|
A sample section of the spectrum of Sirius at 200 nm observed
by Glenn Wahlgren with the Goddard High Resolution Spectrograph on the Space
Telescope together with a calculated spectrum that has not yet been adjusted
to improve the fit.
The rotation velocity is known from fitting lines in the visible observed
at high resolution. The spectrum is computed both at 0 km/s rotation
velocity to resolve the blends and at 16 km/s. The 16 km/s spectrum was then
convolved with the instrumental profile. The resolution was not high enough
to resolve the actual structure in the spectrum which is on the order of the
zero rotation line width. Around 201.26 for example the two side bumps are
washed out. Ideally the measurement should have been made at higher resolution.
The calculations are plotted in residual flux but the continuum level for
the observed spectrum has not been set and its position can be adjusted. Except
at 201.02 nm it appears that the observed spectrum should be moved up about 3\%.
That would also bring the minima into better agreement. Either the Mn II line
at 201.0259 is wrong or there is a problem with the reduction at this point
which is near the end of a scan. Note that the minima in the spectrum at
201.1, 201.22, and 201.42 are not line positions. Features in spectrum are
blends of many lines.
Note the Si II line at 201.5 that is computed very much too strong.
That will be corrected in my next calculation for Si II. Note the missing
line at 201.11. That will probably appear when I recompute the Fe group
lines using improved laboratory analyses. The linelist for this spectrum
has not been updated with new calculations. It uses the linelist from my
web site. I am going to update many elements at once to limit the number
of versions of the linelist and also to give me more
time to make comparisons and to check for errors. Fresh calculations can
be found on the website in the {\small /ATOMS} directory.
|
|