On the line shift and oscillator strength of Xe II lines in the spectra of HnMn stars

Aims. The ultimate goal that has motivated this work is to achieve realistic oscillator strength (gf) values to find reliable values of stellar abundances. We aim to compare the gf valúes of Xe ii lines found with different theoretical and experimental methods. Methods. We have undertaken calculations using the quasirelativistic and relativistic Hartree-Fock methods. Then we compare these results with those previously obtained from UVES spectra of HgMn stars. Results. 1) Our theoretical gf values are more realistic than those previously obtained for most lines. When we consider only unblended, isolated, relatively noise-free lines, however, our theoretical gf values and Yuce's stellar values differ little from each other. 2) In a discussion of the origin of the previously observed discrepancy between the wavelengths of Xe ii lines deducted from stellar spectra and those published by National Institute of Standards and Technology (NIST), we conclude that stellar wavelengths could be considered the standard wavelengths whenever the densities in stellar atmospheres are smaller than 1 × 1016 part. cm-3.Fil: Di Rocco, Hector Omar. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física Arroyo Seco; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Cruzado, Alicia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Marchiano, Paula Esther. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

On the line shift and oscillator strength of Xe II lines in the spectra of HnMn stars

Aims. The ultimate goal that has motivated this work is to achieve realistic oscillator strength (gf) values to find reliable values of stellar abundances. We aim to compare the gf valúes of Xe ii lines found with different theoretical and experimental methods. Methods. We have undertaken calculations using the quasirelativistic and relativistic Hartree-Fock methods. Then we compare these results with those previously obtained from UVES spectra of HgMn stars. Results. 1) Our theoretical gf values are more realistic than those previously obtained for most lines. When we consider only unblended, isolated, relatively noise-free lines, however, our theoretical gf values and Yuce's stellar values differ little from each other. 2) In a discussion of the origin of the previously observed discrepancy between the wavelengths of Xe ii lines deducted from stellar spectra and those published by National Institute of Standards and Technology (NIST), we conclude that stellar wavelengths could be considered the standard wavelengths whenever the densities in stellar atmospheres are smaller than 1 × 1016 part. cm-3.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Convolution of Ultradistributions, Field Theory, Lorentz Invariance and Resonances

In this work, a general definition of convolution between two arbitrary Ultradistributions of Exponential type (UET) is given. The product of two arbitrary UET is defined via the convolution of its corresponding Fourier Transforms. Some examples of convolution of two UET are given. Expressions for the Fourier Transform of spherically symmetric (in Euclidean space) and Lorentz invariant (in Minkowskian space) UET in term of modified Bessel distributions are obtained (Generalization of Bochner’s theorem). The generalization to UET of dimensional regularization in configuration space is obtained in both, Euclidean and Minkowskian spaces As an application of our formalism, we give a solution to the question of normalization of resonances in Quantum Mechanics. General formulae for convolution of even, spherically symmetric and Lorentz invariant UET are obtained and several examples of application are given.Facultad de Ciencias Exacta

On the line shift and oscillator strength of Xe II lines in the spectra of HnMn stars

Aims. The ultimate goal that has motivated this work is to achieve realistic oscillator strength (gf) values to find reliable values of stellar abundances. We aim to compare the gf valúes of Xe ii lines found with different theoretical and experimental methods. Methods. We have undertaken calculations using the quasirelativistic and relativistic Hartree-Fock methods. Then we compare these results with those previously obtained from UVES spectra of HgMn stars. Results. 1) Our theoretical gf values are more realistic than those previously obtained for most lines. When we consider only unblended, isolated, relatively noise-free lines, however, our theoretical gf values and Yuce's stellar values differ little from each other. 2) In a discussion of the origin of the previously observed discrepancy between the wavelengths of Xe ii lines deducted from stellar spectra and those published by National Institute of Standards and Technology (NIST), we conclude that stellar wavelengths could be considered the standard wavelengths whenever the densities in stellar atmospheres are smaller than 1 × 1016 part. cm-3.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

The spectroscopic orbits and physical parameters of GG Carinae

Aims. GG Car is an eclipsing binary classified as a B[e] supergiant star. The aims of our study are to improve the orbital elements of the binary system in order to obtain the actual orbital period of this system. We also compare the spectral energy distribution of the observed fluxes over a wide wavelength range with a model of a circumstellar envelope composed of gas and dust. This fitting allows us to derive the physical parameters of the system and its environment, as well as to obtain an estimation of the distance to GG Car. Methods. We analyzed about 55 optical and near infrared spectrograms taken during 1996-2010. The spectroscopic orbits were obtained by measuring the radial velocities of the blueshifted absorptions of the He I P-Cygni profiles, which are very representative of the orbital motion of both stars. On the other hand, we modeled the spectral energy distribution of GG Car, proposing a simple model of a spherical envelope consisting of a layer close to the central star composed of ionized gas and other outermost layers composed of dust. Its effect on the spectral energy distribution considering a central B-type star is presented. Comparing the model with the observed continuum energy distribution of GG Car, we can derive fundamental parameters of the system, as well as global physical properties of the gas and dust envelope. It is also possible to estimate the distance taking the spectral regions into account where the theoretical data fit the observational data very well and using the set of parameters obtained and the value of the observed flux for different wavelengths. Results. For the first time, we have determined the orbits for both components of the binary through a detailed study of the He I lines, at λλ4471, 5875, 6678, and 7065 Å, thereby obtaining an orbital period of 31.033 days. An eccentric orbit with e = 0.28 and a mass ratio q = 2.2 ± 0.9 were calculated. Comparing the model with the observed continuum energy distribution of GG Car, we obtain T eff = 23 000 K and log g = 3. The central star is surrounded by a spherical envelope consisting of a layer of 3.5 stellar radii composed of ionized gas and other outermost dust layers with E B-V = 0.39. These calculations are not strongly modified if we consider two similar B-type stars instead of a central star, provided our model suggests that the second star might contribute less than 10% of the primary flux. The calculated effective temperature is consistent with an spectral type B0-B2 and a distance to the object of 5 ± 1 kpc was determined.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

