RHESSI Paris WG4 Tuesday 27-Jul-04 Kaspi: Fe feature I * Motivation: a photon spectrum from shutter state 3 * Phillips ApJ paper, emissivities * Fe/Fe-Ni ratio quite independent of abundances * photon spectra with 2 Gaussians Discussion of photon vs counts spectra (Hurford, Dennis, Hudson) * CHIANTI prediction for the ratio does not match the July 23 data - cluster of points from early phase is quite different - errors are small, especially for the A3 state Discussion of error bars (Gallagher, Hurford, Hudson) Discussion of why theory is so far from observation (Demoulin, Dennis, Smith, Hurford) * counts spectrum for this case being discussed is POOR Discussion of how to do the fits (Hurford, Dennis, Hudson): huge absorption at low energies suggests that the detector response is responsible * consistency between two flares (23 Jul 02, 23 Apr 03) * significant disagreement with 2 Nov 03, discrepancy as large as 4x and not simply multiplicative Discussion of microphonics contribution to resolution (Smith, Hurford) * DEM? Double-thermal fits using GOES for lower T (???) * centroids of emission vary systematically with energy, in the known sense of higher energies at higher altitudes Question about consistency of small isothermal error bars and large spatial dependence of centroid position (Demoulin, Fletcher, Hurford, Dennis) * conclusions: ongoing work, hoping for DEM and imaging spectroscopy Dennis: Fe feature II * assumption that the Fe lines are always thermal Discussion of this assumption (Hudson, Caspi) * 26 Apr 03 photon spectrum, showing background plotted as though solar in origin - @ A3, it's significant even at low energies * thermal spectra from CHIANTI * centroid (peak energy) as a function of temperature; equivalent width; flux ratio * count-rates spectra for 21-apr-02, showing background feature at 11 keV, for G4 Plot (D. Smith) of W L-shell complex, showing peaks at 10 keV, 8.4 keV, etc., which should be in the SRM but may not be handled correctly. G1 should not show these features because it uses Mb, not W. Discussion * 26 Apr 03 RESIK event, all 3 state; T ~ 2.5 keV and 1.5 keV; 6.71 keVs Discussion of the appearance of the spectrum (Gallagher) * later spectrum from same: T ~ 2.56 keV single temperature * comparison of RESIK, RHESSI, GOES: no evidence of strong low-T DEM peak * equivalent widths => Fe abundance estimates, but not at peak times * Fe/FeNi ratio; Phillips hand corrections to FeNi feature help * conclusions: Fe/H ~ 4*photospheric?; T, poster add-on Discussion of imaging background (Demoulin; Hurford) Hudson: Fe in microflares * analysis of Hannah's microflare list (GOES class A, B) shows that most have Fe feature emission, implying high temperatures