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At least 127 records · Page 7
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NASA NTRS1979

Infrared images of Jupiter at 5-micrometer wavelength during the Voyager 1 encounter

A coordinated program to observe Jupiter at high spatial resolution in the 5-micrometer wavelength region was undertaken to support Voyager 1 imaging and infrared radiation experiment targeting. Jupiter was observed over a 5-month period from Palomar and Mauna Kea observatories. The frequency of observations allowed the selection of interesting areas for closer Voyager examination and also provided good short-term monitoring of variations in cloud morphology. Significant global changes in the 5-micrometer distribution are seen over this time period.

Terrile, R. J.↗
NASA NTRS1979

Jupiter's cloud distribution between the Voyager 1 and 2 encounters - Results from 5-micrometer imaging

As part of a continuing effort of ground-based support for Voyager target selection, infrared images in the 5-micrometer wavelength region were acquired in preparation for the Voyager 2 flyby of Jupiter. Observations were made during May 1979 from the Palomar 5-meter telescope and the new 3-meter NASA Infrared Telescope Facility at Mauna Kea and are compared to previous observations. Variations seen in the 5-micrometer flux distribution suggest global patterns of clouding over of some Jovian belts and clearing of others. These data were used to predict the Jovian cloud distribution at the time of the Voyager 2 encounter in order to target the imaging and infrared experiments to areas free of high obscuring clouds.

Terrile, R. J.↗
NASA NTRS1980

QSO evolution and the intergalactic medium

A model is developed of a cold, photoionized intergalactic medium in which only discrete, evolving sources (quasars) produce the observed extragalactic hard X-ray background. Constraints on the model are imposed by observed optical depth limits to various redshifts, far UV and visible flux measurements, X-ray background and source counts in the region 2-6 keV, and it makes use of results of the Palomar Bright Quasar Survey and the Braccesi Quasar survey to obtain expressions for the quasar evolution function, absolute luminosity, present number density and switch-on redshift. Results of computer modeling reveal an intergalactic medium with a density with respect to closure less than 0.35, temperature of 16,000 K and fractional ion abundances of approximately 0.000001 for H I and 0.001 for He II, under the assumption of a Hubble constant of 50 km/sec per Mpc. In addition, spectral indices of -0.4 and -1.3 are obtained for the regions of the emission spectrum above and below 4 x 10 to the 18th Hz.

Sherman, R. D.↗
NASA NTRS1981

A spectrophotometric search for the halo of Markarian 10

Observations of a faint halo around the Mk 10 galaxy nucleus with the Palomar multichannel spectrophotometer reveal blue continuum emission forbidden lines of O II and O III, the hydrogen Balmer series, and stellar absorption series. The flux is detected at the surface brightness of 27.2 + or - 0.2 mag arc/sq sec at wavelengths of 5000 A at the radial distance of 27 kpc from the nucleus. The surface photometry of the inner parts of Mk 10 are depicted, and the radial brightness profile is decomposed into disk and bulge components. No evidence of a halo component was observed; the extended bulge is sufficient for the stabilization of the disk against bar-like instabilities.

Williams, T. B.↗
NASA NTRS1980

Two-dimensional photometry of planetary nebulae

Monochromatic images of three planetary nebulae, NGC 6720, NGC 7662 and NGC 2392, were taken using narrow band interference filters centered on the forbidden emission lines of Oxygen I, II, III, Nitrogen II, Sulfur II and the permitted emission lines of Hydrogen I, Helium I and Helium II. The data was taken with a silicon intensified vidicon using the Palomar 1.5 meter telescope and was recorded digitally to an encoding level of 12 bits. The data was processed at the Image Processing Laboratory of the Jet Propulsion Laboratory. The calibrated images were used to investigate the three dimensional structure of the nebulae and to generate two-dimensional electron and temperature maps.

Kupferman, P. N.↗
NASA NTRS1981

Results of a new approach to determining the density function in the galactic plane - The local system

Star counts in the directions of 15 opaque CO clouds of known distance are used to determine the density function in the galactic plane of the local system of apparently enhanced stellar density. Counts were made on Palomar Sky Survey blue prints in the directions of the highest opacity portions of 15 molecular clouds. Average values of the density functions obtained are found to be significantly less than unity for clouds more distant than 800 pc regardless of galactic longitude, confirming the presence of the local mass density enhancement. Data suggest that the local system represents a density enhancement of a factor of 2 over a region of approximately 500 pc. An empirical relationship is also determined between the distance to a molecular cloud and the number of foreground stars projected on it, which may be useful in determining distances to clouds nearer than 3 kpc. The potential of the Space Telescope for complete stellar mass determinations out to a distance of 1 kpc is pointed out.

