共查询到20条相似文献，搜索用时 15 毫秒
1.
In 2006, a complete database of the international campaign on photometric observations of the Galilean satellites of Jupiter in the 1997 epoch of mutual occultations and eclipses was published. Only two thirds of the observations were considered by other authors beforehand. In this study, we have processed the whole observational database with an original technique in order to obtain the astrometric data. We determined 301 relative positions of the satellites from photometric observations performed at 50 observatories around the world. The results are put into a common database of all observations of the natural planetary satellites called the Natural Satellites Data Center (NSDC) available on the Internet site http://www.sai.msu.ru/neb/nss/index.htm. The influence of random and systematic errors on the accuracy of determining the coordinates of satellites has been analyzed. It has been shown that the largest systematic errors are caused by inaccurate elimination of the background of the photometric measurements and by the erroneous data on the albedo of satellites. The actual accuracy of astrometric results is 0.05″ and 0.07″ in right ascension and declination, respectively. New recommendations for photometric observations of satellites during the considered phenomena have been developed in order to avoid the systematic errors. 相似文献
2.
T.P. Kiseleva I.S. Izmailov A.A. Kiselev E.V. Khrutskaya M.Yu. Khovritchev 《Planetary and Space Science》2008,56(14):1908-1912
Astrometric and photometric observations of major planets, their satellites and asteroids have been made with the 26-in. refractor of the Pulkovo observatory during the period from 1995 to 2006. The CCD (ST6) and photographic observations were carried out. Accurate relative position of satellites of Jupiter and Saturn have been derived. The positions of Saturn have been calculated using the theoretically predicted coordinates of satellites relative to the planet without measurements of the photographic images of the planet. Also the observations of Hale-Bopp comet and Mercury transit have been made. The 26-in. refractor has been included into the international campaign PHEMU-2003: photometric CCD observations of mutual occultations and eclipses of Galilean satellites. The light curves of the events have been obtained and parameters of the events have been determined. 相似文献
3.
We report on first results of a comprehensive study of interacting andmerging processes between spiral galaxies and small
satellites to investigatethe effects of such events on the disk component of spirals. Analysis ofour newly obtained photometric
data of about 125 edge-on galaxiesin optical and in NIR shows that there are considerable differencesbetween interacting and
non-interacting galaxies concerning their absolutedisk scale parameters as well as their ratios (h/z
0).In comparison with normal spirals, the average heating factor perpendicular tothe disk plane of mergers is about 1.5. The
most striking feature of thedistributions of (h/z
0) for both normal galaxies and mergers, is thetotal lack of typical flat disk axis ratios (i.e. that of late type ones)of
(h/z
0) > 6 for mergers.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
In this paper, we analyze the results of ground-based and space-born photometric observations of the major satellites of Uranus—Miranda, Ariel, Umbriel, Titania, and Oberon. All sets of photometric observations of the satellites available in the literature were examined for uniformity and systematic differences and summarized to a unified set by wavelength ranging from 0.25 to 2.4 μm. This set covers the interval of phase angles from 0.034° to 35°. The compound phase curves of brightness of the satellites in the spectral bands at 0.25, 0.41, 0.48, 0.56, 0.75, 0.91, 1.4, and 1.8 μm, which include a pronounced opposition surge and linear part, were constructed. For each satellite, the geometric albedo was found in different spectral bands taking into account the brightness opposition effect, and its spectral dependence was studied. It has been shown that the reflectance of the satellites linearly depends on the wavelength at different phase angles, but has different spectral gradients. The parameters of the phase functions of brightness, including the amplitude and the angular width of the brightness opposition surge, the phase coefficient, and the phase angle at which the nonlinear increase in brightness starts, were determined and their dependences on wavelength and geometric albedo were analyzed. Our investigations show that, in their optical properties, the satellites Miranda and Ariel, Titania and Oberon, and Umbriel present three types of surfaces. The observed parameters of the brightness opposition effect for the Uranian satellites, some ice satellites of Jupiter and Saturn, and the E-and S-type asteroids are analyzed and compared within the framework of the coherent backscattering and mutual shadowing mechanisms. 相似文献
5.
