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1.
The light curves of the totally eclipsing system TT Hya inUBV colours observed by Kulkarni and Abhyankar during 1973–77 have been analysed by Kopal’s frequency domain method with slight modification. We find ys (primary) = 0.104 ± 0.005, yg (secondary) = 0.215 ± 0.008 and i = 89‡ ± 1‡. The value of yg obtained in this study is smaller than that determined earlier by Kulkarni and Abhyankar by the method of Russell and Merrill; this confirms the undersized nature of the secondary component.The ultraviolet colour excess of the secondary is also confirmed.  相似文献   

2.
A detailed analysis of characteristics of coronal mass ejections and flares associated with deca-hectometer wavelength type-II radio bursts (DH-CMEs and DH-flares) observed in the period 1997–2008 is presented. A sample of 62 limb events is divided into two populations known as after-flare CMEs (AF-CMEs) and before-flare CMEs (BF-CMEs) based on the relative timing of the flare and CME onsets. On average, AF-CMEs (1589 km s−1) have more speed than the BF-CMEs (1226 km s−1) and the difference between mean values are highly significant (P∼2%). The average CME nose height at the time of type-II start is at larger distance for AF-CMEs than the BF-CMEs (4.89 and 3.84 R o, respectively). We found a good anti-correlation for accelerating (R a=−0.89) and decelerating (R d=−0.78) AF-CMEs. In the case of decelerating BF-CMEs, the correlation seems to be similar to that for decelerating AF-CMEs (R d=−0.83). The number of decelerating AF-CMEs is 51% only; where as, the number of decelerating BF-CMEs is 83%. The flares associated with BF-CMEs have shorter rise and decay times than flares related to AF-CMEs. We found statistically significant differences between the two sets of associated DH-type-II bursts characteristics: starting frequency (P∼4%), drift rate (P∼1%), and ending frequency (P∼6%). The delay time analysis of DH-type-II start and flare onset times shows that the time lags are longer in AF-CME events than in BF-CME events (P≪1%). From the above results, the AF-CMEs which are associated with DH-type-II bursts are found to be more energetic, associated with long duration flares and DH-type-IIs of lower ending frequencies.  相似文献   

3.
The 64 asteroids with reliably known rotational properties [rotation period P, magnitude B(1, 0) and maximum change of magnitude Δm] are studied. A plot of B(1,0) vs P illustrates that smaller asteroids tend to rotate faster than larger asteroids. The mean P for all 64 asteroids is 8.8 hr. The class of irregular asteroids (taken to be those with Δm >0.38, i.e., those whose axes differ by more than 40%) called group C are studied separately; they are shown to rotate much faster (mean P = 7.7 hr) than the remaining more regular asteroids (mean P = 9.2 hr). The smaller bodies are more irregular on the average. These results are interpreted in terms of a model in which collisions break asteroids into irregular fragments. Since angular momentum is transmitted in such collisions, significant increases in the mean can occur in the angular velocity of the largest fragment. The effect of interasteroid collisions on the mean orbital parameters is briefly discussed and is shown to be masked by selection effects.  相似文献   

