IUE-FLUXCAL: CALSPEC-Calibrated IUE White Dwarfs

CALSPEC-Calibrated IUE White Dwarfs ("IUE-FLUXCAL")

Bohlin & Bianchi 2018, AJ, accepted

Introduction

Fig. 7 from Bohlin & Bianchi (2018) showing discrepant regions of the star GRW+70 5824. Inserts show ratio of IUE to CALSPEC/STIS in 20 Å (SWP) and 40 Å (LWP) bins, respectively.

IUE-FLUXCAL is a collection spectral energy distributions (SEDs) for six white dwarfs in the HST CALSPEC database that are also observed by IUE. Composite IUE SEDs of each white dwarf are constructed by co-adding available low-resolution NEWSIPS spectra. The published paper compares the IUE to CALSPEC in 20 Å bins for SWP and 40 Å bins for LWP or LWR. A global average of these binned ratios across all six white dwarfs define corrections to the IUE NEWSIPS flux scale. This HLSP provides the co-added IUE SEDs of the six white dwarfs, as well as the table of IUE-to-CALSPEC flux ratios required to calibrate IUE data onto the HST standard scale.

Description of Data Products

Each of the six white dwarfs have SEDs available in both TXT and FITS format. The available columns in the SED files are:

WAVELENGTH - Wavelength in vacuum in Angstroms.
NET - The averaged net signal in linearized IUE Flux Number (FN) units per second.
FLUX - The average flux in ergs cm^-2 s^-1 Angstrom^-1.
BKG - The background signal (same units as NET column).
UNCERTAINTY - The formal, propagated uncertainty as the "error-in-the-mean" (same units as FLUX column).
NPTS - The number of observations averaged.
TIME - The total exposure time in seconds.
RMS - The RMS scatter among the observations as a percent.

There are two slight differences in the column labels between the FITS and TXT files, e.g., "NET" in the FITS versions and "NET/time" in the TXT versions, and "RMS" in the FITS versions and "RMS(%)" in the TXT versions, but both the FITS and TXT columns have the same definition and values. The FITS primary headers also contain a list of all the IUE observation IDs that went into the SED coadd, stored as DATA<nnn> keywords, e.g., DATA001, DATA002, etc. These individual IUE data files are available at MAST using the DOI 10.17909/T94M4K, while this HLSP has a DOI of dx.doi.org/10.17909/T9QD6J.

In addition to the SEDs, two tables are provided that have the IUE-to-CALSPEC flux ratios in different wavelength bins. IUE NEWSIPS spectra should be multiplied by the average corrections in these tables to place them on the HST/CALSPEC scale. The two text tables contain the correction ratios for SWP and LWP/LWR, respectively, and can be interpolated to define the IUE correction at intermediate wavelengths.

Data Access

Correction Tables	LWP/LWR (TXT)	SWP (TXT)
Target	SED Files
G191B2b	TXT	FITS
GD153	TXT	FITS
GD71	TXT	FITS
GRW+70 5824	TXT	FITS
HZ21	TXT	FITS
HZ43	TXT	FITS