Other Spectra

There are a large number of spectrum files available for use in Calibration Database System (CDBS). Some of these are discussed in the SYNPHOT Data User’s Guide. Any file in CDBS can be used if the user is able to determine a valid path name for the file.

For example, the Bruzual Synthetic Spectral Atlas (table B4) can be found in the CDBS directory “crgridbz77$”, so to specify the F2V file from this atlas. Use filename “crgridbz77$bz_19.fits” in the ETC user input form as shown below.

A complete list of the access mode for each of the available catalogs is as follows:

Spectra Set Access mode
HST Calibration Spectra crcalspec$zzzzzz_nnn.fits
Kinney and Calzetti crgridkc96$xxxx_template.fits
AGN atlas crgridagn$xxxx_template.fits
Galactic Atlas crgridgalactic$zzzz_template.fits
Bruzual 1977 crgridbz77$bz_nn.fits
Gunn and Stryker 1983 crgridgs$gs_nn.fits
Bruzual et al 1979-1983 crgridbz77$bz_nn.fits
Jacoby, Hunter and Christian 1984 crgridjac$jc_nn.fits
Buser and Kurucz 1979
where ? is one of (a,b,c,d,m,s)
Bruzual and Charlot 1995 crgridbc95$templates/bc95_x_XXXX.fits

Available Spectra Which Cannot be Used Directly by the ETC

Spectra Set Access mode
Castelli and Kurucz 2003,2004 ck04models$
Pickles 1998
(or dat_uvk)
Kurucz 1993 k93models$

The Complete Set of HST Standard Spectra (CALSPEC and CALOBS)

CALSPEC contains the composite stellar spectra that are the fundamental flux standards for HST calibrations. All files are in machine independent binary FITS table format. Information about the pedigree of a given spectrum is in the header of the FITS table file. Further details about these files as well as access to these files can be found at the CALSPEC webpage If the ETC returns an error when attempting to access one of the CALSPEC spectra, please download it and enter it as a user-supplied spectrum. Current CALSPEC spectra may be downloaded from the CALSPEC FTP site

CALOBS contains several versions of the ultraviolet (UV) and optical spectra of the fundamental flux standards used for HST calibrations. Some of these files contain the original data obtained from different sources (UV: VOYAGER2 or IUE; optical: Oke, Tapia or Stone; or STIS), while others contain corrected or updated versions. Updates to the flux distributions are indicated by file names with the same root name but incremental version number. The earlier versions are retained for comparison purposes. All files are in machine independent binary FITS table format. Information about the pedigree of a given spectrum is in the header of the FITS file. Further details as well as these files can be found at The CALOBS webpage Note that for the cases when the CALSPEC data is updated after the ETC software is released, the ETC will not be able to access the most recent files, but only those that were available at the time of the build. If the ETC error produces an error when trying to access and HST Standard, review the update history at the bottom of the CALSPEC page to determine if the model you want to use was updated before or after the build. If updated after you want to use the previous version of the model.

Note that photometric calculations in vegamags use a slightly different Vega spectrum than the model available to the ETC listed in the menu for HST Standard Star Spectra. The version used by the ETC is the version used by pysynphot.

How to provide “Other HST Spectrum” to the ETC

To use one of the CDBS supplied spectrum file, select the “Other HST Spectrum” option in section 3 of the ETC input form and type the file path in the text box as shown below: