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NASA NTRS1977

An optical catalog of quasi-stellar objects

A catalog containing the basic optical information on all QSOs which have been certainly identified, meaning that redshifts have been measured (complete to August 1976), is given. Included are the coordinate designations, other names, equatorial coordinates, visual magnitudes, (U-B) and (B-V) colors, emission-line redshifts, emission lines detected in the optical spectrum, absorption-line redshifts, and references for finding charts, absorption- and emission-line redshifts, and photometry and polarimetry for 633 QSOs and four BL Lacertae objects. Cross-reference tables are provided for finding coordinate designations of objects known by noncoordinate names.

Burbidge, G. R.↗
NASA NTRS1977

Optical spectrum of HDE 245770 /A0535 + 26/

Narrow-band spectrophotometric observations of HDE 245770 with the multichannel spectrometer and slit spectra obtained with the SIT digital spectrograph at the Cassegrain focus of the 5-m Hale telescope indicate that this star is of spectral type B0 with emission at H-alpha, H-beta, and probably 5876 A of He I. There is some evidence that it is of luminosity class III. The reddening is estimated in various ways and corresponds to a B-V color excess of 0.80. If the star is really a giant, its distance is approximately 1.8 kpc. No variations larger than 1% at the reported 104-x X-ray pulse period are evident in the data in visual magnitude, color, or H-alpha emission intensity. This is not surprising, since the optical star is much more luminous than the X-ray object, and the heating effect of the X-ray source (which is assumed to be one component of a binary) on the B0 star's atmosphere can produce at most a few percent modulation in visual light.

Wade, R. A.↗
NASA NTRS1977

Survey of the BY Draconis syndrome among dMe stars

Results are reported for a BVr photometric survey of 22 dK, dKe, dM, and dMe stars conducted to search for slow quasi-sinusoidal fluctuations in V (the BY Draconis syndrome). The (B-V) and (V-r) color indices are determined in an attempt to detect wavelength-dependent color changes produced by starspots and to infer starspot temperatures. It is found that nine of the stars exhibit variations in V of the order of 0.05 to 0.10 magnitude on a time scale of days or weeks, that at least three more display changes in mean light level over a period of years, that the stars generally tend to become redder at minimum light, and that some of the stars show no detectable color changes over their photometric cycle. The color data are taken to suggest a probable temperature difference of about 200 to 500 K between the stellar photospheres and starspots if the V variations are attributed to dark spots. It is concluded that the BY Draconis syndrome is clearly a very common occurrence among dMe stars.

Bopp, B. W.↗
NASA NTRS1977

Ultraviolet observations of 3C 273 by the ANS

Five-band spectrophotometry between rest wavelengths of 1340 A and 2850 A is presented. The 2200-A absorption feature seems to be present in 3C 273 with a depth appropriate for an internal reddening of E(B-V) = 0.13. The dereddened ultraviolet flux distribution can be described by a power law of spectral index 1.21. This power law can account for the observed flux in X-rays. It provides more photons than needed to excite the observed H-beta by photoionization and Fe II lines by resonance fluorescence. The emission-line flux ratios, Ly-alpha/C IV/ semiforbidden C III/H-beta are 100/80/60/10.

Wu, C.-C.↗
NASA NTRS1977

Asteroid compositional types and their distributions

A table is presented listing the compositional types chosen for 336 main-belt asteroids, twelve Mars-crossers, two Hildas, and nine Trojans. There are about 100 asteroids with polarimetric data, 126 with reflection spectra, 165 with radiometric diameters, and 300 with UBV colors. Absolute visual magnitudes V(1,0 were computed from the blue magnitudes listed by Gehrels and Gehrels (1977) and B-V colors either known or estimated according to the type. The sample of main-belt asteroids classified in the table is complete to mean opposition apparent magnitude B(a,0) = 12. The frequencies of the compositional types are discussed. Attention is also given to the distributions over diameter and the distributions over heliocentric distances.

Zellner, B.↗
NASA NTRS1978

Photoelectric photometry of J V

UBV photometry of J V (Amalthea) near greatest western elongation shows this satellite to be about one magnitude fainter than previously believed. It is observed to be very red, having a B-V color index near + 1.5 mag. Unlike the Galilean satellites, J V appears to be a low-albedo object.

Millis, R. L.↗
NASA NTRS1978

Spectral variations in brightest cluster galaxies

Multichannel-spectrometer scans of 56 of the brightest galaxies in faint clusters have been examined for evidence of color evolution. The dispersion introduced into the sample by some 25% of the galaxies which have unusual spectra is shown to be sufficient to obscure evolutionary variations. On omitting these galaxies it is found that over a time equivalent to a redshift of 0.46, B-V decreases by no more than 0.04 mag. A comparative analysis of the spectral energy distributions suggests that their differences may be due to a combination of the dispersion in metallicity among the members of the sample and to anomalous reddening of individual galaxies.

