Search

Mutual event observations between the two components of 90 Antiope were carried out in 2007-2008. The pole position was refined to lambda0 = 199.5+/-0.5 eg and beta0 = 39.8+/-5 deg in J2000 ecliptic coordinates, leaving intact the physical solution for the components, assimilated to two perfect Roche ellipsoids, and derived after the 2005 mutual event season (Descamps et al., 2007). Furthermore, a large-scale geological depression, located on one of the components, was introduced to better match the observed lightcurves. This vast geological feature of about 68 km in diameter, which could be postulated as a bowl-shaped impact crater, is indeed responsible of the photometric asymmetries seen on the "shoulders" of the lightcurves. The bulk density was then recomputed to 1.28+/-0.04 gcm-3 to take into account this large-scale non-convexity. This giant crater could be the aftermath of a tremendous collision of a 100-km sized proto-Antiope with another Themis family member. This statement is supported by the fact that Antiope is sufficiently porous (~50%) to survive such an impact without being wholly destroyed. This violent shock would have then imparted enough angular momentum for fissioning of proto-Antiope into two equisized bodies. We calculated that the impactor must have a diameter greater than ~17 km, for an impact velocity ranging between 1 and 4 km/s. With such a projectile, this event has a substantial 50% probability to have occurred over the age of the Themis family., Comment: 30 pages, 3 Tables, 8 Figures. Accepted for publication in Icarus

The International Halley Watch was established to coordinate, collect, archive, and distribute the scientific data from Comet P/Halley that would be obtained from both the ground and space. This paper describes one of the end products of that effort, namely the IHW Digital Archive. The IHW Digital Archive consists of 26 CD-ROM's containing over 32 gigabytes of data from the 9 IHW disciplines as well as data from the 5 spacecraft missions flown to comet P/Haley and P/Giacobini-Zinner. The total archive contains over 50,000 observations by 1,500 observers from at least 40 countries. The first 24 CD's, which are currently available, contain data from the 9 IHW disciplines. The two remaining CD's will have the spacecraft data and should be available within the next year. A test CD-ROM of these data has been created and is currently under review.

The paper presents an analysis of a set of CCD images of Comet Halley which were taken in the light of the CN radical to search for evidence of a 2.25-day and/or a 7.37-day periodicity in the evolution of the CN jets. It is found that, for a phase sorted set of CCD images, the geometry of the CN jets is more easily understood when a 7.37-day periodicity is assumed. The extent of the CN jets indicates a dominant periodicity that is greater than 2.25 days.

Forty-three cold, dense molecular clouds are digitized from the Palomar Observatory Sky Survey glass plates and presented with epoch 1950.0 equatorial coordinates. Regardless of the cloud's extent, the digitized area is limited to a 23 arcmin square on the sky with pixel size of about 1.3 arcsec. The optical maps presented herein are useful for comparing complementary molecular cloud maps from radio or infrared instruments and can be obtained in FITS format for use on astronomical image-processing systems.

The status of the current microdensitometers used for digitizing astronomical imagery is discussed. The tests and improvements that have and can be made to the Photometric Data System PDS microdensitometer are examined. The various types of microdensitometers that currently exist in the world are investigated. Papers are presented on the future needs and the data processing problems associated with digitizing large images.

The eye as an efficient selection device for determining what is important in astronomical imagery can be greatly aided by the computer. A suitable facility, called the Interactive Astronomical Data Analysis Facility (IADAF), has been developed for the display and analysis of astronomical imagery by the Laboratory for Astronomy and Solar Physics. The Laboratory for Astronomy and Solar Physics currently has approval to fly two experiments on Spacelab. The Solar Extreme Ultraviolet Telescope (SEUTS) is to be used for the study of several fundamental problems of solar physics. The Ultraviolet Image Telescope for Astronomical Investigations (UIT) is to provide direct imagery of selected fields of view throughout the sky. A description is given of IADAF, taking into account its 16-bit computer and the COMTAL image processing display system. The use of IADAF by SEUTS and UIT is discussed.

Nightly mean intensity tracings of the spectrum of a Centauri in the neighborhood of lines from multiplets 41 and 43 Fe I are presented for ten consecutive nights. On some nights, broad, shallow absorption features appear at the positions of the Fe I lines.

The present paper describes several software techniques that can be used to get the 'most' out of an image without destroying or adding any information. A simple overview is given of a general image-processing system, a number of systems in current use are listed, and three types of processing tasks are delineated: image diagnostics, subjective enhancement, and quantitative restoration. Examples of each of these types are discussed in some detail, including histogram, differences, and Fourier analysis for image diagnostics; contrast stretching, edge enhancement, and pseudocolor displays for subjective enhancement; and photometric correction, contouring, and geometric correction for quantitative restoration.

This paper presents the techniques needed to convert the International Ultraviolet Explorer (IUE) high-resolution echelle spectra into useful scientific data. The image is obtained with a digitally controlled vidicon camera system. The processes that must be carried out on the image include: noise removal, correction for geometric and optical distortion, nonuniform photometric corrections, and two-dimensional wavelength determination. Results from the breadboard camera system are presented.

A comparison of the vignetting function for Apollo 15, 16 and 17 35-mm cameras is presented. A technique for removing this effect is described and demonstrated on an image of the L4 point of the earth-moon system.

