EDS Configurations: Event Burst Catcher
- General Description
- Detailed Description
- Triggers
- Reduction requirements and options
- Gain and offset
The generic Binned Burst Catcher configurations are designated with a
character string beginning with CB,
e.g. CE_16us_64M_0. Before describing the structure of
Event Burst Catcher data, we review how the burst catching works.
Two Event Analyzers are required to catch bursts: one for the trigger,
the other for the catcher. The Data Buffer in the catcher EA is
divided into four equal parts, one per "Interval". If, say, the
trigger is activated during Internal N, the trigger EA will discover
this fact during Interval N+1 and the burst flag will be set. During
Interval N+2, the flag causes the catcher EA to read into its memory
the data for Interval N-1 (the oldest in the Data Buffer) while at the
same time accumulating data from Interval N+2 in the appropriate
quarter buffer. During the accumulation of N+3 data, the N data are
read out, as are the post-onset N+1 and N+2 data. The readouts then
cease, yielding a train of data comprising four quarters the second of
which contains the burst onset. For more details about how
Burst Catcher modes works, please consult the Technical
Appendix.
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 PCU ID, PHA channel band, etc. Thus, an individual event word, with its particular combination of ones and zeros, picks out, say, one PCU ID, one PHA channel band, etc. The time stamps occupy the Time column, but are also encoded in the event word.
The name of the configuration provides a summary of the properties of
the corresponding data. For Event Burst Catcher data, the format
gives
As a special case, there are also GoodXenon1 and GoodXenon2 burst
catchers.
For example, in the CE_8us_32B_0 configuration, 32
histograms with ~8-microsecond resolution are accumulated from
channels 0 to 256, with the "B" channel distribution/binning
scheme. For a complete list of Binned Burst Catcher
configurations, see the RXTE
PCA Configurations page. For more details about these
configurations, please consult the Technical Appendix.
The Event Burst Catcher mode captures 33,767 events (plus time
markers) each time a trigger signal is recieved. If the trigger is
high-priority, the data are immedidately transferred to the
spacecraft. If the trigger is low-priority, the data from the current
trigger is stored and data from the previous trigger is sent to the
spacecraft.
The remainder of the details of the event burst catcher are the same
as the generic event mode.
The Event Burst Catcher modes are triggered by a second EA running
a Burst Trigger Mode. The trigger EA is synchronized with the catcher
EA, so the data have the same Intervals. The ModeSpecific
column in the XTE_SA extension of the trigger data file
contains the times of trigger activation. A zero denotes no activation.
These configurations will also trigger HEXTE.
There are two flavors of Burst Triggers: High
Priority and Low Priority. The corresponding configurations have names
beginning with T, e.g. or
TLA_1s_10_249_1s_500_F and TLM_31us_0_249_500ms_QN,
respectively. The format for the High Priority Trigger is
gives
Low priority triggers are denoted TLM, THM, or TEM, for triggers based
on count rate, hardness ratio, or edge, respectively.
For a complete list of Burst Trigger
configurations, see the RXTE
PCA Configurations page. For more details about these
configurations, please consult the Technical Appendix.
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 CE_8us_32B_0 configuration, the step size is really
1/2**17
seconds, i.e. 7.6293945 microseconds. To derive this number, work out the nearest inverse power of two from the configuration name.
The configuration name gives the number of channel bands, but not the channel boundaries themselves, which are denoted by a code letter. To derive the channel boundaries, either look them up in the Technical Appendix, or run fdump the data file and look at the header of the Event column. The value of the TEVTB2 keyword gives the channel boundaries. The energy resolution also depends on the configuration: the bins in any spectrum you extract will be the same as the channel bands in the configuration
Spectra and light curves may be extracted from Event Burst Catcher
mode data in much the same way as for Event mode data using the
ftool seextrct. Apart from adjusting screening criteria, your primary reduction options include:
Gain and offset corrections are applied by the EDS to generic Event data.
General Description
Detailed Description
CE_ttt_ccX_l
Burst Trigger Modes
TLA_ttt_ll_hh_rrr_ccc_b
Time resolution
Energy resolution and channel boundaries
Reduction requirements and options
For complete details on working with Event mode data, see the RXTE
Cookbook recipe
Reduction and Analysis of PCA Event-Mode Spectra.
Gain and offset
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 13:45:43 EDT.