4.
Earlier models of compressible, rotating, and homogeneous ellipsoids with gas pressure are generalized to include the presence of radiation pressure. Under the assumptions of a linear velocity field of the fluid and a bounded ellipsoidal surface, the dynamical behaviour of these models can be described by ordinary differential equations. These equations are used to study the finite oscillations of massive radiative models with masses 10M and 30M in which the effects of radiation pressure are expected to be important.Models with two different degrees of equilibrium are chosen: an equilibrium (i.e., dynamically stable) model with an initial asymmetric inward velocity, and a nonequilibrium model with a nonequilibrium central temperature and which falls inwards from rest. For each of these two degrees of equilibrium, two initial configurations are considered: rotating spheroidal and nonrotating spherical models.From the numerical integration of the differential equations for these models, we obtain the time evolution of their principal semi-diametersa 1 anda 3, and of their central temperatures, which are graphically displayed by making plots of the trajectories in the (a 1,a 3) phase space, and of botha 1 and the total central pressureP c against time.It is found that in all the equilibrium radiative models (in which radiation pressure is taken into account), the periods of the oscillations of botha 1 andP c are longer than those of the corresponding nonradiative models, while the reverse is true for the nonequilibrium radiative models. The envelopes of thea 1 oscillations of the equilibrium radiative models also have much longer periods; this result also holds for the nonequilibrium models whenever the envelope is well defined. Further, as compared to the nonradiative models, almost all the radiative models collapse to smaller volumes before rebouncing, with the more massive model undergoing a larger collapse and attaining a correspondingly larger peakP c.When the mass is increased, the dynamical behavior of the radiative model generally becomes more nonperiodic. The ratio of the central radiation pressure to the central gas pressure, which is small for low mass models, increases with mass, and at the center of the more massive model, the radiation pressure can be comparable in magnitude to the gas pressure. In all the radiative models, the average periods as well as the average amplitudes of both thea 1 andP c oscillations also increase with mass.When either rotation or radiation pressure effects or both are included in the equilibrium nonradiative model, the period of the envelope of thea 1 oscillations is increased. The presence of rotation in the equilibrium radiative model, however, decreases this period.Some astrophysical implications of this work are briefly discussed.  相似文献   

5.
Measurements of the Paschen discontinuity in stars withT eff104K leads to the conclusion that theD P/DB ratio increases with temperature faster than expected. The increase ofD P/DB with (logg)–1 is also steep.
Résumé Les mesures de la discontinuité de Paschen dans les étoiles deT eff104K nous montrent que le rapportD P/DB augmente avec la température plus rapidement que prevu. L'augment deD P/DB avec (logg)–1 est aussi remarquable.
  相似文献   

6.
The POMME survey (Pixel Observations of M31 with MEgacam) monitored two fields in the disc of M31 using MegaCam at CFHT over a timespan of 2.5 months in three filters (g′,r′,i′). Covering a large fraction of the disc of M31, it yields an unprecedented view on Cepheids, eclipsing binaries and microlensing events in M31. In this contribution we present the first results on the Cepheid populations in M31. Using difference imaging we detect more than 2500 Cepheids in the period range from 2 to 80 days, making the catalogue the largest and most homogeneous database of M31 Cepheids to date. The period distribution peaks at logP[day]≈0.63. We confirm the presence of a second peak in the period distribution at logP[day]≈1.13, consistent with previous findings on smaller samples, and which is also present in Galactic Cepheids, unlike those at the lower metallicities of the LMC. Using the Fourier parameters derived from light curve fitting we identify 200 first overtone pulsators among the POMME Cepheids. On-going work will include the derivation of period-luminosity relations and the extension of the analysis to eclipsing binary systems, yielding an improved distance to M31 and tighter constraints on systematics affecting the period-colour-metallicity-luminosity relations.  相似文献   

7.
Use is made of 93,106 parallaxes from the Hipparcos catalog, with a mixture of spectrum-luminosity classes, to derive the position of the Galactic plane. The reduction technique, mixed total least squares-least squares, takes into account the errors in the parallaxes, and the condition that the direction cosines of the Galactic pole have unit Euclidean norm is rigorously enforced. To obtain an acceptable solution it is necessary to eliminate the stars of classes O and B that belong to the Gould belt. The Sun is found to lie 34.56±0.56 pc above the plane. The coordinates of the Galactic pole, l g , b g, are found to be: l g =0.°004±0.°039; b g =89.°427±0.°035.This agrees well with what radio observations find and demonstrates that the IAU's recommendation in 1960 to use only radio observations to determine the Galactic pole, although correct at the time because of the paucity of optical observations, can no longer be justified given the plethora of observations contained in the Hipparcos catalog and an adequate reduction technique, unavailable in 1960. The reduction technique is also demonstrably superior to others because it involves fewer assumptions and calculates smaller mean errors. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
Solar irradiance measurements from the ACRIM experiment show a clear response to the rotation periods of g-mode oscillations (l = 1, 2, and 3) and their first harmonics. Peaks in the ACRIM spectrum at 16.6, 18.3, 20.7, 36.5, and - 71 days all lie within about 1% of periods arising from g-mode rotation. This means that the g-modes are a fundamental cause of irradiance fluctuations. On time scales of months and less they modulate the irradiance by means of transient flows of global scale which they stimulate in the Sun's convective envelope. Dimensional arguments indicate that the flows carry up heat at an average rate 10-3 L which is not in conflict with observed changes in the irradiance. Five additional tests for g-modes and large-scale convection are given. An instability is described which undermines diffusion models of sunspot energy storage.  相似文献   

