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1.
Photometric and spectroscopic characteristics of the WN5+O6 binary system, V444 Cyg, were studied. The Wilson‐Devinney (WD) analysis, using new BV observations carried out at the Ankara University Observatory, revealed the masses, radii, and temperatures of the components of the system as MWR = 10.64 M⊙, MO = 24.68 M⊙, RWR = 7.19 R⊙, RO = 6.85 R⊙, TWR = 31 000 K, and TO = 40000 K, respectively. It was found that both components had a full spherical geometry, whereas the circumstellar envelope of the WR component had an asymmetric structure. The O – C analysis of the system revealed a period lengthening of 0.139 ± 0.018 syr–1, implying a mass loss rate of (6.76 ± 0.39) ×10–6 M⊙ yr–1 for the WR component. Moreover, 106 IUE‐NEWSIPS spectra were obtained from NASA's IUE archive for line identification and determination of line profile variability with phase, wind velocities and variability in continuum fluxes. The integrated continuum flux level (between 1200–2000 Å) showed a mild and regular increase from orbital phase 0.00 up to 0.50 and then a decrease in the same way back to phase 0.00. This is evaluated as the O component making a constant and regular contribution to the system's UV light as the dominant source. The C IV line, originating in the circumstellar envelope, had the highest velocity while N IV line, originating in deeper layers of the envelope, had the lowest velocity. The average radial velocity calculated by using the C IV line (wind velocity) was found as 2326 km s–1 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

2.
The spectral energy distributions between λ 3700 Å and λ 8100 Å of the binary systems COU1289 and COU1291 have been measured with the Carl‐Zeiss‐Jena 1 m telescope of the Special Astrophysical Observatory. Their B, V, R magnitudes and B – V colour indices were computed and compared with earlier investigations. Model atmospheres of both systems were constructed using a grid of Kurucz blanketed models, their spectral energy distributions in the continuous spectrum were computed and compared with the observational ones. The model atmosphere parameters for the components of COU1289 were derived as: T aeff = 7100 K, T beff = 6300 K, log g a = 4.22, log g b = 4.22, R a = 1.50 R⊙, R b = 1.40 R⊙, and for the components of COU1291 as: T aeff = 6400 K, T beff = 6100 K, log g a = 4.20, log g b = 4.35, R a = 1.47 R⊙, R b = 1.12 R⊙. The spectral types of both components of the system COU1289 were concluded as F1 and F7, and of the system COU1291 as F6 and F9. Finally the formation and evolution of the systems were discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

3.
Photometric BV light curves of BO CVn obtained in 1992 and new times of minima are presented. The primary minimum shows a transit, whereas the secondary minimum, shows an occultation. The system may be classified as an A‐type W UMa system. A complete study of minima allows one to detect a possibly increasing period by about 0.037 s/yr. This indicates that the conservative mass transfer rate from the less massive component to the more massive one is 1.57 10—10M⊙ /yr. Because of the variable period, the new ephemeris is determined for future observations. Using the Wilson‐Devinney code a simultaneous solution of the B and V light curves is also performed. The analysis shows that the system is in a contact configuration with q = 0.205 ± 0.001 and fillout factor (f) = 0.18, T1 = 7240 K (fixed), T2 = 7150± 10 K. The high orbital inclination i = 87°.54 ± 0.26 was con firmed by photometric observations of the secondary minimum.  相似文献   

4.
Cross correlations between observed and synthetic spectra are used to discover yet another satellite of BM Ori with the following characteristics: effective temperature Teff = 4000 K, radius R = 16R⊙, mass M = 1.8M⊙, spectral type K7 III, absolute bolometric stellar magnitude Mb = + 4m·0, axial rotation velocity V sini = 85 km/s, and relative luminosity 0.005 near the V band. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 111–120 (February 2006).  相似文献   

