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1.
A method of measuring the radial component of plasma velocity (or azimuthal electric field) in the equatorial plane of the plasmasphere, and of measuring the flux of plasma between the plasmasphere and the ionosphere is presented. The method uses measured rates of change of phase path and group delay of whistler-mode VLF signals transmitted between geomagnetically conjugate points.Results from four nights are in general agreement with results published by others—equatorial radial velocities of tens of metres per second (azimuthal electrical fields of one or two tenths of a mV/m), fluxes a few times 1012 m?2 s?1-and illustrates the potential and limitations of the method.  相似文献   

2.
E. Miner  J. Young 《Icarus》1976,28(1):43-51
Five-color photoelectric lightcurves of asteroid 433 Eros were obtained on 9 nights during the 1974/75 apparition. Although color differences due to changing solar phase angle were detected, color differences during a single rotation of Eros are less than 1%. Amplitudes of up to 1m.44 were measured, and there are indications that three reversals in the relative depths of the two minima occured between late December 1974 and late January 1975. The absolute visual magnitude at primary maximum, corrected to zero phase and to one AU from Earth and Sun, is about V0(1,0) = 10m.8.  相似文献   

3.
We show that smoothed time series of 7 indices of solar activity exhibit significant solar cycle dependent differences in their relative variations during the past 20 years. In some cases these observed hysteresis patterns start to repeat over more than one solar cycle, giving evidence that this is a normal feature of solar variability. Among the indices we study, we find that the hysteresis effects are approximately simple phase shifts, and we quantify these phase shifts in terms of lag times behind the leading index, the International Sunspot Number. Our measured lag times range from less than one month to greater than four months and can be much larger than lag times estimated from short-term variations of these same activity indices during the emergence and decay of major active regions. We argue that hysteresis represents a real delay in the onset and decline of solar activity and is an important clue in the search for physical processes responsible for changing solar emission at various wavelengths. The High Altitude Observatory is sponsored by the National Science Foundation.  相似文献   

4.
We present observations of magnitude-phase dependences of three low-albedo asteroids down to phase angles of 0.1–0.2°. Data were obtained during 40 nights from 1994 to 1995 within the joint observational program at ESO and Kharkiv Astronomical Observatories with the aim to reach as low phase angles as possible. All three low-albedo asteroids may display a small nonlinear increase in magnitude-phase dependence at subdegree phase angles. The phase curves of 50 Virginia and 102 Miriam are poorly approximated by the HG function. Rotation periods of the asteroids were also determined: 14.310±0.010 hours for 50 Virginia, 6.030±0.001 h for 91 Aegina and 15.789± 0.003 h for 102 Miriam.  相似文献   

5.
We present the results of photometric observations of trans-neptunian object 20000 Varuna, which were obtained during 7 nights in November 2004-February 2005. The analysis of new and available photometric observations of Varuna reveals a pronounced opposition surge at phase angles less than 0.1 deg with amplitude of 0.2 mag relatively to the extrapolation of the linear part of magnitude-phase dependence to zero phase angle. The opposition surge of Varuna is markedly different from that of dark asteroids while quite typical for moderate albedo Solar System bodies. We find an indication of variations of the scattering properties over Varuna's surface that could result in an increase of the lightcurve amplitude toward zero phase angle. It is shown that a similar phase effect can be responsible for lightcurve changes found for TNO 19308 (1996 TO66) in 1997-1999.  相似文献   

6.
Results of broad-band photoelectric photometry of 139 Juewa during 5 consecutive nights in March 1974 are presented. The synodic period found is 20.9 hr. A linear phase coefficient, β = 0.080 ± 0.004, is determined between phase angles of 0.9° to 1.5°. This value is similar to that for the lunar highlands and for three other asteroids (4 Vesta, 20 Massalia, 110 Lydia) at similar phase angles, indicating that these surfaces have comparable porosities. The composite lightcurve presented covers 80% of the rotational period; short timescale features in the lightcurve are seen which correspond to topography a few kilometers in size.  相似文献   

