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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The intrinsic values and color excesses of (B-V) for 115 F-K supergiants

Color excesses in B-V are determined indirectly from a study of Stromgren's b-y color for a sample of F0 - K5 supergiants. The resulting E(B-V)'s are estimated to have an expected precision of + or - 0.05. With the calculated color excesses and the observed values of B-V given in various catalogs, the run of B-V with spectral type is obtained. This B-V/(spectral type) relationship is compared with those found previously by other investigators.

Kelsall, T.↗
NASA NTRS1972

Intrinsic B-V color for galactic cepheids and some comments on the Sandage-Tammann relationship

Transformations are found for converting the b-y color excesses for Cepheids given by Williams (1966) and Kelsall (1971) into B-V excesses. The combination of these results with the E(B-V)'s determined by Sandage and Tammann (1971) gives precise data for eighty-eight galactic Cepheids. The period-color and period-color-(amplitude defect) relationships, that are germane to the LogP intervals 0.4 to 1.4 and 0.4 to 1.3, respectively, are found.

Kelsall, T.↗
NASA NTRS1972

Stellar ultraviolet colors and interstellar extinction

A sample of celescope results is studied. Most of the sample stars belong to the Orion and Vela regions. Stars with visual excess E(B-V) less than 0.05 are selected in order to derive relationships of intrinsic color index versus spectral type. The resulting intrinsic color-color relations are compared with existing blanketed and unblanketed model calculations. Finally, the preceding intrinsic relations are utilized to derive some results on interstellar extinction. Owing to the rather large scatter in the celescope data, the Vela stars give the more significant results because their visible excess E(B-V) is, in general, larger than that for the Orion stars.

Peytremann, E.↗
NASA NTRS1975

UBV photometry of asteroid 433 Eros

UBV observations of asteroid 433 Eros were conducted on 17 nights during the winter of 1974/75. The peak-to-peak amplitude of the light curve varied from about 0.3 mag to nearly 1.4 mag. The absolute V magnitude, extrapolated to zero phase, is 10.85. Phase coefficients of 0.0245 mag/degree, 0.0009 mag/degree, and 0.0004 mag/degree were derived for V, B-V, and U-B, respectively. The zero-phase color of Eros (B-V = 0.88, U-B = 0.50) is representative of an S (silicaceous) compositional type asteroid. The color does not vary with rotation. The photometric behavior of Eros can be modeled by a cylinder with rounded ends having an axial ratio of about 2.3:1.

Millis, R. L.↗
NASA NTRS1972

Ultraviolet photometry of globular clusters

Filter photometry measurements of the integrated light from several globular clusters between 1500 and 4000 A are discussed. The techniques and problems associated with carrying out photometry of faint extended sources with the OAO-2 instrumentation are described first. The energy distribution for globular clusters determined from these data are corrected for interstellar extinction on the basis of B-V color excesses and a mean ultraviolet extinction curve. The results are compared with synthetic cluster calculations. The ultraviolet energy distribution is primarily determined by the number of stars at the blue end of the horizontal branch.

Welch, G. A.↗
NASA NTRS1973

Ultraviolet photometry from the orbiting astronomical observatory. 8: The blue Ap stars

The filter photometers in the Wisconsin Experiment Package on OAO-2 were used to obtain data for a carefully selected set of 24 blue Ap stars and 31 comparison standard B and A dwarfs and giants for a program of relative photometry. Observations were made in seven bandpasses over the effective wavelength range 1430A-4250A. The Ap stars observed include members of the Si, Hg-Mn and Sr-Cr-Eu peculiarity classes. Most of them are too blue in B-V for their published MK spectral classes. The blue Ap stars are markedly deficient in emitted ultraviolet flux and are underluminous as compared to normal stars with the same UBV colors. The Hg-Mn stars appear less flux deficient in the ultraviolet for their UBV colors than do Si or Sr-cr-Eu stars. Most of the Ap stars observed possess ultraviolet flux distributions, or ultraviolet color temperatures, consistent with their published MK spectral classes to well within the classification uncertainties.

Leckrone, D. S.↗
NASA NTRS1973

Properties of optical radiation of variables and quasars

Photoelectric observations in the system UBV are considered for 42 variable stars, six quasars and Sco XR-1 with U-B and B-V colors of different type radiations. There are regressive dependences for nearly all the objects. On the Delta V/Delta B, Delta U/Delta B plane the objects were divided according to the types and situated along the bands. The directions of these bands are in agreement with values of A for different types of radiation.

Lukatskaya, F. I.↗
NASA NTRS1973

Simultaneous electrophotometric and spectral observation of N Del 1967

Eleven spectrograms of low dispersion and more than sixty observations in the UBV system are obtained. The light of the nova is found to be unchanging except for J. D. 2439703. With the increase of (B-V) both (U-B) and spectrophotometric temperature decreases. An attempt was made to connect the light variation with the ones in the continuous spectrum.

Lenderman, Y. I.↗
NASA NTRS1973

CPD-31 1701, an extremely helium-rich subluminous O-type star.

The bluest of thee 1500 southern OB stars discovered during an extensive photometric (UBV) and spectroscopic (MK) study of galactic structure in the southern hemisphere is discussed. The spectrum of this strikingly peculiar star is completely dominated by lines of neutral and ionized helium, most of which are extremely Stark-broadened. The spectral type is 08, with V = 10.52, B-V = -0.31, and U-B = -1.17. The absolute magnitude is probably +3. Located in the plane of the Milky Way, the CPD 31 1701 is hot, very underluminous, and extremely helium-rich.

