394 research outputs found

    About the chemical composition of delta Scuti - the prototype of the class of pulsating variables

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    We present chemical abundances in the photosphere of őī\delta Scuti -- the prototype of the class of pulsating variables -- determined from the analysis of a spectrum obtained at Terskol observatory 2 meter telescope with resolution R=52,000R=52,000, signal to noise ratio 250. VLT and IUE spectra were used also . Abundance pattern of \dsct consists of 49 chemical elements. The abundances of Be, P, Ge, Nb, Mo, Ru, Er, Tb, Dy, Tm, Yb, Lu, Hf, Ta, Os, Pt, Th were not investigated previously. The lines of third spectra of Pr and Nd also are investigated for the first time. The abundances of heavy elements show the overabundances with respect to the Sun up to 1 dex. The abundance pattern of \dsct is similar to that of Am-Fm stars.Comment: 8 pages, 2 figures, subm. to Proc. of IAU Symp. 22

    The evolutionary status of the UX Orionis star RZ Piscium

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    The star RZ Psc is one of the most enigmatic members of the UX Ori star family. It shows all properties that are typical for these stars (the light variability, high linear polarization in deep minima, the blueing effect) except for one: it lacks any signatures of youth. With the Li I line, as a rough estimate for the stellar age, we show that the "lithium" age of RZ Psc lies between the age of stars in the Pleiades (approximately 70 Myr) and the Orion (approximately 10 Myr) clusters. We also roughly estimated the age of RZ Psc based on the proper motion of the star using the Tycho-2 catalog. We found that the star has escaped from its assumed birthplace near to the Galactic plane about 30-40 Myr ago. We conclude that RZ Psc is a post-UXOr star, and its sporadic eclipses are caused by material from the debris disk

    The structure and kinematics of the the Galaxy thin gaseous disc outside the solar orbit

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    The rotation curve of the Galaxy is generally thought to be flat. However, using radial velocities from interstellar molecular clouds, which is common in rotation curve determination, seems to be incorrect and may lead to incorrectly inferring that the rotation curve is flat indeed. Tests basing on photometric and spectral observations of bright stars may be misleading. The rotation tracers (OB stars) are affected by motions around local gravity centers and pulsation effects seen in such early type objects. To get rid of the latter a lot of observing work must be involved. We introduce a method of studying the kinematics of the thin disc of our Galaxy outside the solar orbit in a way that avoids these problems. We propose a test based on observations of interstellar CaII H and K lines that determines both radial velocities and distances. We implemented the test using stellar spectra of thin disc stars at galactic longitudes of 135{\degr} and 180{\degr}. Using this method, we constructed the rotation curve of the thin disc of the Galaxy. The test leads to the obvious conclusion that the rotation curve of the thin gaseous galactic disk, represented by the CaII lines, is Keplerian outside the solar orbit rather than flat.Comment: 33 pages, 18 figures, accepted for publication in Publications of the Astronomical Society of the Pacific, 2015. February

    The chemical composition of a mild barium star HD202109

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    We present the result of chemical abundances of a mild barium star HD202109 (zeta Cyg) determined from the analysis of spectrum obtained by using a 2-m telescope at the Peak Terskol Observatory and a high-resolution spectrometer with R=80,000, signal to noise ratio >100. We also present the atmospheric parameters of the star determined by using various methods including iron-line abundance analysis. For line identifications, we use whole-range synthetic spectra computed by using the Kurucz database and the latest lists of spectral lines. Among the determined abundances of 51 elements, those of P, S, K, Cu, Zn, Ge, Rb, Sr, Nb, Mo, Ru, Rh, Pd, In, Sm, Gd, Tb, Dy, Er, Tm, Hf, Os, Ir, Pt, Tl, and Pb have not been previously known. Under the assumption that the overabundance pattern of Ba stars is due to wind-accretion process, adding information of more element abundances enables one to show that the heavy element overabundances of HD202109 can be explained with the wind accretion scenario model.Comment: 10 pages, Accepted by Astronomy and Astrophysic

    The different faces of branes in Double Field Theory

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    We show how the Wess-Zumino terms of the different branes in string theory can be embedded within double field theory. Crucial ingredients in our construction are the identification of the correct brane charge tensors {and the use of the} double field theory potentials that arise from dualizing the standard double field theory fields. This leads to a picture where under T-duality the brane does not change its worldvolume directions but where, instead, it shows different faces depending on whether some of the worldvolume and/or transverse directions invade the winding space. As a non-trivial by-product we show how the different Wess-Zumino terms are modified when the brane propagates in a background with a non-zero Romans mass parameter. Furthermore, we show that for non-zero mass parameter the brane creation process, when one brane passes through another brane, gets generalized to brane configurations that involve exotic branes as well
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