7.
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   

8.
The photoelectricB andV colour observations of the Lyrae-type eclipsing binary CN And were made on four nights at the Ege University Observatory. The new light elements, which were calculated by adding new times of minima obtained during the observations to the previous ones, were given. The light curve of the system varies cycle by cycle and the variation is discussed in some extent.  相似文献   

9.
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   

10.
Two colour (B and V) photoelectric observations of EB-type eclipsing binary GO Cyg were carried out for 15 nights during October and December 1996. Three new times of minimum lights have been derived. With these and previously published times of minimum lights, a continuous period increase of dP/dt = 1.51 × 10-7 d yr-1 was estimated from the quadratic light element. B and V light curves have been analyzed by the method of the Wilson and Devinney Differential Correction. GO Cyg is confirmed to belong to the group of near contact systems based on light curve analysis and its absolute dimensions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
We present a spectrophotometric study of short-term optical variability in the quiescent black hole X-ray transient V404 Cyg. This includes two nights of high-time-resolution H α spectroscopy with which we resolve much of the time variability, and a further six nights of archival spectroscopy with lower time resolution but higher spectral resolution. We find significant variability in most of the data considered, with both the H α line and the continuum often varying in a correlated way. This includes both dramatic flares lasting a few hours in which the line flux nearly doubles and lower-level flickering. The strongest flares involve development of asymmetry in the line profile, with the red wing usually strongest independent of orbital phase. It is unclear why this is the case, but we discuss several possible explanations. We consider the energetics of the flares and compare with plausible models including chromospheric activity on the companion star, local magnetic reconnection events within the disc and varying irradiation from close to the black hole. Based on the line profile changes during the flares, we conclude that the most likely origin for the variability is variable photoionization by the central source, although local flares within the disc cannot be ruled out.  相似文献   

12.
We report the results of spectral and photometric observations of SU UMa. Available spectra from International Ultraviolet Explorer (IUE) and CCD photometry of five nights were used. Some profiles revealing the variations of some spectral lines at different times are presented. There is variation with time for photometric observations and the brightness of SU UMa is changed from 12.9 mag. to 15.6 mag in 5 nights with clear display of burst. The ultraviolet luminosity for emitting region is in the range of (6.9*1030 erg s−1). The mass accretion rate is in the range of (9.8*10−13 M⊙yr−1). The line flux modulations at different times can be explained in terms of the mass transfer instability model (Bath 1973).  相似文献   

13.
O.G. Franz  R.L. Millis 《Icarus》1975,24(4):433-442
UBV measurements of Dione, Tethys, and Enceladus were made with an area-scanning photometer on several nights during the 1972/1973 and 1973/1974 apparitions of Saturn. The observed brightness variations have been separated into two components—one a function of orbital position, the other a function of solar phase angle. Dione and Tethys are brightest near greatest eastern elongation and faintest near greatest western elongation. The reverse is true of Enceladus. Opposition surges are observed for Dione and Tethys.  相似文献   

14.
R.L. Millis 《Icarus》1973,19(2):247-286
UBV observations of Iapetus on 34 nights have revealed a 0.30-mag difference in the depths of two successive minima in the light curve of this satellite. The difference can be explained by a two-hemisphere model with the leading darker hemisphere having a much stronger variation in brightness with solar phase angle than the trailing brighter hemisphere. Aside from the variation in the depths of the minima, the general character of the light and color curves is similar to that reported by earlier investigators.  相似文献   

15.
UBV photoelectric light curves of the eclipsing variable DK Cyg, were obtained in four nights of September 1986. They are compared with the previous light curves of the system. The primary shows a transit, so the star maybe classified with the A-type WUMa systems. Two salient points arise from the light curves: first, the secondary maximum is increasing in brightness, and secondly, the secondary minimum is varying in depth. These changing patterns of surface brightness may be due to the instabilities of an energy transfer process between the components. The (O-C) diagram shows a parabolic trend, indicating a seculariy increasing period.  相似文献   

