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The signal identification process is described. The Goldstone radio spectrum environment contains signals that are a potential source of electromagnetic interference to the Goldstone tracking receivers. The identification of these signals is accomplished by the use of signal parameters and environment parameters. Statistical data on the Goldstone radio spectrum environment from 2285 to 2305 MHz are provided.
Absorption dips which recur with a period of 2985 s have been observed from the X-ray burst source 4U 1915-05. It is suggested that the dips are caused by obscuration of the X-ray source by material at the point where the gas stream from the companion meets the accretion disk, and that the 2985 s periodicity is the orbital period of the binary system. These observations represent the first direct evidence of the binary nature of X-ray burst sources. In addition, a new optical identification of 4U 1915-05 is suggested: a 22 magnitude candidate observed in a CCD image of the optical field at the arcsec-accurate HRI X-ray position.
It is estimated that the local volume density of BL Lac objects which emit greater than 10 to the 44th ergs/s in the 0.5-4.5 keV band is about 10 to the -7th/cu Mpc. This is based on identifications of bright X-ray sources, and the fact that Einstein X-ray observations detect BL Lac objects over a wide, continuous range of flux up to the thresholds of the all-sky X-ray surveys. Since this density is of the same order of magnitude as the local density of Seyfert galaxies, or local density of optically selected quasars, emitting X-rays at the same luminosity, we argue that the difference between these particular astronomical classifications is not solely due to the orientation of a relativistic beam.
The optical identification of the X-ray source 1E 0104.2 + 3153 is complicated by the close projection of a broad absorption-line (BAL) QSO (z = 2.027) 10 arcsec from a giant elliptical galaxy (z = 0.111) at the center of a compact group of galaxies. At only 1.2 de Vaucouleur radii (16 kpc for H sub 0 = 100 km/s Mpc) this QSO-galaxy projection is the closest yet discovered. Based upon current observations, the source of the X-ray emission cannot be conclusively determined. Present in the BAL QSO spectrum are extremely strong Ca II H and K absorption lines due to the intervening galaxy, the first optical detection of the cold interstellar medium in an elliptical galaxy. The strength of these lines (EW = 2 and 1 A) requires observation through several interstellar clouds in the line of sight to the QSO. By its proximity to the central regions of the elliptical galaxy and the relative distances of the galaxy and QSO, this QSO is a particularly good candidate for observing dramatic transient gravitational lensing phenomena due to halo stars in the foreground galaxy.
The tentative identification of liquid nitrogen as the source of the 2.16-micron absorption band in the spectrum of Triton has suggested a surface model in which nitrogen, together with the previously identified methane, occur in some kind of chemical association. Water frost may be another surface chemistry component, and dark, photochemically-produced particles occur as a minor contaminant of the ices or liquid. Temperature is noted to be a critical factor in the surface model, because the calculated subsolar surface temperature of Triton lies near nitrogen's melting-freezing temperature. The present modeling of Triton suggests nitrogen's occurrence in the form of fine grains.
In the radio spectrum of the envelope of the evolved carbon star IRC +10216, the fraction of lines from exotic molecules seldom or never observed in the terrestrial laboratory is exceptionally high. At least 20 lines have not been identified, and it is not known whether one, two, or a number of new molecules are involved. It is shown in the present investigation that nine of the previously unidentified lines in IRC +10216 are produced by SiCC, a radical long known to exist in stellar atmospheres. The true ground-state geometry of this radical has only been obtained recently on the basis of an elegant two-photon ionization experiment in a supersonic molecular beam. Information regarding the molecular geometry and lower rotational levels of SiCC is presented in a graph. The intensities of the SiCC lines confirm the assignments, yield new data on the temperature and density in the envelope of IRC +10216, and indicate that the amount of SiCC there is substantial.
