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1.
XY Leo (BD+18° 2307, p = 0d .28) was observed each season from 1992 through 1995 at Yunnan Observatory with the 1 m telescope and 37 new heliocentric times of minimum light were determined. The newly expanded database of the minimum times,including these new epochs, definitely confirm the sine-like variation of its O–C values. Observations and analyses strongly supported the viewpoint that the variation of the O–C values of the minimum times is mainly caused by the light- time effect. Based on this newly expanded database, new light elements for the eclipsing system XY Leo and new light-time orbit for this complex system have been obtained with much better accuracy than before by means of the least squares fitting to the light-time equation. It's also noted that the additional period variation for XY Leo probably may not be ruled out besides the light-time effect. The method of analysis and the discussion of the results are presented in this paper. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
The period of the β Cephei variable, BW Vulpeculae, is increasing all the time at a rate of (14.24±0.20) × 10?10d/d. Also, the residual in the time of light maximum shows a quasi-sinusoidal variation with a period of about 26.3 years and an amplitude of 0.022 – 0.024 days. If this is interpreted as the light-time effect in a binary orbit, then the orbit will have a size a sin i = 1.91 – 2.08 AU and an eccentricity e = 0.52.  相似文献   

3.
We present new CCD photometric observations of V1044 Her obtained on May 22, 23 and 24, 2015. From our data, we derived five new light curve minimum times. Combining our new results with previously available CCD light minimum times, we derived an updated ephemeris and discovered that the period of this binary system exhibits an oscillation. The cyclic variation may be caused by the light-time effect via the presence of a third body or magnetic activity cycle. We calculated the corresponding period of the third body to be 14.1 ± 1.4 years or magnetic cycle to be 12.2 ± 0.7 years. We analyzed our new asymmetric light curves to obtain photometric solutions and starspot parameters using the Wilson and Devinney program. The final results show that V1044 Her is a contact binary system with a degree of contact factor f = 3.220( ± 0.002)%.  相似文献   

4.
VZ Cnc is a population I double mode high amplitude δ Scuti variable. We observed the star and collected the data from January 2007 to January 2009 to determine 14 times of maximum light. We also searched its times of maximum light from other papers and from IBVS and got 57 values. We collected a total of 194 times of maximum light and used them to perform an (O-C) analysis and concluded that there may be no tendency of binary orbital light time effect. But by parabola tendency, it shows a continuous period increasing at the rate of 1.4×10−8 per year; this is compatible with the stellar evolution model calculation both in direction and size.  相似文献   

5.
Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable.  相似文献   

6.
New time-series photometric observations of BL Cam in the V band and white light were made during 2005 to 2007 at the Xinglong Station of China. The frequency analysis confirms two closely separated frequencies, 25.181 d-1 and 25.571 d-1, but the frequency of 31-32 d-1 reported in the literature was not detected in the new data. New times of maximum light were determined from both our light curves and those available on Internet, allowing a more comprehensive study of the O - C diagram, together with the times of maximum light in the literature. A new interpretation, including the period increasing before 1988 and decreasing since 1992 of BL Cam and the light-time effect in a binary system, looks plausible.  相似文献   

7.
An analysis of the available photoelectric times of minima of KO Aql, TV Cas and Z Her, which are suspected to be in pre-main sequence phase of evolution, reveals that KO Aql shows a secular increase in its orbital period at the rate of 4·34 × 10−8 day per cycle while the period of TV Cas has been decreasing at the rate of 4·08 × 10−9 day per cycle. Z Her does not show any period change at all. The orbital period of any binary system which is in the pre-main sequence phase will be systematically affected because of ′ shrinking′ dimensions of the components. A simple formula for the characteristic period change, defined by (P/P), is derived from a consideration of the conservation of total energy and total angular momentum for a binary system whose components are still in the process of contraction or expansion. The derived formula is applied to the above systems to see whether theoretical characteristic period changes agree with the observed values. The systems are assumed to evolve independently in the pre-main sequence phase in accordance with the model calculations of Iben (1965). It is found that there is no agreement between theoretical and observed characteristic period changes. This suggests that KO Aql and TV Cas may not be in the pre-main sequence phase. We do not have sufficient data for Z Her to judge its evolutionary status by the present procedure; this is also true of TT Hya. We suspect that the period changes observed in KO Aql and TV Cas may be due to light-time effect.  相似文献   

