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Library of IUE Echelle Spectra for White Dwarfs

9 January 2017: A software error caused incorrect spectral types, V magnitudes, effective temperatures, and surface gravities to be displayed for targets in the table at the bottom of the page. This has been corrected as of the posted date.

An atlas of IUE Echelle spectra for a total of 55 white dwarfs has been created by Jay Holberg and collaborators. The main reference to the original work is Holberg, Barstow & Sion 1998, ApJS, 119, 207. A brief summary of the project is provided in the Introduction section below.

In the interest of preserving this information, as well as to update the file formats to better align with modern conventions, MAST provides these data files as a High Level Science Product (HLSP). The differences between the MAST HLSP data and the original data are fairly non-intrusive, but we summarize these differences now:

  • The names of the FITS files have been changed to follow MAST's HLSP guidelines. These file names are different from the original names in the Holberg et al. archive. A complete translation table can be found here for reference with older publications who used the original data.
  • The spectra are no longer stored as non-homogeneous arrays in the primary HDU. Instead, the spectra are stored as binary FITS tables in the first extension. See the Data Format section below for complete documentation.
  • Additional keywords have been added to the primary header to include important metadata such as coordinates, exposure times, etc. These are all taken or derived from the original NEWSIPS .mxhi files at MAST, and are listed in the Data Format section below. However, the data values of the spectra themselves are unchanged, e.g., the wavelengths, fluxes, flags, are all identical to the original data files.

Our intention is to preserve the spectral data as provided by the Holberg et al. team and serve that data in an improved format, with supplemental metadata provided. We hope our version of these data files are somewhat easier to use than the original. However, users who are concerned about backwards compatibility with the original version are encouraged to do their own comparisons and determine if these new files are sufficient for their use. Please direct any questions to the MAST Archive (archive@stsci.edu).


Introduction

The project seeks to increase the signal-to-noise of white dwarf spectra by combining all observations of a given target into a single, epoch-combined spectrum. There are two types of FITS files associated with this HLSP. Order-combined spectra are stored as "_sci.fits" files, while epoch-combined spectra are stored as "_coadd.fits" files. To construct the order-combined spectra, Holberg et al. used IDL procedures to extract orders 71-121 from the NEWSIPS .mxhi versions of the IUE observations for their targets. These order-combined spectra are truncated to cover 1150-1950 Å and interpolated onto a uniformly sampled wavelength scale. The NEWSIPS data quality flags are mapped into an array, with a few additional conditions applied, and the spectra are low-pass filtered. To create epoch-combined spectra, the "_sci.fits" files for a given star are matched using a single, constant wavelength shift, determined using narrow features in the spectra, and co-added weighted by the flux uncertainties (ignoring bad values based on the quality flags). For full details, refer to the original publication.

Data Format

The FITS headers and data format of the MAST HLSP files are summarized in this table (show / hide).

Star Atlas, Plot Tool, and Data Download

A complete listing of the white dwarf stars in the atlas is provided in this table (show / hide).

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