9.
The aim of the present paper will be to evaluate numerically Jacobian and other functions which have been discussed in more detail in a previous paper of this series (Edalati, 1978b, Paper XXII), and also choose the most convenient moments to obtain a good determination for the unknown eclipse parametersa andc 0. More than 12 different pairs ofg-functions for real values ofm have been investigated numerically and diagrammatically. The behaviour ofg-functions depends but very little on different combination of the moments, and related diagrams are approximately the same asg 2 andg 4 (Kopal and Demircan, 1978, Paper XIV).The behaviour of the vanishing Jacobian, arising from different pairs ofg-functions for real values ofm1 has been shown diagrammatically in terms ofa andc 0. Accordingly, we obtain the optimum combination of the moments (i.e.,A 6,A 7,A 8 andA 9) ing-functionsg 7 andg 8. It has been noted that the behaviour of theg-functions which depend on the combinations of the higher order moments (i.e.,m5) have been ruled out, because the proportional error of the momentsA 2m increases with increasing values of realm. The automated method has been tested successfully on the light curve of RT Per (Mancusoet al., 1977; Edalati, 1978a). Finally, a comparison is given of the elements of RT Per arising from two different pairs ofg-functions, i.e.,g 2,g 4 (Edalati, 1978a) andg 7,g 8 for the light curves analysis.  相似文献   

10.
Kotov  V. A.  Haneychuk  V. I.  Tsap  T. T.  Hoeksema  J. T. 《Solar physics》1997,176(1):45-57
The CrAO-WSO-network experiment was designed for detection of low-degree oscillations of the Sun representing either its normal g -modes or those driven by, e.g., rapid (hypothetical) rotation of the central solar core. The Doppler-shift measurements were made in 1974–1995 at both sites during about 13600 hr, in all. Taking into account the upper limit (0.08 m s-1) for amplitudes of potential g-modes, attention is paid to the Sun's behaviour at frequencies near the 9th daily harmonic (period P 160.The two main issues follow from analysis of the combined CrAO-WSO data: (a) in 1974–1982 the primary period of solar pulsation was P 0160.0099 ± 0.0016 ± 0.0016 min, but (b) during the last 13 yr it attained a new value, P 1 159.9654 ± 0.0010 min, which happens to be a near-annual sidelobe of P 0. We find therefore that the phase stability of the 160-min mode is no longer present: it appears to be splitted at least into a pair of oscillations,P 0 and P 1, having perhaps different physical origins. But the most striking is the fair coincidence of the strongest peaks in the two data sets: CrAO (1974–1995): P = 159.9662 ±0.0006 min, WSO (1977–1994): P = 159.9663 ± 0.0007 min. The existence of two frequencies,P -1 0 and P -1 1, with their separation corresponding to 1-yr period, seems to be difficult to explain in terms of gravity g modes.  相似文献   

11.
analysis of new X-ray and optical data confirms that the X-ray luminosityL x of a cluster of galaxies is strongly dependent on its richness. The radio powerP 1445 of clusters at 1445 MHz is independent of richness, but is greater on the average for clusters with dominant cD galaxies than for those withou. The radio emission depends on the activity of one of the brightest galaxies; dominant cD galaxies are often responsible for radio emission, especially if they have double or multiple nuclei. For a given richness, high values ofL x andP 1445 sometimes occur together, but no strict correlation betweenL x andP 1445 exists. Possible tests of thermal-bremsstrahlung and inverse-Compton theories for the X-ray emission are mentioned.  相似文献   

