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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
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NASA NTRS1983

Three years of photometry of IM Pegasi = HR 8703

Differential photometry of this K1 IV-III p RS CVn-type binary in 1978-79, 1979-80, and 1980-81 at eight different observatories shows that the variability, discovered originally by Herbst, is periodic. The mean of three different determinations of the photometric period was 24(d).39 + or 0(d).03, about 1 percent shorter than the orbital period of 24(d).649 determined spectroscopically by Harper. The total range observed during these three years was for V from 5(m).60 to 5(m).85. The light curve was nearly sinusoidal but always noticieably asymmetric, with the sense reversing sometime between 1979-80 and 1980-81.

Eaton, J. A.↗
NASA NTRS1983

Worldwide photometry and lightcurve observations of 1 Ceres during the 1975-1976 apparition

Lightcurves and UBV photometry of Ceres from the 1975-1976 apparition are presented. The synodic period is 0.37812 + or 0.00004 day, the mean absolute V magnitude is 3.61 + or 0.03, and the phase coefficient is 0.040 + or - 0.001 mag/deg. The U-B and B-V phase coefficients are +0.0015 + or - 0.0007 and +0.0006 + or - 0.0003 mag/deg, respectively. The colors at zero phase are B-V = +0.70 + or - 0.01 and U-B = +0.41 + or 0.01.

Tedesco, E. F.↗
NASA NTRS1983

Worldwide photometry and lightcurve observations of 16 Psyche during the 1975-1976 apparition

Twenty-six lightcurves of Psyche are presented together with UBV photometry and phase functions from 1975 and 1976. Combining photometric data from this opposition with those from previous apparitions resulted in a mean phase coefficient in V of 0.026 + or - 0.002 mag/deg. No significant phase-dependent variation in the U-B color could be determined from the data; the B-V color, however, displayed a reddening with phase of 0.0010 + or - 0.0004 mag/deg. It is concluded that compositional variations over Psyche's surface are minor, and that Psyche's opposition effect is typical of that for other well-observed asteroids. Psyche's behavior is accounted for if, to the first order, its shape is that of a triaxial ellipsoid with axial ratios near 5:4:3.

Tedesco, E. F.↗
NASA NTRS1983

Infrared (JHK) photometry of asteroids. II

JHK (1.2, 1.6, and 2.2 micron) photometry for 38 asteroids of various spectral classifications is reported. M asteroids tend to have infrared colors intermediate between the color domains of E and P asteroids. A few D asteroids have redder J - H colors than most C asteroids. The unusually red J - H color of 246 Asporina indicates it is a member of the A class.

Veeder, G. J.↗
NASA NTRS1983

Five years of photometry of Sigma Geminorum

Thirteen observatories have collaborated in obtaining five years of photoelectric photometry for the bright, K1 III RS CVn binary Sigma Geminorum. Except for one year, the light curve has exhibited two minima which are separated by approximately half a cycle. At the 1977.2 epoch of discovery one minimum was shallower, but as of 1982.2 they have become comparable in depth. During the 1979-80 season, the light curve changed shape rapidly, with the shallower minimum becoming as deep as the other within a period of no more than 80 days. The overall brightness range during the five years in V has been 4.13-4.29 mag, and it is found that the times of both minima can be fit with a photometric period of 19.423 days.

Fried, R. E.↗
NASA NTRS1983

Photometry of resolved galaxies. III - GR 8

Photometry of 84 resolved stellar images in GR 8 is presented. The numbers are derived by applying point spread function fitting techniques on digital images obtained with a three-phase Texas Instruments CCD. The resulting color-magnitude diagrams are discussed. These data are compared with theoretical stellar evolutionary tracks and similar results for other resolved galaxies.

