An IUE Time Series Browse Derck Massa SGT

An IUE Time Series Browse Derck Massa (SGT, Inc. ) Michael Van Steenberg (NASA’s GSFC)

Introduction The International Ultraviolet Explorer (IUE) was launched in 1978 and turned off in 1996 after more than 17 years of operation IUE performed pointed observations, obtaining spectra in two UV wavelength bands: • 1150 £ l £ 1980 Å • 1850 £ l £ 3350 Å At one of two spectral resolutions: • low resolution (5 -8 Å - depending on l) • high resolution (0. 1 -0. 3 Å)

Thus, an IUE spectrum came in one of four modes: • • short wavelength low resolution long wavelength low resolution short wavelength high resolution long wavelength high resolution IUE obtained more than 100, 000 spectra of roughly 9300 objects, making it one of the most prolific astronomical missions to date.

Time Series Many IUE observations were time series of specific objects such as binary and variable stars, explosive stars, AGN, QSOs, BL Lac objects, etc. IUE’s longevity resulted in repeated observations of “popular” objects -- serendipitous time series. Defining a time series as: 10 or more observations of an object in the same dispersion/wavelength mode over the lifetime of IUE then 50% of the 100, 000 IUE observations are in time series

There are time series for over 700 different objects. (Number of sets not equal to number of objects -- often an object has both a long and short wavelength series. ) Camera Disp Sets No. of Spectra Mean no. In Set SW Low 462 16955 36. 3 SW High 316 12515 39. 6 LW Low 352 12640 35. 9 LW High 251 8106 32. 3

Unfortunately Only a fraction of the series were published, and those often cover a small portion of the final data. The published data are presented in very different formats, making comparisons of series from different epochs or different objects difficult. Phenomena common to several series may escape detection without a common format. Display techniques have improved greatly since the late 1970’s and early 1980’s.

The Temporal Browser IUE time series are a remarkable scientific resource and will not be duplicated in foreseeable future. • span more than 17 years • observations by the same instrument in 4 modes To fully utilize this resource, the data must be made accessible for researchers to determine whether data for a particular object exist and to assess whether the data warrant further investigation.

However, even preliminary inspection can require a considerable effort since one must • • Determine the relevant spectra Acquire the spectra Cull the data for instrument specific problems Assemble the data in a form amenable for inspection It is desirable, therefore, to process all of the IUE time series once and for all, providing the astronomical community with a tool which will avoid considerable duplication of effort.

To make these valuable data more accessible, we have constructed a prototype IUE Temporal Browser