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STIS Next Generation Spectral Library
Version 2 based on AR 11755, GO 11652
March 2010

Sara R Heap, NASA/Goddard Space Flight Center, Sara.R.Heap@nasa.gov
Don Lindler, Sigma Space Corporation, Don.J.Lindler@nasa.gov

Introduction

Figure 1. Histogram of offsets from the slit center. The slit is 4 pixels = 0.2" wide.
As originally proposed by Michael Gregg and Dave Silva (GO 9088, 9786, 10222), the Next Generation Spectral Library (NGSL) would contain "600 stars for use in modeling the integrated light of galaxies and clusters... Such a library will surpass all extant compilations and have lasting archival value, well into the Next Generation Space Telescope era." So far, the NGSL consists of spectra for 374 stars, all observed in the same way, and all spectra covering the spectral range, ~0.2-1.0 μ, at a resolving power R ~1000.

As shown in Figure 1, most target stars were not well centered in the 52X0.2E1 entrance slit. In AR 10659, we worked to derive a wavelength-dependent correction to the slit throughput as a function of offset from the slit center. In February 2008, we delivered Version 1 of the NGSL to MAST. The V1 library contained the spectra of 374 stars produced by custom pipeline processing and post-pipeline processing including the predicted correction for the slit throughput as well as correction for grating scatter. All steps are documented in the readme file (PDF).

In GO/CAL 11652, we derived an improved slit-throughput correction based on post-SM4 observations of a standard star (BD+75D325), which was stepped across the slit. The observations and analysis are described here. In AR 11755, we incorporated the observed slit-throughput corrections in this new version of the Next Generation Spectral Library.

Download the Library

The Next Generation Spectral Library is contained in three files, which you can download. A table lists all the stars in the library and gives their J2000 equatorial coordinates, Johnson B and V magnitudes, and spectral type, as extracted from SIMBAD. Plots of the spectra of all NGSL stars are also available in a single file (1.5 MB). Each plot compares the Version-2 spectrum with the Version-1 spectrum of each star. The title gives the star name and the offset from slit center in pixels. Version-1 spectrum is plotted in light blue-green. Version-2 spectrum is plotted in black if the measured offset from slit center is less than 0.9 pixels, and in red when the offset is greater than 0.9 pixels (to indicate that the slit throughput correction is unreliable). The exact boundary between correctable and uncorrectable spectra is not known but could be derived from proposed Cycle-18 observations. Finally, the spectral data are available in a single ZIP file (18.3 MB). The spectrum of each star is written as a FITS binary table. The file contents and format are described here.

Preview and Download Selected Spectra

You can view a listing to select the ones you want to see and/or download. The listing includes items: target name, RA, Dec, Johnson B and V magnitudes, B-V color, and spectral type. Click on the column header to sort the table by that item. Click in the Preview column to view a plot of the spectrum at low resolution (10-point binning). Use the Mark button to indicate the spectra of interest and then click on the "Download marked data" button above the table to download the spectra and preview files as a tar file to your computer. The file contents and format are described here.