The field of gamma-ray astronomy in the energy range from ten to several hundred MeV is severely limited by the angular resolution that can be achieved by present instruments. The identification of some of the point sources found by the COS-B mission and the resolution of detailed structure existing in those sources may depend on the development of a new class of instrument. The coded aperture mask telescope, used successfully at X-ray energies hold the promise of being such an instrument. A prototype coded aperture telescope was operated in a tagged photon beam ranging in energy from 23 to 123 MeV. The purpose of the experiment was to demonstrate the feasibility of operating a coded aperture mask telescope in this energy region. Some preliminary results and conclusions drawn from some of the data resulting from this experiment are presented.
X-ray emission from two BL Lacertae objects (H2155-304 and PKS 0548-322) has been studied with the High-Resolution Imager and Monitor Proportional Counter (MPC) on the Einstein Observatory. The high-spatial-resolution observations confirm the identification of these X-ray sources with the BL Lac objects and give a source size less than about 2 arcsec. Variations in the X-ray intensity and spectrum of these sources were detected over time scales of a few hours from analysis of the MPC observations.
A systematic search of the IRAS point-source catalog has led to the identification of eight new nearby stars that are Vega-like in terms of their large 60-micron excess. These stars are distinguished by the predominance of spectral type A and the absence of double stars in the Vega-like group. Both effects are intuitively consistent with the interpretation that the 60-micron excess radiation is due to a disk of protoplanetary material, suggesting an early phase in the evolution of a planetary system; however, this distribution can also be due to luminosity and brightness selection effects.
The identification of a fifth serendipitous Einstein source with a new BL Lac object in a very luminous galaxy is reported. The resolved component is well fitted by an exponential disk with scale length 18 kpc and absolute magnitude of roughly -24.2. A redshift of 0.237 is derived from stellar absorption features. No emission lines are seen in the 3200-9000 A wavelength range. Decomposition of the optical spectrum into a standard galaxy plus a power law yields a spectral index of 0.5 + or - 0.5, significantly flatter than in the average BL Lac object. Linear polarization of the nonstellar component is about 6 percent in the 4500-7000 A wavelength range. The X-ray flux in the 0.3-3.5 keV band is 1.16 x 10 to the -11th ergs/sq cm/s, corresponding to a luminosity of 3.5 x 10 to the 45th ergs/s . The radio flux density is 85.6 mJy at 20 cm and 54.5 mJy at 6 cm.
Because of their proximity, the Magellanic Clouds provide the opportunity to conduct a detailed study of the history and current state of star formation in dwarf irregular galaxies. There is considerable evidence that star formation in the Clouds was and is proceeding in a manner different from that found in a typical well-ordered spiral galaxy. Star formation in both Clouds appears to have undergone a number of relatively intense bursts. There exist a number of similarities and differences in the current state of star formation in the Magellanic Clouds and the Milky Way. Examination of Infrared Astronomy Satellite (IRAS) sources with ground based telescopes allows identification of highly evolved massive stars with circumstellar shells as well as several types of compact emission line objects.
Based on optical photometry, the identification of the X-ray source 1E 0630+178 with a blue object inside the Einstein error circle is reported. The question of whether the X-rays could be thermal emission from the surface of a neutron star is addressed. The new optical data confirm that relative fluxes in the optical, X-ray, and gamma-ray bands closely match those of the Vela pulsar. The Vela pulsar is adopted as an 'observational model' for Geminga, whereby only the lack of radio emission from Geminga remains to be accounted for. Previous observational results and theoretical models for Geminga are reviewed in light of the new findings.
The current status of the reconstruction of major biomass fire events at the Cretaceous-Tertiary boundary is discussed. Attention is given to the sources of charcoal and soot, the identification of biomass and fossil carbon, and such ignition-related problems as delated fires, high atmospheric O2 content, ignition mechanisms, and the greenhouse-effect consequences of fire on the scale envisioned. Consequences of these factors for species extinction patterns are noted.
Accurate frequencies for the lowest rotational transitions of five transition metal hydrides (CrH, FeH, CoH, NiH, and CuH) in their ground electronic states are reported to help the identification of these species in astrophysical sources from their far-infrared spectra. Accurate frequencies are determined in two ways: for CuH, by calculation from rotational constants determined from higher J transitions with an accuracy of 190 kHz; for the other species, by extrapolation to zero magnetic field from laser magnetic resonance spectra with an accuracy of 0.7 MHz.
