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1.
The 1974–1988 Crimean measurements of the solar line-of-sight velocity continue to show the presence of a statistically significant periodicity P
1 = 160.009 (±) min with an average harmonic amplitude of about 21 cm s–1. The period is supposed to be that of the global pulsation of the Sun but with a little-known physical mechanism of excitation.The new observations give some evidence for the existence of a second periodicity, P
1 = 160.014 (±) min. It is hypothesized that the appearance of P
1 might be a sidelobe mode (of the P
0-oscillation) induced by rapid rotation of the central solar core.It is also noted that the spacing, in frequency, between P
0 and P
1, corresponds to a beat period of 10 ± 3 yr, which happens to be in good agreement with the average duration of the 11 yr cycle of the magnetic activity of the Sun. Accordingly, we suppose that the phase shift of the P
0-mode between the 1974–1982 and 1986–1988 time intervals reflects a remarkable change of the general magnetic field of the Sun in the course of the 22 yr solar cycle. 相似文献
2.
We have constructed the bolometric light curve of SN 1993J based on UBVRI(JHK) photometric data obtained from various sources
and assumingA
V = 0 and a distance modulus of 27.6. Effective temperatures and photosphere radius at various times have been obtained from
detailed blackbody fits. The bolometric light curve shows two maxima. The short rise time to the second maximum, and the luminosities
at the minimum and the second maximum are used to constrain the properties of the progenitor star. The total mass of the hydrogen
envelope MH, in the star is found to be ≲ 0.2 M⊙ at the time of explosion, and the explosion ejected about 0.05 M⊙ of Ni56. Thin hydrogen envelope combined with a sufficient presupernova luminosity suggest that the exploding star was in a binary
with a probable period range of 5yr ≤P
orb
≤ 11yr. 相似文献
3.
Periodicities in the occurrence rate of solar proton events 总被引：1，自引：0，他引：1
Power spectral analyses of the time series of solar proton events during the past three solar cycles reveal a periodicity around 154 days. This feature is prominent in all of the cycles combined, cycles 19 and 21 individually but is only weak in cycle 20. These results are consistent with the presence of similar periodicities between 152 and 155 days in the occurrence rate of major solar flares, the sunspot blocking function (P
s
), the 10.7 cm radio flux (F
10.7) and the sunspot number (R
z
). This suggests that the circa 154-days periodicity may be a fundamental characteristic of the Sun. Periods around 50–52 days are also found in the combined data set and in the three individual cycles in general agreement with the detection of this periodicity in major flares in cycle 19 and inP
s
,F
10.7, andR
z
in cycle 21. The cause of the 155 day period remains unknown. The spectra contain lines (or show power at frequencies) consistent with a model in which the periodicity is caused by differential rotation of active zones and a model in which it is related to beat frequencies between solar oscillations, as proposed by Wolff. 相似文献
4.
A. A. Galal H. A. Deebes Maha S. Quassim Shahinaz Yousef 《Earth, Moon, and Planets》1995,70(1-3):151-162
TheK
p-indices measured at Misallat station [ø = 29°45 N; = 30°54 E] during the period 1958–1989, have been compared with the data of two geomagnetic stations; one of them has similar longitude as Misallat and the second has almost similar latitude. The spectra of daily and hourly data of the three stations are compared together to define the latitude and longitude-effects on the detected periodicities. Daily periodicities ofK
p-index activities at the values 32.7, 21.2, 12.9, 11.6 and 9.2 days have been obtained to be common in the spectra of the three stations. The existence of 5-days periodicity in these stations has also been detected. 相似文献
5.
According to the data of optical observations of the Tuorla Observatory in Finland, using the power spectrum method, DCF (Discrete Correlation Function) method, and Jurkevich method, respectively, we analyzed the periodicity of the long-term light variation of the BL Lac object 1ES 1959+650, and obtained its light period to be P =1.4±0.3 yr. Assuming that the origin of the periodicity is concerned with the accretion disk, we obtained the region where the instability of this source occurs being R =9.65 Rg, here Rg represents the Schwarzschild radius. 相似文献
6.
