ALBERT

Description: A summary of results of Einstein satellite observations of clusters of galaxies is provided, and X-ray luminosities or upper limits for 27 clusters are reported. Newly reported clusters with interesting morphologies are presented, and a brief discussion of the data in relation to theories of cluster formation and evolution is given.

Description: Field tests of SETI (Search for Extraterrestrial Intelligence) prototype hardware and software began in March 1985 at Goldstone. With emphasis on the sky survey component of the NASA SETI search strategy, the article describes the survey characteristics, the detection strategy, and preliminary results of system tests.

Description: The effects of strong frozen-in vertical magnetic fields on nonradial oscillation spectra in neutron stars are investigated theoretically, focusing on the surface layers near the polar cap of a cylindrically symmetric neutron-star model with shear-supporting crust and molten-crust oceans. The pulsation equations are derived; analytical estimates are obtained; and the results of numerical experiments are presented in tables and graphs. Significant modifications in the frequencies and displacements of the modes are found when a magnetic field is present: Alfven-like g modes (designated magneto-gravity), pseudotoroidal a modes with periods less than 100 ns for a 1-TG field, p-mode displacements almost totally parallel to the field, and a mode spectrum for periods of 100 microsec or more comprising only t, s, and p modes at 1 TG.

Description: The dust jet model for production of narrow gamma-ray lines from SS 433 is examined and shown to be implausible. Sputtering rates at disk temperatures are high, and self-absorption rates in the disk and jet are important; both imply that dust particles would easily be destroyed. The energy deposited in the dust jet particles by collisions with the ambient protons should be radiated in the optical and infrared in amounts greatly exceeding that observed. The dust momentum pumps ambient gas out of the beam at rates which imply that for the steady state, the ambient gas has to have an initial temperature exceeding one million K. The ambient medium is also required to have densities exceeding those postulated for the H-alpha-emitting gas jet, and the interaction within the gas jet material would result in appreciable broadening of the H-alpha emission lines. At present, there is no viable model for the steady state production of the gamma-ray line radiation.

Description: In an effort to understand the systematics of the H2 emission from planetary nebulae, a program of near-infared spectroscopy using the University of Texas infrared reticon spectrometer was started. This instrument has a 1x32 element InSb photodiode array as a detector. All of the observations reported were made on the McDonald Observatory 2.7 m telescope, with spectra resolving power lambda/delta lambda = 600. The spectral coverage allows the measurement strengths of Brackett gamma He I 2.113 microns, HE II 2.189 microns and the v = 1=0 S(1) line of H2 at 2.122 microns. One of the most important advantages of this instrument is that we are able to resolve H2 from the adjacent He I line. Most previous observations of planetaries have been made at spectral resolving powers of about 100, which blend these lines. The contribution of the He I line has generally been dismissed as being unimportant, but we show that this may not be valid. Our higher resolving power also improves the line-to-continuum contrast; in some cases, the continuum is the limiting factor in detecting faint lines.

Description: Far-infrared continuum studies from the Kuiper Airborne Observatory are described that are designed to fully exploit the small-scale spatial information that this facility can provide. This work gives the clearest picture to data on the structure of galactic and extragalactic star forming regions in the far infrared. Work is presently being done with slit scans taken simultaneously at 50 and 100 microns, yielding one-dimensional data. Scans of sources in different directions have been used to get certain information on two dimensional structure. Planned work with linear arrays will allow us to generalize our techniques to two dimensional image restoration. For faint sources, spatial information at the diffraction limit of the telescope is obtained, while for brighter sources, nonlinear deconvolution techniques have allowed us to improve over the diffraction limit by as much as a factor of four. Information on the details of the color temperature distribution is derived as well. This is made possible by the accuracy with which the instrumental point-source profile (PSP) is determined at both wavelengths. While these two PSPs are different, data at different wavelengths can be compared by proper spatial filtering. Considerable effort has been devoted to implementing deconvolution algorithms. Nonlinear deconvolution methods offer the potential of superresolution -- that is, inference of power at spatial frequencies that exceed D lambda. This potential is made possible by the implicit assumption by the algorithm of positivity of the deconvolved data, a universally justifiable constraint for photon processes. We have tested two nonlinear deconvolution algorithms on our data; the Richardson-Lucy (R-L) method and the Maximum Entropy Method (MEM). The limits of image deconvolution techniques for achieving spatial resolution are addressed.

Description: Far infrared photometry of comet Halley was obtained from NASA's Kuiper Airborne Observatory. The brightness of the comet decreases by nearly a factor of two on the second day in phase with the variability observed in blue light by IUE during the same time period. The energy distribution also varies significantly with a shallower (cooler) spectrum on the second day indicating fewer small particles on that day. Observations 30 and 60 arcsec away from the nuclear condensation show lower 50 to 100 microns color temperatures on both dates. This is consistent with observations by Giotto and Vega which indicate a higher proportion of large particles away from the nucleus.

Description: From the Kuiper Airborne Observatory, far infrared emission were detected from 4 molecular clouds in the outer galaxy. Eleven areas in 6 clouds were observed at 50 and 100 microns. The far-infrared luminosities indicate the presence of stars with spectral types ranging from B3 to O7. Therefore, despite the fact that these clouds have lower CO line temperatures than comparable clouds in the inner galaxy, they are giving birth to massive stars.

Description: A sample of 14 low-mass premain-sequence stars were studied in the far-infrared. There is evidence for outflowing material around twelve of these stars; in most cases the evidence includes broad wings on the profiles of the CO J = 2 to 1 line. Ten of the objects were detected (5 sigma) at 100 micros, and seven were mapped at 50 and 100 micros. The far-infrared emission makes a significant contribution to the total luminosity of the objects. It is found that the force available from radiation pressure is not sufficient to drive the outflows. Any process which taps the same energy source as does the present stellar luminosity must have high efficiency.

Description: Far-infrared (50-100 micrometers) photometric mapping and near-infrared spectroscopic mapping of the Herbig-Haro 1-2 region are presented. Both lobes of the double-lobed far-infrared source in this region are found to be nearly coincident with recently discovered radio continuum sources. The dust temperature structure around each peak is not spherically symmetric, suggesting either that the far-infrared sources are centrally heated or that the dust column density is highly nonspherically symmetric. The results are consistent with a picture in which each far-infrared lobe contains a highly obscured young star surrounded by a highly nonspherically symmetric dust cloud. A complementary study by Strom et al. (1985) is pointed out.