Herbst, W.↗
NASA NTRS1981

Thermal response of Saturn's ring particles during and after eclipse

The investigation is based on data which were obtained on May 18, 1978, at the 5-m Hale telescope on Palomar Mountain. A Ge:Ga bolometer was used at the f/70 Gregorian focus; a cold interference filter limited the wavelength response to between 16 and 26 micrometers. A brightness asymmetry is observed between the ansae of all three rings; the largest asymmetry occurs in the C ring. The simplest explanation of such asymmetries is just the eclipse cooling and subsequent heating of similar particles at different radial distances from Saturn, coupled with the different travel times from eclipse exit to east ansa. The observed eclipse cooling and subsequent heating in Saturn's B ring support the idea that the uppermost surface of the particles is of low-conductivity water frost, similar to the uppermost surface of the Galilean satellites (omitting Io).

Froidevaux, L.↗
NASA NTRS1982

A new intermediate Seyfert galaxy - X-ray, optical, and radio properties

It is shown that the X-ray source X0459 + 034 is a Seyfert galaxy of intermediate type, and optical spectroscopy and radio observations were performed to study the nature of the object. The object appears almost stellar and slightly diffuse on Palomar Sky Survey prints. The source is identified as a Type 1.5 Seyfert with broad and narrow line components of redshift 0.016 + or - 0.001, according to H-Beta line profile. In addition, the broad line component H-Beta equivalent width is larger than that of the narrow line component by a factor of three. Finally, it is shown that this is a weak radio source with a steep nonthermal spectrum and an angular extent of approximately 3 in., and the composite radio-to-X-ray spectrum suggests that in different spectral regions, different relativistic electron populations or emission mechanisms are contributing factors.

Ghigo, F. D.↗
NASA NTRS1981

InSb heterodyne receivers for submillimeter astronomy

InSb hot electron bolometer mixer receivers have been developed for submillimeter line studies of the interstellar medium up to about 500 GHz. The receivers have been used aboard the NASA Kuiper Airborne Observatory which is transported to about 12,000 km by a C141 aircraft. Data have been obtained on new interstellar lines (such as the ground-state fine structure transition of atomic carbon at 492 GHz) and such molecular transitions as carbon monoxide and water. Other data were obtained at ground level using the 5-cm Hale telescope at Mount Palomar and the NASA Infrared Telescope facility at Mauna Kea, HI. The heterodyne bolometers have reached noise temperatures of less than 400 K at all frequencies to 500 GHz.

Phillips, T. G.↗
NASA NTRS1983

Two hot, low-field magnetic DA white dwarfs

Two hot stars discovered in the Palomar Green survey which were found to exhibit peculiarly broad and strong Balmer lines possibly indicative of low magnetic fields are discussed. The stars, PG 1658+441 and PG 0136+251, were found to have extended trough-shaped Balmer and Lyman-alpha line profiles when compared to nonmagnetic dwarfs of similar temperatures. Further observations of PG 1658+441 show it to correspond to a 30,000 K pure hydrogen atmosphere and confirm its nature as a magnetic object with a longitudinal field strength of about 0.7 megagauss and a mean surface field of about 2.3 megagauss. PG 0136+251 is found to be a hotter star (40,000-50,000 K) with weaker lines. Although no strong evidence for magnetic line splitting was obtained, it is argued that neither a high surface gravity nor very rapid rotation can account for the Balmer line shapes. Results thus extend the range of magnetic degenerates to include very hot white dwarfs, and demonstrate the usefulness of line-widths as indicators of possible low-field magnetic sources.

Liebert, J.↗
NASA NTRS1983

Spectroscopy of blue stellar objects

Spectra have been obtained for the brightest objects from a list of blue stellar objects found in a Palomar Schmidt field centered on Kapteyn Selected Area 28. Four of the objects presented here comprise a complete sample of objects with UV excess and magnitudes brighter than or equal to B = 16.3 mag. The object with the largest UV excess is a previously undiscovered quasar of redshift 0.25 and cataloged B magnitude of 15.6 mag. The object shows some evidence of variability. Spectroscopy for one bright object in a companion field centered on Selected Area 29 is also presented.

Mitchell, K. J.↗
NASA NTRS1982

Cooled grating array spectrometer for 0.6-5 microns

A grating spectrometer, designed to illuminate an array of 122 InSb photodiodes with minimum aberrations and maximum speed, has been constructed. The instrument will be used on the 5 meter Hale telescope at Palomar Observatory, and is easily adaptable to telescopes of various focal ratios. A resolving power of 100-1000 can be obtained at wavelengths between 0.6 microns and 5 microns with remotely interchangeable gratings. The spectrometer is sufficiently compact to fit on the 8-inch work surface of a commercially available dewar, and uses simple on-axis spherical and paraboloidal optical elements. The camera mirror produces an f/2.5 beam which, with the 0.2 mm detectors, allows a 3-in. focal-plane aperture on the 5 meter telescope. All rays fall within a 100 microns blur circle at all points along the array. Distortions have been corrected with a tilted field flattening lens in front of the detector.

