CHIANTI - an atomic database for emission lines - III. Continuum radiationand extension of the ion database

CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities and electron excitation data for a large number o f ions of astrophysical interest. This database allows the calculation of t heoretical line emissivities necessary for the analysis of optically thin e mission line spectra, and includes also a suite of IDL (Interactive Data La nguage) programs to calculate optically thin synthetic spectra and to perfo rm spectral analysis and plasma diagnostics. The first version (1.0) of the CHIANTI database was released in 1996 (Dere et al. 1997) and has been extensively used for analysis of line spectra fro m astrophysical sources by the scientific community. The present paper describes the first major update to the CHIANTI database which will subsequently be labeled version 2.0. The update consists of the addition of a large number of new ions, the revision of existing data for s ome ions and the inclusion of an IDL procedure to calculate the continuum. The CHIANTI atomic database and supporting IDL routines are freely availabl e through the internet.