Spectroscopy isn’t easy – Learn to be cautious!

1. Spectroscopy isn’t easy – Learn to be cautious! Dr Peter Young Rutherford Appleton Laboratory, UK Dr Peter Young, Rutherford Appleton Laboratory

2. Blending lines • There are many emission lines in the EUV, and blending of lines needs to be considered • The degree of blending often varies with solar conditions • e.g., a high temperature line will only become apparent in flares or the cores of active regions, for example • The CHIANTI database is very useful for identifying potential blends • try the ch_ss.pro routine • The extent of blending can often be assessed by measuring another emission line from the blending ion Dr Peter Young, Rutherford Appleton Laboratory

3. Multiple Gaussian fits • Sometimes it is not possible to simply fit a single Gaussian to a spectral feature • eis_auto_fit uses the MPFIT procedures which can be easily modified for fitting multiple Gaussians • For some features it is necessary to have a ‘customised’ fitting function, e.g., • the line widths are forced to be the same • line separations are forced to be the same Dr Peter Young, Rutherford Appleton Laboratory

4. Atomic data • The dominant ions in the EIS wavelength bands are from the iron ions which are amongst the most complex of astrophysical ions • Recent improved atomic data are available for Fe XII, Fe XIV, but still not perfect • Fe XI has a number of problems, with many of the lines not having reliable identifications • The EIS spectra will prove very valuable for assessing the accuracy of the atomic data • The CHIANTI team (amongst others) will actively use the EIS spectra to identify any problems in the database • recent example: Fe XIII Dr Peter Young, Rutherford Appleton Laboratory