The superposition of the X-ray, optical, and radio imagery of supernova remnants in the Cygnus Loop region is described. The radio data of the region was obtained using the Westerbork interferometer, and the optical image was recorded by the NASA Wide Field Camera. The X-ray imagery was obtained using the High Resolution Imager. The mechanisms by which the supernova ejecta and the swept-up material shock the interstellar medium are studied by the resampling of the imagery onto a common celestial grid. The initial results indicate a radio arc in the northeastern portion of the region that is along the faintest outermost filaments, and a separate radio arc along the brightest filaments.

A description is given of the Interactive Astronomical Data Analysis Facility (IADAF) which performs interactive analysis of astronomical data for resident and visiting scientists. The facilities include a Grant measuring engine, a PDS 1010A microdensitometer, a COMTAL image display system and a PDP 11/40 computer system. Both hardware and software systems are examined, including a description of thirteen overlay programs. Some uses of the IADAF are indicated.

DIDCS is an interactive image display and manipulation system that is used for a variety of astronomical image reduction and analysis operations. The hardware system consists of a PDP 11/40 main frame with 32K of 16-bit core memory; 96K of 16-bit MOS memory; two 9 track 800 BPI tape drives; eight 2.5 million byte RKO5 type disk packs, three user terminals, and a COMTAL 8000-S display system which has sufficient memory to store and display three 512 x 512 x 8 bit images along with an overlay plane and function table for each image, a pseudo color table and the capability for displaying true color. The software system is based around the language FORTH, which will permit an open ended dictionary of user level words for image analyses and display. A description of the hardware and software systems will be presented along with examples of the types of astronomical research that are being performed. Also a short discussion of the commonality and exchange of this type of image analysis system will be given.

Photometry of the lunar libration region L4 obtained in double umbra during the lunar orbital flight of Apollo 15 is reported. A four-minute photographic exposure of the region centered at celestial coordinates 23 h 14 m, -1.8 deg was made using a 35-mm camera at f/1.2 in the command module pilot's window. The film had been calibrated to the sun's surface brightness, and scene brightness information was converted to digital form, followed by high-speed digital processing with vignetting removal to obtain absolute photometric values. Results reveal an elliptical brightness region 16 x 12 deg in extent with an absolute brightness of 3.3 x 10 to the -14th sun surface brightness units. The mass of the scattering material responsible for the effect is estimated to be between 6 x 10 to the 18th and 2 x 10 to the 7th g.

The International Ultraviolet Explorer spectral image processing system is an on-line interactive system which provides data on the UV spectra of astronomical objects in the wavelength range 1000 to 3200 A. In operation for one year, the image processing system accepts two-dimensional images transmitted digitally from the satellite's SEC vidicon cameras. The system extracts spectral intensity as a function of wavelength and removes background, scattered light, halation and echelle effects.

During the commissioning phase of IUE observations were made of a selection of hot stars: the white dwarf HZ43, the hot subdwarf BD +75 deg 325, the nucleus of the planetary nebula NGC 6826, the dwarf nova SS Cygni, and the peculiar object Eta Carinae. The observations were made in the low dispersion mode and the data have been reduced using a preliminary calibration. The results are presented and discussed for each object.

A report on the initial performance of the IUE satellite, launched in January, 1978, is given. Attention is given to optical performance, camera performance, background corrections, photometric performance, and data reduction. Samples of high-dispersion and low-dispersion spectra are shown. A remaining problem of proper separation of high dispersion orders in data reduction is discussed.

The paper describes the general design, instrumentation, and ground control system of the International Ultraviolet Explorer (IUE) satellite, which will serve as an astronomical observatory providing both high and low resolution UV spectra of sources other than the sun. Basic data are given on the telescope, the UV-visible converter, the spectrograph optics, the camera response, and the communications systems.

A television tube is a useful way to record a many-element picture such as is obtained from an echelle spectrograph. The signal on the tube target is scanned and relayed to the data-processing center where it must be reconstituted into the scene that was present in the focal plane of the spectrograph camera. A typical television frame will contain four million bits of information which must be processed to remove transmission errors and random noise pulses, to remove periodic noise, to correct for optical and electrical distortion, to remove sensitivity variations across the face of the tube, to calibrate from the photoelectrons back to incident energy, and to provide a wavelength scale. Results of a study of these problems is presented.

Guidelines for the preparation of systems analysis and programming work statements are presented. The data is geared toward the efficient administration of available monetary and equipment resources. Language standards and the application of good management techniques to software development are emphasized.

Atmospheric and abundance analyses of photoelectric standard star 29 Psc

Hydrogen line blanketed stellar model atmospheres

Coefficients for linear and nonlinear limb darkening in early type stars

Sigma Orionis E hydrogen-deficient atmosphere, using grid of constant-flux model atmospheres to determine abundances of five elements

Nonlinear limb darkening for early stars

Helium-carbon star BD plus 10 degrees 2179 reanalyzed by grid of constant flux models containing right amount of C

Hydrogen abundance in white dwarfs, discussing inconsistencies in mass and bolometric magnitude models for Sirius and Eri B

Carbon content of helium star from coude spectrograms analysis based on flux constant model atmospheres

Profiles of the last few Balmer lines (H12-H27) and the full profiles of the H gamma line were computed for a grid of hydrogen line blanketed model atmospheres. The use of the last hydrogen line and the equivalent width of H gamma provide a quick means of estimating the effective temperature and surface gravity of B stars. Regression curves relating the quantum number of the last hydrogen line to the electron density in the model atmosphere are given. Futhermore, it is shown that the difference in the gravity determination deduced from H gamma equivalent widths using the Edmonds-Schuter-Wells formalism and the Griem wing formulae is, at worst, 0.18 in the common logarithm.