themselves are strings of ones and zeros, the combinations of which define the properties of each event with respect to a template of all possible properties within the configuration. This template is broken up into sections which, depending on the particular configuration, refer to things like Detector ID, PHA channel, etc. Thus, an individual event word, with its particular combination of ones and zeros, picks out, say, one Detector, one PHA channel, etc. The time stamps occupy the Time column, but are also encoded in the event word. The cluster position (see below) occupies the ClstrPosition column.
The naming convention of the configuration provides a summary of the
properties of the data. > For Event List data, the format
gives
For example, in the E_8us_256_DX1F configuration, events
are time-stamped with 8-microsec resolution, in 256 PHA channel bands.
"DX1F" designates that 5 event bytes are to be included in the
telemetry, giving full spectral and timing resolution with detector ID.
> For more details about the different
HEXTE Event List mode
configurations, please consult the Technical Appendix.
The configuration name does not, however, give a complete description of the data. Rather, the key to understanding your Event data lies in "decoding" the event word template. The template itself occupies the TEVTB4 keyword in the header of the XTE_SE extension. It is written in DDL - the Data Descriptor Language - and can be displayed on the screen using the ftool fkeyprint. But since the TEVTB4 keyword can be somewhat long, it is often better to look first at the neighbouring - and complimentary - TDDES4 keyword. Also written in DDL, the TDDES4 keyword describes which events have been selected by the HEXTE processors. As an example, here is the value of TDDES4 in the E_8us_256_DX1F configuration:
Now let's look at the TEVTB4 keyword for the same E_8us_256_DX1F configuration:
In common with other RXTE science event files, Event mode files have two additional extensions containing good time intervals (GTI). Both are called GTI.
The time resolution for Event configurations is the resolution of the time stamps. This is not necessarily the same as the number in the name of the configuration, which is an approximation. For example, in the E_2ms_256_X05 configuration, the step size is really 1/2**9 seconds, i.e. 1.953125 milliseconds.
The configuration name gives the number of channel bands. For current HEXTE Event configurations there are just two possibilities: the full, 256 channels (e.g. E_2ms_256_X05), or no PHA information at all (e.g. E_8us_0_X06)
Light curves and spectra may be extracted from HEXTE Event list data
using seextrct
Apart from adjusting screening criteria, your primary reduction options include:
Note that both light curves and spectra must be corrected for deadtime
using hxtdead. See the RXTE Cookbook
recipe Reduction and Analysis
of HEXTE Data for further details on working with HEXTE Archive data.
General Description
Detailed Description
E_ttt_ccc_Dxxx
TDDES4 = 'D[0~3] & E[0~131071] & C[0~255] & T[0~16]'
which, broken into its parts, means:
TEVTB4 = 'E[0:63] {6}, E[CAL] {1}, T[0:15;1] {4}, D[0:3] {2},
E[LE1,LE0] {2}, T[0:1;7.62939453125e-6] {17}, C[0:255] {8}'
This looks a bit confusing at first, but the key to understanding what it means is to focus on the non-E tokens:
The E-tokens are for supplemental information about the events, most of which is actually redundant:
The cluster position, encoded as a single integer, occupies the ClstrPosition column. The values it can assume are:
1.5-degree rocking 3.0-degree rocking
1 or 65 on-target 8 or 72 on-target
2 or 66 +1.5 deg 4 or 68 +3.0 deg
32 or 96 -1.5 deg 16 or 80 -3.0 deg
Time and energy resolution
Reduction requirements and options
The ABC of XTE is written and maintained by the RXTE GOF. Please email xtehelp@athena.gsfc.nasa.gov if you have any questions or comments. This particular page was last modified on Tuesday, 14-Sep-1999 13:45:42 EDT.