Subject: JEMX Monday Meeting 2006-01-16

Here is the report from today's meeting:

Participants: SB, JC, NL, CAO, CBJ, NJW

JEM-X status (SB): A gamma-ray burst happened in the
week-end but our Instrument Station failed for a yet
unknown reason so we cannot look at IPF data.
New (minor) hotspot appeared around x=72, y=18 with a
duration around 1500 s. The peak countrate was 16 cts/s
(binsize = 1 s). Concentrated around low pulseheight
(PHA < 100). Observation 2006-01-12.

GPS data availability (JC): Revolution 396 and 397 GPS
data not released yet which is not a nice delay.

Source position determination (NJW): A catalog with all
source detections by j_ima_iros (SRCL-RES) has been
produced for all public data (revol. 28 - 241). The
average position for the best detected sources
(DETSIG > 20) matches the catalog position to
better than 12 arcsec in many cases. The question is how
these results compare with the results of CBJ.
Comment by NL: Work is ongoing to improve the
parameters of j_ima_iros.

Crab position (CBJ,SB): RADEC: 83.6307 22.0176 as
determined by centroiding from CBJ images in the full
energyrange from the central pointings in revol. 239 (we
can add central pointings from revolution 300 as well).
The image matches a Chandra image very well. In the ISDC
reference catalog it is the position of the Crab Pulsar
that is given and that should not be used for this
comparison.
[After meeting: The Crab Nebula position matches very
well the j_ima_iros position, 2.4 arcsec difference].

Gain dependent detction efficiency (SB): A curve has been
produced showing the electronic efficiency derived from an
assumption of the Crab spectrum (power law with photon
index of 2.1). Ratio between the observed countrate and
predicted count rate from spectrum and quantum efficiency
shows that the electronic efficiency starts to drop below
1 alread around 12-15 keV (when moving down in energy).

/NJW

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Niels J. Westergaard
Danish National Space Center
Juliane Maries Vej 30, DK 2100 Copenhagen O
Phone: +45 35325705; FAX:  +45 35362475