5.
We present the first ever study of the bright star HD 1. The star was chosen arbitrarily just because of its outstanding Henry Draper number. Surprisingly, almost nothing is known about this bright 7.m4 star. Our observations were performed as part of the commissioning of the robotic telescope facility STELLA and its fiber‐fed high‐resolution optical echelle spectrograph SES in the years 2007–2010. We found long‐term radial velocity variations with a full amplitude of 9 km s–1 with an average velocity of –29.8 km s–1 and suggest the star to be a hitherto unknown single‐lined spectroscopic binary. A preliminary orbit with a period of 6.2 years (2279±69 days) and an eccentricity of 0.50±0.01 is given. Its rms uncertainty is just 73 m s–1. HD 1 appears to be a G9‐K0 giant of luminosity class IIIa with Teff = 4850±100 K, logg = 2.0±0.2, L ≈ 155 L⊙, a mass of 3.0±0.3 M⊙, a radius of 17.7 R⊙, and an age of ≈350 Myr. A relative abundance analysis led to a metallicity of [Fe/H] = –0.12 ± 0.09. The α ‐element silicon may indicate an overabundance of +0.13 though. The low strengths of some s‐process lines and a lower limit for the 12C/13C isotope ratio of ≥16 indicate that HD 1 is on the first ascend of the RGB. The absorption spectral lines appear rotationally broadened with a v sin i of 5.5±1.2 km s–1 but no chromospheric activity is evident. We also present photometric monitoring BV (RI)C data taken in parallel with STELLA. The star is likely a small‐amplitude (<10 mmag) photometric variable although no periodicity was found (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
We present a detailed, quantitative study of the standard [WC10] Wolf-Rayet central star CPD-56o 8032 based on new high resolution AAT UCLES observations and the Hillier (1990) WR standard model. Our analysis of CPD-56o 8032 gives the wind properties (T *=34500K, lg (L/L )=3.8, lg (M/M a–1)=–5.4,v =225 km s–1) and chemistry (C/He=0.5, O/He=0.1, by number), the latter suggesting an intimate relationship with the Ovi PN central stars and the PG 1159-035 objects. A comparison between the wind properties of CPD-56o 8032 and Sk-66o 40 (WN 10) indicates that low excitation, low wind velocity WR winds are common to both low mass PN central stars (WC sequence) and high mass post-LBV's (WN sequence).  相似文献   

7.
The Hipparcos Space Astrometry Mission photometric observations of V398 Lac, led to the discovery of its variability, allowing to classify it as an eclipsing binary with an orbital period of about 5.4 days. This prompted us to acquire highresolution échelle spectra with the aim of performing accurate radial velocity measurements and to determine the main physical parameters of the system's components. We present, for the first time, a double‐lined radial velocity curve and determine the orbital and physical parameters of the two components, that can be classified both as late B‐type stars. In particular, we obtained an orbital inclination i ∼ 85°. With this value of the inclination, we deduced masses M1 = 3.83±0.35 M⊙ andM2 = 3.29±0.32 M⊙, and radii R1 = 4.89±0.18 R⊙ and R2 = 2.45±0.11 R⊙ for the more massive and less massive components, respectively. Both components are well inside their own Roche lobes. The mass ratio is M2/M1 ∼ 0.86. We derived also the projected rotational velocities as v1 sin i = 79±2 km s–1 and v2 sin i = 19±2 km s–1. Our measurements indicate that the rotation of the primary star is essentially pseudo‐synchronized with the orbital velocity at the periastron, while the secondary appears to rotate very slowly and has not yet attained synchronization. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
HD 147010, which is in the reflection nebula vd B 102, has been found to be a hot Ap silicon star rather than a normal A supergiant. From theUBV and JHK photometry of the star, colour excessE(B - V) of 0.29 and the ratio of total-to-selective absorptionR of 4.3 have been obtained. The high value ofR implies bigger grain size and also confirms the association of the star with the nebula. The dereddened colours of the star can be fitted to a theoretical energy distribution with Teff = 13000 ± 500 K and logg = 3.6 ± 0.2. HD 147010 has also been found to be a spectrum variable; in particular, lines of Cr II show large intensity variations.  相似文献   

