共查询到20条相似文献，搜索用时 625 毫秒
1.
A.V. Poghosyan W. Pfau K.P. Tsvetkova M. Mugrauer M.K. Tsvetkov V.V. Hambaryan R. Neuhuser D.G. Kalaglarsky 《Astronomische Nachrichten》2014,335(4):440-447
We present the archive of the wide‐field plate observations obtained at the University Observatory Jena, which is stored at the Astrophysical Institute of the Friedrich Schiller University Jena. The archive contains plates taken in the period February 1963 to December 1982 with the 60/90/180‐cm Schmidt telescope of the university observatory. A computer‐readable version of the plate metadata catalogue (for 1257 plates), the logbooks, as well as the digitized Schmidt plates in low and high resolution are now accessible to the astronomical community.This paper describes the properties of the archive, as well as the processing procedure of all plates in detail. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
The multicolor light curves (UBVRI) of HU Vir have been analyzed to study starspots for epochs 1987 and 1989. The term 'photometric
imaging' has been used for predicting cool surface spots by photometric data. Assuming the number of spots and the area are
about the same for the two hemispheres, the distributive solar analogy is introduced as a tool to constrain free values of
spot parameters into unique values. Therefore, final fitting parameters are claimed unique in a sense that they are independent
of free initial guesses. The light and color variations of HU Vir are better explained without polar spots. Finally, the spots
are found to be ∼ 1600 K cooler than the T∼ 5000 K of this cool subgiant and cover ∼ %13.9 of the total surface at ±8.0 degrees
from the equator for the epoch 1987. The spots at the epoch 1989 are found to be ∼ 2040 K cooler covering ∼ % 12.7 area at
± 27°.7 latitudes. Problems of photometric imaging and possible solutions with distributive solar analogy have been discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
O. Vaduvescu L. Curelaru M. Birlan G. Bocsa L. Serbanescu A. Tudorica J. Berthier 《Astronomische Nachrichten》2009,330(7):698-707
Besides new observations, mining old photographic plates and CCD image archives represents an opportunity to recover and secure newly discovered asteroids, also to improve the orbits of Near Earth Asteroids (NEAs), Potentially Hazardous Asteroids (PHAs) and Virtual Impactors (VIs). These are the main research aims of the EURONEAR network. As stated by the IAU, the vast collection of image archives stored worldwide is still insufficiently explored, and could be mined for known NEAs and other asteroids appearing occasionally in their fields. This data mining could be eased using a server to search and classify findings based on the asteroid class and the discovery date as “precoveries” or “recoveries”. We built PRECOVERY, a public facility which uses the Virtual Observatory SkyBoT webservice of IMCCE to search for all known Solar System objects in a given observation. To datamine an entire archive, PRECOVERY requires the observing log in a standard format and outputs a database listing the sorted encounters of NEAs, PHAs, numbered and un‐numbered asteroids classified as precoveries or recoveries based on the daily updated IAU MPC database. As a first application, we considered an archive including about 13 000 photographic plates exposed between 1930 and 2005 at the Astronomical Observatory in Bucharest, Romania. Firstly, we updated the database, homogenizing dates and pointings to a common format using the JD dating system and J2000 epoch. All the asteroids observed in planned mode were recovered, proving the accuracy of PRECOVERY. Despite the large field of the plates imaging mostly 2.27° × 2.27° fields, no NEA or PHA could be encountered occasionally in the archive due to the small aperture of the 0.38m refractor insufficiently to detect objects fainter than V ∼ 15. PRECOVERY can be applied to other archives, being intended as a public facility offered to the community by the EURONEAR project. This is the first of a series of papers aimed to improve orbits of PHAs and NEAs using precovered data derived from archives of images to be data mined in collaboration with students and amateurs. In the next paper we will search the CFHT Legacy Survey, while data mining of other archives is planned for the near future (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
5.
