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RXTE GOF: Frequently Asked Questions

Here are some of the most frequently asked questions at the GOF. If you have been reading our ABC Guide and the data analysis recipes in our Cook Book and still have a question, please see if it is answered here before sending it into the help desk. They are somewhat grouped by topic, but you may want to search for the name of a tool or other relevant key word.

Software and general FTOOLS problems:

  • What are the known bugs and how should I report a possible new bug?
  • What is the status of XTE analysis and calibration software?
  • Were can I find out about software updates or read the release notes?
  • Which Platforms and Compilers are used for testing (i.e., guaranteed to function properly)?
  • I am running my own script and the tool isn't working properly.
  • I input a list via the '@filename' option, but the tool seems to have problems finding the files.
  • The processing appears to be taking a VERY long time. Can I speed this up?


General questions and problems:

  • What documentation is available on line or to download as PostScript files?
  • I have an interesting new result from my XTE analysis. How can I alert the community?
  • Is there a standard publication on XTE overall or the PCA/HEXTE in particular that one can/should refer to when writing a paper based on XTE/PCA/HEXTE data?
  • What exactly are the standard products?
  • I have an observation with an F, T and U at the end. What do these letters mean?
  • Can you tell me how fasebin interprets the 't0' column (#5, normally the epoch of periastron) in the case where the eccentricity=0?
  • I heard a rumor that there are only (1,2,3,4) working PCUs on XTE these days. Is it true? (ANSWER)
  • I'm trying to calculate the location of the RXTE satellite with respect to the earth as a function of time. The Orbital Ephemeris files that come with the RXTE observations contain X,Y, and Z coordinates, but I can't seem to find any information on where the X,Y, and Z unit vectors point. Assuming that Z is parallel to the spin axis of the earth, X and Y are still undefined. Where can I find information about the spacecraft coordinatesin these files?


  • When I run xtefilt, it fails giving an error message about not finding the requested ObsId.
  • When I run xtefilt, it produces columns containing only INDEFs, or it errors off saying it cannot find the input files.
  • When I run xtefilt, I see error messages about "columns missing" and "cannot compute" certain quantities. What's wrong?
  • The TIME_SINCE_SAA column in my filter file stays at 100 even through a period when all the PCUs go off for an obvious SAA passage; is this a mistake?


  • I created a file using FXBARY and am trying to process it with SA(SE)EXTRCT but it crashes. How can I fix this?
  • I input a time-range into one of the extractors and get a "no counts" error. What's wrong?
  • I input a channel range into one of the extractors and get unexpected results. What's wrong?
  • Why am I am getting anomalous spikes in my light-curve RATE file?
  • I attempted to make a GTI file using maketime and put it into the extractor, but did not notice that the GTI was empty. The extractor ignored the GTI and took all the data, instead of failing. How can I avoid this?
  • I'd just like to enquire as to the magnitude of the count errors that are created when making lightcurves. When analysing the data I notice that for areas of high activity the error tends to be less than the (square root of number of counts) error expected, by a magnitude of around 5-7, is this reasonable or should I add this error on to the tabulated error?

Background, response, and other PCA issues:

    background models:

  • With all of the different background models available, how do I know which are best for my data?
  • My source is highly variable, sometimes within the range for the faint model and sometimes not. What model should I use?
  • How often are new SAA history files generated, and where do I get them?
  • The background-subtracted light curve (using a background produced by pcabackest) has unexpected variability. Could this be a problem with the background estimator?
  • Do I need to correct for PCA deadtime? If so, how do I correct the background?
  • I'm having trouble downloading the pca_saa_history.gz file required for the latest background modes. When I click on the pca_saa_history.gz link my browser takes me to a page that contains lines of what looks like the start of a FITS file, presumably the beginning of the pca_saa_history file. This is all I seem to be able to find. Is there something that I'm doing wrong?
  • I found the new background files and SAA_HISTORY file from the Quick Guide to Model Files. It said that users can apply the new models to PCU0 by including a few extra steps in their analysis to get more columns in their filter file and calculate a derived quanity. Are these steps necessary for bright sources?
  • I am doing spectral analysis using standard2 data (from the top Xe layer only) during gain epoch 3b. I am using the new faint source backgrounds. The errors that saextrct puts in the .pha file are simply the square root of the predicted counts, which I know isn't the background model error. What errors should I be using for each standard2 channel?
  • I've found two SAA History files in the archive, which one should I use?


  • Why does pcabackest seem to be over-estimating by a significant factor?
  • Can pcabackest create a background for other modes than Standard2?
  • In pcabackest, do I need to apply the gain correction in estimating the background for my observation?
  • While running pcabackest, I get a failure and a message about "Filter file does not cover the time span of the input.". How can I fix this?
  • What are the systematic errors associated with the background modeling of pcabackest?
  • Do you have a new version of the PCADTLC script that will run on the current version of FTOOLS? I have an old version, from FTOOLS 4.2, that was sent by you in July 2000, which does not appear to run properly with the latest version of FTOOLS.

    response matrix:

  • My spectrum shows an unexpected feature around 5 keV; could this be a feature in the response matrix?
  • Do I need to use pcarsp to create a different response matrix for each spectrum?
  • Why does the script pcarsp seem to hang at the xpcaarf step?
  • Is there a considerable roll dependence in the off-axis response of the PCA collimator. That's what the response matrices I've generated with pcarsp are implying, and I'd like a sanity check by a PCA expert.
  • When do I need to consider the propane loss of PCU0?
  • People tell me that spectral indices got harder with the latest version of the response matrix generator. Should I believe it? ANSWER?
  • I'm trying to find the recommended level to set the systematic error to when using xspec. I'm comparing my RXTE observation (epoch 4/L7 faint source model/pcu 0,2, and 3) with a few of the standard xspec models. I've found values for the systematics that you recommend using with the background models, but am I correct in thinking that these are only appropriate for use with lightcurves? When dealing with spectra, it is the systematic error associated with the response matrix that needs to be used, when trying to compare predicted to actual counts. If I'm not on completely the wrong track, then it is the response matrix systematics that I can't find.


  • How do I get absolute times from RXTE data?
  • What are the differences between FXBARY and FAXBARY? (ANSWER?)
  • I'm confused about all these timing keywords.(ANSWER)
  • Can I rely on the times in the data file names themselves, and TSTART and TSTOP within the data files? Where do I get the most accurate timing information for my observation? (ANSWER)
  • Some time ago I needed to produce a list of barycentrically corrected PCA photon arrival times for an optical/X-ray fast correlation. The data mode is E_125us_64M_0_1s. What I did was simply to apply sefilter to remove the markers, then barytime to obtain barycentrically corrected times. What I was left with was a list of corrected arrival times (plus of course an Event column). Now I would like to sub-select this list in a few channel bands and cannot find a good way to do that. Is this possible?
  • I've got a question about faxbary - does the following output indicate that faxbary failed to correct the times or not?
    [sgtl@bastet ~/FAXBARY]$ faxbary 
    Input file name: (gx_LR1_bcor.lc):  
    Output file name: (gx_LR1_bcor_faxb.lc):  
    Orbit ephemeris file(s) (or @filename): (FPorbit_Day2559):  
    **** faxbary v2.1 ****
    running: axBary -i FPorbit_Day2559 -f gx_LR1_bcor_faxb.lc -ra
    1.25000000E+01 -dec -7.30999985E+01 -ref FK5
    axBary: Using JPL Planetary Ephemeris DE-200
    axBary: Using JPL Planetary Ephemeris DE-200
    axBary: Using JPL Planetary Ephemeris DE-200
    axBary: Could not find a Time column in HDU 2

    Other Issues:

  • Can I do a joint fit of HEXTE and PCA? (ANSWER)

ASM Issues:

HEXTE issues:

  • My realtime data do not seem to include the 16s housekeeping required by the tool hxtdead. Can I still correct the data for deadtime?
  • While running hxtdead, I see warning messages about "uld or xuld undfined..." and "Detector 0: Uld data interpolated..."; is this a problem?
  • My caldb installation is incomplete or not up to date, how do I upgrade the current tools?
  • How can I obtain the most recent HEXTE calibrationinfomation?
  • The HEXTE recipe page says that people can just download the canned response matrices, which I would like to do for HEXTE standard mode data. However, I found that the standard mode data is in 64-bins, and the response matrix is in 256 bins. Therefore the canned matrix must be rebinned, yes?
  • *I would like to create light curves and spectra from HEXTE (0,1) but I could not find the conversion between energy and channel. Where can I find this information?
  • I got an error message when using hxtlcurv. What does the following error mean? Warning! Your .pha or .lc file covers time interval 126824688.00100 MET to 126826623.99900 MET but your houskeeping file, FH59_78f30ff-78f4ab0, only covers 126824704.00000 MET to 126831280.00000 MET Correction proceeding but will use average deadtimes at end(s) of file.
  • I get a message from a HEXTE tool telling me to beware of detector 1 on cluster B. What is it talking about and how does it affect my deadtime, spectral and lightcurve analaysis (this was answered within the last three weeks I recall.) ANSWER?
  • I'm trying to separate the on-source off-source data using the fselect command. It asks for a fits file which I want to apply the expression ClstrPosition.eq.0.or.ClstrPosition.eq.3 to. Where is this file?

Data, processing, and distribution:

  • Why haven't I received my data tape yet, and when will I?
  • How do I get the orbit ephemerides for my observations if they are missing from my data?
  • I could not find the realtime data in http://xgo2.nascom.nasa.gov:pub/FITS for my observation from 2 days ago.
  • How do I obtain the PGP software needed to unencrypt my data?
  • With the new electronic distribution system, when does my year proprietary period start?
  • How can I tell when an observation is supposed to go public?
  • I was just beginning to recombine the PCA GoodXenon data from the observation denoted by 70154-01-05-01 using the "make_se" script. The script could not run due to mismatched files. I took a look and nticed that there are three GoodXenon files in the PCA directory for this observation. Since these should be found in pairs, I am assuming one is missing. Can you tell me what has happened here and if the data can be found somewhere?

Other useful links:

If you have a question about RXTE, please send email to one of our help desks.

This page is maintained by the RXTE GOF and was last modified on Wednesday, 24-Aug-2022 11:10:28 EDT.