Garrison, R. F.↗
NASA NTRS1973

Intrinsic ultraviolet colors from OAO-2 Celescope observations for stars on the main sequence.

Intrinsic ultraviolet colors (Vi-V)o have been determined with ultraviolet magnitudes derived from several hundred observations taken with the photometers of OAO-2's Celescope experiment. Relationships between intrinsic ultraviolet color, (B-V)o, and spectral class are presented for main-sequence stars from B 0 to G 3. A brief description of the Celescope and its calibration is included, and a comparison of the determined colors is made with theoretical colors.

Haramundanis, K.↗
NASA NTRS1973

Minor planets and related objects. IX - Photometry and polarimetry of /1685/ Toro.

UBV photometry, lightcurves, a polarization-phase relation, and rotational polarization curves of Toro were obtained, June-August 1972. The average colors are B-V = 0.87 and U-B = 0.47 mag, showing some reddening with phase. The geometric albedo of Toro in the B filter is 0.14 which corresponds to an effective mean radius of 2.2 km plus or minus 0.4 (p.e.). The rotational polarization curves indicate that the lightcurves are mostly due to shape, but some albedo variation over the surface is detected as well. The shape is elongated, and probably irregular, with a cross-sectional area ratio of about 3.2, the maximum effective radius is 2.8 km and the minimum, 1.6 km.

Dunlap, J. L.↗
NASA NTRS1973

The V-K colours of the nuclei of bright galaxies

Photometric observations of the nuclei of the galaxies M32, M33, M51, NGC5195 and M101 are reported. These give U-B, B-V, H-K and V-K colours for each object and the K-L colour for M32. No short-wavelength infra-red excesses are found. For M32, published population models (Spinrad & Taylor) predict a V-K colour too red to be compatible with the observations.

Penston, M. V.↗
NASA NTRS1974

Minor planets and related objects. XV - Asteroid /1620/ Geographos

Analysis of the light curves and color-phase and polarization-phase relations of Geographos according to observations over an eight-month period in 1969. The light curves are relatively smooth with two distinct maxima and minima. The largest amplitude of 2.03 mag is the largest observed on asteroids to date. The average B-V is 0.87 and the average U-B is 0.50. A laboratory model that best reproduced Geographos' light curves was a cylinder having hemispherical ends with a length to width ratio of 2.7; on the basis of this model and a relation of Bowell and Zellner (1973), Geographos was calculated to be approximately 1.50 km wide and 4.0 km long.

Dunlap, J. L.↗
NASA NTRS1974

Ultraviolet photometry from the Orbiting Astronomical Observatory. XI - The 1971 eclipse of 32 Cygni

We observed the 1971 eclipse of 32 Cyg at regular intervals from November 1 to 15 with the wide-band filter photometers aboard OAO-2. Data have been reduced for seven filter bands with effective wavelengths between 4250 and 1430 A. Both the constancy of the light near mid-eclipse for the shorter wavelengths, and the derived energy distribution of the B component over all of these wavelengths indicate that the eclipse was total. The spectral types determined from the photometry of the two components are B5 and K4 Ib, after correction for interstellar reddening of 0.10 mag in B-V.

Doherty, L. R.↗
NASA NTRS1975

Copernicus observations of interstellar absorption at Lyman alpha

Column densities NH of atomic hydrogen have been derived for 40 OB stars from spectral scans at Lyman alpha obtained by the Copernicus (OAO-3) satellite. The stars are all between 60 and 1100 pc away with a range of mean densities n sub H of 0.01 to 2.5 atoms cm-3. The gas to color-excess ratio in clouds varies from 1 to 3 times the mean outside of clouds. The presence of molecular hydrogen correlates with E(B-V), but the best tracer for H2 is atomic hydrogen. The mean density of the gas for all 40 stars is much smaller than the mean of 0.7 atoms cm-3 obtained from 21-cm observations, because the brightest stars with less than average amounts of matter in the line of sight were selected for observation.

Bohlin, R. C.↗
NASA NTRS1974

Photometric properties of the Martian satellites

New photoelectric observations yield V(1, alpha) equals 12.95 + 0.036 alpha + or - 0.05, B-V equals 0.65 + or - 0.03, and U-B equals 0.18 + or - 0.03 for Deimos and V(1, 0) equals 11.9 + or - 0.2 for Phobos. The derived geometric albedos of both satellites are near 0.065. Combined photometric and polarimetric results lead to the conclusion that the satellites have dusty surfaces and are possibly basaltic but more likely carbonaceous in composition.

Zellner, B. H.↗
NASA NTRS1974

Digicon photometry of an intergalactic bridge

Surface brightness and color data are derived for two points in the bridge and tail structure of Arp 295. The best observed point has a surface brightness in V of 25.9 magnitudes per square arc second and (B-V) = +1.00 m. A point on the tail is brighter with the same color.

Beaver, E. A.↗
NASA NTRS1975

The light curve of Comet Kohoutek

Visual estimates of total coma brightness define the light curve of Comet Kohoutek between Nov. 24, 1974 and Feb. 6, 1974. These data are well fitted by straight lines on the M-log r diagram. The preperihelion value of n is 2.2, and the post perihelion value is 3.8 up to January 16. A standstill in the decline is suspected between January 16 and 19. If the standstill is ignored the postperihelion data can be fitted less precisely by a single line with n equals 3.3. From photoelectric measures on four nights between January 5 and 13 after perihelion, n is found to be 4.1. The average B-V with a 32.4 arc sec diaphragm for those four nights is about 0.79; no clear systematic variation with time is noted.

Angione, R. J.↗