We have applied the astrometric techniques devised by Murray for analysis of 48-inch Schmidt photographic data to SuperCOSMOS scans of UK Schmidt plates centred on Kapteyn's Selected Area 94 ( α =2h 53m , δ =0°). In this preliminary study, we combine astrometric data from four short-exposure V -band plates, taken in 1987 August (2 plates) and 1993 August (2 plates), with BVRI photometry from sky-limited plate material, to identify stars with proper motions exceeding 0.1 arcsec yr−1 . This paper discusses the completeness of the resulting sample and presents spectroscopy of 30 stars with μ >0.2 arcsec yr−1 . Based on the latter observations and the distribution in the [H V , ( V − I )] reduced proper-motion diagram, we have classified stars in the complete sample as candidate white dwarfs, main-sequence dwarfs and halo subdwarfs, and derived estimates of the disc and halo luminosity functions. 相似文献
6.
S. Nawar 《Astrophysics and Space Science》1998,262(4):477-483
Photoelectric measurements have been carried out at Kottamia Observatory site to study night sky brightness and the atmospheric
extinction at different wavelengths. The results show that the mean extinction coefficients are k = 0.41, k = 0.28< and k
= 0.17 mag/air mass during autumn season. These values are almost the same as that obtained by Mikhail (1979) at the same
site during the same season. Results of night sky brightness at different altitudes above the horizon have been obtained.
Complete scan each five degrees step in azimuth have been done at altitudes 50°, 60° and 70° to complete the previous measurements
given by Nawar et al. (1995). Far from the diffuse galactic light, slight variations in night sky brightness with azimuth
have been detected.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Photoelectric observations of night sky brightness at different zenith distances in blue, yellow and red colours have been
carried out at Abu-Simbel site. Variations in the night sky brightness and (B-V) colour index with time are detected. These
variations have been explained by the change of the galactic latitude of the observed point with time. The deduced results
of night sky brightness have been compared with that obtained before at other sites. It has been found for both blue and yellow
colours, that Abu-Simbel is the darkest site especially for zenith distances equal or greater than 60°. The present values
of night sky brightness and colour have been obtained for the first time at Abu-Simbel site. The average night sky brightness
at the galactic plane is 22.58 mag/arc sec2 for blue and 21.66 mag/arc sec2 for yellow.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
We describe the archive of scans of the astronomical plates obtained in the observations of comet Hale–Bopp. The observations were carried out from August 17, 1996, to April 29, 1997, at the Zeiss-400/2000 astrograph of the Zvenigorod Observatory of the Institute of Astronomy of the Russian Academy of Sciences (INASAN). The archive contains the images that can be used in astrometric, photometric, and astrophysical studies. In some of the plates, the size of the comet reaches 6.3° (23 cm). In many scans, the details of the cometary tail, including individual jets, vortexes, etc., are clearly distinguishable. The archive of the images is available free. 相似文献
9.
We intend to present two approximate analytic solutions of the two-body problem with slowly decreasing mass which are obtained
through the integration of the Hamilton equations.
The law of mass variation used was m = -αn on the first case, and mi = αimin(i); i = 1,2 on the second which gives rise to
a perturbed Keplerian problem dependent on one and two small parameters respectively.
Practical applications are included.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
H.-J. Tucholke 《Astronomische Nachrichten》1994,315(6):419-426
We measured relative proper motions with a typical accuracy of 1.0 milliarcsec/year (mas/a) for 2000 stars in a 1°4 × 1°4 field around the low-latitude globular cluster NGC 6934. Four plates taken with the Bonn double refractor, spanning an epoch difference of 62 years, were digitized completely. Within the tidal radius of the cluster, we find 106 stars with proper motion errors less than 5 mas/a. Membership probalilities are computed taking into account the individual proper motion errors and the radial distances to the cluster centre. We derive the mean relative proper motion of NGC 6934 using stars with high membership probabilities from radial velocities (Smith and Bell 1986) or from their location in the colour-magnitude diagram (Harris and Racine 1973). The relative proper motions of four Hipparcos stars in the field will be used to obtain the absolute proper motion of NGC 6934 once the extragalactically calibrated Hipparcos Output Catalogue is available. 相似文献
11.