Wilkinson, A.↗
NASA NTRS1978

Minor planets and related objects. XXV - UBV photometry of 145 faint asteroids

Magnitudes and colors on the UBV system are presented for 145 minor planets, including 31 objects in the Eos family, 14 in the Koronis family, 6 in the Nysa family, 11 in the Themis family, 4 Hungarias, 7 Hildas, 8 Trojans, and several objects in unusual orbits. Clearly defined color groups for the Eos, Koronis, Nysa, and Themis family members are strongly suggestive of origin from discrete parent bodies. The Nysas apparently show large light-curve amplitudes. The Mars-orbit crossers 1977RA and 1980 = 1950LA, the earth-orbit crosser 1976UA, and several main-belt asteroids are found to show peculiar colors of unknown significance. The Mars-orbit crosser 1916 = 1953RA appears to be a typical S object, while 1474 Beira and 1977VA show neutral colors. Asteroids at semimajor axis in excess of 4 AU (Trojans preceding and following Jupiter, 279 Thule, and 944 Hidalgo) all belong to a color group centered at B-V = 0.72, U-B = 0.24.

Degewij, J.↗
NASA NTRS1978

A survey of interstellar H I from L-alpha absorption measurements. II

This paper presents interstellar H I column densities, mean H I space densities, total neutral hydrogen column densities, and total mean hydrogen space densities toward 100 stars surveyed in the L-alpha region with the U2 detector of the Copernicus satellite. The data for 47 stars are compared with OAO 2 results, and ratios of gas to E(B-V) color excess are computed for 30 'intercloud' stars, 45 'cloud' stars, and the combined sample of 75 stars. A definitive value of 5.8 x 10 to the 21st power atoms/sq cm per mag is obtained for the mean ratio of total neutral hydrogen to color excess, indicating that this ratio seems to be a constant, independent of location in the sky, except possibly toward stars with anomalous extinction. The anomalous ratio determined for Rho Oph is examined, and the galactic distribution of neutral hydrogen is evaluated. The following values are estimated for matter in the galactic plane within 500 pc of the sun: a total mean hydrogen space density of 1.15 atoms/cu cm, a mean H2 space density of 0.143 molecule/cu cm (possibly a lower limit), and a mean H I space density of 0.86 atom/cu cm (a possible overestimate).

Bohlin, R. C.↗
NASA NTRS1978

1580 Betulia - An unusual asteroid with an extraordinary lightcurve

Results of UBV photometry and polarimetry of 1580 Betulia during its 1976 apparition are presented. The synodic period of rotation is found to be 6.130 hr. The linear phase coefficient and absolute magnitude of the primary maximum in V are 0.032 mag/deg and 14.88, respectively. No color variations with rotation or solar phase angle were detected, the mean colors being B-V = 0.66 and U-B = 0.24. Betulia's light curve is unique among asteroids studied to date in that it displays three maxima and three minima within one rotational cycle, indicative of a region of greater roughness and/or a dark spot on one of its broad faces. Polarization results indicate a low albedo and a mean diameter of about 7 km, establishing Betulia as the first C-type asteroid to be found among the Mars crossers. A model accounting for most features of Betulia's light curve is given by a prolate spheroid rotating about one of its shorter axes having an axis ratio of 1:1.21 with a major topographic feature on one of its broad faces.

Tedesco, E.↗
NASA NTRS1978

Predicted color excess ratios versus interstellar grain size

Various color excess ratios, the ratio (R) of total to selective extinction, and values of the wavelength of maximum interstellar linear polarization (lambda max) are computed and displayed as functions of mean interstellar grain size and absorption coefficients. E(V-K)/E(B-V)-E(u-b)/E(b-y) is shown to be highly sensitive to changes of mean grain size. The shape of the R versus lambda max curve is shown to depend on the amount of absorption initially present in the grains, and on the absorptivity of the material added to the grains. While no simple model of grain growth has been found to fit all the observations, the two stars with the largest values of lambda max (HD 147889 and W67) support the concept of dielectric mantles growing on dielectric grains. It is further shown that more accurate uby and JKL photometry of heavily reddened stars would permit better discrimination between grain growth theories.

Mcmillan, R. S.↗
NASA NTRS1979

Interstellar extinction and ultraviolet flux distribution of Scorpius X-1

Measurements of absorption at 2200 A for Sco X-1 indicate an E(B-V) of approximately 0.28. The distance to Sco X-1 is estimated to be 350 pc while the X-ray luminosity is thought to be 5 times 10 to the 36th ergs/sec. It is found that the de-reddened ultraviolet flux distribution closely resembles a blackbody at 26,000 K. Brightness variations and their relation to flickering phenomena are considered.