G. Giuricin F. Mardirossian M. Mezzetti F. Predolin 《Astrophysics and Space Science》1980,71(2):411-413
Using Wood's (1972) model we have re-analyzed the photoelectric light curve of the eclipsing binary AI Cru, published and unsatisfactorily discussed by Ollongren (1956), in order to obtain reliable photometric elements. Our photometric solution differs considerably from Ollongren's (1956). For our photometric mass ratio,q=0.8, both components, though detached from their Roche lobes, are fairly close to a contact configuration.AI Cru, composed of a brighter and larger B5 primary and a fainter and smaller (around B9.5) secondary, is probably not a normal Main Sequence system, since the ratios of the secondary's mass and radius over the primary's turn out to be larger than expected for main sequence stars of the same spectral types. 相似文献
6.
We present photometric and spectroscopic data on a subset of over 30 oxygen-rich Long Period Variable (LPV) stars which we
have been monitoring between 8/95 & 4/97. With these data, we are attempting to ascertain the relationship of dust formation
to optical period. Our ultimate goal is to determine what conditions lead to dust formation and destruction in these environments,
and whether or not an evolutionary sequence can be inferred for AGB stars also based on their spectra and dust formation.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
7.
B, V andI light curves of the eclipsing binaries HV12634 in the LMV, and HV2208 in the SMC (cf. Westet al., 1992), have been analysed with the aid of optimal curve-fitting techniques. Parameter derivation involves a successive approximations procedure. The results of this are combined with a standard mass:luminosity relation to explore tentative absolute parameters. The combined evidence shows some disparity with standard MS-like models. It also demonstrates some relative insensitivity of photometric analysis, in isolation, to elucidate clear facts on such possibly atypical, remote, hot stars. Auxilliary spectroscopic data are required to resolve remaining ambiguities. 相似文献
8.
9.
N. V. Emelyanov M. V. Andreev A. A. Berezhnoi A. S. Bekhteva S. N. Vashkovyak Yu. I. Velikodskii I. A. Vereshchagina D. L. Gorshanov A. V. Devyatkin I. S. Izmailov A. V. Ivanov T. R. Irsmambetova V. A. Kozlov S. V. Karashevich A. N. Kurenya Ya. V. Naiden K. N. Naumov N. A. Parakhin V. N. Raskhozhev S. A. Selyaev A. V. Sergeev E. N. Sokov M. Yu. Khovrichev E. V. Khrutskaya M. M. Chernikov 《Solar System Research》2011,45(3):264-277
In 2009, in five Russian observatories photometric observations of Jupiter’s Galilean satellites during their mutual occultations and eclipses were carried out. Based on these observations, an original method was used to ascertain astrometric results such as the difference between the coordinates of pairs of satellites. Fifty-three phenomena were successfully observed. A total of 94 light curves of satellites were measured. The error in the coordinates of satellites due to random errors in photometry, calculated on all data obtained, was 0.041″ in right ascension and 0.046″ in declination. The discrepancies between the theory and observations in these coordinates was found to be 0.060″ and 0.057″, respectively. The results were uploaded to the common database for all observations of natural satellites of planets at the Natural Satellites Data Center (NSDC), which is available online at http://www.sai.msu.ru/neb/nss/index.htm. For the first time in the practice of photometric observations of satellites in epochs of mutual occultations and eclipses a new method of observation was tested, which eliminates from astrometric results the major systematic errors caused by an inaccurate account of the background level. The tests were conducted in the Terskol Observatory and the observatory of the Crimean laboratory of the Sternberg State Astronomical Institute of the Moscow State University. The application of the new method showed that the elimination of the background level at these observatories was carried out correctly. 相似文献
10.