Jorda L. Rembor K. Lecacheux J. Colom P. Colas F. Frappa E. Lara L. M. 《Earth, Moon, and Planets》1997,77(3):167-180
We observed comet Hale-Bopp (C/1995 O1) at Pic du Midi Observatory in 1997 from February 2.24 UT to March 31.89 UT with the
1.05-m telescope equipped with a CCD camera and broad- and narrow-band IHW filters. A total of 30000 images were acquired
both during night- and day-time. The images were automatically reduced and all the images obtained within 10 min. were co-added
to give a set of ∼1000 images used during the analysis. We can identify two jets on the images. The position angle of the
brightest jet from February 2.24 UT to March 5.22 UT is measured using an automatic routine which searches for the averaged
position angle of the maximum of brightness at a projected distance of 3200–6100 km from the optocenter. A preliminary model
of nucleus rotation is used to fit the data and retrieve the rotational parameters of the nucleus. The best fit is found for
a source located at a latitude of 64 ± 3°, a sidereal rotation period of 11.35 ± 0.04 h and a right ascension and declination
of the North pole of 275 ± 10° and -57 ± 10°. This preliminary analysis shows no evidence for a precession. Grains with velocities
of 450–600 m s−1 and radii <;∼ 1 μm dominate the optical scattering cross section in the jets.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
M.K. Wallis 《Astrophysics and Space Science》2003,285(2):587-592
It is proposed that genes coding for Aib-polypeptides arose early on in the K/T transition, presumed from the Earth's accretion
of interplanetary (comet) dust. Aib-fungi flourished because of the evolutionary advantage of novel antibiotics. The stress
on Cretaceous biology led directly and indirectly to mass species extinctions, including many dinosaur species, in the epoch
preceding the Chicxulub impact.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
R. A. Knox N. C. Hambly M. R. S. Hawkins & H. T. MacGillivray 《Monthly notices of the Royal Astronomical Society》1998,297(3):839-848
Photographic Schmidt plates are among the most effective tools in wide-field astronomy. One of the principal difficulties of photographic plates when compared to modern detectors is lack of image depth. We present a technique for stacking plates digitized using the SuperCOSMOS microdensitometer, aimed at maximizing the signal-to-noise ratio in faint images. The efficacy of several image combination algorithms is tested by stacking plate frames in the presence of spurious images. We find that an 'average sigma clipping' type pixel rejection in conjunction with our weighting scheme is most effective in delivering a clean, high signal-to-noise ratio stack. The gain in limiting magnitude obtained from stacking is found to be consistent with that expected: Δ M ∼1.5 for a stack of 16 good-quality plates. 相似文献
14.
T. Eisenbeiss C. Ginski M.M. Hohle V.V. Hambaryan R. Neuhuser T.O.B. Schmidt 《Astronomische Nachrichten》2010,331(3):243-249
Since the first optical detection of RX J0720.4–3125 various observations have been performed to determine astrometric and photometric data. We present the first detection of the isolated neutron star in the V Bessel filter to study the spectral energy distribution and derive a new astrometric position. At ESO Paranal we obtained very deep images with FORS 1 (three hours exposure time) of RX J0720.4–3125 in the V Bessel filter in January 2008. We derive the visual magnitude by standard star aperture photometry. Using sophisticated resampling software we correct the images for field distortions. Then we derive an updated position and proper motion value by comparing its position with FORS 1 observations of December 2000. We calculate a visual magnitude of V = 26.81 ± 0.09 mag, which is seven times in excess of what is expected from X‐ray data, but consistent with the extant U, B, and R data. Over about a seven year epoch difference we measured a proper motion of μ = 105.1 ± 7.4 mas yr–1 towards θ = 296.951° ± 0.0063° (NW), consistent with previous data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
On February 8, 1974, Skylab 1 was manoeuvred into a near circular orbit of inclination 50.04° and perigee near 420km. Orbital parameters have been computed at forty-six epochs thereafter using all available observations. Using these orbital elements, supplemented by orbital decay rates derived from NORAD bulletins, 193 values of air density were determined between 23 February, 1974 and 11, August, 1976. Corrected to a fixed height and normalised with respect to exospheric temperature these values reveal the semi-annual variation, exhibiting maxima in March–April and October–November, and minima in January–February and July–August. For 1974–1976 the July minima are more pronounced than the January minima whilst the April and October maxima appear equal. Overall the variation is greater than that indicated by CIRA 1972. 相似文献
16.
