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1.
Searches for periodic variations in the brightness of RY Tauri over various time intervals are conducted on the basis of photoelectric observations made by the author at the Crimean Station of the Shternberg State Astronomical Institute (GAISh) from 1965 through 2000 and of data published by others. The total duration of the series of observations is 12500 days. The existence of a long cycle lasting about 2000 days is confirmed. Short periods owing to rotational modulation of the brightness are not always present. During a time when the brightness of the star was increasing in 1966, a period of 7.5 days showed up. The detection of fluctuations which might be identified with rotational modulation evidently depends on the star’s level of brightness. In 1993 and 1996, respectively, periods of 20.0 and 29.4 days were discovered which are most likely caused by inhomogeneities in the circumstellar disk.  相似文献   

2.
Evren  S.  Ibanoğlu  C.  Tunca  Z.  Tümer  O. 《Astrophysics and Space Science》1986,120(1):97-106
The light curves of V471 Tau obtained in four successive years from 1981 to 1984 are presented. The light variations due to the tidally distorted red dwarf have been computed and subtracted out from the light curves obtained so far. A pure shape of the wave-like distortion has therefore been derived. The period of the retrograde migration has been found to be 182.17 days. On the other hand, the mean brightness of the system seems to vary with a period of about 18 years. The amplitude of the variation is greater at longer wavelength. The periodic variation of the mean brightness resembles the solar cycle of about 11.2 years, which depends upon the number of spots or spot groups.  相似文献   

3.
Dale P. Cruikshank 《Icarus》1985,64(1):107-111
Earth-based observers of Neptune have found that the planet varies in brightness at various wavelengths in ways that suggest that changes occur in the planet's atmosphere on several different time scales. Global inhomogeneities in high-altitude haze distribution that are stable for several days permit measurements of the planet's rotation period (about 18 hr), but this stability sometimes breaks down, obscuring the diurnal lightcurve. In addition, there is an apparent long-term variability of the brightness of Neptune in anticorrelation with the cycle of solar activity. This slow variability of low amplitude may be punctuated by outburst of high-altitude condensation of particles in the atmosphere whose decay time is several months.  相似文献   

4.
Ch. V. Sastry 《Solar physics》1994,150(1-2):285-294
We have mapped the continuum emission from the undisturbed Sun at a wavelength of 8.7 m during 1981–1985 using the large decameter-wave radiotelescope at Gauribidanur, India with a resolution of 26 #x00D7; 38 arc min. During the period August 6–30, 1983, the Sun was exceptionally quiet at meter and decameter wavelengths, and we were able to make maps on several consecutive days. On these days the position of the centroid of the radio Sun agreed quite closely with the center of the optical Sun indicating that there is very little or no contribution from active regions. But the observed peak brightness temperature varied from 100 000 to 700 000 K. The half-power widths of the brightness distribution were in the range of 3 to 4R ⊙. The variations of the brightness temperature and the half-power widths are not correlate. It is therefore suggested that the variations of the brightness temperature are not caused by uniform density variations or due to scattering by an irregular corona.  相似文献   

5.
An historical light curve for the UX Ori star CQ Tau is constructed for the period from 1939 through 2003. The star’s photometric behavior includes a cyclical component with a period of about 21 years. An analysis of the periodogram reveals a shorter cycle with a duration of about 1020 days after this cycle is subtracted. Since the photometric activity of UX Ori type stars is caused by variations in the circumstellar extinction, both of these cycles indicate the existence of large-scale deviations from axial symmetry in the distribution of matter in the circumstellar disk of CQ Tau. The orbiting of these inhomogeneities about the star also causes oscillatory variations in its brightness. An analysis of the color-magnitude diagrams reveals differences in the optical parameters of the circumstellar dust along the line of sight in various phases of the 21-year cycle: absorption by larger particles predominates near the brightness maximum of CQ Tau. This means that the reduced circumstellar extinction in this part of the circumstellar disk is the result of a smaller contribution from small particles; this may be evidence of the onset of a process of coagulation of the dust particles and their conversion into large-scale bodies and planetesimals.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 165–174 (May 2005).  相似文献   

6.
Jerome Apt  Johnny Leung 《Icarus》1982,49(3):427-437
A search was made for periodic fluctuations in the thermal brightness temperatures recorded by the Pioneer Venus orbiter's infrared radiometer. Data were averaged in 10 × 10° latitude-longitude bins for each of the 72 days the instrument was in operation. This time series of thermal brightness temperatures was then analyzed to determine the amplitude of fluctuations at periods from 2 to 64 days at four levels in the atmosphere (at the cloud tops and at approximately 70, 80, and 90 km). The amplitude of such fluctuations is small at equatorial latitudes and increases to a maximum at 60–70° latitude at most altitudes. The period of the highest amplitude fluctuation is 5.3±0.4 days (at all altitudes) except at 70–80°, where a 2.9-day period which appears to correspond to the polar dipole dominates the cloud-top channel. The amplitude of the periodic fluctuations is a maximum at the cloud tops, decreasing to a minimum at the 80-km channel, and increasing again at the 90-km channel.  相似文献   