The photometric solutions of W UMa-type binary BW Dra have been determined by applying the Wilson and Devinney Code toUBV observations of Rucinski and Kaluzny.It is shown that BW Dra is corresponding to a system with an overcontact configuration and smaller mass ratioq=0.392 andUBV light curves give the converging solutions with non-zero third light.It is proved that the components of BW Dra are older stars (the spectral types are G0 and G3, respectively). They could come into contact later stage of evolution. The photometric solution is similar to the results of Kaluzny and Rucinski. According to the photometric solution and spectroscopic results of Batten and Lu, the absolute parameters are presented too. 相似文献
11.
Stephen R. Kane 《Monthly notices of the Royal Astronomical Society》2007,380(4):1488-1496
Of the known transiting extrasolar planets, a few have been detected through photometric follow-up observations of radial velocity planets. Perhaps the best known of these is the transiting exoplanet HD 209458b. For hot Jupiters (periods less than ∼5 d), the a priori information that 10 per cent of these planets will transit their parent star due to the geometric transit probability leads to an estimate of the expected transit yields from radial velocity surveys. The radial velocity information can be used to construct an effective photometric follow-up strategy which will provide optimal detection of possible transits. Since the planet-harbouring stars are already known in this case, one is only limited by the photometric precision achievable by the chosen telescope/instrument. The radial velocity modelling code presented here automatically produces a transit ephemeris for each planet data set fitted by the program. Since the transit duration is brief compared with the fitted period, we calculate the maximum window for obtaining photometric transit observations after the radial velocity data have been obtained, generalizing for eccentric orbits. We discuss a typically employed survey strategy which may contribute to a possible radial velocity bias against detection of the very hot Jupiters which have dominated the transit discoveries. Finally, we describe how these methods can be applied to current and future radial velocity surveys. 相似文献
12.
We have used photometric images of ten barred galaxies in the B and I bands to infer the geometrical and dynamical parameters of their bars: Their length, (R
bar), their strengths, (S
b), and their corotation radii, (R
CR).These parameters have been obtained studying azimuthal profiles from the B and I band images of the galaxies. We find that R
CR is in all cases slightly larger than R
bar, with mean values close to 1.2 R
bar. We have also found a dependence of the ratio R
CR/R
bar on S
bar.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Using Wood's model we have reanalyzed the light curves of the eclipsing binaries QY Aql, V388 Cyg, and HS Her. For QY Aql and HS Her our photometric solutions substantially confirm previous results, thus respectively supporting ansd-d classification and a main sequence detached view. On the other hand, significantly different photometric elements have been derived for V388 Cyg, which is likely to be an evolved contact binary. 相似文献
14.
Vladas Vansevičius Audrius Bridžius Ramutis Drazdys 《Astrophysics and Space Science》2002,280(1-2):31-39
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
15.
Nikolay Emelyanov 《Planetary and Space Science》2008,56(14):1785-1790
We suggest a new approach and develop an original method for deriving astrometric data from the photometry of mutual occultations and eclipses of planetary satellites. We decide to model not the relative apparent motion of one satellite with respect to another satellite but the deflection of the observed relative motion with respect to the theoretical motion implied by appropriate ephemerides.We have attempted to reduce the results of photometric observations of the Gallilean satellites during their mutual occultations and eclipses in 2002-2003. The data of observation for 319 light curves of 106 mutual events were received from the observers. The reliable 245 light curves were processed with our method. Eighty six apparent relative positions have been obtained.Systematic errors arise inevitably while deriving astrometric data. Most of them are due to factors that are unrelated to the methods for deriving astrometric data. The systematic errors are more likely due to incorrect excluding the effect of background on photometric counts. In the case of mutual occultations, the flux drop is determined to a considerable degree by the ratio of the mean albedos of the two satellites. Some mutual event observations revealed wrong adopted values of the mean albedos. 相似文献
16.
