Astronomical instrumentation

Abstract:

The results of extensive IUE monitoring of the optical counterpart of the recurrent periodic LMC X-ray transient A0538-66 are presented. Even when the system is not in outburst dramatic spectral variations occur, accompanied by changes in the temperature and surface area of the continuum emitting region. It is shown that, in spite of these variations, the out-of-outburst data are consistent with constant bolometric luminosity. The optical outbursts can be powered solely by reprocessed X-rays. The long-term and orbital behavior of the system is discussed in the light of these results. From an analysis of apparently undisturbed P Cygni profiles, the mass-loss rate of the primary via its stellar wind is determined to be about 4 x 10 to the -9th solar masses/yr. Infrared photometry reveals an excess at H and K which is too large to be explained by free-free emission from this wind alone.

Abstract:

A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, ’dirty’ silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.

Abstract:

The proposed 15m NNTT offers a gain in collecting area over a 4m telescope of 14 and a gain in speed of up to 200. In this paper the types of problem where the gain in limiting flux is inversely proportional to area (D2-problems) and those in which the gain goes only as the diameter (D-problems) are identified. The performance of the NNTT is compared to a 4m telescope and to the Space Telescope in three configurations. The NNTT isshown to have a small advantage over the Space Telescope for spectroscopy of point sources even at low resolutions. For work on sources of diameter one arcsecond or greater the gains are (formula omitted) a factor of 15. Even for the direct imaging of point sources the NNTT is only a little slower than the Space Telescope when there is no confusion. Three areas of astronomical investigation, studies of star formation, the Galactic halo and high redshift galaxies, are used to illustrate the impact a 15m telescope would make scientifically. These astronomical problems make substantial demands on the telescope performance and instrumentation. If these can be met the NNTT will lead to considerable advancement in the understanding of current problems and, given the order of magnitude improvement in infrared performance and spectroscopic capability, is likely to lead to the discovery of new phenomena. © 1983 SPIE.