7.
Observations of the spotted rotating G8 V star HII 296, a member of the Pleiades cluster, are presented. The star has exhibited stable periodic brightness variations for several years. The apparent rotation period of the star in our observations was 2.53 and 2.58 days. The shape and amplitude of its light curve changed from year to year. During our observational monitoring from September to November 2012, we recorded an almost complete absence of brightness variations in September. A rapid (within a few weeks) and manyfold increase in the brightness variability amplitude was observed in October and November 2012. The changes in the rotation period, amplitude, and shape of the light curve suggest an intense relative motion of spots in latitude and longitude.  相似文献   

8.
The post-common envelope and pre-cataclysmic binary V471 Tau has been observed by the authors since 1973. At least a complete light curve in B and V bands and more than two eclipse timings were obtained in each year. All the available data published so far (including the authors') have been collected and analysed for the brightness and orbital period changes. The system brightened about 0.22 mag in both B and V bands more or less regularly up to 1997 and started to decrease afterwards. A search for periodicity of this variation yields a period longer than 85 yr. In addition to this long-period variation, a small amplitude of about 0.08 mag and short time-interval fluctuations on the mean brightness have been detected. The variations of the mean brightness have been discussed and plausible causes suggested. The changes of the apparent period have been attributed to a third body. Analysis of all the 'observed−calculated' (O−C) data yields a period of 32.4 yr, with a semi-amplitude of 151 s and an eccentricity of 0.30 for the third-body orbit. For orbital inclinations greater than 34° the mass of the third body would possibly match to a brown dwarf. One of the most interesting features in the light curve of V471 Tau is the decrement of the eclipse depth with time. The depth of the eclipse in the B band has been decreased from 0.082 to 0.057 mag over 34 yr. Subtracting the variation of the depth due to the brightening of the red dwarf star, the actual variation in depth, originated from from the white dwarf, was found to be about 0.012 mag. This change in the brightness of the compact object has been attributed to the mass accretion from its primary component via thermally driven wind and/or flare-like events.  相似文献   

9.
Ruzmaikin  A. 《Solar physics》1998,181(1):1-12
We report observations of the large-scale spatial dependence of the Sun's luminosity variations over the period 1993–1995. The measurements were made using a new scanning disk solar photometer at Big Bear Solar Observatory, specially designed to measure large-scale brightness variations at the 10–4 level. Since the level of solar activity was very low for the entire observation period, the data show little solar cycle variation. However, the residual brightness signal I/I (after subtracting the mean, first, and second harmonics) does show a strong dependence on heliocentric angle, peaking near the limb. This is as one would expect if the residual brightness signal (including the excess brightness coming from the active latitudes) were primarily facular in origin. Additional data over the next few years, covering the period from solar minimum to maximum, should unambiguously reveal the large-scale spatial structure of the solar cycle luminosity variations.  相似文献   

10.
We measured the brightness of the white light corona at the total solar eclipses on 1 August 2008 and 22 July 2009, when solar activity was at its lowest in one hundred years. After careful calibration, the brightness of the corona in both eclipses was evaluated to be approximately 0.4×10?6 of the total brightness of the Sun, which is the lowest level ever observed. Furthermore, the total brightness of the K+F-corona beyond 3R ⊙ in both eclipses is lower than some of the previous measurements of the brightness of the F-corona only. Our accurate measurements of the coronal brightness provide not only the K-corona brightness during a period of very low solar activity but also a reliable upper limit of the brightness of the F-corona.  相似文献   

11.
The principal results of a photometric investigation of Nova 1934 DQ Her during 1982–1995 are presented. Simultaneous high-speed UBVRI photometry was used to investigate for the first time the behavior of its brightness on time scales from several days to several years. Relationships are found between the changes in brightness of DQ Her in various regions of the spectrum and the corresponding changes in the energy distribution of its radiation. The observed variations in brightness of the system are caused by the variability in the radiation from the accretion disk with the white dwarf at the center. The brightness variations on the time scale of several days to several dozen days, may be caused by changes in the rate of accretion from the disk onto the white dwarf due to inherent disk instability or by irregular delivery of material in the jet from the red dwarf. Cyclic variations in brightness of DQ Her with an amplitude of several tenths of a magnitude and a characteristic time of about 5 yr, as well as the cyclic variations of the parameter "O-C" with the same characteristic time and amplitude of about 2–4 min may be the response of the accretion disk to activity of the red dwarf itself.Translated fromAstrofizika, Vol. 39, No. 1, pp. 41–55, January–March, 1996.  相似文献   

