Jeff Valenti

Spectroscopy Made Easy (SME) is IDL software and a compiled external library that fits an observed high-resolution stellar spectrum with a synthetic spectrum to determine stellar parameters. The original paper describing SME is Valenti & Piskunov (1996). Subsequent enhancements of the package are described in Piskunov & Valenti (2016).

SME Releases
Version Size Release Date
574 1276 MB 2020-Feb-22
522 414 MB 2016-Jul-15
423 294 MB 2014-May-15
412 294 MB 2014-Mar-04
342 102 MB 2013-Mar-25
312 81 MB 2012-Oct-26

Release 574 introduced a serious bug that caused SME to overestimate the concentration of several negative ions. This resulted in underestimated electron concentration, H concentration, and H opacity. This error is particularly serious for M dwarfs. A new version will be released soon. Release 574 includes automatic continuum matching, more non-LTE grids, improved UV continuous opacities, and additional methods for extracting information from the external library.

Each release includes the SME User Handbook and an SME tutorial. Version 412 and later include a technical note that describes major changes to the way model atmosphere information is stored in SME structures. Each release includes the SME external library, compiled for Linux, OSX, and Windows systems.

Atomic and molecular line data formatted for SME may be obtained from VALD3, which supersedes the previous version of VALD. SME understands extended van der Waals encoding, which is enabled in the VALD3 unit selection configuration page. SME can solve for empirical log(gf) and damping parameters, using an observed spectrum of a star (usually the Sun) as a constraint.

Using empirical line data for wavelength ranges 5164-5190 (Mg b triplet) and 6000-6180 Å, Valenti & Fischer (2005) obtained spectroscopic parameters for 1040 cool stars. Damping wings of the Mg b lines are a useful gravity constraint for dwarfs cooler than about 6200 K. Mass, radius, gravity, and especially age in Table 9 were revised shortly after publication when a software bug was fixed.