Thirty well-exposed photographic plates showing the spectrum of the carbon-dioxide band at 8689 Å in the atmosphere of Venus were obtained during 1968 and 1969. All spectra were obtained at a dispersion of 2 Å/mm for Venus phase angles varying from 10° to 126°. We find rotational temperatures ranging from 236 to 274 K. The average value of the rotational temperature is 246 ± 1 K (one standard deviation); for our 1967 observations, the rotational temperatures ranged from 222 to 248 K, with an average value of 238 ± 4 K. The variation of the equivalent width of the 8689 Å band, with Venus phase angle, was very similar for the two sets of observations (53 plates). The temporal variations, of approximately 30% were comparable with the phase variations over this limited range of phase angle. 相似文献
17.
Vanscheidt R. Bleul H. Manthey E. Jütte M. Pohlen M. Schmidtobreick L. Altmann M. Dieball A. Geffert M. Sanner J. Notni P. Schmoll J. 《Earth, Moon, and Planets》1998,81(3):223-231
Extensive widefield CCD direct imaging of C/1995 O1 (Hale-Bopp) at UBVRI was carried out at Hoher List Observatory with the
1.06 m telescope (field of view 20′ × 20′) and at Potsdam Observatory with the 0.70 m telescope (field of view 8′ × 8′). The
corresponding spatial resolution is 850–1000 km pix-1and 525–590 km pix-1, respectively. The data covers 25 nights from February 20 to April 21, 1997.
In order to quantify the various features in the apparent inner coma we introduce a new tomographic method that minimizes
the morphological bias caused by image processing. The tomographic analysis leads to quantitative maps refering to the position
and intensity of the dust ejections for each image frame. Variability and periodicity within the inner coma can be thoroughly
deduced due to various sets of consecutive nights in the observation period mentioned above. The results are compared with
applications of adaptive Laplace filtering.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
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20.
Voelzke Marcos Rincon Schlosser Wolfgang Schmidt-Kaler Theodor 《Astrophysics and Space Science》1997,250(1):35-51
Photographic and photoelectric observations of comet P/Halley's ion gas coma from CO+ at 4250 ? were part of the Bochum Halley Monitoring Program, conducted from 1986 February 17, to April 17 at the European
Southern Observatory on La Silla (Chile).
In this spectral range it is possible to watch the continuous formation, motion and expansion of plasma structures.
To observe the morphology of these structures 32CO+ photos (glass plates) from P/Halley's comet have been analysed. They have a field of view of 28°.6× 28°.6 and were obtained
from 1986 March 29, to April 17 with exposure times between 20 and120 minutes. All photos were digitized with a PDS 2020 GM
(Photometric Data System) microdensitometer at the Astronomisches Institut derWestf?lischen Wilhelms-Universit?t in Münster
(one pixel= 25 μm × 25 μm ≈ 46′.88×46′.88). After digitization the data were reduced to relative intensities, and the part
with proper calibrations were also converted to absolute intensities, expressed in terms of column densities using the image
data systems MIDAS (Munich Image Data Analysis System; ESO – Image Processing Group, 1988) and IHAP (Image Handling And Processing;
Middleburg, 1983).
With the help of the Stellingwerf-Theta-Minimum-Method (Stellingwerf, 1978) a period of (2.22 ± 0.09) days results from analysis
of structures in the plasma-coma by subtracting subsequent images. This method is also compared with the Fourier method. There
may be a second cycle with a period of about 3.6 days. The idea behind subtracting subsequent images is that rotation effects
are only 10% phenomena on gas distribution. Difference images are than used to suppress the static component of the gas cloud.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献