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1.
We present observations of the Centaur (32532) 2001 PT13 taken between September 2000 and December 2000. A multi-wavelength lightcurve was assembled from V-, R- and J-band photometry measurements. Analysis of the lightcurve indicates that there are two peaks of slightly different brightness, a rotation period of 0.34741±0.00005 day, and a maximum photometric range of 0.18 mag. We obtained VRJHK colors (V-R=0.50±0.01, V-J=1.69±0.02, V-H=2.19±0.04, and V-K=2.30±0.04) that are consistent with the grey KBO/Centaur population. The V-R color shows no variation as a function of rotational phase; however, we cannot exclude the possibility that rotational variations are present in the R-J color. Assuming a 4% albedo, we estimate that 2001 PT13 has an effective diameter of 90 km and a minimum axial ratio a/b of 1.18. We find no evidence of a coma and place an upper limit of 15 g s−1 on the dust production rate. 相似文献
2.
J.L. Dunlap 《Icarus》1976,28(1):69-78
Ten lightcurves and UBV photometry of 433 Eros were obtained between August 1972 and May 1975. The absolute magnitude of the lightcurve maximum is 10.75 and the phase coefficient is 0.025 mag/deg. There may be a small difference in B-V color between the northern and southern hemispheres. The pole of the axis of rotation is directed toward λ0 = 16°, β0 = 12°, ecliptic longitude and latitude, respectively, and the rotation is direct with a sidereal period of 0.d219599 or 5h16m13s4 ± 0.s2. The dimensions derived from the polarimetric albedo and the lightcurve amplitudes are 12km × 12km × 31km for a smooth cylinder with hemispherical ends. 相似文献
3.
Low-resolution spectra of the Io plasma torus have been obtained on 10 and 11 February 1992 (2 days after the Ulysses encounter) using the 2 m telescope of the Bulgarian National Observatory. The spectra show the forbidden line emissions of S+ (λλ 6716, 6731 Å) and S2+ (λ 6312 Å). Measured intensities are compared with a Voyager-type model. The intensity distribution of [SII] is found to deviate from the model predictions which indicates a change in the torus at the Ulysses encounter when compared with the Voyager epoch. A corotating structure was observed, both in [SII] and [SIII], at λIII = 170°, showing that the torus was not azimuthally symmetric. The λ 6716/λ 6731 and λ 6731/ λ 6312 line ratios indicate a higher electron density at the time of the Ulysses observations. Additionally, the shift of the torus caused by the dawn-dusk electric field could be observed. Peak intensities in [SII] were found at 5.66 ± 0.02 RJ on the West ansa and 5.91 ± 0.04 RJ on the East. 相似文献
4.
We present photometric observations of Centaur (60558) 2000 EC98 and trans-neptunian object (55637) 2002 UX25 at different phase angles and with different filters (mainly R but also V and B for some data). Results for 2000 EC98 are: (i) a rotation period of 26.802±0.042 h if a double-peaked lightcurve is assumed, (ii) a lightcurve amplitude of 0.24±0.06 for the R band, (iii) a phase curve with H=9.03±0.01 and G=−0.39±0.08 (R filter) and H=9.55±0.04 and G=−0.50±0.35 (V filter) or a slope of (R filter) and 0.22±0.06 (V filter), (iv) the color indices B-V=0.76±0.15 and V-R=0.51±0.09 (for α=0.1-0.5°) and 0.55±0.08 (for α=1.4-1.5°). The rotation period is amongst the longest ever measured for Centaurs and TNOs. We also show that our photometry was not contaminated by any cometary activity down to magnitude ?27/arcsec2. For 2002 UX25 the results are: (i) a rotation period of 14.382±0.001 h or 16.782±0.003 h (if a double-peaked lightcurve is assumed) (ii) a lightcurve amplitude of 0.21±0.06 for the R band (and the 16.782 h period), (iii) a phase curve with H=3.32±0.01 and G=+0.16±0.18 or a slope of (R filter), (iv) the color indices B-V=1.12±0.26 and V-R=0.61±0.12. The phase curve reveals also a possible very narrow and bright opposition surge. Because such a narrow surge appears only for one point it needs to be confirmed. 相似文献
5.
Marek J. KOZUBAL Forrest W. GASDIA Ronald F. DANTOWITZ Peter SCHEIRICH Alan W. HARRIS 《Meteoritics & planetary science》2011,46(4):534-542
Abstract– A calibrated lightcurve is presented of the near‐Earth asteroid 2008 TC3, obtained before it impacted Earth on October 7, 2008. The asteroid was observed in unfiltered images from the end of astronomical twilight until the object entered Earth’s shadow about 2 h later. The observations covered a wide range of phase angles from 14.79° to 2.93°, during which the asteroid ranged from 82,000 km to 29,000 km distance from the observer. A method is presented for obtaining photometrically filtered brightness values for the asteroid using unfiltered imaging techniques. Over 1,700 images of the asteroid produce a lightcurve with a peak‐to‐peak variation in V of 0.76 magnitude. Analysis of the lightcurve yields values for H = 30.86 ± 0.01 and G = 0.33 ± 0.03. Combined with other constraints on the kinetic energy and diameter of the asteroid, which suggest a low 1.8 g cm?3 density and albedo 0.05 ± 0.01, the value of H implies an asteroid of about 4.1 m in diameter, 28 m3 in volume, and 51,000 kg in mass. The determined value of G is out of range for normal, larger asteroids of albedo 0.05–0.15. 相似文献
6.
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
7.
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
8.
A worldwide photometric investigation of the asteroid 324 Bamberga was conducted during the period September–November 1978. The full-cycle lightcurve shows two maxima and two minima with a maximum amplitude of 0.075 mag; the rotation period was found to be Psyn = 29.h42 ± 0.h01. A linear least-squares solution of the phase relation gives βy = (0.334 ± 0.001) mag/degree and V0 (1, 0) = (7.17 ± 0.01) mag. The color indices measured are B-V = 0.69, U-B=0.36, in agreement with the C taxonomic type given for 324 Bamberga. The very long period indicates 324 Bamberga is an unusual object among asteroids with diameters greater than 200 km. 相似文献
9.
Photoelectric lightcurves of 304 Olga were obtained at Table Mountain Observatory in 1978 near opposition. From these observations, and several observations made from Lowell Observatory a month later, we obtain a rotation period of 18.36 ± 0.02 hr and lightcurve amplitude of 0m·20. The range of solar phase angle covered by the observations is from 2°·0 to 22°. The resulting phase function is well fit by the Bowell and Lumme model (1979, in Asteroids, T. Gehrels, Ed., pp. 132–169, Univ. of Arizona Press, Tucson), with Q = 0.02. This low value of Q is suggestive of a low-albedo object. 相似文献
10.
Based on currently available observations of 28 maser sources in 25 star-forming regions with measured trigonometric parallaxes,
proper motions, and radial velocities, we have constructed the rotation curve of the Galaxy. Taking different distances to
the Galactic center R
0, we have estimated the peculiar velocity of the Sun, the angular velocity of Galactic rotation, and its three derivatives.
For R
0 = 8 kpc, we have found the circular velocity of the Sun to be V
0 = 243 ± 16 km s−1, which corresponds to a revolution period of 202 ± 10 Myr. We have obtained the Oort constants A = 16.9 ± 1.2 km s−1 kpc−1 and B = −13.5 ± 1.4 km s−1 kpc−1. Our simulation of the influence of a spiral density wave has shown that the peculiar velocity of the Sun with respect to
the local standard of rest and the component (V
⊙)LSR depend significantly on the Sun’s phase in the spiral wave. 相似文献
11.
Photometric observations of 11 near-Earth asteroids were made within a regular NEA CCD photometric programme at Ondejov Observatory in the first half of 1994. This paper shows obtained R lightcurves, V-R, R-I, and B-V color indices, and rotation preriods for 6 of them. Among the presented results, the most interesting are those for (4954) Eric, for which we obtained several high-quality lightcurves and which seems to indicate a surface heterogeneity, (1864) Daedalus, for which interesting comparison with older observations by Gehrelset al. (1971) can be made, and 1993 VW, for which the unusual color characteristics were observed. Two (1994 AW1 and 1994 GY) of the other three observed objects have fast rotations with periods of about 2.5 hours and relatively low amplitudes. Subsequent analysis of additional lightcurve data for 1994 AW1 has revealed a presence of two periods in its lightcurve (Pravecet al. 1995). The last object presented here is 1994 JF1, for which only lower limits on period and amplitude were determined. 相似文献
12.
Seitaro Urakawa Shin-ichiro Okumura Tsuyoshi Sakamoto Shinsuke Abe Kohei Kitazato Sunao Hasegawa Nobuyuki Kawai Shogo Nagayama Michitoshi Yoshida 《Icarus》2011,215(1):17-26
We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 h) and 0.0993 day (2.38 h), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L1:L2:L3 = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around λ = 310°, β = −10°, or λ = 132°, β = −17°. The nutation angle is approximately constant at 65°. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L1:L2:L3 = 1.5:1.5:1.0. The pole orientation is around λ = 330°, β = −27°. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface. 相似文献
13.
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
14.
E.F. Tedesco R.C. Taylor J. Drummond D. Harwood I. Nickoloff F. Scaltriti V. Zappalà 《Icarus》1983,54(1):30-37
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
15.
B. G. Piner S. C. Unwin A. E. Wehrle P. G. Edwards A. L. Fey K. A. Kingham 《New Astronomy Reviews》1999,43(8-10)
We have produced 22 VLBI images of the TeV blazar Markarian 421 at 11 epochs, including a Space VLBI observation with the HALCA satellite. We measure the speeds of the three innermost jet components to be 0.64±0.33, 0.48±0.09, and 0.06±0.09c (H0=65 km s−1 Mpc−1). Interpretation of these subluminal speeds in terms of the high Doppler factor demanded by the TeV observations is discussed. 相似文献
16.
Based on data for 102 OB3 stars with known proper motions and radial velocities, we have tested the distances derived by Megier
et al. from interstellar Ca II spectral lines. The internal reconciliation of the distance scales using the first derivative
of the angular velocity of Galactic rotation Ω′0 and the external reconciliation with Humphreys’s distance scale for OB associations refined by Mel’nik and Dambis show that
the initial distances should be reduced by ≈20%. Given this correction, the heliocentric distances of these stars lie within
the range 0.6–2.6 kpc. A kinematic analysis of these stars at a fixed Galactocentric distance of the Sun, R
0 = 8 kpc, has allowed the following parameters to be determined: (1) the solar peculiar velocity components (u
⊙, v
⊙, ω
⊙) = (8.9, 10.3, 6.8) ± (0.6, 1.0, 0.4) km s−1; (2) the Galactic rotation parameters Ω0 = −31.5 ± 0.9 km s−1 kpc−1, Ω′0 = +4.49 ± 0.12 km s−1 kpc−2, Ω″0 = −1.05 ± 0.38 km s−1 kpc−3 (the corresponding Oort constants are A = 17.9 ± 0.5 km s−1 kpc−1, B = −13.6 ± 1.0 km s−1 kpc−1 and the circular rotation velocity of the solar neighborhood is |V
0| = 252 ± 14 km s−1); (3) the spiral density wave parameters, namely: the perturbation amplitudes for the radial and azimuthal velocity components,
respectively, f
R
= −12.5±1.1 km s−1 and f
ϑ
= 2.0 ± 1.6 km s−1; the pitch angle for the two-armed spiral pattern i = −5.3° ± 0.3°, with the wavelength of the spiral density wave at the solar distance being λ = 2.3 ± 0.2 kpc; the Sun’s phase in the spiral wave x
⊙ = −91° ± 4°. 相似文献
17.
V. V. Bobylev 《Astronomy Letters》2010,36(9):634-644
We analyze the three-dimensional kinematics of about 82 000 Tycho-2 stars belonging to the red giant clump (RGC). First, based
on all of the currently available data, we have determined new, most probable components of the residual rotation vector of
the optical realization of the ICRS/HIPPARCOS system relative to an inertial frame of reference, (ω
x
, ω
y
, ω
z
) = (−0.11, 0.24, −0.52) ± (0.14, 0.10, 0.16) mas yr−1. The stellar proper motions in the form μα cos δ have then be corrected by applying the correction ω
z
= −0.52 mas yr−1. We show that, apart from their involvement in the general Galactic rotation described by the Oort constants A = 15.82 ± 0.21 km s−1 kpc−1 and B = −10.87 ± 0.15 km s−1 kpc−1, the RGC stars have kinematic peculiarities in the Galactic yz plane related to the kinematics of the warped stellar-gaseous Galactic disk. We show that the parameters of the linear Ogorodnikov-Milne
model that describe the kinematics of RGC stars in the zx plane do not differ significantly from zero. The situation in the yz plane is different. For example, the component of the solid-body rotation vector of the local solar neighborhood around the
Galactic x axis is M
32− = −2.6 ± 0.2 km s−1 kpc−1. Two parameters of the deformation tensor in this plane, namely M
23+ = 1.0 ± 0.2 km s−1 kpc−1 and M
33 − M
22 = −1.3 ± 0.4 km s−1 kpc−1, also differ significantly from zero. On the whole, the kinematics of the warped stellar-gaseous Galactic disk in the local
solar neighborhood can be described as a rotation around the Galactic x axis (close to the line of nodes of this structure) with an angular velocity −3.1 ± 0.5 km s−1 kpc−1 ≤ ΩW ≤ −4.4 ± 0.5 km s−1 kpc−1. 相似文献
18.