9.
We present the results of our investigation of the geometrical and physical parameters of the W UMa‐type binary V404 Peg from analysis of CCD (BVRI) light curves and radial velocity data. The photometric data were obtained during 2010 at Ankara University Observatory (AUO). Light and radial velocity observations were analyzed simultaneously by using the well‐known Wilson‐Devinney (2007 revision) code to obtain absolute and geometrical parameters. Our solution indicates that V404 Peg is an A‐type overcontact binary with a mass ratio of q = 0.243 and an overcontact degree of f = 32.1 %. Combining our light curves with the radial velocity curves from Maciejewski & Ligeza (2004), we determined the absolute parameters of this system as follows: a = 2.672 R⊙, M1 = 1.175 M⊙, M2 = 0.286 M⊙, R1 = 1.346 R⊙, and R2 = 0.710 R⊙. Finally, we discuss the evolutionary condition of the system (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
In this paper we present Physical Parameter Eclipse Mapping (PPEM) of UBVRI eclipse light curves of UU Aqr from high to low states. We used a simple, pure hydrogen LTE model to derive the temperature and surface density distribution in the accretion disc. The reconstructed effective temperatures in the disc range between 9000 K and 15000 K in the inner part of the disc and below 7000 K in the outer parts. In the higher states it shows a more or less prominent bright spot with Teff between about 7000 K and 8000 K. The inner part of the disc (R < 0.3R) isL1 optically thick at all times, while the outer parts of the disc up to the disc edge (0.51 ± 0.04RL1 in the high state and 0.40 ± 0.03RL1 in the low state) deviate from a simple black body spectrum indicating that either the outer disc is optically thin or it shows a temperature inversion in the vertical direction. While during high state the disc is variable, it appears rather stable in low state. The variation during high state affects the size of the optically thick part of the disc, the white dwarf or boundary layer temperature and the uneclipsed component (originating in a disc chromosphere and/or cool disc wind), while the actual size of the disc remains constant. The difference between high and low state is expressed as a change in disc size that also affects the size of the optically thick part of the disc and the presence of the bright spot. Using the PPEM method we retrieve a distance for UU Aqr of 207±10 pc, compatible with previous estimates.  相似文献   

11.
New BV light curves and times of minimum light for the short period W UMa system LO And were analyzed to derive the preliminary physical parameters of the system. The light curves were obtained at Ankara University Observatory during 5 nights in 2003. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson‐Devinney 2003 code. The present solution reveals that LO And has a photometric mass ratio q = 0.371 and is an A‐type contact binary. The period of the system is still increasing, which can be attributed to light‐time effect and mass transfer between the components. With the assumption of coplanar orbit of the third body the revealed mass is M3 = 0.21M⊙. If the period change dP/dt = 0.0212 sec/yr is caused only by the mass transfer between components (from the lighter component to the heavier) the calculated mass transfer rate is dm/dt = 1.682×10−7M⊙/yr. The absolute radii and masses estimated for the components, based on our photometric solution and the absolute parameters of the systems which have nearly same period are R1 = 1.30R⊙, R2 = 0.85R⊙, M1 = 1.31M⊙, M2 = 0.49M⊙ respectively for the primary and secondary components. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
The dependence on the temperature of photospheric line‐depth ratios (LDRs) in the spectral range 6190–6280 Å is investigated by using a sample of 174 ELODIE Archive stellar spectra of luminosity class from V to III. The rotational broadening effect on LDRs is also studied. We provide useful calibrations of effective temperature versus LDRs for giant and main sequence stars with 3800 ≃ Teff ≃6000 K and v sin i in the range 0–30 km s–1. We found that, with the exception of very few line pairs, LDRs, measured at a spectral resolution as high as 42 000, depend on v sin i and that, by neglecting the rotational broadening effect, the Teff determination can be wrong by ∼100 K in the worst cases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
The recent VIIth Catalogue of Galactic Wolf-Rayet Stars lists 227 Population I WR stars, comprising 127 WN, 87 WC, 10 WN/WC and 3 WO stars. Additional discoveries bring the census to 234 WR stars. A re-determination of the optical photometric distances and the galactic distribution of WR stars shows in the solar neighbourhood a projected surface density of 2.7 WR stars per kpc2, a N WC/N WN number ratio of 1.3, and a WR binary frequency of 40 %.The galactocentric distance (R WR) distribution per subtype showsR WN and R WC decreasing with WN and WC subtypes. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