12.
We present the R c-band light curves for components A and B of the gravitationally lensed quasar SBS 1520+530 obtained during 2001–2005 with the 1.5-m Russian-Turkish Telescope (RTT-150) at the TUBITAK National Observatory (Turkey). Based on an analysis of the data for the period 2001–2002, we have estimated the time delay of the brightness fluctuations between components A and B of the quasar to be 128 days. This time delay agrees with its previously published values for the periods 1999–2001 and 2003–2004. Using all of the published data on the brightnesses of components A and B of SBS 1520+530 for the 6-year period, we have found at least two microlensing events. One event has the pattern of a long-term linear trend; the duration of the other event is several hundred days.  相似文献   

13.
We present new photometric data and analyze long-term UBV observations of three candidates for protoplanetary nebulae—F supergiants with infrared excesses at high Galactic latitudes—IRAS 18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All these stars exhibit quasi-periodic low-amplitude variations caused by pulsations against the background of long-term brightness trends. For IRAS 18095+2704=V887 Her, we have found a pulsation period of 109 days and revealed a linear brightness trend—the star brightens at constant (within the limits of the measurement errors) yearly mean color indices. The light curve of IRAS 19386+0155=V1648 Aql in 2000–2008 is represented by a wave with a fundamental period of 102 days whose modulation with a close period of 98 days leads to variations with a variable amplitude. V1648 Aql also shows a systematic rise in V brightness along with a reddening. IRAS 19500–1709=V5112 Sgr exhibits irregular pulsations with periods of 39 and 47 days. The long-term variability component of V5112 Sgr may indicate that the star is binary.  相似文献   

14.
R.L. Millis 《Icarus》1977,31(1):81-88
Measurements of the brightness and B-V color index of the leading and trailing hemispheres of Iapetus during the past five apparitions of Saturn are presented. The dependence of brightness on solar phase angle is determined for the two faces of the satellite. After correction for solar phase angle and distance effects, the brighter trailing hemisphere of Iapetus was found to be constant in brightness and color index throughout the interval covered by the observations. The brightness of the dark leading hemisphere, however, decreased by about 0.2 mag over the same period, and its B-V color index reddened by 0.05 mag. These changes are interpreted as evidence for the existence of a bright southern pole cap on Iapetus.  相似文献   

15.
Statistics on the temporal variability of uv cloud features on Venus during 66 days of nominal mission imaging by the Pioneer Venus Orbiter Cloud Photopolarimeter reveal at least five types of systematic variability on large scales: (1) a low-latitude global-scale wave of period 3.94 ± 0.1 days corresponding to longitudinal motion of the dark equatorial band and propagating westward relative to the mean flow; (2) a midlatitude wave of period 5.20 ± 0.2 days corresponding to wavenumber 1 oscillations of the latitude of the bright polar bands and propagating eastward relative to the mean flow; (3) ～2- to 3-week fluctuations in the slope of longitudinal cloud brightness power spectra at intermediate wavenumbers manifested by variations in the intensity of large bow-shaped features; (4) ～2-month variations in polar region brightness consistent with polar brightening episodes observed from Earth; and (5) a monotonic decrease in the disk-integrated brightness of Venus during the nominal mission which may be either a true time variation or a solar-locked longitudinal dependence of brightness. Small-scale features appear to correlate with large-scale albedo patterns. Specifically, cellular features exist primarily where large-scale dark material is present, while the orientation of streak features with respect to latitude circles oscillates with the same ～4-day period as the large-scale features at low latitudes. The wide range of time scales present in the data suggests the complexity of Venus stratospheric dynamics. Extended observations over many years may be becessary to define the general circulation.  相似文献   

16.
We present our photoelectric U BV observations of the candidate protoplanetary object IRAS 22223+4327 during four visibility seasons. The star exhibited periodic brightness variations with the maximum amplitudes \(\Delta U = 0\mathop .\limits^m 23, \Delta B = 0\mathop .\limits^m 18, and \Delta V = 0\mathop .\limits^m 12\) and a time scale of about 90 days, which is equal to the period derived by other authors from radial velocities. During these brightness variations, a correlation is observed between the (B-V) color index and brightness, which is characteristic of pulsations. We estimated the star’s spectral type from our photometric data to be F8 I. We detected a “deficit” of light in the U band. The star’s mean brightness and its spectral type appear to have not changed in the past half a century.  相似文献   