The correlation coefficient (r) between the maximum amplitude (R
m) of a sunspot cycle and the preceding minimum aa geomagnetic index (aa
min), in terms of geomagnetic cycle, can be fitted by a sinusoidal function with a four-cycle periodicity superimposed on a declining
trend. The prediction index (χ) of the prediction error relative to its estimated uncertainty based on a geomagnetic precursor method can be fitted by a
sinusoidal function with a four-and-half-cycle periodicity. A revised prediction relationship is found between the two quantities:
χ<1.2 if r varies in a rising trend, and χ>1.2 if r varies in a declining trend. The prediction accuracy of R
m depends on the long-term variation in the correlation. These results indicate that the prediction for the next cycle inferred
from this method, R
m(24)=87±23 regarding the 75% level of confidence (1.2-σ), is likely to fail. When using another predictor of sunspot area instead of the geomagnetic index, similar results can be
also obtained. Dynamo models will have better predictive powers when having considered the long-term periodicities. 相似文献
7.
Periodicities in the solar differential rotation,surface magnetic field and planetary configurations
Using Greenwich data on sunspot groups during 1874–1976, we have studied the temporal variations in the differential rotation parametersA andB by determining their values during moving time intervals of lengths 1–5 yr successively displaced by 1 yr. FFT analysis of the temporal variations ofB (orB/A) shows periodicities 18.3 ± 3 yr, 8.5 ± 1 yr, 3.9 ± 0.5 yr, 3.1 ± 0.2 yr, and 2.6 ± 0.2 yr at levels 2. This analysis also shows five more periodicities at levels 1–2. The maximum entropy method is used to set narrower limits on the values of these periods. The reality of the existence of all these periodicities ofB (orB/A ) except the one at 2.8 yr is confirmed by analyzing the simulated time series ofB andB/A with values ofA andB randomly distributed within the limits of their respective uncertainties. Four of the prominent periods ofB agree, within their uncertainties, with the known periods in the the large-scale photospheric magnetic field. The deviations from the average differential rotation are larger near the sunspot minima. On longer time scales, the variations in the amount of sunspot activity per unit time are well correlated to the variations in the amplitudes of the torsional oscillation represented by the 22-yr periodicity inB. All the periods inB found here are in good agreement with the synodic periods of two or more consecutive planets. The possibility of planetary configurations providing perturbations needed for the Sun's MHD torsional oscillations is speculated upon and briefly discussed. 相似文献
8.
The thermoluminescence (TL) profile of the GT14 Ionian Sea core has been recently analyzed in connection with other records of solar activity. Phenomenological similarities among the TL profile, the radiocarbon record in tree-rings and the variations of the mean anuual sunspot number R
z suggest a solar control of the TL signal. In this paper we consider new readings of the TL profile of the GT14 core which were obtained at different glow temperatures. While the main spectral peaks discussed in previous papers are observed in all readings, a few new significant periodic components may now be separated from the noise background. Among these, a strong 22 yr (Hale) cycle is evident, together with a periodicity of 28.5 yr which has already been detected in the spectrum of the sunspot number series. We finally test the temporal persistency of the main TL periodic components by using a cyclogram method and we explore the effects of background noise by considering the TL profile of bleached samples. 相似文献
9.
GPS measurements were collected within the framework of the VLNDEF (Victoria Land Network for DEFormation control) project, which was started in 1999 with the aim of detecting crustal deformation in Northern Victoria Land (Antarctica). The network was established in 1999 and is composed of one permanent station (TNB1), which has been observing since 1998, and 28 periodically surveyed control points. Three complete campaigns and some partial surveying of the network have been carried out to date.Data processing and analysis have been performed using an undifferenced approach for the network position within the ITRF. A double-differences-based strategy has been applied for movement detection. The data processing and analysis of results have been carried out for all available data, both periodically acquired and long time series.GPS measurements collected between December 1999 and February 2006 indicate a mean “absolute” motion of the region of ve = 11.3 mm/yr and vn = − 11.1 mm/yr and rock uplift rates of vu = 2.8 mm/yr. These values are consistent with Antarctic plate motion and the general postglacial rebound models of the region. The relative motions within VLNDEF are small and only few points show velocities greater than the confidence levels. 相似文献
10.
J. R. Donnison 《Earth, Moon, and Planets》1987,38(3):263-272
Short-period comets with P 15 yr represent one of the most complete comet samples. The magnitude distribution of these comets was analysed using a maximum likelihood method. The brightness (magnitude) index for the comets with H
10 11 mag was estimated together with the large sample errors and found to be 0.62 ± 0.09. It was clear that many faint comets with H
10 > 11 mag remain to be discovered. Some of the faint, smaller comets have probably been removed from the distribution altogether.Observational selection was also apparent for the sample of comets with perihelia q < 1.5 AU. It was found that comets satisfying the combined criteria P 15 yr, H
10 11 mag, q < 1.5 AU probably represent the most complete set of comets available. The brightness index of this sample estimated by maximum likelihood was 0.69 ± 0.14. This translates into a mass distribution index s of 1.69 ± 0.14 indicating that most of the mass is contained in a few of the larger comets rather than spread throughout the smaller ones. This distribution, although modified by mass loss, is most likely to have been produced by a process of particle accretion. 相似文献
11.