Hoessel, J. G.↗
NASA NTRS1983

CCD photometry of the BL Lacertae object 1400+162 and the associated group of galaxies

Surface photometry of the BL Lacertae object 1400+162 and an apparently associated group of galaxies has been obtained using a CCD camera. Observations were made in V, broad bandpasses centered on 0.75 micron and 1.0 micron and with no filter. The colors of all but two of the galaxies suggest they are ellipticals, with the colors of the remaining two considerably bluer. Analysis using a method described by Schechter and Press (1976) suggests the group is a small one. The group may be similar to the one associated with the quasar 3C 273. The spectral index of the BL Lac object is 1.49 + or 0.21. This value allows, but does not require, the presence of an underlying elliptical galaxy. The radio-optical and optical-X-ray indices for 1400+162 are similar to values found for quasars.

Weistrop, D.↗
NASA NTRS1983

Ultraviolet photometry of dwarf novae in outburst

Broad-band photometry from the Astronomical Netherlands Satellite of five dwarf novae at 1550, 1800, 2200, 2500, and 3300 A is presented. EM Cyg in standstill exhibits a flux excess at 3300 A. The lack of a strong extinction feature at 2200 A is seen as suggesting that the reddening is small toward all five systems. Using an independent estimate of the distances, mass flux rates are derived by fitting steady-state, optically thick accretion disk models to the observed UV luminosity. The rate is found to be 3 x 10 to the 17th g/s for Z Cam and EM Cyg in outburst and a factor of 3 smaller of Z Cam in standstill. The models, however, do not reproduce the slope of the Balmer continuum. Of special interest are the observations of outburst rises of SS Aur, SU UMa, and EM Cyg. SS Aur exhibits an exponential increase at a rate of 3.5 mag in 0.5 d. The outburst in EM Cyg also reveals an exponential rise, but at a rate of only 1.2 mag per day.

Wu, C.-C.↗
NASA NTRS1983

Photometry and polarimetry of Saturn at 2640 and 7500 A

Voyager 2 photometric and polarimetric data are reduced and tabulated, with spatially resolved limb-to-terminator scans across Saturn's equatorial zone providing information on the altitude distribution of UV-absorbing hazes, together with the phase function and polarizing properties of stratospheric and tropospheric aerosols. It is found that the UV photometry and polarimetry are best fit by Rayleigh's phase matrix. A stratospheric haze of small particles is allowed as long as the optical depth is near unity or less, and the center of the haze layer is in the 30 to 70 mbar region. The altitudes presently derived for three latitudes agree with those obtained by ground-based methane band studies and analyses from Pioneer 11. A high altitude absorber is abundant in the polar regions.

West, R. A.↗
NASA NTRS1983

Luminosity distributions for Virgo cluster galaxies. I Near-infrared surface photometry of 81 disk systems

I-band (8500 A) surface photometry of 81 galaxies in Virgo provides the basis for comparing the disk properties of S0 galaxies with those of Sa, Sb, and Sc systems. No significant difference is found in the distributions of either central surface brightness or exponential scale length between S0's and later Hubble types. Because the I-band is dominated by contributions from the old-disk population, this result suggests that the factors which control the distribution of luminous disk material in all types of disk systems are identical. Evidently, environmental factors have not played a significant role in affecting the star-forming histories of the Virgo disks.

Boroson, T. A.↗
NASA NTRS1983

Photoelectric photometry of selected SAO stars. III

Photometric observations of 131 SAO stars for use in calibrating data obtained from the Near Infrared Photographic Sky Survey (NIPSS) are reported. The serial numbers of the primary NIPSS program fields in which the photometry was done are shown along with the approximate position of each field and the number of stars observed in each field. The observations are listed, showing the SAO numbers of the program stars, their 1950 equatorial coordinates, the V magnitudes, and the (V-R) and (V-I) color indices. The mean errors in magnitudes and color indices obtained by averaging deviations from the mean for each star are on the order of 0.02 mag.