17.
We present the results of our study of Jupiter and its radiation belts with a resolution of 6 arcsec at a frequency of 30 GHz using the RATAN-600 radio telescope and a MARS matrix radiometer with a sensitivity of about 6 mK ?1/2. We monitored the integrated emission from the Jovian disk with a signal-to-noise ratio of more than 1000 for 30 days and showed its radio emission to be highly stable (≈1%). Based on daily data for the one-dimensional radio brightness distribution over the disk, we mapped the longitudinal radio brightness distribution over 100 rotation periods of Jupiter around its axis. Neither hot nor cold spots with a temperature contrast of more than 1 K were detected; their contribution to the total radio flux from the Jovian disk was no more than 0.2%. The one-dimensional latitudinal (longitude-averaged) distribution obtained on VLA with a similar resolution is shown to be an order of magnitude less uniform than the one-dimensional longitudinal (latitude-averaged) distribution obtained on RATAN-600. We have studied the radiation belts at such high frequencies for the first time and estimated their intensities and variability levels under the effect of external factors. The variable component of the radiation belts was shown to have not exceeded 0.5% of the integrated spectrum of Jupiter over the entire period of its observations. We estimated the contribution of the Galilean satellites (“Galilean noise”) in low-resolution observations; the accuracy of allowing for this noise is determined by the accuracy of estimating the temperatures of the satellites at the observing frequency. The uncertainty in the total flux does not exceed 0.1%.  相似文献   

18.
We present and discuss the results of our long-term JHKLM photometry for two RV Tau stars (R Sge and RV Tau) and the yellow supergiant V1027 Cyg, a candidate for protoplanetary nebulae. The amplitude of the infrared brightness variations in R Sge and RV Tau over fourteen years of observations was 0 . m 9?1 m ; the infrared brightness variations in V1027 Cyg over eighteen years did not exceed 0 . m 25. The infrared brightness and color of R Sge fluctuated about their gradually changing mean values; the infrared brightness variations agree with a period of 70.77 days. The periodic J brightness and J-H color variations in R Sge can be explained by temperature pulsations with ΔT ≤ 200 K and radial pulsations with [ΔR/R] ≤ 0.2. From 1995 to 2008, the mean J brightness of RV Tau increased, while its mean J-H color index decreased; the variations in the mean J brightness can be associated mainly with stellar temperature variations; a periodic component with P = 78.73 days is observed in the infrared brightness and color fluctuations. The variations in the mean J brightness and J-H color index of the supergiant V1027 Cyg over eighteen years of observations did not exceed a few hundredths of a magnitude; both temperature and radial pulsations may be present in the observed J brightness variations. The most probable period of the infrared brightness fluctuations in V1027 Cyg is 237 ± 2 days. The dust shell of R Sge may consist of two layers with grain temperatures of ～1000 and ～700 K; the optical depth at 1.25 µm is ～0.02 and ～0.24, respectively. The grain temperatures in the circumstellar dust shells of the supergiants RV Tau and V1027 Cyg are ～600 K (RV Tau) and ～700 K (V1027 Cyg). Their optical depths at 1.25 µm are ～0.24 (RV Tau) and ～0.008 (V1027 Cyg).  相似文献   

19.
This is an examination of the hypothesis that the appearance of a component with a negative displacement of about −25 km/s in the lines of the sodium resonance doublet can serve as an indicator of the near-term onset of a visual light minimum of a star with R Coronae Borealis type variability. This effect has been observed three times since 1994 in connection with a brightness minimum: twice for a day or a few days before the beginning of a drop in brightness (1995, 1998) and, perhaps, once during the first days of a minimum (2003). Similar changes have been noted in one of the lines of the infrared CaII triplet at 854.2 nm. __________ Translated from Astrofizika, Vol. 50, No. 4, pp. 603–620 (November 2007).  相似文献   

20.
After 26 years from the major event of 1990, in early 2016 the puzzling symbiotic binary MWC 560 has gone into a new and even brighter outburst. We present our tight BVRCIC photometric monitoring of MWC 560 (451 independent runs distributed over 357 different nights), covering the 2005–2016 interval, and the current outburst in particoular. A stricking feature of the 2016 outburst has been the suppression of the short term chaotic variability during the rise toward maximum brightness, and its dominance afterward with an amplitude in excess of 0.5 mag. Similar to the 1990 event when the object remained around maximum brightness for ∼6 months, at the time Solar conjunction prevented further observations of the current outburst, MWC 560 was still around maximum, three months past reaching it. We place our observations into a long term contex by combining with literature data to provide a complete 1928–2016 lightcurve. Some strong periodicities are found to modulate the optical photometry of MWC 560. A period of 1860 days regulate the occourence of bright phases at BVRC bands (with exactly 5.0 cycles separating the 1990 and 2016 outbursts), while the peak brightness attained during bright phases seems to vary with a ∼9570 days cycle. A clean 331 day periodicity modulate the IC lightcurve, where the emission from the M giant dominates, with a lightcurve strongly reminiscent of an ellipsoidal distortion plus irradiation from the hot companion. Pros and cons of 1860 and 331 days as the system orbital period are reviewed, waiting for a spectroscopic radial velocity orbit of the M giant to settle the question (provided the orbit is not oriented face-on).  相似文献   

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