rvs_read_grid

The rvs_read_grid command creates an SQLite database catalog of stellar template spectra, which is the first step in the rvspecfit template preparation pipeline.

Purpose

This command scans a directory of FITS files containing stellar template spectra (typically PHOENIX models) and creates a database that catalogs all the templates with their atmospheric parameters (Teff, log g, [Fe/H], [α/Fe], etc.). The database is used by subsequent commands in the pipeline.

Basic Usage

rvs_read_grid --prefix /path/to/templates/ --templdb files.db

Command Line Options

Required Options

--prefix PATH

The location of the input template grid directory. This should contain the FITS files with stellar template spectra.

--templdb FILENAME

The filename where the SQLite database describing the template library will be stored. Default: files.db

--update

Update an existing database in place by appending only newly discovered templates (matched by relative filename). By default, existing database files are recreated.

Header Keyword Mapping Options

--keyword_teff KEYWORD

The FITS header keyword for effective temperature. Default: PHXTEFF

--keyword_logg KEYWORD

The FITS header keyword for surface gravity (log g). Default: PHXLOGG

--keyword_metallicity KEYWORD

The FITS header keyword for metallicity [Fe/H]. Default: PHXM_H

--keyword_alpha KEYWORD

The FITS header keyword for alpha enhancement [α/Fe]. Default: PHXALPHA

Parameter Naming Options

--name_metallicity NAME

The internal name for the metallicity parameter. Default: feh

--name_alpha NAME

The internal name for the alpha enhancement parameter. Default: alpha

File Selection Options

--glob_mask PATTERN

The glob pattern to find the spectral FITS files. Default: */*fits

Additional Parameters

--extra_params PARAM_LIST

Extra template parameters to store in the database. Format: comma-separated list of internal_name:FITS_keyword pairs.

Example: --extra_params vmic:VMIC,vsini:VSINI would store microturbulence and rotational velocity if those keywords exist in the FITS headers.

Examples

Basic Usage with PHOENIX Templates

rvs_read_grid --prefix /data/PHOENIX-ACES-AGSS-COND-2011/ \
              --templdb phoenix_templates.db

Custom Header Keywords

For templates with non-standard FITS keywords:

rvs_read_grid --prefix /data/custom_templates/ \
              --templdb custom.db \
              --keyword_teff TEMP \
              --keyword_logg GRAVITY \
              --keyword_metallicity MH \
              --keyword_alpha ALPHA_FE

Including Extra Parameters

To store additional parameters like microturbulence velocity:

rvs_read_grid --prefix /data/PHOENIX-ACES-AGSS-COND-2011/ \
              --templdb phoenix_with_vmic.db \
              --extra_params vmic:VMIC

Different File Organization

For templates organized differently:

rvs_read_grid --prefix /data/templates/ \
              --templdb templates.db \
              --glob_mask "*.fits"

Update Existing Database with New Files

If you add new template FITS files to an existing library, you can append them without rebuilding the database:

rvs_read_grid --prefix /data/templates/ \
              --templdb templates.db \
              --glob_mask "*.fits" \
              --update

Output

The command creates an SQLite database with two main tables:

  1. files table: Contains one row per template spectrum with: - filename: Path to the FITS file (relative to prefix) - teff: Effective temperature - logg: Surface gravity - feh (or custom name): Metallicity - alpha (or custom name): Alpha enhancement - Additional parameters if specified - id: Unique integer identifier - bad: Boolean flag for problematic spectra

  2. grid_parameters table: Metadata about the grid structure

Notes

  • By default, the command recreates the database file if it already exists

  • Use --update to keep existing rows and add only new files

  • All FITS files must contain the specified header keywords, or the command will fail

  • The database stores relative paths, so the --prefix must be used consistently in subsequent commands

  • Templates are assigned sequential integer IDs starting from 0

Error Handling

Common errors and solutions:

“No FITS templates found”

Check that the --prefix path is correct and contains FITS files matching the --glob_mask pattern.

“Keyword for [parameter] [keyword] not found”

The specified FITS header keyword doesn’t exist in one or more template files. Check the FITS headers or adjust the keyword parameters.

See Also