首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 218 毫秒
1.
We present BVR full-light curves of V388 Cyg to provide a complete photometric solution for the first time. The light curves show a high degree of asymmetry (O'Connell effect). The maxima at 0.25 phase (Max I) are 0.023, 0.018 and 0.012 mag higher than those at 0.75 phase (Max II) in B , V and R , respectively. Three possible spot models are applied to fit the asymmetric light curves of V388 Cyg, in order to explain the O'Connell effect. We conclude that the model of the cool spot on the cooler star is the most reasonable model for V388 Cyg. The continuous period variation is confirmed by recently collected times of minima, including one minimum that is determined in this paper. The period decrease rate is estimated as d p /d t =−2.055×10−7 d yr−1 .  相似文献   

2.
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   

3.
Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1⋅m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0⋅m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1⋅m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.  相似文献   

4.
We present the spectroscopy of nova V2467 Cyg acquired at the Loiano Observatory, Italy, during the first six months after the outburst. We have used the optical spectroscopy to study the physical properties of the ejected material and the photometry to estimate the nova distance. V2467 Cyg is a fast nova, with decline rates by two or three magnitudes of 7.6 and 14.6 days respectively. The light curve exhibited oscillations during the transition stage. The nova achieved an absolute magnitude at maximum in the range –8.5… –9.1. The distance is in the range 2.6… 3.6 kpc. V2467 Cyg showed an early appearance of forbidden lines during the transition stage. Its evolution is similar to the behavior of V1494 Aql (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
We present the results of our spectroscopic and photometric observations of the classical symbiotic star V1413 Aql in 2003–2007, which cover the transition phase of its hot component from activity to quiescence. Various quiescence criteria for the hot component of the system are analyzed. Judging by its photometric characteristics, the system had not yet returned to quiescence by 2007, although a fairly strong He II λ4686 Å line observed previously during quiescence in 1993 appeared in its spectrum. We model the continuum energy distribution for V1413 Aql based on a standard three-component model and a model with an accretion disk. Analysis of the forbidden [O III] and [Ne III] lines shows that the neon abundance in V1413 Aql may be enhanced with respect to the oxygen abundance. The cool component of V1413 Aql has been found to be a variable M5-type red giant, with the variability amplitude at λ = 7500 Å being at least 2 m .  相似文献   

6.
We present new results of our UBV photometry for HD 179821=V1427 Aql, an F supergiant with an infrared excess, from 2000 to 2008. The semiregular low-amplitude (ΔV = 0. m 05−0. m 20) photometric variability of the star with a cycle period from 130 to 200 days is caused by pulsations, along with the instability of a variable stellar wind. V1427 Aql also exhibits a long-term trend in the brightness and colors that is probably attributable to a change in the stellar temperature as a result of mass loss episodes, which cause variations in the continuum formation level. We present the results of our JHKLM photometry for V1427 Aql in 1992–2008. We trace the trend in the near-infrared brightness, which agrees with the long-term variability in the V band. Based on broadband photometry, we have determined the color excess for V1427 Aql: E(B−V) = 0.7. Based on low-resolution spectroscopy, we have estimated the stellar temperature and revealed variability of the Hα line caused by a change in the contribution from the emission component. The hypotheses of whether the star belongs to post-AGB objects or to massive yellow hypergiants are discussed.  相似文献   

7.
Using measured radial velocity data of nine double lined spectroscopic binary systems NSV 223, AB And, V2082 Cyg, HS Her, V918 Her, BV Dra, BW Dra, V2357 Oph, and YZ Cas, we find corresponding orbital and spectroscopic elements via the method introduced by Karami and Mohebi (Chin. J. Astron. Astrophys. 7:558, 2007a) and Karami and Teimoorinia (Astrophys. Space Sci. 311:435, 2007). Our numerical results are in good agreement with those obtained by others using more traditional methods.  相似文献   

8.
We present new multicolour (UBVRCIC) photometric observations of classical symbiotic stars, EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, Draco C1, AG Peg, and AX Per, carried out between 2007.1 and 2011.9. The aim of this paper is to present new data of our monitoring programme, to describe the main features of their light curves (LC) and to point problems for their future investigation. The data were obtained by the method of the classical photoelectric and CCD photometry (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

