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1.
UBV observations of asteroid 433 Eros were conducted on 17 nights during the winter of 1974/75. The peak-to-peak amplitude of the lightcurve varied from about 0.3 mag to nearly 1.4mmag. The absolute V mag at maximum light, extrapolated to zero phase, is 10.85. Phase coefficients of 0.0233 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. The asteroid is rotating about a short axis with the north pole at λ0 = 15° and β0 = 9°.  相似文献   

2.
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 detected, the mean colors being B?V = 0.66 and U?B = 0.24. Betulia's lightcurve 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 lightcurve 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.  相似文献   

3.
C. Blanco  S. Catalano 《Icarus》1979,40(3):359-363
A lightcurve of Vesta, obtained on four nights between June 23 and 30 June 1978 during the coordinated campaign for the determination of the rotation period, is presented. The observations were performed at the 91-cm telescope of the Catania Observatory employing UBV filters and a photon counting photometer. The V lightcurve apparently shows a single maximum, suggesting that the 5h20m29s.2 period is the correct one. Features are evident near the maximum and the minimum closely resembling those of Johnson's lightcurve of 22 December 1950 and Taylor's of January 21, 1973. The amplitude in V light is 0m.105 and small variations are also found in the color indices. The largest color variation is for the U-V with Δm = 0.m.05, which is slightly larger than the value 0m.02 found by T. Gehrels [Astron. J.72, 929 (1967)]. The maximum and minimum values occur at the same phase with respect to the maximum V light as found by Gehrels, i.e., Vesta appears bluer near 0p.25 and redder near 0p.7. Corrections with the solar phase angle were made using the coefficients given by Gehrels for the B-V and U-V while a new value of 0.036 mag/deg was assumed for the V observations. The available amplitudes of Vesta's lightcurve were analyzed with respect to the longitude position and the solar phase angle.  相似文献   

4.
The asteroid 133 Cyrene was observed photometrically on 17 nights during oppositions in 1979 and 1980. The synodic period of rotation was found to be 12.h708 ± 0.h001 with an amplitude of ～0.m30 during both oppositions. At large phase angles, the phase relation is quite ordinary (βv ≈ 0.025 mag/degree); however, the low phase angle observations reveal a dramatic opposition brightening, ～0.2 mag/degree near zero phase angle. The absolute magnitude, V(1,0), extrapolated with the above linear phase coefficient, is 8.40. The following color indicates were also measured: B- V = 0.90, U-B = 0.51.  相似文献   

5.
We present 26 lightcurves of 16 Psyche from 1975 and 1976. The synodic period during this apparition was 4h.1958. Combining photometric data from this opposition with those from previous apparitions allowed us to derive a mean phase coefficient in V of 0.026 ± 0.002 mag/deg and to establish that Psyche's absolute V0 magnitude and rotational amplitude vary with aspect; at 90° aspect, V0(1, 0) = 6.27 ± 0.05 and the lightcurve amplitude is 0.30 mag, while at 0° or 180° aspect, V0(1, 0) = 6.02 ± 0.02 and the amplitude is ?0.03 mag. This behavior is accounted for if, to first order, Psyche's shape is that of a triaxial ellipsoid with axial ratios near 5:4:3. Colors at zero phase are U-B = 0.26 ± 0.01 and B-V = 0.71 ± 0.01. Color phase coefficients are <0.001 mag/deg in U-B and 0.0010 ± 0.0004 mag/deg in B-V.  相似文献   

6.
The results of modified objective grating observations and photoelectric as well as photographic photometry of the open cluster NGC 2374 are presented. The cluster contains at least twenty stars as definite members down tom v ≈ 15mag. There is a uniform extinction ofE(B - V) = 0.175 mag and the distance is 1.2 ± 0.1 kpc. The most likely age of this cluster is 7.5 ×107 years.  相似文献   

7.
We present 19 lightcurves of asteroid 1 Ceres obtained during a global campaign in 1975–1976. The synodic period is 0.37812 ± 0.00004 day. The mean absolute V magnitude is 3.61 ± 0.03 and the phase coefficient is 0.40 ± 0.001 mag/deg. The U-B and B-V phase coefficients are +0.0015 ± 0.0007 and +0.0006 ± 0.0003 mag/deg, respectively. The colors at zero phase are B-V = +0.70 ± 0.01 and U-B = +0.41 ± 0.01.  相似文献   

8.
G.W. Lockwood 《Icarus》1977,32(4):413-430
The brightnesses of Titan, Uranus, and Neptune in b (4718 ÅA) and y (5508 ÅA) have increased linearly since 1972 at rates ranging from 0.005 to 0.025 mag yr?1. The observations were made differentially on a number of nights each season with respect to a network of comparison stars whose relative magnitudes were determined by independent measurements. Solar phase coefficients were derived for each object, and all observations have been normalized to zero solar phase angle and mean heliocentric distances. No explanation for the changes has been found, but a possible influence of solar activity upon planetary albedo is suggested by the fact that all of the objects observed have brightened during the declining half of the solar cycle.  相似文献   

9.
Hans Josef Schober 《Icarus》1976,28(3):415-420
The minor planet 79 Eurynome was observed during the 1974 opposition for four nights in November, using a photoelectric photometer attached to the 60 cm telescope at the Observatoire de Haute Provence, France. A synodic period of Psyn = 5h 58m46s ± 6s m.e. was derived. The total amplitude of the lightcurve is only 0.05 mag. The lightcurve shows a double maximum and double minimum. Both minima appear to be at the same level. Observations were carried out in an instrumental filter system (UBV)' Results are shown only for V′, but U′ and B′ measurements supplement the conclusions concerning the rotation. The phase angle α, covered by the observations, ranges from 3 to 5°. The present results for 79 Eurynome rule out the longer period of 0d.49830 derived by F. Scaltriti and V. Zappalà in favor of their possible period of 0d.24915.  相似文献   

10.
Voyager full-disk images of Io, available at solar phase angle of α = 2?29° and 101?159°, allow comparisons of the satellite's near-opposition photometric behavior with Earth-based results and the determination of the phase curve out to very high phase angles. The near-opposition data were reduced iteratively for self-consistent phase and rotation curves in each Voyager filter; the resulting phase coefficients, geometric albedos, and rotational lightcurves are consistent with Earth-based findings, except for a previously noted tendency for Voyager to yield somewhat redder spectral information. The derived near-opposition phase coefficients, ranging between 0.016 and 0.024 mag/ deg, decrease with increasing wavelength, a trend weakly noted in some Earth-based observations. The full, α = 2?159° phase curves allow the first direct determination of the phase integral of Io at several wavelengths: q rises from ≈0.7 in the ultraviolet to ≈0.8 in the orange. Combination of the Voyager phase integrals with Earth-based albedo information leads to a best estimate of the bolometric Bond albedo of 0.50 ± 0.10, a value consistent with, but slightly below, previous estimates.  相似文献   

11.
We present BVR full-light curves of V388 Cyg to provide a complete photometric solution for the first time. The light curves show a high degree of asymmetry (O'Connell effect). The maxima at 0.25 phase (Max I) are 0.023, 0.018 and 0.012 mag higher than those at 0.75 phase (Max II) in B , V and R , respectively. Three possible spot models are applied to fit the asymmetric light curves of V388 Cyg, in order to explain the O'Connell effect. We conclude that the model of the cool spot on the cooler star is the most reasonable model for V388 Cyg. The continuous period variation is confirmed by recently collected times of minima, including one minimum that is determined in this paper. The period decrease rate is estimated as d p /d t =−2.055×10−7 d yr−1 .  相似文献   

12.
A photometry in the V, R, I (Cousins) system has been performed for stars in the galaxy Cassiopeia 1. The resulting colour-agnitude (CM) diagram of Cas 1 reveals the existence of blue stars and the absence of red ones. From an analysis of the CM diagram of the galaxy it is concluded that Av = 4.0 mag, and the distance modulus (m – M)o = 24.5 mag, corresponding to a distance of 790 kpc. The visual magnitude of the galaxy is V = 14m.62 (Mv = −13m.8) and the colour index (V – R) = 0.89 mag. From the distance determination the galaxy Cassiopeia 1 is a member of the Local group.  相似文献   

13.
F. Scaltriti  V. Zappalà 《Icarus》1977,31(4):498-502
Photoelectric observations of the minor planet 63 Ausonia were obtained on 12 nights during the 1976 opposition at the Astronomical Observatory of Torino. A complete lightcurve with two maxima and two minima was observed with a maximum amplitude of 0.47 mag. The synodic period of rotation, never before determined photoelectrically, was found to be 9h17m48s ± 5s. The absolute magnitude of the primary maximum, V0(1, 0) = 7.49 mag, and the phase coefficient, βv = 0.035 mag/deg, were deduced by the magnitude-phase relation. Comparison with other observations is briefly discussed and a mean radius is determined from a previous value of the geometric albedo.  相似文献   

14.
Our CCD photometry of Nova Scuti 2005 N.1 shows it to be a fast nova, characterized by   t 2= 15  and   t 3= 28d  , affected by an   E ( B − V ) ∼ 1.9  mag reddening, appearing at a position     (±0.04 arcsec)     (±0.09 arcsec, J2000) and peaking at   V ∼ 11.1  mag on ∼September 28.1 ut . Absolute spectrophotometry places it within the Fe  ii class. The profile of emission lines is characterized by a double peak with a velocity separation of 690 km s−1 and a width at half intensity of 1200 km s−1. The distance to the nova is  4 ± 1 kpc  , and its height above the Galactic plane is   z = 80 ± 20  pc. The highly crowded field affects a possible identification of the progenitor, whose pre-outburst magnitude should, however, have been  22 < V < 25  mag, thus below the limit of photographic surveys. A deep   B V R C I C  photometric sequence is provided to support continued observations of the advanced decline phases.  相似文献   

15.
Photoelectric UBV observations of RR Tauri show three components of its brightness variations: permanent short-term fluctuations (range≦ 0.2 mag, duration 101 days), slow variations of the “maximum brightness” (range 1 mag, duration 102…103 days) and unperiodic minima (range≦ 2 mag, duration 20 days). The hypothesis that these minima are produced by clouds of circumstellar condensation products is suggested. From photometry and spectral-type determination of a number of surrounding stars we conclude, that in “maximum brightness” no circumstellar extinction can be detected, provided the spectral type is B9V.  相似文献   

16.
We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,respectively.No reliable intraday variability is detected,but possible variability is detected on 16 nights.Their relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three wavebands.The bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet model.When combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term timescale.Some possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to 2017.Possible explanations about these periods are given.  相似文献   

17.
New photoelectric observations of Pluto, made in 1971, 1972, and 1973, show that the amplitude of the 6-day rotational light variation is larger (about 0.22 mag) and the mean magnitude is fainter (V0 = 15.1) than during earlier periods of observation. The change is interpreted as due to a large obliquity of the rotational axis (probably larger than 50°). The phase coefficient of Pluto is about 0.05 mag/deg at 1° solar phase angle.  相似文献   

18.
F.A. Franklin  A.F. Cook 《Icarus》1974,23(3):355-362
We present photometry, V and (B - V), of Iapetus at six western elongations (the phase of maximum brightness) that span a range in solar phase, α, from ≈6° to <0°.4, and we find that a substantial opposition effect, >0.12 mag (V), is present. We make a few cautious remarks about the possible relevance of the use of this result to interpret the phase curve of Saturn's ring. We also give a few measures of Rhea and Hyperion, at α ? 0.3°, and more of Titan, which indicate that the latter has been anomalously bright during much of 1973 and 1974, sometimes by nearly 0.1 mag (V).  相似文献   

19.
The problem of solar wind-magnetosphere coupling is investigated for intense geomagnetic storms (Dst < -100nT) that occurred during solar cycle 23. For this purpose interplanetary plasma and field data during some intensely geo-effective transient solar/interplanetary disturbances have been analysed. A geomagnetic index that represents the intensity of planetary magnetic activity at subauroral latitude and the other that measures the ring current magnetic field, together with solar plasma and field parameters (V, B, Bz, σB, N, and T) and their various derivatives (BV,-BVz, BV2, -BzV2, B2V, Bz2V, NV2) have been analysed in an attempt to study mechanism and the cause of geo-effectiveness of interplanetary manifestations of transient solar events. Several functions of solar wind plasma and field parameters are tested for their ability to predict the magnitude of geomagnetic storm.  相似文献   

20.
Lunar electric fields,surface Potential and Associated Plasma Sheaths   总被引：1，自引：0，他引：1  
This paper reviews the electric field environment of the Moon. Lunar surface electric potentials are reported as follows: Solar Wind - Dayside: øo + 10 to + 18 V Solar Wind - Terminator: øo ç ? 10 to ? 100 V Electron and ion densities in the plasma sheath adjacent to each surface potential regime are evaluated and the corresponding Debye length estimated. The electric fields are then approximated by the surface potential over the Debye length. The results are: Solar Wind - Dayside: Eo ? 10 V m?1 outward Solar Wind - Terminator: Eo ç 1 to 10 V m?1 inward These fields are all at least 3 orders of magnitude higher than the pervasive solar wind electric field; however they are confined to within a few tens of meters of the lunar surface.  相似文献   

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