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1.
A very accurate imitation of Hipparcos and Tycho Hp, B T, andV T magnitudes was made using W, B, V, R magnitudes from the Tien Shan photometric catalogue. The calculated magnitudes were compared to the observed ones. It is shown that there are systematic differences between calculated and observed magnitudes. The systematic errors are supposed to be bound up with the sky scanning procedure on the Hipparcos satellite. Polynomials in powers of coordinates have been proposed to take into account the systematic errors. 6558 stars have been found to be appropriate high-precision photometric standards. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
We present a method and results of evaluation of the photometric systems (PSs) proposed for the GAIA mission. The method, however, can be applied for the analysis of virtually any multicolour PS designed for the global investigation of the Galactic stellar populations. Performance of the 1F, 2A and 3G PSs is evaluated taking into account their ability to simultaneously determine the main stellar parameters,T eff, log g, [M/H] and E B-V, for a large variety of stars down to G ∼ 20. The representative Galactic stellar populations were constructed and employed for evaluation of the PSs. Despite the fact that the 2A and 3G PSs perform significantly better than the 1F (presently adopted as a baseline PS for GAIA), we conclude that still there is no photometric system proposed to date, which would allow to achieve the scientific objectives of the GAIA mission. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
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   

4.
The stellar composition of the Tycho-2 Catalogue in the range B-V = 0· m 75–1· m 25 has been reproduced through Monte Carlo simulations. For young and old stars of the red giant clump (RGC), the red giant branch, subgiants, red dwarfs, and thick-disk giants, we have specified the distributions in coordinates, velocities, B-V, and M V as a function of B-V and calculated their reduced proper motions, photometric distances from the (B-V)-M V calibration, and photoastrometric distances from the reduced proper motion-M V calibration. Our simulations have shown the following: (1) a sample of thin-disk giants within 500 pc with an admixture of less than 10% of other stars can be produced; (2) a sample of dwarfs within 100 pc almost without any admixture of other stars can be produced; (3) the Local Spiral Arm affects the RGC composition of any magnitude-limited catalog in favor of giants younger than 2 Gyr; (4) the samples produced using reduced proper motions can be used for kinematic studies, provided that the biases of the quantities being determined are simulated and taken into account; (5) the photometric distances correlate with the photoastrometric ones because of the correlation between the proper motion and magnitude; (6) the photometric distances are closer to the true ones for the red giant branch and red dwarfs as the categories of stars with a clear (B-V)-M V relation, while the photoastrometric distances are closer to the true ones for the RGC, subgiants, and thick-disk giants; (7) the calculated distances differ systematically from the true ones, but they can be used to analyze the three-dimensional distribution of stars. Our simulations confirm the validity of our previous selection of RGC stars from Tycho-2.  相似文献   

5.
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   

6.
The photometrically determined mean surface magnetic fields BS need a revision. None of the stars for which BS can be measured directly by Zeeman line splitting fulfils the relation between the photometric parameter Δ(V1 – G) and the mean surface field BS, which is used by NORTH , CRAMER and MAEDER to determine BS for other B2 – A3 stars. The ratio BeffMax/BS for stars, which define North's relation, shows unreasonable large values.  相似文献   

7.
We present the results of absolute photometry – the absolute brightness HV, the effective diameter, (B)VR color indices, composite light curves, period of rotation and amplitude of variations – of several small asteroids in the inner main-belt: 1344 Caubeta, 1401 Lavonne, 2947 Kippenhahn, 3913 Chemin, 3956 Caspar, 4375 Kiyomori, 4555 1987 QL, 5484 Inoda, 5985 1942 RJ, 6949 Zissell and main-belt asteroid 6867 Kuwano. The photometric observations of these objects were made in the period 2007–2009 as part of a project of photometric studies of small main-belt asteroids that involves a collaboration of a number of asteroid photometrists around the world.  相似文献   