9.
Orbital period variations of two neglected Algol type binaries, CC Her and XZ Aql, are studied based on all available times of minima. In the case of CC Her, it is found that the O –C curve displays a tilted sinusoidal variation with an eccentricity of 0.54 ± 0.03 and a period of 52.4 ± 0.4 yr, which can be explained by the light‐time effect due to the presence of an unseen component. The course of the orbital period change in XZ Aql appears less reliable but its O –C curve can be represented by a periodic variation with a period of 36.7 ± 0.6 yr superimposed on an upward parabola. The parabolic variation indicates a secular period increase with a rate of dP /dt = 7.1 s per century. The corresponding conservative mass transfer from less massive component to the more massive one is about 3.26 × 10–7 M⊙ yr–1. It is interesting to see that the O –C variation of CC Her displays no evidence (as upward parabola) on the mass transfer characteristic for Algols. The periodic change of the orbital period of XZ Aql, like CC Her, may be caused by the presence of the thirdbody. The lower limits of the masses of the hypothetical unseen components for CC Her and XZ Aql are found to be 2.69 M⊙ and 0.47 M⊙, respectively. The third body of CC Her should be detectable not only spectroscopically but also photoelectrically, if it exists. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
Elemental abundances of the moderately rotating B9–A3 stars λ UMa, 59 Her, 14 Cyg and 29 Cyg have been derived in a consistent manner with previous studies of this series from spectrograms obtained with Reticon and CCD detectors. The derived elemental abundances show that λ UMa is a mild Am star, while 59 Her is slightly metal-rich. Although 14 Cyg has values closer to solar than these stars, its subsolar Ca and Sc abundances indicate that it might be the hottest known hot-Am star. 29 Cyg is a metal-poor λ Boo star.  相似文献   

11.
《New Astronomy》2004,9(1):51-57
We have conducted high-speed photometric observations of the suspected cataclysmic variable V747 Cyg. The literature data about the spectra of this star are conflicting. Zwitter and Munari [A&AS 107 (1994) 503] obtained spectroscopic observations which confirmed the cataclysmic variable nature of V747 Cyg, whereas Downes et al. [AJ 110 (1995) 1824] have concluded that this object may be a Be + M binary rather than a cataclysmic variable. Our observations revealed the complete absence of the rapid flickering in this star at a millimagnitude level. This phenomenon is to be inherent in all cataclysmic variables. Instead, the lightcurves of V747 Cyg showed probably periodic smooth low-amplitude variations that were visible during each observational night. When V747 Cyg was observed in two colours simultaneously, these variations had the equal phases and amplitudes. A periodogram analysis revealed probable periods of 5.77, 7.41 and 7.59 h. These periods and the amplitude as well as the oscillation behaviour in the different colours are typical of variable Be stars. Hence, V747 Cyg may be a variable Be star but not a cataclysmic variable.  相似文献   

12.
The systematic UBV observations of six variable post-AGB supergiants in 1991–1999 are presented. Their variability is analyzed. The coolest stars V1027 Cyg and V354 Lac exhibit bimodal pulsations with variable amplitudes. Apart from pulsations, the hotter stars V887 Her and IRAS 19386+0155 show light variations associated with a stellar wind. A variable stellar wind appears to be mainly responsible for the photometric variations in the still hotter stars SAO 163075 and IRAS 20572+4919. Distinct trends in the yearly mean brightness have been found in three of the six supergiants studied, with the trend amplitude being independent of the spectral range. They are interpreted as the result of dust envelopes composed of large grains with R=A V /E(B?V)≥7 becoming optically thin.  相似文献   

13.
The results of new UBV photometric observations of V1357 Cyg in primary minimum are presented. Observations were carried out from 1996 up to now with 60 cm telescope in Crimea with the goal to study additional radiation that was detected in the mean light curve of this system near orbital phase 0.0. The properties of this additional radiation are also considered.  相似文献   

14.
Photoelectric light curves of the double-lined binaries XY Cet and V380 Cyg, known to be detached systems, have been reanalyzed by means of Wood's program in order to obtain homogeneous photometric elements. Masses, radii and luminosities are given.We find that the basic elements of both components of the metallic-line binary XY Cet are consistent with current views of the metallicity phenomenon. The early-type system V380 Cyg turns out to be composed of an evolved (giant) primary and a Main Sequence companion.  相似文献   