12.
Continuous wavelet transform and cross‐wavelet transform have been used to investigate the phase periodicity and synchrony of the monthly mean Wolf (Rz) and group (Rg) sunspot numbers during the period of June 1795 to December 1995. The Schwabe cycle is the only one common period in Rg and Rz, but it is not well‐defined in case of cycles 5–7 of Rg and in case of cycles 5 and 6 of Rz. In fact, the Schwabe period is slightly different in Rg and Rz before cycle 12, but from cycle 12 onwards it is almost the same for the two time series. Asynchrony of the two time series is more obviously seen in cycles 5 and 6 than in the following cycles, and usually more obviously seen around the maximum time of a cycle than during the rest of the cycle. Rg is found to fit Rz better in both amplitudes and peak epoch during the minimum time time of a solar cycle than during the maximum time of the cycle, which should be caused by their different definition, and around the maximum time of a cycle, Rg is usually less than Rz. Asynchrony of Rg and Rz should somewhat agree with different sunspot cycle characteristics exhibited by themselves (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
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   

14.
Photospheric models were calculated for 90 stars with effective temperatures between 2500 K and 41600 K for five logg-values ranging from 1 to 5. Molecule formation was taken into account. In order to have an idea about possible instabilities in the different stellar layers some quantities, characteristic for convection and turbulence were calculated, such as the Rayleigh-, Reynolds-, Prandtl- and Péclet-numbers. It turned out that all the investigated stars contain unstable layers, including the hottest. Nevertheless, only stars with effective temperatures of 8300 K or less contain layers where the convective energy transport is important. For all stars the convective velocities were calculated and also the generated mechanical fluxes in the convection zones were tabulated.Under the hypothesis that this mechanical energy flux is responsible for the heating of the corona, coronal models were constructed for the Sun and for some stars with effective temperatures between 5000 K and 8320 K for logg-values of 4 or 5.For Main Sequence stars the largest fluxes are generated in F-stars; stars withT eff=7130 K and logg=4 possess also the hottest and most dense coronas with a computed temperature of 3.7·106 K and logN e =10.5.The solar corona computed in this way, on the basis of a photospheric mechanical flux of 0.14·108 erg cm–2 sec–1, has a temperature of 1.3·106 K and logN e =9.8. This density is apparently too high, but even when including in the computations all theoretical refinements proposed in the last few years by various authors it does not appear possible to obtain a solar coronal model with a smaller density.However, when taking into account the inhomogeneous structure of the chromosphere and by associating the calculated mechanical fluxes to the coarse mottles, and lower fluxes to the undisturbed regions we find a mean coronal temperature of 1.1·106 K and a mean logN e -values of 9. The computed velocity of the solar wind at a distance of 104 km above the photosphere has a value between 7 and 11 km sec–1. These latter values are in fair agreement with the observations.  相似文献   

15.
Pulsar nulling is not always a random process; most pulsars, in fact, null non-randomly. The Wald–Wolfowitz statistical runs test is a simple diagnostic that pulsar astronomers can use to identify pulsars that have non-random nulls. It is not clear at this point how the dichotomy in pulsar nulling randomness is related to the underlying nulling phenomenon, but its nature suggests that there are at least two distinct reasons that pulsars null.  相似文献   