8.
A new general expression for the theoretical momentsA 2m of the light curves of eclipsing systems has been presented in the form of infinite series expansion. In this expansion, the terms have been given as the product of two different polynomials which satisfy certain three-term recursion formulae, and the coefficients diminish rapidly with increasing number of terms. Thus, the numerical values of the theoretical momentsA 2m can be generated recursively up to four significant figures for any given set of eclipse elements. This can be utilized to solve the eclipse elements in two ways: (i) with an indirect method (for the procedures see Paper XIV, Kopal and Demircan, 1978), (ii) with a direct method as minimization to the observational momentsA 2m (area fitting). The procedures given in Paper XIV for obtaining the elements of any eclipsing system consisting of spherical stars have been automated by making use of the new expression for the momentsA 2m of the light curves. The theoretical functionsf 0,f 2,f 4,f 6,g 2 andg 4 which are the functions ofa andc 0, have been used to solve the eclipse elements from the observed photometric data. The closed-form expressions for the functionsf 2,f 4 andf 6 have also been derived (Section 3) in terms of Kopal'sI-integrals.The automated methods for obtaining the eclipse elements from one minimum alone have been tested on the light curves of YZ (21) Cassiopeiae under the spherical model assumptions. The results of these applications will be given in Section 5 which follows a brief introduction to the procedure we followed.  相似文献   

9.
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   

10.
Interstellar and atmospheric extinctions redden the observational photometric data and they should be handled rigorously. This paper simulates the effect of reddening for the modest case of two main sequence T 1 = 6500 K and T 2 = 5500 K components of a detached eclipsing binary system. It is shown that simply subtracting a constant from measured magnitudes (the approach often used in the field of eclipsing binaries) to account for reddening should be avoided. Simplified treatment of the reddening introduces systematics that reaches ∼0.01 mag for the simulated case, but can be as high as ∼0.2 mag for, e.g., B8 V-K4 III systems. With rigorous treatment, it is possible to uniquely determine the colour excess value E(B−V) from multi-colour photometric light curves of eclipsing binaries.  相似文献   

11.
Some properties of the quantitiesB 2m (Smith, 1977) inherent in the frequency-domain approach have been deduced, and a general expression for them in terms of the eclipse elementsr 1,2,i andL 1 of the basic model has been presented (Section 2).An expansion for the loss of light (1–l) into a Fourier sine series alone have been introduced, and its coefficientsb m presented (Section 3) in terms of the same eclipse elements. A method of increasing the rate of convergence of this series has been given in Section 4. The methods for obtaining the elements of eclipsing binaries by making use of all these quantities in the frequency-domain can likewise be generalized to cover the photometric effects of gravitational and radiative interaction between the components.  相似文献   

12.
A review of selected photometric and spectrophotometric properties of magnetic stars is given. It is shown that unreddened B–V of magnetic stars around B9 type can be transformed to log Te using the calibration for normal stars and no systematic errors are introduced. Mechanisms of light variability are discussed. It is concluded that different mechanisms must be operating in different stars. Recently obtained photometric observations of short-period variability by KURTZ and Hβ variability by MADEJ et al. are discussed. An information about internal structure and the atmospheric structure of these stars can be derived from these observations.  相似文献   

13.
UBV photometric observations and elements of TT Hydrae obtained by Kulkarni and Abhyankar (1980) are combined with the radial velocity curve of Popper (1979, personal communication) to derive the absolute dimensions and. a model of this important Algol system. While the photometric ratios of radii inV andB are in agreement givingk = 0.3812 for a limb darkening coefficient ofx = 0.6, application of Irwin’s (1947) method givesx = 0.4 forU. The primary is found to be a main sequence Al V star of mass 2.61M ⊙ and radius 2.01 R⊙, and the secondary is classified as a Kl III star of mass 0.70M ⊙ and radius 5.33R ⊙. The observed Fourier coefficients for the light outside the eclipse agree with those calculated from theory for the reflection and ellipticity effects. The system shows an ultraviolet excess of 0.5 to 0.6 magnitudes during primary eclipse, which is attributed to an asymmetric circumstellar distribution of matter around the primary. The evolutionary status of the secondary, which does not appear to fill its Roche lobe completely, is discussed.  相似文献   

14.
The results of photometric astrometry, a method of determining the orientation of a rotation axis, as applied to asteroid 44 Nysa are presented. The pole orientation of Nysa was found to be λ0 = 100°, β0 = +60° with an uncertainty of 10°. The sidereal period is 0d.26755902 ± 0.00000006, and the rotation prograde. Refinements to, and limitations of, the application of the method of photometric astrometry are discussed. In light of the results presented herein, we believe that all photometric astrometry pole determinations of the past should be redone.  相似文献   