15.
In this study we present photometric observations of the eclipsing binary KR Cyg made in 1999 and 2000. The observations of the eclipsing binary KR Cyg have been carried out in B, V and R colours at the Ege University Observatory. A new seasonal light curves are presented. New times of minima and ephemerides are given. Based on a statistical analysis of the times of minima obtained by photoelectric photometry, the orbital period of the system is found to be constant. The photometric mass ratio of the system is well determined. The corresponding light curves were analyzed by the Wilson-Devinney code. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

16.
New photoelectric and CCD observations of the eclipsing contact binary systems V344 Lac and V1191 Cyg are presented and analyzed. All available times of minimum light were used to study period changes of the systems and determine up-to-date ephemerides. The orbital period of V1191 Cyg is found to be increasing at a very fast rate. The photometric elements were determined using the new light curve, radial-velocity curve and broadening function fitting code ROCHE.  相似文献   

17.
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   

18.
The paper contains an analysis of the structure of envelopes ejected during the outbursts of Novae. The data used for this purpose: (a) Direct photographs of envelopes and the photographs taken with the use of different colour filters; (b) Spectra of envelopes. The envelope of DQ Her is studied most carefully. The analysis of all available data for the envelopes around DQ Her and V 603 Aql permits us to outline a morphological model of these envelopes, see Figure 3. It appears, that the structure of both these envelopes is approximately identical and that the difference in the observed properties of the photographic images of the nebulae (Figure 2 and Figure 4) is connected with a difference in the orientation of the polar axes of the envelopes relative to the line of sight. The envelope ejected during the outburst of T Aur (Figure 5) reveals the same properties, which are characteristic for the envelopes of DQ Her and V 603 Aql.From this we conclude that the distribution of gases inside the envelopes of the majority of Novae is approximately of the same character. This speaks in favour of the presence of certain forces around many Novae, which guide the motion of ejected plasma along some quite definite directions inside rather small solid angles. It seems that the only conceivable forces of this type may be the forces of a magnetic nature. This hypothesis for example permits us to explain the difference between the envelope of GK Per (Figure 1) and the envelopes of DQ Her, V 603 Aql, T Aur (Figures 2, 4 and 5).Comparing the velocity of expansion of the envelope of DQ Her and the rate of change of its angular size we computed that the distance to DQ Her is equal to 320 pc.On the base of photographs of the envelope of DQ Her it is found that in 1968 the fluxF H of radiation in the H-line was equal to (6±2)×10–12 ergs/cm2sec, whereas the mass of the envelope was equal to 1029 G and its electronic concentrationn e to 2×103 cm–3. Several hypotheses, which may explain the stratification of emission from different elements inside the envelope are discussed.  相似文献   

19.
The Behlen observatory 0.76 m telescope CCD photometer is used to obtain 347 observations of the short period (P0d.4) eclipsing binary star V719 Her. The observations done withV andR bandpass filters were made on 6 nights in 1993. Previously published light elements and the present five timings of minimum provide a new epoch and a more accurate orbital period of 0.4009828 days. Our analyses show that the period of the system appears to decrease. We recommend future monitoring of the eclipse minima for this system. No published spectral classification for V719 Her exists. From the color,V-R=0.391, we estimate it to be about F5.The 1993 version of the Wilson Devinney model gave the photometric solutions. The adopted solution indicates that V719 Her is a W UMa type contact binary. The mass ratio,q=(m 2/m 1, where star 1 eclipse at the primary minimum)=0.296 suggests that V719 Her is a WUMa system with type-A (transit during primary eclipse) configuration. The secondary minimum shows a total eclipse. V719 Her with period less than 0.5 and spectral class F5, is probably a zero-age contact system. Since our photometric solution shows that the luminosity difference between the components is very large, we suspect that V719 Her is most likely a single line spectroscopic binary. We recommend spectroscopic study of this system.  相似文献   

20.
The W UMa-type systems (OO Aql, V839 Oph, V566 Oph, and SW Lac) were observed photoelectrically in two wavebands (B andV) during the years 1982–1983. The light curves of these systems are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined. The absolute elements and the period variations of these systems are discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号