Five well observed recent mutual phenomena (1 occultation, 4 eclipses) of the Galilean satellites have been analysed and four fitting parameters determined for each event.The times of mid-minima are well determined in all cases (generally to within a second or two), but the separation and velocity parameters depend on the penumbral illumination modelling. For this reason, parameters derived from eclipses are somewhat less well determined than from occultations.Taken together with the dependence on the inherent surface reflection properties of the rearward satellite, the results indicate that Asknes et al.'s (1984) suggestion of order 0.01 arcsec accuracies on positional determinations from mutual phenomena data represents rather a lower limit to the real errors in most cases. 相似文献
17.
The evolutionary status of a sample of 31 W UMa-type systems (20 of W, 9 of A, and 2 of A/W sub-class) is examined and discussed on the basis of their positions in the H-R, mass-radius and mass-luminosity diagrams. The absolute elements of these systems have been evaluated by use of their spectroscopic and photometric data as they were found in the literature. Since different analysis methods have been used by the various investigators this gives the opportunity to make different H-R, mass-radius and mass-luminosity diagrams, according to the method used, and compare the results.Moreover, from the spectral type-period diagram of those systems that have spectral types from O to G2 it was found that all of them lie in the evolved region. Finally, the log (L
l/L
s) log (M
l/M
s) diagrams are presented and discussed. 相似文献
18.
We present a software package developed for the automatic 4-D stellar parameterization. The package can be adopted to virtually
any multicolour photometric system. Procedure of simultaneous determination of T
eff, log g, [M/H] and E
B-V is very flexible and can be performed by applying various photometric parameters(magnitudes, colour indices etc.). Any changes
of the photometric systems, weighting schemes or parameterization criteria can be implemented easily.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
This study of the orbital evolution and encounters of distant satellites of planets is aimed at determining their origin. It is also important for understanding the distribution of matter in the early stages of evolution of the Solar System. The mutual encounter of satellites is very weak because of their small sizes and masses. However, at very large time intervals, mutual encounter can be quite close to significantly changing the orbits of satellites. In order to study these factors, we have developed a special method and computer programs. For 107 distant satellites of Jupiter, Saturn, Uranus, and Neptune, motion parameters have been determined using observational data. On the basis of these parameters, a numerical integration of the equations of motion of the satellites has been carried out in time intervals of several thousand years. Using the original method of frequency analysis, we found rather simple analytical functions that correspond to the results of the numerical integration and make it possible to calculate orbital parameters at any time during a long interval. These tools make it possible to conduct extensive studies of changes in the form and relative position in space of the orbits of distant satellites of Jupiter, Saturn, Uranus, and Neptune. Several examples illustrate the possibilities offered by these tools. The computer software in the form of a service ephemeris of satellite orbits over a long interval of time is available via the Internet (http://www.sai.msu.ru/neb/nss/evolu0e.htm) on the website of the State Astronomical Institute of the Moscow State University. 相似文献
20.
Using recently published determinations of the diameters and orbital elements of the uranian satellites and assuming reasonable dissipation functions and rigidities for icy satellites, the eccentricity decay times for the satellites were calculated. For the inner three, decay times are on the order of 107–108 years, making it difficult to understand why these satellites still have their observed eccentricities. The three inner satellites have a near-commensurability in their mean motions that may be able to force their eccentricities at some time in the future, but cannot force them now. Several possible explanations exist: (1) The reported eccentricities are incorrect, and are in fact near-zero. (2) The reported mean motions are incorrect, and an exact commensurability exists. (3) The physical properties that we have assumed for the satellites are grossly in error (e.g., dissipation function Q is in reality very large). (4) The system is evolving very rapidly, perhaps from a previous state of higher eccentricity. Cases 1 and 2 are unlikely when one considers the quality of existing data. Case 3 would be more consistent with non-icy compositions. Cases 2 and 4 would imply some tidal heating of the satellites, particularly Ariel. A new lower bound of ～ 1.7 × 104 on the Q of Uranus is calculated from the mass of Ariel and its proximity to Uranus. 相似文献