Search results

582 records were found.

Spectrophotometric and broad-band photoelectric observations of Eros are reported. No existing meteorite spectrum matches the asteroid data directly. Assemblages of iron or stony-iron with ordinary-chondrite material generate the best match for the reflectivity curve of Eros. Variability was found in the 0.6 micron band and V-R and V-I colors.
Interference filters centered at 0.365, 0.387, 0.406, 0.484, and 0.514 microns have been selected to represent UV continuum, CN emission, C3 emission, blue continuum, and C2 emission in cometary spectra, respectively. Adopted magnitudes and colors of this filter system are presented for 50 standard stars, ranging in bue magnitude from 4 to 12, in spectral type from O to K, and distributed primarily around equatorial regins of the sky. The tabulated uncertainties are generally of the order of 0.02 mag or smaller; the zero points of the photometric system are chosen so that blue continuum magnitudes are approximately equivalent to Johnson B, and so that color indices average zero for solar analog stars.
Photoelectric photometry of six earth-approaching asteroids is presented. The selection criterion was that they were close enough in 1986 to be observed by radar. Rotation periods were obtained for 1986 DA, 3199, 3103, and 1983 RD. 1986 JK and 1986 RA showed no detectable brightness variations during the monitoring time on several nights each, and therefore were either seen pole-on or have long rotation periods. Asteroids 1986 JK and 1986 RA are of taxonomic class C, 1986 DA and 3103 of class X, 1983 RD of class Q, and only 3199 of the class S that was previously believed to be predominant among earth-approaching asteroids.
Two lightcurves have been obtained of the periodic comet Tempel 2 during May and June 1988, using a CCD camera, as well as five photoelastic photometer lightcurves. On each observational occasion, two uneven maxima were observed which suggest that the lightcurves in question are not products of an active spot on the comet, but rather are true reflections from an elongated rotating nucleus that are being observed through a transparent coma. A comparison of CCD and photoelectric photometry leads to an encouragement of users of the latter to sustain their efforts with such instruments.
Photometric observations of 10 small asteroids (10 km or less in diameter), obtained using the 1.5-m Mt. Lemmon and 2.3-m Kitt Peak telescopes of the University of Arizona during 1986-1987, are reported. The instrumentation and data-reduction techniques employed are described, and the results are presented in tables and light-curve plots and briefly characterized.
Seyfert galaxies nuclear regions, noting multicolor photometric measurements between 0.3 and 1.6 micron and measurements of M87 jet at 1.55 micron
It is demonstrated that the use of an imaging CCD detector array allows photometric observations of comparatively faint asteroids moving rapidly through a complex background of star images. The shortage of observing time is alleviated by taking advantage of the presence of comparison stars that are observed simultaneously on the CCD imaging area and at small angular separations from the asteroid. These reference stars allow the effects of thin cirrus clouds or haze to be compensated to a degree adequate for the acquisition of scientifically original data.
This paper reports new photoelectric photometry of the nucleus of P/d'Arrest (1976e) during August 4, 5, and 6, 1976 (UT), just before perihelion passage. The comet appeared as a bright stellar nucleus with a faint surrounding coma. The average visual magnitude from the nuclear region (16-arcsec diaphragm) was 11.60. The visual brightness varies with an amplitude of 0.15 plus or minus 0.02 mag. There is evidence for a period of 5.17 plus or minus 0.01 hr. We interpret such a periodic variation as due to the rotation of the nucleus. The colors of the nuclear region are very similar to those of a solar-type star, and they do not vary significantly with aspect angle.
The first asteroid lightcurves have now been made with a new technique of CCD photometry. The apparent magnitude is fainter (V>17) than what can be done with the 1.52-m Catalina reflector with a photomultiplier photometer. With the CCD system, however, the lightcurve shows remarkably good repetition; finding the asteroid is, of course, no problem as the object is recognized later by its motion on the CCD. Asteroid 1985RV has a lightcurve amplitude of about 0.4 mag and its period of rotation P = 4.0 hours, on the assumption that the lightcurve has two maxima and two minima as is the case for nearly all other asteroids. The diameter is about 3 km. 1985RV is a first example of results that are being obtained on asteroids and comets with CCD in the Catalinas, Kitt Peak, and Cerro Tololo.
Want to know more?If you want to know more about this cutting edge product, or schedule a demonstration on your own organisation, please feel free to contact us or read the available documentation at http://www.keep.pt/produtos/retrievo/?lang=en