Known Issues and Limitations

1. Cross-talk between sources. It is a fundamental property of coded mask instruments, that every source in the field of view contributes as background for all other observed sources. In this sense, cross-talk is unavoidable. Specifically, strong bursts from one source will introduce Poisson noise in the light curves for all other sources. The new light-curve extraction method introduced with the OSA 11 release provides very good separation of the sources, but cross talk cannot be fully eliminated. An important new feature is an automatic search for bursts in the count rate records. This allows to identify the bursting source (or provide evidence that the burst is caused by a fluctuation in the instrument background). (See further details in the JEM-X Analysis User Manual).

2. Flux extraction methods. The flux of a given source can be obtained either with the ``standard'' extraction or with mosaic_spec. In cases when the fluxes obtained with the two methods differ, it is advised to consider the one obtained from the standard extraction (SPE level, see next point, however). For weak sources, not detected in individual science windows,, the mosaic_spec option is generally preferred. For stronger sources, the use of j_ima_iros is recommended.

3. PIF-option and mosaic_spec. It is not trustable to extract spectra of strong sources with mosaic_spec from images obtained with the PIF-option. On the other hand, for sources not detected at single SCW level, but visible only in the mosaic, the analysis conducted at SPE (and LCR) level can provide erroneous results from another source in the FOV. In case of differences, between the methods, the user should check the coordinates used for computing the spectrum.

4. Handling of Restricted Imaging data. The use of the ‘REST’ telemetry format has been discouraged since 2004. It has turned out to be difficult to interpret data taken with this format, specifically the energy resolution is very poor. Analysis of REST-format data was only supported in OSA-5 or earlier versions.

5. The source position reported in columns RA_OBJ and DEC_OBJ of JMXi-SRCL-RES will always be the one found by j_ima_iros. Columns RA_CAT and DEC_CAT reflect the catalog position if a user catalog has been defined. The SPE and LCR levels will read the RA_OBJ and DEC_OBJ columns and do the extraction using those. In order to force the use of the catalog positions - which is recommended - the JMXi-SRCL-RES table must be manipulated e.g. by an ftool, to update columns RA_OBJ and DEC_OBJ.

6. The source coordinates found by j_ima_iros may deviate from the true positions and this can occasionally cause inaccurate flux reconstructions from j_src_spectra or j_src_lc. If a good source position is available, it is better to force these coordinates by use of a user catalogue. An example is given in the cookbook (but see also point ).

7. When not using the j_ima_iros method for extraction of light curve for weak sources, these may be contaminated by counts from stronger sources in the FOV. This happens because the source extraction does not take into account the presence of the other sources.

8. the parameters relative to the j_ima_iros method for extraction of light curve are passed over only if the parameter LCR_useIROS=yes, otherwise they are not considered. You might notice that if LCR_useIROS=yes, the parameter LCR_doBurstSearch will always default to ``yes'', without any impact.

9. If LCR_useIROS=yes, the parameter LCR_timeStep is set to the default value of 4 if it is set to a value less than 0.1s.

10. GUI issue: you can enter up to 7 digits for real numbers, the others will be discarded. However, if you close a GUI tab and then reopen it, only two digits will be retained and one should take take to enter the missing ones. This is probably a feature of the root-based GUI, which was not possible to correct.