From the analysis of the 13-color photometry and spectroscopy of
HD 184279 (V 1294 Aql), we have found that for the last 10 years, this atar presents a pseudo period of 5.0 years both in light and radial velocity. There is a phase difference of 0.148 P (8.9 months) between the maximum of light and the minimum of radial velocity. The magnitude of the star changes by 0.4 mag. and the radial velocity shows a range ef 185 km/sec. A comparison with theoretical models give ua an Teff.<=28, 700 K with log.g<=4.0 in agreement with spectroscopic determinations.
The atar is reaching the maximum of light and some of their shell features are decreasing, a probable indication that the atar may return to a quiesent stage on its evolution, or it will continue the cyclic behaviour that has characterize it for the last 10 years. Its observation in UV and IR wavelenghts should be very important to measure the wind that may be present in the well developed shell surrounding the atar.
The modern generation of electronic detectors, such as the CCD, have made improved photometry possible, especially at magnitudes near photographic plate limits and at wavelengths extending to the near infrared. Vigorous efforts should now be made to extend measurements to longer wavelengths since VandenBerg and Bell (1985) have recently calculated BVRI synthetic isochrones. Consequently, we have embarked on a program of CCD BVRI photometry for determining the ages of globular clusters.
From BVRI CCD frames obtained with the 1.54 Danish telescope at ESO-La Silla we have at this moment completed the reductions of the following 5 globular clusters: NGC 104 (47 Tuc), NGC 2298, NGC 5139 ( 0) Cen), NGC 6121 (M4), and NGC 6362. For these clusters, we have derived ages all close to 17x10^0y. Providing strong evidence that the globular cluster system is coeval, and that the epoch of the galactic contraction was short.
The progress in the investigation of Be stars during the past decade was enabled mainly thanks to high-resolution echelle spectrographs. Such instruments made possible to carry out multi-line studies of line profile variations and to search for correlations between photospheric and circumstellar phenomena. The Heros team was one of the most active in this field during the last decade. Here we summarize the most important achievements reached by the group.
The paper presents a detailed theoretical analysis of geometricoptical f-number and effective f-number of optical systems. There are derived formulas for calculation of effective f-number for imaging of axial and non-axial parts of object. Moreover, there is presented a simple method for measuring a transparency of optical system which is needed for calculation of effective f-number, and a method for measuring aperture’s angle is presented as well which is needed for calculation of geometric-optical f-number of optical system. and V práci je podrobně teoreticky analyzována problematika geometricko-optického clonového čísla a efektivního clonového čísla optické soustavy. Jsou odvozeny vztahy pro výpočet efektivního clonového čísla pro případ zobrazení osových i mimoosových částí předmětu. Dále je ukázán způsob měření propustnosti optické soustavy potřebné k výpočtu efektivního clonového čísla a také způsob měření aperturního úhlu, který je nutný k výpočtu geometricko-optického clonového čísla.
V tomto příspěvku si ukážeme, jak lze proměřování fotometrických charakteristik fotoblesku pomocí světelného čidla systému Vernier využít při výuce fyziky na středních školách., Vít Bednář, Jiří Tesař, Vladimír Vochozka., and Obsahuje bibliografii
Photometric and spectrographic observations of this δ Sct variable are presented in Fig. 1 of this paper. A comparison of photometric data over a period of 17 years indicates a binary nature of this variable. A tentative period of seven years has been derived. Applying relations applicable to this group of stars it has been shown that this variable is a giant star with a radius of about 2.6 Rθ pulsating in its first overtone.