15.
General properties of Luminous Blue Variables (LBV) have been reviewed by Lamers(1987). The LBV's are all close to the Humphreys-Davidson luminosity upper limit. The semi periods of the photometric microvariations withV 0.1 m are about twice as large as for normal supergiants of the sameL andT eff, and 4–20 times larger than the fundamental mode for radial pulsations. So, it is likely due to nonradial pulsations. During shell ejections, which accompanied by moderate photometric variations ofV 1 m ,L bol remains constant. This fact has been explained by the quasiperiodic variations ofT eff and the radius of pseudo-photosphere (Lamer 1986). LBV's are less stable than normal supergiants so that any internal instability has more effect on their envelopes. The nature of these instabilities remains unknown. We have found some interesting peculiarities which can throw light to this problem.  相似文献   

16.
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   

17.
We present and apply a new computer program named SpotModeL to analyze single and multiple bandpass photometric data of spotted stars. It is based on the standard analytical formulae from Budding and Dorren. The program determines the position, size, and temperature of up to three spots by minimizing the fit residuals with the help of the Marquardt‐Levenberg non‐linear least‐squares algorithm. We also expand this procedure to full time‐series analysis of differential data, just as real observations would deliver. If multi‐bandpass data are available, all bandpasses can be treated simultaneously and thus the spot temperature is solved for implicitly. The program may be downloaded and used by anyone. In this paper, we apply our code to an ≈23 year long photometric dataset of the spotted RS CVn giant IM Peg. We extracted and modelled 33 individual light curves, additionally, we fitted the entire V dataset in one run. The resulting spot parameters reflect the long term light variability and reveal two active longitudes on the substellar point and on the antipode. The radius and longitude of the dominant spot show variations with 29.8 and 10.4 years period, respectively. Our multicolour data suggests that the spot temperature is increasing with the brightening of the star. The average spot temperature from V, IC is 3550 ± 150 K or approximately 900 K below the effective temperature of the star.  相似文献   

18.
On the basis of the effective temperature scale proposed previously for cool carbon stars (Paper I), other intrinsic properties of them are examined in detail. It is shown that the major spectroscopic properties of cool carbon stars, including those of molecular bands due to polyatomic species (SiC2, HCN, C2H2 etc.), can most consistently be understood on the basis of our new effective temperature scale and the theoretical prediction of chemical equilibrium. Various photometric indices of cool carbon stars also appear to be well correlated with the new effective temperatures. Furthermore, as effective temperatures of some 30 carbon stars are now obtained, the calibration of any photometric index is straightforward, and some examples of such a calibration are given. In general, colour index-effective temperature calibrations for carbon stars are quite different from those for K-M giant stars. It is found that the intrinsic (R —I)0 colour is nearly the same for N-irregular variables in spite of a considerable spread in effective temperatures, and this fact is used to estimate the interstellar reddening of carbon stars. An observational HR diagram of red giant stars, including carbon stars as well as K-M giant stars, is obtained on the basis of our colour index-effective temperature calibrations and the best estimations of luminosities. It is shown that carbon stars and M giant stars are sharply divided in the HR diagram by a nearly vertical line at aboutT eff = 3200 K (logT eff = 3.50) and the carbon stars occupy the upper right region of M giant stars (except for some high luminosity, high temperature J-type stars in the Magellanic Clouds; also Mira variables are not considered). Such an observational HR diagram of red giant stars shows rather a poor agreement with the current stellar evolution models. Especially, a more efficient mixing process in red giant stars, as compared with those ever proposed, is required to explain the formation of carbon stars.  相似文献   

19.
We have examined a sample of 150 elliptical galaxies taken from a recent survey (Bursteinet al., 1987) which includes also new CCD photometric data. The fits of total luminosityL versus three different diameter indicators (i.e., the effective diameterD e, theD n diameter proposed by Dressleret al. (1987), and the isophotal diameterD 0 at 25 mag arc sec–2) had given no sign of environmental effect on such quantities. A comparison with previous results based on lower quality data was carried out in order to check the reliability of different photometries and statical tools used.Our main conclusion is that the luminosity-diameter relation seems to be universal in the range of luminosities spanned by our sample; so environmental effects, if present, must be smaller than observational errors.  相似文献   

20.
We present the results of a three-year-long monitoring of atmospheric extinction over Mount Shatdzhatmaz (2112 m) in Northern Caucasus in a photometric band with λ eff = 480 nm and the results of measurements of precipitable water vapor (PWV), which characterizes the atmospheric transparency in the near infrared. The yearly mean fraction of photometric weather is estimated to be 50% of the clear night time. The yearly median extinction is 0ṃ21; themedian PWV on clear nights is 7.7 mm.  相似文献   

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