Scharlach, W. W. G.↗
NASA NTRS1984

Multicolor photometry of outer Jovian satellites

Multicolor photometry was obtained of satellites J6 Himalia, J7 Elara, and J10 Lysithea in the prograde cloud of outer Jovian satellites, and of J8 Pasiphae, J9 Sinope, and J11 Carme in the retrograde cloud. The data for J9 are fragmentary; otherwise, the satellites all look like C-class asteroids, except J11, which shows a remarkable brightness in the ultraviolet. The absence of D-class spectra among the outer Jovian satellites suggests that they were not derived from the same population as the outer-belt and Trojan asteroid populations.

Tholen, D. J.↗
NASA NTRS1984

Infrared photometry of Comet Bowell and other comets

Broad-band and intermediate-band infrared photometry of Comets Bowell, Elias, and Gunn is presented. The data for Comet Bowell show that the strongly depressed albedo near 3 microns observed by Campins and colleagues (1982) is very broad and extends at least to 4 microns. Scattering calculations indicate that existing infrared data do not provide direct, observational evidence for the presence of H2O ice. However, the material responsible for the 3-micron absorption observed by Campins and colleagues remains therefore unidentified.

Dwek, E.↗
NASA NTRS1984

Voyager disk-integrated photometry of Io

The results of a comprehensive analysis of disk-integrated photometry of Io derived from Voyager images are presented. Phase curves, rotation curves, and geometric albedos consistent with earth-based observations of Io are obtained, except for a previously noted tendency for the Voyager data to yield somewhat redder colors. It is demonstrated that the phase coefficient decreases with increasing wavelength. The phase integral ranges from about 0.7 in the ultraviolet to about 0.8 in the orange. The Bond albedo is estimated at 0.50 + or -0.10, a value consistent with, though slightly below, previous earth-based estimates.

Simonelli, D. P.↗
NASA NTRS1984

Multi-spectral Observations of the Star Formation: the Role of Far Infrared Photometry

The study and analysis of complex astrophysical process requires a multispectral approach employing many of the tools of modern astronomy. The study of the interaction of early type stars with the interstellar medium is an example of this point. Two examples of multi-spectral studies of individual objects are reviewed. The predominent theme is the combination of high resolution far infrared photometry, radio images and millimeter-wave spectroscopy with the radio sensitive to the ionization, the millimeter-wave lines showing the structure and excitation of the gas and the far infrared providing a picture of the energetics of the dust which connects the star to the interstellar medium. Multispectral observations of FIRSSE and IRAS objects are discussed.

Schwartz, P. R.↗
NASA NTRS1984

Reduction to Outside the Atmosphere and Statistical Tests Used in Geneva Photometry

Conditions for creating a precise photometric system are investigated. The analytical and discriminatory potentials of a photometry obviously result from the localization of the passbands in the spectrum; they do, however, also depend critically on the precision attained. This precision is the result of two different types of precautions. Two procedures which contribute in an efficient manner to achieving greater precision are examined. These two methods are known as hardware related precision and software related precision.

Rufener, F.↗
NASA NTRS1984

Time Series Photometry with a CCD Camera

Time series observations of a field in the cluster NGC 4755 with a CCD camera are used to show that differential photometry between stars on the CCD frame is limited in accuracy mostly by photon statistics, over a 5 magnitude range. Scintillation noise appears to be almost entirely suppressed. The maximum accuracy possible is limited by the storage capacity of the CCD to about 0.001 mag.

Walker, A. R.↗
NASA NTRS1984

Photometry with Multi-anode Microchannel Arrays (mamas) and Charge Injection Devices (cids)

The characteristics of two kinds of detectors are summarized with emphasis on those aspects that would affect their use in high accuracy astronomical photometry. The first type, the multianode microchannel arrays (MAMA), are a family of pulse counting array detectors. Components and operation principles are reviewed and quantum efficiency, noise characteristics, and dynamic range characteristics are described. The second type, charge injection devices (CID), are discussed in reference to their applicability to photometric detection at optical wavelengths.

Timothy, J. G.↗