323,233 research outputs found
Third body effects in the period changes of two Algol binaries: V342 Aql and TW Lac
No full text32nd International Physics Congress of Turkish-Physical-Society (TPS) -- SEP 06-09, 2016 -- Bodrum, TURKEYThe O - C diagrams of two Algol-type eclipsing binaries V342 Aql and TW Lac have been analyzed with the least-squares method by using all available minima times. The period changes in their O - C diagrams have been discussed with respect to the Light-Time Effect (LITE) that originates from gravitational influence of a third body. New LITE elements, orbital periods and possible minimum masses of third bodies are given.Turkish Phys So
The surprisingly carbon-rich environment of the S-type star W Aql
No full textContext. W Aql is an asymptotic giant branch (AGB) star with an atmospheric elemental abundance ratio C/O approximate to 0.98. It has previously been reported to have circumstellar molecular abundances intermediate between those of M-type and C-type AGB stars, which respectively have C/O < 1 and C/O > 1. This intermediate status is considered typical for S-type stars, although our understanding of the chemical content of their circumstellar envelopes is currently rather limited.Aims. We aim to assess the reported intermediate status of W Aql by analysing the line emission of molecules that have never before been observed towards this star.Methods. We performed observations in the frequency range 159-268 GHz with the SEPIA/B5 and PI230 instruments on the APEX telescope. We made abundance estimates through direct comparison to available spectra towards a number of well-studied AGB stars and based on rotational diagram analysis in the case of one molecule.Results. From a compilation of our abundance estimates and those found in the literature for two M-type (R Dor, IK Tau), two S-type (chi Cyg, W Aql), and two C-type stars (V Aql, IRC +10 216), we conclude that the circumstellar environment of W Aql appears considerably closer to that of a C-type AGB star than to that of an M-type AGB star. In particular, we detect emission from C2H, SiC2, SiN, and HC3N, molecules previously only detected towards the circumstellar environment of C-type stars. This conclusion, based on the chemistry of the gaseous component of the circumstellar environment, is further supported by reports in the literature on the presence of atmospheric molecular bands and spectral features of dust species which are typical for C-type AGB stars. Although our observations mainly trace species in the outer regions of the circumstellar environment, our conclusion matches closely that based on recent chemical equilibrium models for the inner wind of S-type stars: the atmospheric and circumstellar chemistry of S-type stars likely resembles that of C-type AGB stars much more closely than that of M-type AGB stars.Conclusions. Further observational investigation of the gaseous circumstellar chemistry of S-type stars is required to characterise its dependence on the atmospheric C/O. Non-equilibrium chemical models of the circumstellar environment of AGB stars need to address the particular class of S-type stars and the chemical variety that is induced by the range in atmospheric C/O
First results from TOO observations of the Aql X-1 field with INTEGRAL
No full textWe present results of observations of the Aql X-1 field
performed in March-April 2003 with the INTEGRAL observatory. This
TOO (Target Of Opportunity) INTEGRAL
observations was initiated upon receiving an
indication from the ASM/RXTE that the source started an outburst. Thirteen
X-ray sources were detected by the INTEGRAL imagers, JEM-X and IBIS, during
these observations. We present a preliminary spectral and timing analysis for
several bright sources in the field, Aql X-1, X1901+03, 4U1907+097,
XTE J1908+094 and X1908+075. We also detected two X-ray bursts from
Aql X-1 near the end of the general outburst episode
Multisite Observations of delta Scuti Stars 7 Aql and 8 Aql (a New delta Scuti Variable): The Twelfth STEPHI Campaign in 2003
No full textpeer reviewedWe present an analysis of the pulsation behavior of the delta Scuti stars 7 Aql (HD 174532) and 8 Aql (HD 174589), a new variable star, observed in the framework of the STEPHI XII campaign during 2003 June and July; 183 hr of high-precision photometry were acquired by using four-channel photometers at three sites on three continents during 21 days. The light curves and amplitude spectra were obtained following a classical scheme of multichannel photometry. Observations in different filters were also obtained and analyzed. Six and three frequencies have been unambiguously detected above a 99% confidence level in the range 190-300 muHz and 100-145 muHz in 7 Aql and 8 Aql, respectively. A comparison of observed and theoretical frequencies shows that 7 Aql and 8 Aql may oscillate with p-modes of low radial orders, typical among delta Scuti stars. In terms of radial oscillations the range of 8 Aql goes from n=1 to 3, while for 7 Aql the range spans from n=4 to 7. Nonradial oscillations have to be present in both stars as well. The expected range of excited modes according to a nonadiabatic analysis goes from n=1 to 6 in both stars
Analysis of the massive eclipsing binary V1441 Aql