Nordholt, J. E.↗
NASA NTRS1982

Multiple object fiber optics spectrograph feed for the Hale telescope

The preliminary design for a computer-controlled fiber-optics feed linking the 5-m Hale telescope at Palomar Observatory to the entrance slit of an astronomical spectrograph is presented. A 76-mm square field will be divided into ten strips containing two movable fibers each; the fibers can be moved by stepper-motor-driven lead screws to any position on the strip. The device is designed to allow the simultaneous spectrographic observation of many astronomical objects in a small angular field. A prototype feed using two fibers and manually commanded digital control is described in detail. Test observations of two bright O stars made in April, 1981 using the prototype with the Hale telescope are considered sufficiently positive to warrant construction of the 20-fiber feed, which would enhance the spectrographic-survey effectiveness of the telescope by a factor of ten.

Tubbs, E. F.↗
NASA NTRS1983

A large molecular cloud toward the SNR W50 and SS 433

The CO 1 yields 0 transition at 115 GHz has been mapped over an area of more than 6 deg sq toward W50, the extended SNR surrounding the peculiar object SS 433. W50 is found to lie at the end of a filamentary molecular cloud 4 deg long and 1 deg wide that closely matches a conspicuous dust lane on the Palomar Sky Survey; the cloud's kinematic distance is within 0.7 of 2.2 kpc, in agreement with the distance 2-3.3 kpc estimated for the SNR, and its mass is about 120,000 solar masses. Though there is little evidence of star formation in the molecular filament, or evidence of an interaction between the filament and W50 (or SS 433), the positional coincidence of the two, their similar distance, and their displacement nearly two molecular scale heights from the plane all suggest a physical relationship or common origin. One possibility is that both the molecular filament and the stellar progenitor of W50 were ejected from a large active molecular complex lying in the plane at l = 40 deg.

Huang, Y.-L.↗
NASA NTRS1983

A nebula around Nova BT Monocerotis

H-alpha observations of Nova BT Mon obtained on December 15, 1981 using an 800x800-pixel CCD detector on the double spectrograph of the 5-m Hale telescope at Palomar Observatory are reported. The reciprocal dispersion at H-alpha was 6.04 A/pixel and the angular scale along the 1.0-arcsec-wide east-west slit was 0.58 arcsec/pixel; resolution of the combined, processed image is about 12 A. A ring-shaped nebular emission with a center displaced slightly from the stellar image and an expansion distance to BT Mon of about 1800 pc was detected. The velocity diameter is found to be about 1500 km/sec along the ridge line and 2100 km/sec along the 10-unit contour. The mass of the visible nebula is estimated as 0.00003 solar mass, similar to the BT Mon ejection mass determined by Schaefer and Patterson (1983).

Marsh, T. R.↗
NASA NTRS1984

Planet-crossing asteroid survey

The planet-crossing asteroid survey was begun in 1973 in order to study those asteroids which may intersect the orbits of the inner planets. Throughout the history of the survey, many of the various classes of asteroids were investigated. The near-Earth objects including the Apollo, Amor, and Aten families were studied in addition to asteroids whose orbits cross that of Mars, and some objects which are generally confined to the main belt. Observing was done on the 18 inch Schmidt telescope at the Palomar Mtn. Observatory. Typically, two consecutive photographs of a favorable field are taken. The exposure times of the films are usually twenty minutes and ten minutes, respectively. The telescope is guided at sidereal rate, so that asteroids will leave short trailed images. The films are then scanned for trails. By comparing the two films, the direction and approximate rate of motion of an asteroid may be determined.

Wilder, P. D.↗
NASA NTRS1984

Photographic surveys of the southern sky

Parameters of the UK 1.2 meter Schmidt telescope are described. Plates taken with this instrument are in two categories, those for systematic sky surveys and those taken at the request of research users. A collaborative project with the European Southern Observatory was undertaken to obtain a two-color survey of the sky south of -20 deg declination to complement the Palomar survey. A near infrared survey of the Galactic Plane and the Megallanic Clouds is being done. The area south of -20 deg and the zone between 0 deg and -15 deg are also being surveyed. Pending a decision on survey parameters, all available A quality prism plates are being retained to form a basis for systematic survey. Nearly half the plates taken on a service basis for the UK astronomical community are to fulfill nonsurvey requests. Plates taken for surveys which are not of A grade quality are also made available for research purposes.

Sim, M. E.↗