1 Introduction

 

The IUE NEWSIPS processing system was developed with the aim of creating a "Final Archive'' of IUE data to be made available to the astronomical community as a legacy after the end of the project. This archive would include all the IUE spectra re-processed with improved algorithms and up-to-date calibrations. The NEWSIPS processing system is fully described by Nichols & Linsky (1996) and Nichols (1998). Technical details are given in the NEWSIPS Manual (Garhart et al. 1997). The introduction of new techniques to perform the geometric and photometric corrections led to a substantial improvement in the signal-to-noise ratio of the final spectra. Further improvements in the quality of the high resolution data arise from the new method to determine the image background and from the improved ripple correction and absolute calibration (Cassatella et al. 1999, hereinafter Paper II). The background subtraction has always been one of the more critical issues in the processing of IUE high resolution spectra, particularly at the shortest wavelengths, where orders crowd and an accurate estimate of the background is essential for a correct flux extraction. This problem has been overcome in NEWSIPS through the derivation of a bi-dimensional background (see Smith 1999 for a description of the method).

The goal of the INES processing system was to correct the deficiencies found during the scientific evaluation of the data processed with NEWSIPS for the IUE Final Archive, and to provide the output data to the users in a simple way requiring a minimum knowledge of the operational and instrumental characteristics of IUE (Wamsteker et al. 1999). The modifications introduced in the processing of low resolution data have been described by Rodríguez-Pascual et al. (1999, Paper I). As for high resolution data, the INES system provides two output products derived from the NEWSIPS MXHI (i.e. high resolution extracted spectra) files: the "concatenated'' spectrum, where the spectral orders are merged eliminating the overlap regions, and the "rebinned'' spectrum, which is the concatenated spectrum resampled to the low resolution wavelength step. Both concatenated and rebinned spectra include an error vector calibrated in absolute flux units. The inconsistency between the high resolution short and long wavelength scales in NEWSIPS has been corrected for in the INES concatenated spectra.

 

 

Table 1: Radial velocities obtained from NEWSIPS high resolution spectra

Target	SWP	LWP	LWR
RR Tel	$-69.5 \pm 6.5$ [106] em. lin.	$-49.3 \pm 3.0$[170] em. lin.	$-51.0 \pm 4.4$ [132] em. lin.
$\zeta$ Oph	$-24.7 \pm 3.9$ [60] SII, SiII	$-13.4 \pm 2.6$ [24] FeII,MnII	$-10.2 \pm 2.5$ [69] FeII, MnII
BD+28 4211	$-22.8 \pm 6.4$ [130] SII, SiII, CII	$-\phantom{1}5.3 \pm 3.6$ [40] MgII K	$-\phantom{1}1.1 \pm 4.8$ [21] MgII K and H, MgI
HD 60753	$\phantom{-}18.8 \pm 6.6$ [62] SII, OI, SiII	$\phantom{-}32.4 \pm 6.9$ [70] MgII K	$\phantom{-}29.5 \pm 5.8$ [24] MgII K and H, MgI
HD 93521	$-38.8 \pm 4.0$ [68] SII, OI, SiII	$-20.7 \pm 6.9$ [6] MgII K	$-19.9 \pm 5.4$ [18] MgII K and H
BD+75 325	$-16.4 \pm 4.6$ [121] SII, SiII, CII	$\phantom{-1}6.2 \pm 2.2$ [43] MgI	$\phantom{-1}6.6 \pm 3.1$ [33] MgII K
$\lambda$ Lep		$\phantom{-}21.2 \pm 3.9$ [37] MgII K, MgI	$\phantom{-}19.5 \pm 4.9$ [44] MgII K and H
$\zeta$ Cas		$-\phantom{1}1.1 \pm 4.2$ [9] MgII K	$\phantom{-1}1.5 \pm 4.4$ [72] MgII K and H
$\eta$ UMa		$-\phantom{1}1.1 \pm 3.1$ [17] MgII K	$\phantom{-1}3.1 \pm 7.1$ [82] MgII K and H

The entries for each star are: mean radial velocity, rms (km s^-1), number of measurements, and lines used (em.lin.: emission lines).
All measurements refer to the large aperture.

In the first part of this paper we discuss the overall quality of NEWSIPS high resolution spectra in terms of accuracy, stability and repeatability of wavelength and flux measurements (Sect. 2). The second part deals with the INES processing of high resolution data, describing the order concatenation and rebinning procedures (Sects. 3.1 and 3.2, respectively). Finally, the application of the correction to the wavelength scale is discussed (Sect. 4).