8.
The O − C diagram for the eclipsing binary system TY Boo was constructed with the new minima times observed at the Ankara University Observatory along with the collected ones from the literature. The O − C diagram shows a cyclic variation superimposed on a quadratic variation. The quadratic variation can be explained in terms of mass loss/exchange mechanism in the system while the cyclic variation is attributed to a possible light-time effect caused by a third body revolving around the close binary.  相似文献   

9.
This paper presents charge-couple device (CCD) photometric observations for the eclipsing binary AW UMa. The V-band light curve in 2007 was analyzed using the 2003 version of the Wilson–Devinney code. It is confirmed that AW UMa is a total eclipsing binary with a higher degree of contact f=80.2% and a lower mass ratio of q=0.076. From the (O−C) curve, the orbital period shows a continuous period decrease at a rate of dP/dt=−2.05×10−7 d yr−1. The long-term period decrease suggested that AW UMa is undergoing the mass transfer from the primary component to the secondary one, accompanied by angular momentum loss due to mass outflow L 2. Weak evidence indicates that there exists a cyclic variation with a period of 17.6 yr and a small amplitude of A=0. d 0019, which may be attributed to the light-time effect via the third body. If the existence of an additional body is true, it may remove a great amount of angular momentum from the central system. For this kind of contact binary, as the orbital period decreases, the shrinking of the inner and outer critical Roche lobes will cause the contact degree f to increase. Finally, this kind of binary will merge into a single rapid-rotation star.  相似文献   

10.
New photoelectric times of maximum light of the large amplitude SX Phoenicis star CY Aquarii are analyzed together with times of maximum light in the literature. The general shape of the fitted curve of the observed minus calculated (O-C) times of maximum light suggest the duplicity of the variable star, which causes long-term period variations in the light-time. The period changes of CY Aqr are probably consequences of a continuously increasing period combined with the light-time effect in a binary system. The secondary companion is less massive. Some spectroscopic orbital elements are derived from the O-C diagram. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
This is an analysis of certain aspects of using the CLEAN algorithm for Fourier analysis of short segments of time series and of time series consisting of short segments of length ΔT separated by very long irregular gaps. It is assumed that the time series contain a harmonic component of amplitude A with a period longer than the length of the longest of the segments of the time series plus white noise with dispersion N2. Reliability plots are constructed for determining the ranges of the parameters (ν, ϕ) for which the CLEAN procedure can be used to determine the values of ν, the frequency, and ϕ, the phase of the harmonic component, with a given accuracy. The results of this analysis are used to search for harmonic components in the variation of the Hβ line profile in spectra of the triple star δ Ori A obtained in 2004 with the BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences. __________ Translated from Astrofizika, Vol. 50, No. 2, pp. 281–297 (May 2007).  相似文献   

12.
Seven new precise times of minimum light have been gathered for the triple eccentric eclipsing binary YY Sgr (P = 2d.63, e = 0.16). Its O--C diagram is presented and improved elements of the apsidal motion and the light-time effect are given. We found a new short period of the third body of about 18.5 years in an eccentric orbit (e 3 ≃ 0.4).  相似文献   

