Subject: JEM-X Monday Meeting 2005-11-07

2005-11-07
Present: CAO, NL, CBJ, NJW

JEMX status (CBJ): Gamma Ray Burst in the JEMX FOV: GRB 051105b
                   ~0.7 Crab in the peak. IBAS position confirmed with a
                   precision an arcmin. No other sources seen in the field.
                   Usual JMX1 performance. Hot spot activity at low level.

Gain correction (CAO): Revols 300 - 372 checked for gain correction quality.
          A webpage under www.spacecenter.dk/~oxborrow/sdast/GAIN/results.html
          is maintained to report on the gain fitting results. There should
          be a link from the ISDC home page for easy access for INTEGRAL
          users. The page will be updated to include all revolutions from
          the beginning of the mission. Example of strange result: Revol 358.
          
Crab calibration in revol 365 (NJW): The Crab spectra at nominal gain and
          at low gain (20 pha-chan/keV and 14 pha-chan/keV resp.) were compared
          and with j_cor_gain-6.4 the spectra turn out right with Xe peak
          around 29.8 keV. j_cor_gain-6.3 cannot cope with such an period
          of low gain (036500800010, 036500800020, and 036500800030).
          The 'predicted ARF' based on the Be absorption, the electronic/
          rejection efficiency as derived by Soren Brandt, and the j_src_spectra
          collection efficiency (derived from comparing with an 'all detector'
          spectrum) is higher than the 'necessary' ARF (derived from
          forcing a fit to the nominal Crab spectrum). This seems to indicate
          that there is a loss of counts at lower energies (3-10 keV)
          which is not well explained. Next step will be to
          make an XSPEC fit of a raw Crab spectrum to see if the results are
          consistent.


Neural network source position (CBJ): Direct positions from fitting a gauss
          function in the images from IDL software. After optimizing small
          correction constants the determination of positions has improved
          to 9 arcsec (RMS) for DETSIG > 20. (The Crab has been excluded
          from this analysis. Its catalog position does not match the
          JEMX position).
          After neural treatment the RMS goes down to 6 arcsec. The time
          parameter has the largest effect which cannot be explained
          immediately.

GX 3+1 analysis (NL): Search for short periods during the burst - but in vain.

/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