We report on simultaneous Einstein and IUE observations of the dM5e flare star Proxima Centauri during a 5 hour period in 1980 August. A major X-ray flare was observed in its entirety with the Einstein IPC; the flare exhibited a peak luminosity, L x ~ 2 x 10 28 ergs s-1 , and a maximum temperature, T ~ 27 x 10 6 K. We present a detailed X-ray light curve, temperature determinations during various intervals, and UV line fluxes before, during and after the flare. There is indirect evidence for a "two-ribbon flare"-like prominence eruption. The previous detection of quiescent coronal emission is also confirmed, but the coronal luminosity of 1980 August, L cor ~ 5 x 10 26 ergs s-\ is less than it was in 1979 March, L cor ~ 2 x 10 27 ergs s~1 ; the temperature remains the same, T ~ 4 x 10 6 K. We calculate a ratio of coronal to bolometric luminosity, L C or/L b oi ~ 8 x 10" 5 to 3 x 10 _4 , about 100 times the solar ratio. The corona of Proxima Cen is analyzed in the context of static loop models, from which we conclude that less than 6% of the stellar surface seems to be covered by X-ray emitting active regions.

A catalog of 732 optically selected, nearby poor clusters of galaxies covering the entire sky north of −3 • declination is presented. The poor clusters, called WBL clusters, were identified as concentrations of 3 or more galaxies with photographic magnitudes brighter than 15.7, possessing a galaxy surface overdensity of 10 4/3 . These criteria are consistent with those used in the identification of the original Yerkes poor clusters, and this new catalog substantially increases the sample size of such objects. These poor clusters cover the entire range of galaxy associations up to and including Abell clusters, systematically including poor and rich galaxy systems spanning over three orders of magnitude in the cluster mass function. As a result, this new catalog contains a greater diversity of richness and structures than other group catalogs, such as the Hickson or Yerkes catalogs. The information on individual galaxies includes

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The Solar X-ray Imager (SXI) was launched 23 July 2001 on NOAA's GOES-12 satellite and completed post-launch testing 20 December 2001. Beginning 22 January 2003 it has provided nearly uninterrupted, full-disk, soft X-ray solar images, with a continuous frame rate significantly exceeding that for previous similar instruments. The SXI provides images with a 1 min cadence and a single-image (adjustable) dynamic range near 100. A set of metallic thin-film filters provides temperature discrimination in the 0.6 -6.0 nm bandpass. The spatial resolution of approximately 10 arcsec FWHM is sampled with 5 arcsec pixels. Three instrument degradations have occurred since launch, two affecting entrance filters and one affecting the detector high-voltage system. This work presents the SXI instrument, its operations, and its data processing, including the impacts of the instrument degradations. A companion paper (Pizzo et al., this issue) presents SXI performance prior to an instrument degradation that occurred on 5 November 2003 and thus applies to more than 420000 soft X-ray images of the Sun.