The distribution of galaxies in the pencil-beam surveys of Broadhurstet al. which proved periodical across 8–10 consecutive steps in a flat dust model withq
0=0.5 is found to reveal extended periodicity up to 16–17 phase-coherent steps, covering the total sample, in a flat, moderately inflationary model withq
0=–0.5 (vacuum/dust ratio 2/1). In the latter model the vacuum component helps to reach the critical density and lengthens the expansion time-scale. It is shown that the explanation of the found periodicity as a consequence of space compactification as suggested by G. Paál twenty years ago in connection with apparent quasar periodicities is still possible. 相似文献
12.
We investigate the relative motion of three stars, ADS 7446, 9346, and 9701, based on long-term observations with the Pulkovo
26-inch refractor. The relative motion of all three stars shows a perturbation that could be produced by the gravitational
influence of an invisible companion. For ADS 7446, we have determined the orbit of the photocenter with a period of 7.9 yr;
the mass of the companion is more than 0.4M
⊙. For ADS 9346, we have determined the radial velocities of the components: −14.60 km s−1 for A and −13.94 km s−1 for B. For ADS 9346 and 9701, we have determined the dynamical parallaxes, 24 and 20 mas, respectively, which are larger
than those in the Hipparcos catalog by 5 mas, and calculated the orbits by the apparent motion parameter (AMP) method. The
new orbit of ADS 9346 is: a = 5″.2, P = 2035 yr, and e = 0.46 at the system’s mass M = 2.5M
⊙. The new orbits of ADS 9701 are: (a = 2″.9, P = 829 yr, e = 0.54, M = 4.3M
⊙) and (a = 3″.8, P = 1157 yr, e = 0.53, M = 5.0M
⊙). 相似文献
13.
The long-lived cosmochronometer87Rb (T
1/2=4.8×1010 yr) is studied. As its origin is partly due tos- and partly tor-process nucleosynthesis it can provide information about the time histories of these processes. The methods of using87Rb quantitatively for a chronological analysis are described. Tentative calculations based on existing experimental data are also presented. The data indicate a larger-process age than thes-process age. 相似文献
14.
We have investigated spectral features of strong radio burst emission for the 21st cycle of solar activity. The maximum daily radio fluxes in 8 frequency ranges are analyzed. For every year, the classification of these daily spectra is obtained by the cluster analysis method.We have shown that strong bursts are characterized by the stable shape of the mean radio emission spectra. For these bursts the total level of radio emission does not depend on the phase of the solar 11-yr cycle and varies with the quasi-period of 4 yr.The basic features of burst spectra can be explained by the gyrosynchrotron radiation of nonthermal electrons and plasma radiation at the second harmonic of plasma frequency. We supposed that in the generation region of centimetric emission, if the strength of the magnetic field B 100 G, the number of microbursts can amount to (6–7) × 103. In the generation region of decimetric emission, the energy of Langmuir waves changes as W
l
n
e
0.4. 相似文献
15.
H. H. Faria E. Echer N. R. Rigozo L. E. A. Vieira D. J. R. Nordemann A. Prestes 《Solar physics》2004,223(1):305-318
The objective of this paper is to compare the spectral features of the recently derived Group Sunspot Numbers (R
G) and the traditional Wolf Sunspot Numbers (R
Z) for the 1700–1995 period. In order to study the spectral features of both time series, two methods were used, including: (a) the multitaper analysis and (b) the wavelet analysis. Well-known features of the solar variability, such as the 98.6-yr (Gleissberg cycle), 10–11-yr (Schwabe cycle) and 5-yr (second solar harmonic) periodicities were identified with high confidence using the multitaper analysis. Also observed was a larger amount of power spread in high frequencies for R
Z than for R
G spectra. Furthermore, a multitaper analysis of two subsets, A (1700–1850) and B (1851–1995), has indicated that the main differences occurred in the first subset and seem to be due to uncertainties in the early observations. The wavelet transform, which allows observing the spectra evolution of both series, showed a strong and persistent 10–11-yr signal that remained during the whole period. The Meyer Wavelet Transform was applied to both R
Z and R
G. This study indicates that the main spectral characteristics of both series are similar and that their long-term variability has the same behavior. 相似文献
16.
