National Aeronautics and Space Administration

EDS Configurations: Good Xenon

• General Description
• Detailed Description
• Time and energy resolution
• Reduction requirements and options
• Gain and offset

The Good Xenon configurations use two Event Analyzers simultaneously to provide detailed spectral and temporal information about every event that survives background rejection. There are two pairs of Good Xenon configurations:

1. Good_Xenon1_2s with Good_Xenon2_2s (the 1 and 2 denote the two EAs; the 2s is the readout time)

2. Good_Xenon1_16s with Good_Xenon2_16s (again, the 1 and 2 denote the two EAs; 16s is the readout time).

Files containing Good Xenon 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 - one for the PCU ID, one for the anode ID, and one for the PHA channel. Thus, an individual event word, with its particular combination of ones and zeros, picks out one PCU ID, one anode ID and one PHA channel. The time stamps occupy the Time column.

The key to understanding and manipulating your Good Xenon data lies in "decoding" the event word template. The template itself occupies the TEVTB2 keyword in the header of the XTE_SE extension and is written in DDL - the Data Descriptor Language. Its value for Good Xenon is:

(M[1]{1},S[Zero]{6},D[0:4]{3},E[0:63]{6},C[0:255]{8})

• (M[1]{1}... ) - Unlike other event mode configurations, each row in a Good Xenon file contains only one kind of event, namely, valid science events. Like other other event mode configurations, these science events are identified with an M-token, the value of which is M[1]{1}.

• S[Zero]{6} -Housekeeping check. Each valid bitmask is preceded by six zeroes.

• D[0:4]{3} - Detectors 0-4, i.e. PCUs 0-4 (DDL's : symbol indicates a range). The {3} means that three bits are used to identify the PCU: 000 identifies PCU0, 001 PCU1, and so on.

• E[0:63]{6} - Detector element, i.e. xenon anode. The {6} means that six bits are used to identify the Xe anode: 000001 identifies X1L, 000010 X1R, and so on. Note that some software, notably sefilter, requires the binary substring to be entered as a base-ten number, e.g. 1 identifies X1L, 2 X1R, 4 X2L, 8 X2R, and so on.

• C[0:255]{8} - PCU Channel. Good Xenon provides the full 256 channel range. The {8} means that eight bits are used to identify one of the 2**8 channels.

For complete details on working with Event mode data and GoodXenon data, see the RXTE Cookbook recipe Reduction and Analysis of PCA Event-Mode Spectra.

A further option is to convert the data from their event-word format into the more understandable, but more expansive, event file format which has explicit columns for the PCU ID etc. - similar to ASCA and ROSAT event lists. The conversion is effected, when you merge the two EAs, by running xenon2fits with the wrtparm=a option. Note that you will have to use the extractor ftool rather than seextrct to extract events. You will, however, be able to read the entire events file into xronos which cannot handle bitmasks at the moment.