14.
Detached eclipsing binaries constitute potential accurate distance tracers. They are also useful as the test bench of stellar evolution. In BD–00° 3357 eclipses are partial and its orbital period is 1.d4. Our combined spectroscopic and photometric solution yields secure parameters of this system. The model of the star was obtained using the Wilson‐Devinney method. As result we obtained a semi major axis of 7.65 R⊙ and a mass ratio of 0.78. The derived masses and radii are M 1 = 1.73 M⊙,M 2 = 1.34 M⊙R 1 = 1.78 R⊙, R 2 = 1.32 R⊙, respectively. These values correspond to the slightly evolved F0 and F6.5 components, both slightly less than 1Gyr old. The distance of the star was estimated to be 310 ± 60 pc, and the corresponding photometric parallax is 3.24 ± 0.74 mas. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
In this study we determined precise orbital and physical parameters of the very short‐period low‐mass contact binary system CC Com. The parameters are obtained by analysis of new CCD data combined with archival spectroscopic data. The physical parameters of the cool and hot components are derived as Mc = 0.717(14) M⊙, Mh = 0.378(8) M⊙, Rc = 0.708(12) R⊙, Rh = 0.530(10) R⊙, Lc = 0.138(12) L⊙, and Lh = 0.085(7) L⊙, respectively, and the distance of the system is estimated as 64(4) pc. The times of minima obtained in this study and with those published before enable us to calculate the mass transfer rate between the components which is 1.6 × 10–8 M⊙ yr–1. Finally, we discuss the possible evolutionary scenario of CC Com (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
The semi‐regular variable star RU Vulpeculae (RU Vul) is being observed visually since 1935. Its pulsation period and amplitude are declining since ∼1954. A leading hypothesis to explain the period decrease in asymptotic giant branch (AGB) stars such as RU Vul is an ongoing flash of the He‐burning shell, also called a thermal pulse (TP), inside the star. In this paper, we present a CCD photometric light curve of RU Vul, derive its fundamental parameters, and test if the TP hypothesis can describe the observed period decline. We use CCD photometry to determine the present‐day pulsation period and amplitude in three photometric bands, and high‐resolution optical spectroscopy to derive the fundamental parameters. The period evolution of RU Vul is compared to predictions by evolutionary models of the AGB phase. We find that RU Vul is a metal‐poor star with a metallicity [M/H] = –1.59 ± 0.05 and an effective surface temperature of Teff = 3634 ± 20 K. The low metallicity of RU Vul and its kinematics indicate that it is an old, low‐mass member of the thick disc or the halo population. The present day pulsation period determined from our photometry is ∼108 d, the semiamplitude in the V ‐band is 0.39 ± 0.03 mag. The observed period decline is found to be well matched by an evolutionary AGB model with stellar parameters comparable to those of RU Vul. We conclude that the TP hypothesis is in good agreement with the observed period evolution of RU Vul. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
We present an analysis of BV R light curves of an eclipsing binary CK Bootis, a system with a very small mass ratio. The light curves appear to exhibit a typical O'Connell effect. The light curves are analyzed by means of the latest version of the WD program. The asymmetry of the light curves is explained by a cool star spot model. The simultaneous BV R synthetic light curve analysis gives a tiny mass ratio of 0.12, an extremely large fill‐out factor of 0.65, and a very small difference between the component temperatures of 90 K. The absolute parameters of the system were also derived by combining the photometric solutions with the radial velocity data. The mass of the secondary is very low (0.15 M⊙) and it continues losing mass. Thirty seven new times of minimum are reported. It is found that the orbital period of the system has a quasi periodic variation, superimposed on a period increase. The long‐term period increase rate is deduced to be dP/dt = 3.54x10–7 d yr–1, which can be interpreted as being due to mass transfer from the less massive star to the more massive component. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

