5 BEGINNING ANALYSIS OF IUESIPS EXTRACTED DATA

  The routines described below allow the user to begin the analysis of IUESIPS slit-integrated extracted files. Due to the variations in the IUESIPS software over the lifetime of the mission, there are a number of corrections specific to IUESIPS data that are addressed in this chapter. Calibrations and sensitivity corrections are covered as well. Note that these steps are already taken care of with NEWSIPS data and the user need not worry about them. See Section 4.1 for instructions on how to read MXLO data.

Many of these routines use or create four arrays designated as H, W, F, Q, which have the following meanings:

H

A scale factor record (an integer vector, e.g., as returned by IUESPEC).

W

Wavelengths, (Å possibly non-linear.

F

Slit-integrated flux at each wavelength (erg cm^-2 s^-1 Å^-1 ). If the data are not calibrated, the units are ``flux numbers''.

Q

Data quality $\epsilon$ (IUESIPS) flags associated with each wavelength.

The exposure time is required to apply the absolute calibration. The IUEDAC procedures interactively query the user for the exposure time, rather than rely on the exposure time contained in the IUE label. In some instances (e.g., if you submit a batch job), you cannot enter values interactively. The IUEDAC procedure, HFIX, allows you to enter and store corrected values of the exposure time and other information in advance of the actual reduction step.

HFIX,'IMAGET' 

HFIX displays the first ten lines of the label, and asks you to verify the exposure time, giving you the opportunity to change it. The THDA (as stored in the header) is also displayed, and you will be asked whether you want to change the value, and if you would like the correction to be applied. Please note that only the LWR degradation correction has been implemented at this writing.