The initial goal of this project was to examine the quiescent X-ray light curve of the recurrent X-ray/optical nova Cen X-4 throughout its 15.1-hr orbital period. Using these observations the pre-outburst conditions of the binary would be investigated and the relationship between soft X-ray transients and persistent low-mass X-ray binaries would be established. ROSAT-PSPC observations were scheduled for 1991 August 9-13. Unfortunately, failure of the satellite's attitude control system near the end of the all-sky survey severely curtailed science operations for much of 1991, and the requested observations of Cen X-4 were never taken. Since the stated goal could not be accomplished, the time and resources of this project were used in support of two other ROSAT programs for which I am co-investigator: 'Identification of LMC X-ray Sources Using ROSAT-HRI Images' and 'X-ray Light Curve for an Eclipsing Black-Hole Binary'. The results of these investigations are described.
The Rosat Position Sensitive Proportional Counter (PSPC) spectra of a sample of 35 X-ray selected Narrow Emission Line Galaxies (NELGs) are presented. Of these 35 objects, 16 are from the Rosat International X-ray Optical Survey (RIXOS) and the remaining 19 were discovered during the optical identification of Rosat U.K. deep survey sources. A power law model with low energy absorption set at the Galactic value is found to be a good fit for all sources. The results indicate that the spectral slope of NELGs is flatter than that of active galactic nuclei.
Work on NAG5-3288 ("White Dwarf Pulsars") has been fully integrated with the identically titled project NAG5-4734. The final report below is the same, since the data analysis and interpretative work are integrated, as are the resulting (previous and in-pipeline) publications. The proposal was designed to study pulse and orbital modulations in candidate DQ Herculis stars. Data on 5 stars were obtained. The best results were obtained on YY Draconis, which exhibited a strongly pulsed hard X-ray flux, and even suggested a transition between one-pole and two-pole emission during the course of the observation. This result is being readied for inclusion in a comprehensive study of YY Draconis. A strong pulsation appeared to be present also in H0857-242, but with a period of - 50 minutes, confusion with the first harmonic of the satellite's orbital frequency is possible. So that result is uncertain and is "on ice". A negative result was obtained on 4UO608-49 (V347 Pup), suggesting either that the X-ray identification is incorrect, or that the source is very transient. Finally, data was obtained on V1432 Aql and WZ Sge, respectively the slowest and fastest of these stars. Combined with the ASCA data, the high-energy data demonstrates the latter to contain a white dwarf rotating with P = 27.87 s (Patterson et al. 1998, PASP, 110, 403). Optical photometry contemporaneous with the X-ray data was obtained of V1432 Aql, in order to study the variations in the eclipse waveform. As anticipated, the width and centroid of the eclipse appeared to vary with the 50-day "supercycle".
This proposal was designed to study pulse and orbital modulations in candidate DQ Herculis stars. Data on 5 stars were obtained. The best results were obtained on YY Draconis, which exhibited a strongly pulsed hard X-ray flux, and even suggested a transition between one-pole and two-pole emission during the course of the observation. This result is being readied for inclusion in a comprehensive study of YY Draconis. A strong pulsation appeared to be present also in H0857-242, but with a period of about 50 minutes, confusion with the first harmonic of the satellite's orbital frequency is possible. So that result is uncertain. A negative result was obtained on 4UO608-49 (V347 Pup), suggesting either that the X-ray identification is incorrect, or that the source is very transient. Finally, data was obtained on V1432 Aql and WZ Sge, respectively the slowest and fastest of these stars. Combined with the Advanced Satellite for Cosmology and Astrophysics (ASCA) data, the high-energy data demonstrates the latter to contain a white dwarf rotating with P = 27.87 s. Optical photometry contemporaneous with the X-ray data was obtained of V1432 Aql, in order to study the variations in the eclipse waveform. As anticipated, the width and centroid of the eclipse appeared to vary with the 50-day "supercycle". A paper reporting this study is now in preparation.