18.
We have used two robotic telescopes to obtain time‐series high‐resolution optical echelle spectroscopy and VI and/or by photometry for a sample of 60 active stars, mostly binaries. Orbital solutions are presented for 26 double‐lined systems and for 19 single‐lined systems, seven of them for the first time but all of them with unprecedented phase coverage and accuracy. Eighteen systems turned out to be single stars. The total of 6609 R = 55000 échelle spectra are also used to systematically determine effective temperatures, gravities, metallicities, rotational velocities, lithium abundances and absolute Hα‐core fluxes as a function of time. The photometry is used to infer unspotted brightness, V – I and/or b – y colors, spot‐induced brightness amplitudes and precise rotation periods. An extra 22 radial‐velocity standard stars were monitored throughout the science observations and yield a new barycentric zero point for our STELLA/SES robotic system. Our data are complemented by literature data and are used to determine rotation‐temperature‐activity relations for active binary components. We also relate lithium abundance to rotation and surface temperature. We find that 74% of all known rapidly‐rotating active binary stars are synchronized and in circular orbits but 26% (61 systems) are rotating asynchronously of which half have Prot > Porb and e > 0. Because rotational synchronization is predicted to occur before orbital circularization active binaries should undergo an extra spin‐down besides tidal dissipation. We suspect this to be due to a magnetically channeled wind with its subsequent braking torque. We find a steep increase of rotation period with decreasing effective temperature for active stars, Prot α T–7eff, for both single and binaries, main sequence and evolved. For inactive, single giants with Prot > 100 d, the relation is much weaker, Prot α T‐1.12eff. Our data also indicate a period‐activity relation for Hα of the form RHα α P0.24rot for binaries and RHα α P‐0.14rot for singles. Its power‐law difference is possibly significant. Lithium abundances in our (field‐star) sample generally increase with effective temperature and are paralleled with an increase of the dispersion. The dispersion for binaries can be 1–2 orders of magnitude larger than for singles, peaking at an absolute spread of 3 orders of magnitude near Teff ≈ 5000 K. On average, binaries of comparable effective temperature appear to exhibit 0.25 dex less surface lithium than singles, as expected if the depletion mechanism is rotation dependent. We also find a trend of increased Li abundance with rotational period of form log n (Li) α –0.6 log Prot but again with a dispersion of as large as 3‐4 orders of magnitude (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

19.
The physical and geometrical parameters of the individual components of the binary system Hip11253 (HD14874) are estimated. We used the method described in previous papers, which consists in getting the best fit between the entire observational spectral energy distribution of the system and the synthetic ones, created from model atmospheres. The parameters of the individual components of the system are derived as: T eff a = 6030 ± 100 K, T eff b = 4470 ± 130 K, log g a = 4.27 ± 0.13, log g b = 4.04 ± 0.13, R a = 1.22 ± 0.09R⊙, R b = 1.32 ± 0.20R⊙, with the G0 and K4.5 spectral types for the primary and secondary components, respectively. The synthetic magnitudes of both components were calculated using the Johnson-Cousins, Strömgren, and Tycho photometrical systems. Finally the formation and evolution of the system was discussed.  相似文献   

20.
We present the first long‐term Johnson UBVR observations and comprehensive photometric analysis of the W UMa‐type eclipsing binary V2612 Oph. Observations in the time interval between 2003 and 2009 enabled us to reveal the seasonal and long‐term variations of the light curve. Hence, we found that the mean brightness level of the light curve shows a variation with a period of 6.7 years. Maximum and minimum brightness levels of the light curve exhibit a variation from year to year which we attribute to a solar‐like activity. The O – C variation of eclipse timings of the system shows a decreasing parabolic trend and reveals a period decrease at a rate of P = 6.27×10‐7 day yr‐1 with an additional low‐amplitude sinusoidal variation that has a similar period as the long‐term brightness variations. Our light curve analysis shows that the system is a W‐subtype W UMa eclipsing binary. We calculated masses and radii of the primary and secondary components as M1 = 1.28 M⊙, M2 = 0.37 M⊙ and R1 = 1.31 R⊙, R2 = 0.75 R⊙, respectively. The derived absolute photometric parameters allow us to calculate a distance of 140 pc, which confirms that the system is a foreground star in the sky field of the Galactic open cluster NGC 6633. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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