Wu, C.-C.↗
NASA NTRS1979

Minor planets and related objects. XXVII - Lightcurves of 887 Alinda

Eleven light curves and UBV photometry of the Amor asteroid Alinda, a candidate for having a cometary origin, are analyzed. A probable rotation period of 73 h 58 m + or - 3 m (p.e.) is derived on the assumption of two maxima and two minima per cycle in a composite light curve. An absolute V magnitude of 14.10 + or - 0.08 and a phase coefficient of 0.042 + or - 0.003 mag/deg in V are obtained, along with a B-V color of 0.86 + or - 0.02 and a U-B color of 0.50 + or - 0.05, both extrapolated to zero phase. The rotation period is shown to be the longest yet observed for an asteroid. It is concluded that the colors of Alinda are not unusual for an asteroid, that Alinda is probably not an extinct cometary nucleus, that the slow rotation may be a consequence of one or more collisions, and that the pole of Alinda may be nearly perpendicular to the ecliptic.

Dunlap, J. L.↗
NASA NTRS1979

Secondary standards for BVRI photometry

A thorough test of Fernie's instrumentation system for matching the Johnson BVRI photometric system has been made. From 1,526 observations of 186 stars in the Arizona-Tonantzintla Catalogue, there were found excellent transformations, except for a slight curvature in the (B-V) transformation, which is easily removed, and a difficulty in (R-I) for highly reddened stars. Photometric values and their uncertainties are given for all the stars, and these are of sufficient quality to serve as secondary standards in BVRI for small- to moderate-size telescopes (1-m).

Moffett, T. J.↗
NASA NTRS1979

IUE and visual spectrophotometry of 3C 120 and Markarian 79

Low-resolution ultraviolet spectra have been obtained with IUE and combined with similar visual observations. The continua of both objects show an excess of flux in the neighborhood of 3000 A. In both objects there appears to be a depression near 2200 A, which is probably the ultraviolet interstellar absorption feature centered at 2175 A. The strength of this feature suggests E(B-V) values of 0.22 and 0.38 for Mrk 79 and 3C 120, respectively. The ratio of intensities of L-alpha to H-beta is abnormally small compared with the radiative recombination ratio; the discrepancy is removed in 3C 120 and much reduced in Mrk 79 if the reddening values just mentioned are adopted. The C IV to L-alpha line intensity ratio is abnormally high in these objects compared with that for quasars. Although both objects have strong Fe II lines in the visual, there is no Fe II absorption or emission in the ultraviolet.

Oke, J. B.↗
NASA NTRS1980

An investigation of previously derived Hyades, Coma, and M67 reddenings

New Hyades polarimetry and field star photometry were obtained to check the Hyades reddening, which was found to be nonzero in a previous study (Taylor, 1978). The new Hyades polarimetry implies essentially zero reddening. Four photometric techniques which are assumed to be insensitive to blanketing are used to compare the Hyades to nearby field stars and are found to yield essentially zero reddening. A simultaneous solution for the Hyades, Coma, and M67 reddenings is made, and the results are E(B-V) = 3 plus or minus 2(sigma) mmag, -1 plus or minus 3(sigma) mmag, and 46 plus or minus 6(sigma) mmag, respectively.

Taylor, B. J.↗
NASA NTRS1979

Brightness, density, and color profiles of three globular clusters - NGC 6440, 6541, and 7099

Using short-exposure SEC television camera observations, the radial distribution profiles of surface brightness, B-V colors and star densities are determined in three globular clusters, NGC 6440, 6541 and 7099, from about 2-200 arc sec from the cluster centers. Good agreement is found between the surface-brightness profiles and the star-density distributions; both can be fitted well with a King-type curve, and no significant evidence for a presence of cusp at r greater then 3 arc sec is observed. Also determined for the three clusters were central surface brightnesses, core radii, central mass densities, total cluster masses, relaxation times and central escape velocities. In addition, an upper limit of 5000 solar masses is placed on the mass of a possible central black hole in these clusters.

Williams, T. B.↗
NASA NTRS1980

The remaining large minor planets with unknown rotational properties - 31 Euphrosyne and 65 Cybele

Photoelectric photometry results are presented for 31 Euphrosyne and 65 Cybele. The rational properties of the asteroids were found to be quite similar, both in period and maximum amplitude. Evidence was found for an opposition effect for 65 Cybele. The B-V and U-B colors were determined to be plus 0.67 and plus 0.30 for 31 Euphrosyne, plus 0.73 and plus 0.23 for 65 Cybele. Recent observations of 65 Cybele occulting a star have shown evidence of a possible satellite for this minor planet.

Schober, H. J.↗