No full textWe present new spectroscopic observations of the early type, double-lined eclipsing binary V1441 Aql. The radial velocities and the available photometric data obtained by ASAS is analysed for deriving the parameters of the components. The components of V1441 Aql are shown to be a B3 IV primary with a mass M-p = 8.02 +/- 0.51 M-circle dot and radius R-p = 7.33 +/- 0.19 R-circle dot and a B9 III secondary with a mass = 1.92 +/- 0.14 M-circle dot and radius R-s = 4.22 +/- 0.11 R-circle dot. Our analyses show that V1441 Aql is a doublecontact system with rapidly rotating components. Based on the position of the components plotted on the theoretical Hertzsprung-Russell diagram, we estimate that the ages of V1441 Aql is about 30 Myr, neglecting the effects of mass exchange between the components. Using the UBVJHK magnitudes and interstellar absorption we estimated the mean distance to the system V1441 Aql as 550 +/- 25 pc. (C) 2014 Elsevier B.V. All rights reserved.TUBITAK National Observatory (TUG)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [11BRTT150-198]; EBILTEM Ege University Research CenterEge University [2013/BIL/018]; Turkish Scientific and Technology CouncilTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112T263]; Italian Minister dell'Istruzione, Universita e Ricerca (MIUR)We thank to TUBITAK National Observatory (TUG) for a partial support in using RTT150 telescope with project number 11BRTT150-198. We thank to EBILTEM Ege University Research Center for a partial support with project number 2013/BIL/018. We also thank to the staff of the Bakirlitepe observing station for their warm hospitality. This study is supported by Turkish Scientific and Technology Council under project number 112T263. This work was partially supported by the Italian Minister dell'Istruzione, Universita e Ricerca (MIUR). The following internet-based resources were used in research for this paper: the NASA Astrophysics Data System; the SIMBAD database operated at CDS, Strasbourg, France; and the ar chi iv scientific paper preprint service operated by Cornell University
Elemental abundance analyses with DAO spectrograms. XXXVIII. The SB2 stars HR 104 (A2 V) and \u3b8 Aql (B9.5 III)
No full textThe study of the elemental abundances of double-lined spectroscopic binaries should provide information on the chemical differentiation of a once uniform prestellar nebula. To determine the effective temperatures and surface gravities of the primary and secondary stellar components of HR 104 and \u3b8 Aql, we used parameters derived from their orbital analyses and the requirement of equal abundances derived from Fe I and Fe II lines. For constraints we had optical region spectrophotometry for \u3b8 Aql and the large equivalent width ratios for the many spectral metal lines which were produced in both stellar atmospheres for HR 104. Since the primary stars were much brighter than the secondary stars, the abundances are considerably better determined for the primary stars. For HR 104 A we found T<inf>eff</inf> = 9875 K, log g = 4:26, and \u3be = 1:7 km s 121; for HR 104 B T<inf>eff</inf> = 7200 K, log g = 4:26, and \u3be = 0:6 km s 121; for \u3b8 Aql A T<inf>eff</inf> = 10400 K, log = 3:63, and \u3be = 0:3 km s 121; and for \u3b8 Aql B Teff = 10250 K, log = 4:20, and \u3be = 1:9 km s 121. The abundances of HR 104 A, HR 104 B, and \u3b8 Aql A are best described as the solar pattern. Those of \u3b8 Aql B suggest a weak nonmagnetic CP star pattern. While there is no trace of the Hg II 3984 line for \u3b8 Aql, the most extreme observed abundance anomalies for the secondary are those of Ca, V, Mn, and Ni. Further study of this hot marginal Am star could provide insights into the origin of the nonsolar chemical abundances.Peer reviewed: YesNRC publication: Ye
Discovery of an old nova shell surrounding the cataclysmic variable V1315 Aql
No full textFollowing our tentative discovery of a faint shell around V1315 Aql reported in Sahman et al., we undertook deep Hα imaging and intermediate-resolution spectroscopy of the shell. We find that the shell has its geometric centre located on V1315 Aql. The mass, spectral features, and density of the shell are consistent with other nova shells, rather than planetary nebulae or supernova remnants. The radial velocity of the shell is consistent with the systemic velocity of V1315 Aql. We believe this evidence strongly suggests that the shell originates from an earlier nova event. This is the first nova shell discovered around a nova-like and supports the theory of nova-induced cycles in mass transfer rates (hibernation theory) first proposed by Shara et al
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql
No full textWe performed high-resolution optical spectroscopy and X-ray observations of the recently identified Mira-type symbiotic star EF Aql. Based on high-resolution optical spectroscopy obtained with the Southern African Large Telescope (SALT), we determine the temperature (∼55 000 K) and the luminosity (∼5.3 L⊙) of the hot component in the system. The heliocentric radial velocities of the emission lines in the spectra reveal possible stratification of the chemical elements.We also estimate the mass-loss rate of the Mira donor star. Our Swift observation did not detect EF Aql in X-rays. The upper limit of the X-ray observations is 10-12 erg cm-2 s-1, whichmeans that EF Aql is consistent with the faintestX-ray systems detected so far. Otherwise we detected it with the UltraViolet and Optical Telescope (UVOT) instrument with an average UVM2 magnitude of 14.05. During the exposure, EF Aql became approximately 0.2 UVM2 magnitudes fainter. The periodogram analysis of the V-band data reveals an improved period of 320.4 ± 0.3 d caused by the pulsations of the Mira-type donor star.Fil: Stoyanov, K. A.. Bulgarian Academy of Sciences; BulgariaFil: Ilkiewicz, K.. Polish Academy of Sciences; PoloniaFil: Luna, Gerardo Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Nacional de Hurlingham; ArgentinaFil: Mikołajewska, J.. Polish Academy of Sciences; PoloniaFil: Mukai, K.. National Aeronautics and Space Administration; Estados Unidos. University of Maryland; Estados UnidosFil: Martí, J.. Universidad de Jaén; EspañaFil: Latev, G.. Bulgarian Academy of Sciences; BulgariaFil: Boeva, S.. Bulgarian Academy of Sciences; BulgariaFil: Zamanov, R. K.. Bulgarian Academy of Sciences; Bulgari
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