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ATOMDB Version 1.3.1 Release Notes

Version 1.3.1 Improvements

Version 1.3.1 uses the same underlying atomic database (APED) as V1.3.0. The only change is that the continuum emission is now calculated out to 50 keV, rather than stopping at 10 keV. This means that ATOMDB can now be used with redshifted observations, where previously the cutoff at 10 keV became awkward. The discerning user will notice the line emissivities are very slightly changed, especially at high temperatures. This is due to increased radiative recombination cascades from high-energy electrons; APEC considers only electrons that contribute to the continuum, and so increasing the continuum range from 10 keV to 50 keV increased the amount of RRC and thus the cascades. The change is less than 1% for all lines, however, which is far smaller than our expected accuracy.

For completeness, we include the Version 1.3.0 Improvements and Caveats below.

Version 1.3.0 Improvements

1. This release contains dielectronic recombination lines for K shell transitions in Fe XVIII - Fe XXIV. We have not yet included collisional excitation rates for these lines, although we expect to in the next release. Dielectronic recombination, however, is the dominant source of 6.5-6.8 keV emission lines. The data for these lines was kindly provided by Dr. Verne Jacobs, based on his paper Jacobs et al. 1989 Phys Rev A, 39, 2411.
2. V1.3.0 also corrects an error in the Li-like Ni XXVI line emissivities at 10^8 K and above. Incorrect values of the excitation rate coefficient were used leading to large overestimates of the Ni XXVI line emission for these temperatures. The problem did not affect results below this temperature. Thanks to Dr. Eugene Churazov for bringing it to our attention.
3. This release also corrects some transition probabilities in H-like ions. This error affects the line emissivity calculations for a low-density collisional plasma at the 1-2% level, but would be important if the radiative rates found in APED are used for other purposes. Thanks to Yair Krongold-Herrera for discovering the problem.

Version 1.3.0 Caveats

1. We still have very little data on the delta n >= 1 transitions from L-shell ions of Ne, Mg, Al, Si, S, Ar, or Ca, with the exception of Lithium-like ions. X-rays from these lines are largely below 0.25 keV, and as a result, our spectral calculations in this range are very deficient. We are working on this problem.
2. Only for some of the strongest lines do we include lines from levels above n=5.
3. Despite the addition of the Fe XVIII - Fe XXIV dielectronic recombination lines, we still do not include the so-called "cold" Iron line at 6.4 keV, which arises out of Fe I - Fe XVII ions. We are also missing some inner shell excitation transitions, for example from Fe XVI and O VI. We hope to include these data in the next release.
4. These models are derived from theoretical atomic data for which few experimental measurements have been made. Most emissivities are thought to be good to better than 30 percent; however, larger discrepancies are being found in some caes, likely the result of incomplete atomic physics. Such cases are under investigation as part of the Emission Line Project.
5. We note that the line ratio of Fe XVII 15.014 to Fe XVII 15.261 is about 15 to 20 percent larger than the measured ratio (see Brown et al. 1998, ApJ, 502, 1015). While the discrepancy is within our expected uncertainties, it is quite likely that this discrepancy will be noticeable even at moderate (CCD) resolution.