Faria H. H. Echer E. Rigozo N. R. Vieira L. E. A. Nordemann D. J. R. Prestes A. 《Solar physics》2004,223(1-2):305-318
The objective of this paper is to compare the spectral features of the recently derived Group Sunspot Numbers (R
G) and the traditional Wolf Sunspot Numbers (R
Z) for the 1700–1995 period. In order to study the spectral features of both time series, two methods were used, including: (a) the multitaper analysis and (b) the wavelet analysis. Well-known features of the solar variability, such as the 98.6-yr (Gleissberg cycle), 10–11-yr (Schwabe cycle) and 5-yr (second solar harmonic) periodicities were identified with high confidence using the multitaper analysis. Also observed was a larger amount of power spread in high frequencies for R
Z than for R
G spectra. Furthermore, a multitaper analysis of two subsets, A (1700–1850) and B (1851–1995), has indicated that the main differences occurred in the first subset and seem to be due to uncertainties in the early observations. The wavelet transform, which allows observing the spectra evolution of both series, showed a strong and persistent 10–11-yr signal that remained during the whole period. The Meyer Wavelet Transform was applied to both R
Z and R
G. This study indicates that the main spectral characteristics of both series are similar and that their long-term variability has the same behavior. 相似文献
17.
An examination of the existing period searches for 2CG195 + 4 leads to the conclusion that the 59 second periodicity is highly
significant only for the 1981 March 17–18 detection of Bignami, Caraveo & Paul (1984). The statistical significance is increased
substantially if the pulsation period is half the previously reported value. The period derivative is not well determined.
Here we propose that 2CG 195 + 4 is a neutron star powered by accretion from a low (≲ 1M
⊙) mass main-sequence companion. A distance of a few hundred pc would imply that the neutron star is a fast rotator and is
spinning down. 相似文献
18.
N. T. Kaltcheva 《Astrophysics and Space Science》1990,173(1):69-76
Photographicuvby photometry of 15 stars in the open cluster M52 (NGC 7654) has been obtained. The distance modulusV
o–M
v=11.3±0.1 and mean cluster reddeningE(B–V)=0.57 are determined. Some basic physical characteristics of 30 stars with observeduvby values are obtained as well as a numerical estimation of the open cluster age 9.6×107 yr is made. 相似文献
19.
Ts. G. Tsvetkov 《Astrophysics and Space Science》1993,203(2):247-256
Physical parameters and radial pulsation modes are determined for three Delta Scuti stars in the Praesepe cluster: HD 73345, HD 73712, and HD 73746. Their agest and evolutionary massesM
eare interpolated in the track systems of Iben (1967) and Paczyski (1970). By combining these age estimates with our previous results for nine other Delta Scuti-stars in the Praesepe cluster (Tsvetkov, 1989), the following weighted mean age estimates of this cluster are obtained: (14.2 ± 1.3) × 108 yr (Iben) and (5.4 ± 0.4) × 108 yr (Paczyski). Age and evolutionary mass estimates of the twelve cluster variables are also obtained in the modern track system of Maeder and Meynet (1988), in which the weighted mean cluster age is (15.3 ± 1.0) × 108 yr.Pulsation massesM
Qcalculated from the fitting formulae of Faulkner (1977) and Fitch (1981) as well as massesM
g=gR
2 / G were evaluated for the twelve cluster variables by Tsvetkov (1990) or in the present paper. In most cases there is a satisfactory agreement between our estimates of massesM
e,M
g, andM
Q.Due to a large disagreement between the long period and low luminosity of the star HD 73746, its radial pulsation mode and pulsation massM
Qcannot be evaluated. 相似文献
20.
The periodicities of monthly values of major flare numbers and comprehensive major flare index (CFI) have been studied for the 20th solar cycle. It has been proved that the periodicity 152 days exists also in the southern (S) solar hemisphere. This periodicity has been previously defined in the earlier cycles to be a northern (N) periodicity, but it has migrated to the southern hemisphere (S) during the cycles 19, 20, 21. For the whole solar disk data, it has been found that the periodicity at 78.43d is much remarkable than its first harmonic at 156.86d. We have also detected very strong periodicity at 548.96d in N-hemisphere while a strong one has been found near 100d in both solar hemispheres. The detected periodicities at 80±2d and 101-+1d seems to have a global origin . The 87.1d periodicity is present and it is suggested that it is related to 88d periodicity attributed to the tidal influence of the planet Mercury on sunspots. Both hemispheres present their periodicities independently. 相似文献