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. 
