Access the PICKLES ATLAS.
A Stellar Spectral Flux Library by A.J. Pickles
This library of wide spectral coverage, consists of 131 flux calibrated stellar spectra, encompassing all normal spectral types and luminosity classes at solar abundance, and metal-weak and metal-rich F-K dwarf and G-K giant components. Each spectrum in the library is a combination of several sources overlapping in wavelength coverage. The creator of the library has followed precise criteria in combining sources and to assembling the most reliable spectra. As part of the selection criteria prior to combination, all input sources were checked aginst the SIMBAD database and against the colors and line strengths as derived by the observed spectra themselves, in order to esure they had similar spectral types.
The following list contains the above mentioned input sources is given, numbered according to Table 1 in the original paper.
- Sviderskiene (1988)
- Heck et al. (1984)
- Gunn and Stryker (1983)
- Kiehling (1987)
- Jacobi, Hunter and Christian (1984)
- Silva and Cornell (1992)
- Pickles (1985)
- Pickles and van der Kruit (1990)
- Serote Roos, Boisson and Joly (1996)
- Danks and Dennefeld (1994)
- Lancon and Rocca-Volmerange (1992)
- Dallier, Boisson and Joly (1996)
- Kleinmann and Hall (1986)
- Cohen et al. (1995, 1996a, 1996b)
- Fluks et al. (1994)
Table 1 of the Pickles Stellar Flux Library precisely identifies which of the above sources entered the combination to create the complete set of spectral types. The output wavelength grid was chosen to be 1150-25000 Angstrom, with a sampling interval of 5 Å per pixel and resolution of 500 Å . In the end, two separate libraries were created, UVILIB and UVKLIB, which cover the spectral range 1150-10620 Å, and Å1150-25000 , respectively. In fact, only half of all spectral types in the library (mainly later types of solar abundance) have longer spectral coverages available.
The following quick-look table gives an idea of the spectra available. Spectra are ordered by progressive number, according to the spectral type (decreasing effective temperature) and luminosity class. The same ordering sequence is valid for both the UVILIB and the UVKLIB libraries, where the suffix "uk" differentiates between two spectra of the same spectral type but with different wavelength coverage (see ahead in the section on the HST version of the Pickles Library).
Table 1: Pickles library spectra
|SPECTRUM ID NO.||SPECTRAL TYPES AND LUMINOSITY CLASS|
Some reasons why it is worth using this library may be summarized as follows:
1) it provides a uniform and complete flux library of observed spectra representing normal stellar types, and
2) each spectrum was put together after selecting the best spectra in each wavelength interval, grouping them by spectral type, luminosity class and abundance (and color and line strength), to produce a final product with a uniform grid.
The TRDS version of the Pickles Library
The library installed in CDBS and distributed within STSDAS is from http://cdsarc.u-strasbg.fr/viz-bin/ftp-index?J/PASP/110/863. This library is divided into 2 independent subdirectories, according to spectral coverage, and exactly reproducing the structure of the original library by Pickles. Subdirectory dat_uvi groups all spectra derived from all ultraviolet, optical and near infrared sources, in the wavelength range 1150-10620 Å. This library has complete spectral coverage for all components over this wavelength range, and is (in the original library) referred to as UVILIB. Subdirectory dat_uvk groups all spectra that were derived by combining the UVILIB spectra with additional infrared data to a long wavelength limit of 25000 Å. This is originally referred to as UVKLIB. Within each subdirectory each spectrum is given in FITS table format: the first column gives the wavelength for the given spectral range, and the second column gives the flux. Fluxes are tabulated in units of \(erg/s/cm^2/A\) and were calculated by normalizing the original fluxes in the Pickles V band to a 0 magnitude in vegamag. In the vegamag system, Vega has magnitude zero in all passbands.
For the UVILIB spectra, the names of the files are given as pickles_ttt.fits where "pickles", for Pickles, is the library identifier and "ttt" is a number ranging from 1 to 131. For the UVKLIB spectra, the names have the format pickles_uk_ttt.fits, following the same nomenclature, and with the suffix "uk" provided in ordert distinguish them from the shorter wavelength library.
The complete list of stars of different spectral type and luminosity class together with the corresponding Pickles file is presented in Table 2. The effective temperature information is extracted from Table 2 of Pickles (1998). A "w" or an "r" preceding the spectral type indicates a weak or rich metallicity in respect to solar.
Table 2: Spectral type and Effective temperature
A similar list applies to the UKVKLIB library. For these spectra the names have the format "pickles_uk_ttt.fits". A reduced form of Table 2 can also be found in the dat_uvi and dat_uvk subdirectories of the link at the top of the page, and is named pickles.fits for the spectra in dat_uvi, and pickles_uk.fits for the spectra in dat_uvk directory. A "w" or an "r" preceding the spectral type indicates a weak or rich metallicity in respect to solar.
Use with Pysynphot
Use of these spectra should be exactly similar to other libraries already available in pysynphot. The desired spectrum is provided in input in any of the synphot tasks as appropriate with no particular syntax. For examples on how to use spectra from the pysynphot atlas library, please refer to the Astrolib Pysynphot User's Guide.
Pickles, A. J. 1998, PASP, 110, 863
Below is an example of a standard header file for the spectrum pickles_uk_51.fits. This spectrum corresponds to a star of spectral type F5IV and covers a range in wavelength of 1150 to 25000 Angstrom as can be assumed by the suffix "uk", which indicates a spectrum of the UVKLIB library.
SIMPLE b T Fits standard BITPIX i 16 Bits per pixel NAXIS i 0 Number of axes EXTEND b T File may contain extensions DATE t '2007-01-11T21:02:21' Date FITS file was generated IRAF-TLM t '16:02:37 (11/01/2007)' Time of last modification COMMENT t FITS (Flexible Image Transport System) format is defined in'Astronomy COMMENT t and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H ORIGIN t 'STScI-STSDAS/TABLES' Tables version 2002-02-22 FILENAME t 'pickles_uk_51.fits' name of file NEXTEND i 1 number of extensions in file COMMENT1 t spectral type: F5IV COMMENT2 t metallicity: solar COMMENT3 t original filename: ukf5iv.dat HISTORY t File created by F.R.Boffi. HISTORY t SEDs from Pickles UVKLIB Library (1998, PASP 110, 863). HISTORY t Wavelength is in Angstrom. HISTORY t Fluxes are tabulated in units of erg/s/cm2/A HISTORY t and were calculated by normalizing the original fluxes HISTORY t in the Pickles V band to a 0 magnitude in vegamag. HISTORY t In the vegamag system, Vega has magnitude zero in all passbands. HISTORY t Please refer to the SYNPHOT manual for further information.