L. V. Glazunova 《Astronomy Letters》2011,37(6):414-419
Based on two high-dispersion spectra of the close binary BW Boo, we have detected lines of the secondary component whose contribution
to the combined spectrum does not exceed 2%. We have determined the rotation velocities of the components and spectroscopic
orbital elements. Numerous lines of neutral and ionized iron have been used to determine the effective temperature and surface
gravity for the primary component. The photometric light curves for this binary have been solved for the first time. Its primary
component is an A2Vm star with a mass of 2 ± 0.1M
⊙ and a radius of 1.9 ± 0.4R
⊙. Its rotation velocity is 2 km s−1, which is a factor of 18 lower than the pseudo-synchronous velocity for this component. The G6 secondary component, a T Tau
star, has a rotation velocity of 17 km s−1, amass of 1.1M
⊙, and a radius of 1 R
⊙. The age of the binary has been estimated to be 107 yr. 相似文献
19.
We present results of a ground-based observational study of the Hayabusa mission target near-Earth Asteroid (25143) Itokawa. Our data consist of BVRI-filter CCD photometry and low resolution CCD spectroscopy, from which the asteroid's rotation period, axial ratio, broadband colors, and taxonomic classification are derived. Analysis of the R-filter lightcurve data shows a synodic rotation period of 12.12±0.02 h, consistent with results from other observers. We observed a maximum peak-to-peak amplitude of 1.05 magnitudes, which—depending on the taxonomic class assumed when correcting for phase angle effects—implies a minimum axial ratio of 2.14. The shape of the rotation lightcurves varies considerably between data sets due to the changing viewing geometry. The lightcurve data from this study has been included in the shape model analysis of Kaasalainen et al. (2003 Astron. Astrophys, 405, L29-L32) and the Hapke analysis of Lederer et al. (2005 Icarus 173,153-165). Color variations were also observed, with the interpolated color indices at lightcurve midpoint being: (B-V)=0.94±0.05, (V-R)=0.40±0.06, and (V-I)=0.74±0.07. Our low resolution Palomar spectra from March 2001 covered a wavelength range of 0.3-1.0 μm. We measured a spectral slope of 9.3±0.3%/100 nm between 0.55-0.70 μm and a deep 1 μm absorption (equivalent ECAS color: w-x=−0.111±0.003, v-x=0.031±0.003). Comparison of our spectra with published ECAS data from Zellner et al. (1985 Icarus 61, 355-416) indicates that this object is most likely of Q- or S-type, similar to ordinary chondrite meteorites. Our data are more consistent with a Q-type body when both the spectroscopic data and the available BVRI photometry are taken into account. 相似文献
20.
Steven J. Ostro Alan W. Harris Donald B. Campbell Irwin I. Shapiro James W. Young 《Icarus》1984,60(2):391-403
Results of 13-cm-wavelength radar observations and V-filter photoelectric observations of Ra- Shalom during its 1981 Aug–Sep apparition are reported. The radar data yid detections of echoes in the same sense of circular polarization as transmitted (i.e., the SC sense) as well as in the opposite (OC) sense. The estimate of the ratio of SC to OC echo power, μc = 0.14 ± 0.02, indicates that most, but certainly not all, of the backscattering is due to single reflections from surface elements that are fairly smooth at decimeter scales. The value obtained for the OC radar cross section on Aug 26 (1.2 ± 0.3 km2) is about three times larger than those obtained on Aug 23, 24, and 25. The echo bandwidth appears to be within about 1.5 Hz of 5.0 Hz on each date. The photoelectric data suggest a value, Psyn = 19.79 hr, for the synodic rotation period, and yield a composite lightcurve with two pairs of extrema. Combining this value for Psyn with a firm lower bound (4 Hz) on the maximum echo bandwidth yields a lower bound of 1.4 km on the maximum distance between Ra-Shalom's spin axis and any point on its surface. 相似文献