13.
A technique developed for analysing line profiles with both speed and high accuracy was used to study the physical conditions of a coronal formation near a quiescent prominence. Detailed analyses of five coronal lines (Fe xiv λ 5303, Fe x λ 6374, Ni xv λ 6702, Fe xv λ 7059, and Fe xi λ 7892) provided total intensities, Doppler width temperatures, ionization temperatures, and velocities. Dissimilar spatial fluctuations in intensity are obvious for ions grouped according to (low vs high) ionization potentials. The intensity of the green line shows a local minimum around the observed quiescent prominence; a corresponding but much more diffuse pattern is visible in the red line intensity. Large differences are observed in temperatures derived by different means. In particular, , while , and . The differences between and are taken as direct evidence of temperature inhomogeneity. One can thus put little significance in T e (xi/x). T D(λ5303) and T e (xv/xiv) fluctuate nearly in parallel at each slit height, with a weak local minimum evident around the prominence. The discrepancy between these two can be removed if a non-thermal turbulent motion of 6–16 km s−1 is assumed. Variations with height of both T D(λ5303) and T e (xv/xiv) suggest that the coronal temperature maximum is located no more than 15000 km above the top of spicules. A negative gradient of about 6 deg km−1 is found in the height variation of T D(λ5303). The height variation of the green line wavelength shows that the majority of coronal material in this region is flowing from west to east on the Sun, with the highest velocity of 12 km s−1 found at the lowest heights. This motion is in the same sense as that of the nearby coronal rain, as determined both from the spectra and wavelength-shifted Hα filtergrams. Superposed on the above flow is a systematic velocity field of up to ±5 km s−1. This field similarly reaches maximum amplitudes at lowest heights showing a local maximum around the prominence. On leave from Institute of Earth Science and Astrophysics, Shiga University, Ohtsu 520, Japan, as 1973–75 National Academy of Science/National Research Council Senior Post-Doctoral Research Associate at Sacramento Peak Observatory.  相似文献   

14.
B andV observations of the W Ursae Majoris-type eclipsing variable system AK Her were made on five nights at the Ege University Observatory. Several times of minima were obtained during the observations and the new light elements were calculated. The light-time period was found to be about 75.72 years. The light curve of the system appears to change in each cycle for both colours. The secondary minimum of the system seems to be a total eclipse with a duration of about 42 m .5.  相似文献   

15.
Several new times of minimum light recorded with photoelectric or CCD means have been gathered for the eccentric eclipsing binary V889 Aql (P = 11.1 days, e = 0.37). Its O–C diagram is presented, and improved elements of the apsidal motion and the light-time effect (LITE) are given. We found a long apsidal motion period of about 24 400 ± 2400 years and a period of the third body of about 52 ± 2 years.  相似文献   

16.
In this study we present the results of the preliminary analysis of the period variation of V839 Oph based on the extensive series of minima times collected from the literature. The character of the (O–C) diagram can be approximated with a cyclic variation superimposed on a quadratic variation. The quadratic variation can be explained in terms of mass exchange/loss mechanism in the system, while the cyclic variation could be attributed to the light-time effect of a gravitationally bound third body to the system or the magnetic activity cycle of the primary component.  相似文献   

17.
Series of photometric CCD observations of the asynchronous polar BY Cam in a low accretion state (R = 14m–16m) were made on the K-380 telescope at the Crimean Astrophysical Observatory (CrAO) over 100 hours in the course of 31 nights during 2004–2005. A period of P 1 = 0.137120±0.000002 days was found for the variations in the brightness, along with less significant periods of P 2 = 0.139759±0.000003 and P3 = 0.138428±0.000002 days, where P2 and P3 are obviously the orbital and rotation periods, while the dominant period P1 is the sideband period. A modulation in the brightness and an amplitude of 0.137 days in the oscillations at the orbital-rotational beat period (synodic cycle) of 14.568±0.003 day are found for the first time. The profile of the modulation period is four humped. This indicates that the magnetic field has a quadrupole component, which shows up well during the low brightness state. Accretion takes place simultaneously into two or three accretion zones, but at different rates. The times of the times of maxima for the main accretion zone vary with the phase of the beat period. Three types of variation of this sort are distinguished: linear, discontinuous, and chaotic, which indicate changes in the accretion regimes. At synodic phases 0.25 and 0.78 the bulk of the stream switches by 180°, and at phase 0.55, by ∼75°. At phases of 0.25–0.55 and 0.55–0.78, the O-C shift with a period of 0.1384 days, which can be explained by a retrograde shift of the main accretion zone relative to the magnetic pole and/or a change in the angle between the field lines and the surface of the white dwarf owing to the asynchronous rotation. For phases of 0.78–1.25 the motion of the accretion zone is quite chaotic. It is found that synchronization of the components occurs at a rate of less than dProt/Prot∼10−9 day/day. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 121–137 (February 2006).  相似文献   

