Supplemental Data Access

As described elsewhere, the ASPCAP analysis for DR17 was performed using a new synthetic spectral library that was constructed using the synthesis code Synspec, which allows for non-LTE populations to be provided, which was done for Na, Mg, K, and Ca. This differs from previous data releases, which used the synthesis code Turbospectrum, which does not allow for NLTE populations to be specified. On the other hand, Turbospectrum performs the radiative transfer calculations in spherical geometry for the largest stars (logg <= 3.0), while Synspec calculates using plane-parallel geometry. The same stellar atmospheres are adopted for both syntheses, which are calculated with spherical geometry for logg <= 3.0. Furthermore, all synthesis codes include a large amount of atomic and molecular data, and the two synthesis codes may differ in some regards, such that, even for models where NLTE effects are not included and both codes use plane-parallel geometry, the results are not identical.

To aid users who might want to dig deeper into these issues, we provide several supplemental ASPCAP analyses, with different synthetic libraries, in addition to the default DR17 analysis:

• default DR17 analysis: Synspec with NLTE for Na, Mg, K, Ca
• As noted in the Caveats, a bookkeeping error related to the LSF grids used for some of the LCO stars was made in the initial DR17 analysis (the synspec file directory), which results to small changes in parameters and abundances for about 113000 stars.
  This has been fixed and the revised version is released in the synspec_rev1 file directory. We recommend users adopt synspec_rev1 results.
• Synspec LTE: Synspec using LTE calculations
• Turbospectrum : Turbospectrum 20, using LTE calculations, with spherical geometry for the radiative transfer for logg <=3.0
• Turbospectrum plane-parallel : Turbospectrum 20, using LTE, but specifying plane-parallel geometry for the radiative transfer for all stars (as is done by Synspec)

For each of these analyses, we provide summary allStar files, as well as all of the support ASPCAP files, in separate directory trees on the SAS. The supplemental results are not available through the CAS.

Synthesis	allStar file	ASPCAP directory
DR17 Synspec rev1	allStar-dr17-synspec_rev1.fits	https://data.sdss.org/sas/dr17/apogee/spectro/aspcap/dr17/synspec_rev1/
DR17 Synspec See Caveat.	allStar-dr17-synspec.fits	https://data.sdss.org/sas/dr17/apogee/spectro/aspcap/dr17/synspec/
Turbospectrum 20	allStar-dr17-turbo20.fits	https://data.sdss.org/sas/dr17/apogee/spectro/aspcap/dr17/turbo20/
Synspec LTE	allStar-dr17-synspec_lte.fits	https://data.sdss.org/sas/dr17/apogee/spectro/aspcap/dr17/synspec_lte/
Turbospectrum 20, plane-parallel	allStar-dr17-turbo20_pp.fits	https://data.sdss.org/sas/dr17/apogee/spectro/aspcap/dr17/turbo20_pp/