16.
The chromospheric phases in the 1971–72 eclipse were observed at wavelength regions containing the K-line of ionized calcium on six nights at ingress and on eight nights at egress at the Okayama Astrophysical Observatory. The linear dispersion of the spectrograms is about 10 Å mm?1. The spectrograms were measured for line intensities of the K-line and for radial velocities of metallic and hydrogen lines. The results are compared with those obtained in the earlier eclipses. The intensities of the chromospheric K-line during this eclipse were relatively ‘weak’ at both ingress and egress and were similar to those in the 1939–40 eclipse. It seems that the chromospheric activity of ζ Aurigae increased after 1939, reached a maximum at 1950–56, and then decreased again until 1971. The radial velocities of the chromospheric lines of hydrogen atoms, ionized calcium, and some other atoms and ions varied with phase showing almost the same characteristic features as in most earlier eclipses. Intensities and velocities were also measured for satellite lines of the K-line.  相似文献   

17.
The photometric observations of the lunar surface during lunar eclipses were carried out on four nights between 1972 to 1978, using the 91 cm reflector of the Dodaira Station of the Tokyo Astronomical Observatory. The photometry was performed in B-, V-, and R-colours, and arranged in accordance with the angular distance from the centre of the Earth's shadow. The results do not show any large systematic differences between the four nights, showing no support for Danjon's proposition.  相似文献   

18.
《Icarus》1986,67(3):375-390
It is considered that some vertical convection as well as possible turbulence in an early phase of solar nebula soon terminates owing to diminution of the temperature dependence of dust opacity due to rapid growth of dust particles. We reexamine settling and growth of dust particles in the subsequent laminar phase of the solar nebula in detail, treating a dust layer as a two-component fluid composed of the dust and the gas. We obtain analytic expressions for the settling path, the growing size, and the settling time. The settling process is divided into two phases, i.e., an early gas-dominant phase and a later dust-dominant phase. So far, only the former phase, where the particle path finally turns from vertical to radial, has been investigated. In the latter phase, dust particles drag the gas, rather than the gas does dust particles. Consequently, the particle path turns from radial to vertical. Dust particles grow most appreciably and rapidly in a radially sweeping phase. The final radii of dust particles at the onset of gravitational instability of the dust layer are 20, 5.9, and 0.60 cm in the Earth's, Jupiter's, and Neptune's zones, respectively. These values are much smaller than those obtained previously by S.J. Weidenschilling [1980, Icarus44, 172–189] and Y. Nakagawa et al. [1981, Icarus45, 517–528]. The total settling times are 1.9 × 103, 4.6 × 103, and 2.8 × 104 years in the above-mentioned three zones, respectively. These are somewhat smaller than those obtained by the previous studies. Most of the settling time is spent in the early vertically settling phase.  相似文献   

19.
The 85-cm telescope at Xinglong station is a prime focus system that operates well with high science outputs. The telescope has been upgraded since 2014 with a new corrector, and new filters and camera, which are provided by Beijing Normal University. The filter set is the Johnson-Cousins U BV RI system. We report the test results of the new system including bias, dark current, linearity, gain and readout noise of the CCD camera. Then we derive accurate instrumental calibration coefficients in U BV RI bands with Landolt standard stars during photometric nights. Finally, we give the limiting magnitudes with various exposure times and signal-to-noise ratios for observers as references.  相似文献   

20.
In this study, photometry was conducted for the W UMa type eclipsing binary BB Peg through V and R Johnson filters during several nights in September and October 2016. The light curves were obtained at Dr. Mojtahedi Observatory, of the University of Birjand, Iran. Data reduction was performed using IRIS software. Orbital parameters were obtained by analyzing the light curves using PHOEBE software. The radial velocity information was then used to obtain the absolute parameters of the system. Some minimum light times were obtained forthe system and variations in the orbital period of BB Peg were analyzed by adding the new minimum light times to the O-C diagram to obtain a new ephemeris for the system. The period change appeared to be due to the light-time effect. A justifiable fit was obtained using the third and fourth stars. However, this fit was not confirmed and it may need revision when further data are obtained. The variation could be attributed to other sources, such as magnetic cycles or non-conservative mass transfer from the system.  相似文献   

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