18.
WASP-33 is a fast rotating, main sequence star which hosts a hot Jupiter moving along a retrograde and almost polar orbit with semi-major axis a=0.02 au and eccentricity provisionally set to e=0. The quadrupole mass moment J2*J_{2}^{\star} and the proper angular momentum S ⋆ of the star are 1900 and 400 times, respectively, larger than those of the Sun. Thus, huge classical and general relativistic non-Keplerian orbital effects should take place in such a system. In particular, the large inclination Ψ⋆ of the orbit of WASP-33b to the star’s equator allows to consider the node precession [(W)\dot]\dot{\Omega} and the related time variation dt d /dt of the transit duration t d . The WASP-33b node rate due to J2*J_{2}^{\star} is 9×109 times larger than the same effect for Mercury induced by the Sun’s oblateness, while the general relativistic gravitomagnetic node precession is 3×105 times larger than the Lense-Thirring effect for Mercury due to the Sun’s rotation. We also consider the effect of the centrifugal oblateness of the planet itself and of a putative distant third body X. The magnitudes of the induced time change in the transit duration are of the order of 3×10−6,2×10−7,8×10−9 for J2*J_{2}^{\star}, the planet’s rotational oblateness and general relativity, respectively. A yet undiscovered planet X with the mass of Jupiter orbiting at more than 1 au would induce a transit duration variation of less than 4×10−9. A conservative evaluation of the accuracy in measuring dt d /dt over 10 yr points towards ≈10−8. The analysis presented here will be applicable also to other exoplanets with similar features if and when they will ne discovered.  相似文献   

19.
New times of light minimum of the short‐period (P = 0d.26) close binary system, VZ Psc, are presented. A period investigation of the binary star, by combining the three new eclipse times with the others collected from the literatures, shows that the variation of the period might be in an alternate way. Under the hypothesis that the variation of the orbital period is cyclic, a period of 25 years and an amplitude of 0.d0030 for the cyclic change are determined. If this periodic variation is caused by the presence of a third body, the mass of the third body (m3) should be no less than 0.081M⊙. Since both components of VZ Psc are strong chromospherically active and the level of activity of the secondary component is higher than that of the primary one, the period may be more plausibly explained by cyclic magnetic activity of the less massive component. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

20.
A new orbital period analysis for U Geminorum is made by means of the standard O–C technique based on 187 times of light minima including the three newest CCD data from our observation. Although there are large scatter near 70,000 cycles in its O–C diagram, there is strong evidence (>99.9% confidence level) to show the secular increase of orbital period with a rate  s−1. Using the physical parameters recently derived by Echevarría et al. (Astron. J. 134:262, 2007), the range of mass transfer rate for U Geminorum is estimated as from −3.5(5)×10−9 M ⊙ yr−1 to −1.30(6)×10−8 M ⊙ yr−1. Moreover, the data before 60,000 cycles shows the obvious quasi-period variations. The least square estimation of a ∼17.4 yr quasi-periodic variation superimposed on secular orbital period increase is derived. Considering the possibility that solar-type magnetic activity cycles in the secondary star of U Geminorum may produce the quasi-period variations of the orbital period, Applegate’s mechanism is discussed and the results indicate such mechanism has difficulty explaining the quasi-period variation for U Geminorum. Hence, we attempted to apply the light-travel time effect to interpret the quasi-period variation and found the perturbation of ∼17.4 yr quasi-period may result from a brown dwarf. If the orbital inclination is assumed as i∼15°, corresponding to the upper limit of mass of a brown dwarf, then its orbital radii is ∼7.7 AU.  相似文献   

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