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ATLAS9 Model Atmosphere Database ("BOSZ")

Bohlin et al. 2017, AJ, 153, 234

See also: Mészáros et al. (2012), AJ, 144, 120


Description of Data Products

Data Access

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See some tutorials.

Latest Updates
November 2017: An additional set of models are made available with metallicity of [M/H] = +0.75.


"BOSZ" stellar atmosphere models are based on ATLAS-APOGEE ATLAS9 (Mészáros et al. 2012) and cover a broad range of effective temperature, surface gravity, metallicity, carbon abundance, and alpha-element abundance. Versions at different instrumental broadenings are provided. See the table in the description section for parameter ranges. Our new BOSZ LTE models have been fit to O,B,A,F,G stars observed with HST/STIS, and those results are compared to fits for the LTE grid from Castelli & Kurucz (2004). The name "BOSZ" comes from a combination of letters in the first and second authors' names.

Description of Data Products

Two version of the files are available, an ASCII text table zipped using "bzip2", and a FITS version with the data stored in a binary FITS table. The files are organized into subdirectories based on parameter grouping as follows:


  • <u> is either "ascii" or "fits", depending on the data format
  • <w> is a 6-digit, zero-padded instrumental broadening
  • <x> is the metallicity value, including '+' or '-'
  • <y> is the carbon abundance value, including '+' or '-'
  • <z> is the alpha-element value, including '+' or '-'
For example, ASCII models with an instrumental broadening R of 200, solar metalicity, solar carbon abundance, and solar alpha-element abundance can be found in:

The format for each part of the file name is described in detail in the Appendix of Bohlin et al. 2017, since, for example, decimals are avoided and some values are rounded in the file names. An example file name is:


  • mm13 → [M/H] = -1.25
  • cp00 → [C/H] = 0.00
  • op00 → [α/H] = 0.00
  • t3500 → Teff = 3500 K
  • g45 → log(g) = 4.5 K
  • v20 → Microturbulent velocity = 2.0 km/s
  • rt0 → Rotational broadening = 0.0 km/s
  • b50000 → Spectral resolution = 50,000

The models include wavelengths from 1000 Å < λ < 32 μm. The ASCII files are zipped with "bzip2", and contain the wavelengths in vacuum in Å, surface brightness (H_BOSZ), and theoretical continuum level. If you need to decompress the files, use the "bunzip2" command. The FITS files have these data in the first FITS extension, in columns called "WAVELENGTH", "SPECIFICINTENSITY", and "CONTINUUM". Note that to convert from surface brightness to flux, use the equation:

F = π * H_BOSZ
where H_BOSZ is the surface brightness in the file. Normally the equation includes a factor of 4*π, but the BOSZ models are already four times larger, so it is only necessary to multiply the surface brightness values by π to convert to flux in erg cm-2 s-1 Å-1.

Data Access

There are a few ways to download models, depending on how many models you want to retrieve.

  1. If < 50,000 files: Use the MAST Web Search Form. If you want to download more than a few files, here's how to use the form to download a lot of files.
  2. All models at Instrument Broadening = 300,000 and a given [M/H]: These tar bundles are provided for convenience, for any other combinations of models, use the search form or wget/cURL.
  3. Programmatic access or large number of models across parameters: Download via cURL or wget commands. The path is:<subdir_path>/<file_name>
    where <subdir_path> and <file_name> are defined above in the Data Format section.