16.
The average profile of Forbush decreases, produced by eastern-, central- and western-region solar flares is obtained separately by superposed epoch analysis for the periods 1966–1969 (qA < 0) and 1971–1979 (qA > 0). It is observed that the recovery of an average Forbush decrease from the maximum depression level is faster for the situation qA > 0 than for the situation qA < 0. This is in accordance with expectations from the drift theory. It is also observed that the drift effect is more pronounced for western-flare Forbush decreases which, of course, have a smaller magnitude compared to eastern- and central-flare Forbush decreases.The average profiles of simple and complex type Forbush decreases are also obtained separately for three periods 1965–1979, 1971–1979, and 1981–1987. It is found that the average profiles of simple and complex type Forbush decreases observed during the period 1965–1969 and 1971– 1979 are quite in agreement with drift theory. The anomalous behavior of average Forbush-decrease profiles during the period 1981–1987, especially in simple type Forbush decreases, is also explained by a drift current sheet tilt model.  相似文献   

17.
Three wavelet functions: the Morlet wavelet, the Paul wavelet, and the DOG wavelet have been respectively performed on both the monthly Wolf sunspot numbers (Rz) from January 1749 to May 2004 and the monthly group sunspot numbers (Rg) from June 1795 to December 1995 to study the evolution of the Gleissberg and Schwabe periods of solar activity. The main results obtained are (1) the two most obvious periods in both the Rz and Rg are the Schwabe and Gleissberg periods. The Schwabe period oscillated during the second half of the eighteenth century and was steady from the 1850s onward. No obvious drifting trend of the Schwabe period exists. (2) The Gleissberg period obviously drifts to longer periods the whole consideration time, and the drifting speed of the Gleissberg period is larger for Rz than for Rg. (3) Although the Schwabe-period values for Rz and Rg are about 10.7 years, the value for Rz seems slightly larger than that for Rg. The Schwabe period of Rz is highly significant after the 1820s, and the Schwabe period of Rg is highly significant over almost the whole consideration time except for about 20 years around the 1800s. The evolution of the Schwabe period for both Rz and Rg in time is similar to each other. (4) The Gleissberg period in Rz and Rg is highly significant during the whole consideration time, but this result is unreliable at the two ends of each of the time series of the data. The evolution of the Gleissberg period in Rz is similar to that in Rg.  相似文献   

18.
The 395 late-type spiral galaxies brighter than 15m in r-band are selected from the Data Release 2 of Sloan Digital Sky Survey and the colormagnitude relations of these galaxies and their disks are investigated. It is found that the colors g − r, r − z and g − z of these galaxies and their disks are strongly correlated with the r-band absolute magnitudes, i.e., the more luminous galaxies (or disks) have the redder colors than the less luminous galaxies (or disks). And the correlation of galaxies is stronger than that of their disks.  相似文献   

19.
The purpose of this paper is to extend the study of the so called p-q resonant orbits of the planar restricted three-body problem to the spatial case. The p-q resonant orbits are solutions of the restricted three-body problem which have consecutive close encounters with the smaller primary. If E, M and P denote the larger primary, the smaller one and the infinitesimal body, respectively, then p and q are the number of revolutions that P gives around M and M around E, respectively, between two consecutive close approaches. For fixed values of p and q and suitable initial conditions on a sphere of radius around the smaller primary, we will derive expressions for the final position and velocity on this sphere for the orbits under consideration.  相似文献   

20.
Radio pulsar B2034\(+\)19 exhibits all three ‘canonical’ pulse-sequence phenomena—that is, pulse nulling, two distinct profile modes and subpulses with periodic modulation. Indeed, the bursts and nulls in the pulsar are short at several score pulses and quasi-periodic such that about 1/3 of the pulses are nulls. The pulsar’s two modes have very different characteristics, the first shows emission almost completely confined to the leading half of the profile and highly modulated in a 2-period odd–even manner; whereas the second mode illuminates both the leading and trailing parts of the star’s profile about equally with the appearance of drift bands at about a 3-period separation. The second mode occurs much less frequently than the first (about 15% of the time) and thus the leading part of the profile has a much larger average intensity than the trailing part. B2034\(+\)19 represents an interesting example of a pulsar with emission primarily in the leading part of its profile window with only occasional illumination in the trailing part. This suggests that there are pulsars that perhaps never emit in a part of their profile window, connecting with earlier work on pulsars with apparent ‘partial cone’ profiles.  相似文献   

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