The spectroscopic orbits and physical parameters of GG car

GG Car is a peculiar B type star with emission lines classified as a B[e] supergiant star. In this work we present a spectral analysis of this system based on spectra obtained at Casleo. We fit the spectral energy distribution adopting a model for the gas and dust circumstellar components and thus we obtain the physical parameters of the star and its environment.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Pseudomonas Aeruginosa Pilin Glycosylation: The Role of the Pilin Glycan in Pilus Solubility, Function, and Assembly Blank

Pseudomonas aeruginosa strains producing group I type IVa pili comprise over 50% of the clinical isolate population. The pilus lateral surface of these strains is characterized by the attachment of an O-antigen repeating unit to each pilin monomer. O-antigen (glycan) structural analysis provided information on two possible characteristics, charge and size. Solubility experiments of fully, partially, and non-glycosylated P. aeruginosa 1244 pili showed that a full length glycan was required for maximum pilus solubility. Reduced solubility suggested an increased pilus surface hydrophobicity which was supported by protein modeling. While having no effect on the wild type strain, ionic strengths found at many host infection sites inhibited surface and subsurface twitching motility of strain 1244G7, an isogenic mutant unable to glycosylate pilin. This effect was reversed by mutant complementation. A PCR method for assigning R-type (glycan) was developed and conducted for 206 clinical isolates. It was expected that the R-types would be evenly distributed across all isolates, but there was a significant prevalence for the R5 type which encodes the O6 serotype. Verification of the R5 strains was conducted with O6 specific antibodies confirming the genetic classification of these isolates. Results suggest that the increased prevalence of the R5-type as the pilin glycan could potentially lead to its use in a multi-component vaccine or therapeutic for P. aeruginosa infections. Clinical isolates were screened for group I pilin producing strains. Unexpectedly, strains producing non-glycosylated group I pilin were found, prompting the characterization of this altered phenotype. Sequencing and complementation results indicated that non-glycosylation was caused by defects in the main components of glycosylation: pilA, pilO, and the O-antigen biosynthesis pathway. Only one co-phenotype was found among these strains, reduced piliation. Additional characterization of the cause for reduced piliation showed that the presence of non-glycosylated pilin alone was enough to reduce surface pili in these mutant clinical isolates. A pilO knockout was engineered which also showed a loss of glycosylation and a marked reduction in piliation. Providing this mutant with a functional pilO complemented both phenotypes. Overall, these results show that the presence of glycan is important for pilus function, solubility and piliation

The spectroscopic orbits and physical parameters of GG Carinae

Aims. GG Car is an eclipsing binary classified as a B[e] supergiant star. The aims of our study are to improve the orbital elements of the binary system in order to obtain the actual orbital period of this system. We also compare the spectral energy distribution of the observed fluxes over a wide wavelength range with a model of a circumstellar envelope composed of gas and dust. This fitting allows us to derive the physical parameters of the system and its environment, as well as to obtain an estimation of the distance to GG Car. Methods. We analyzed about 55 optical and near infrared spectrograms taken during 1996-2010. The spectroscopic orbits were obtained by measuring the radial velocities of the blueshifted absorptions of the He I P-Cygni profiles, which are very representative of the orbital motion of both stars. On the other hand, we modeled the spectral energy distribution of GG Car, proposing a simple model of a spherical envelope consisting of a layer close to the central star composed of ionized gas and other outermost layers composed of dust. Its effect on the spectral energy distribution considering a central B-type star is presented. Comparing the model with the observed continuum energy distribution of GG Car, we can derive fundamental parameters of the system, as well as global physical properties of the gas and dust envelope. It is also possible to estimate the distance taking the spectral regions into account where the theoretical data fit the observational data very well and using the set of parameters obtained and the value of the observed flux for different wavelengths. Results. For the first time, we have determined the orbits for both components of the binary through a detailed study of the He I lines, at λλ4471, 5875, 6678, and 7065 Å, thereby obtaining an orbital period of 31.033 days. An eccentric orbit with e = 0.28 and a mass ratio q = 2.2 ± 0.9 were calculated. Comparing the model with the observed continuum energy distribution of GG Car, we obtain T eff = 23 000 K and log g = 3. The central star is surrounded by a spherical envelope consisting of a layer of 3.5 stellar radii composed of ionized gas and other outermost dust layers with E B-V = 0.39. These calculations are not strongly modified if we consider two similar B-type stars instead of a central star, provided our model suggests that the second star might contribute less than 10% of the primary flux. The calculated effective temperature is consistent with an spectral type B0-B2 and a distance to the object of 5 ± 1 kpc was determined.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

A Mini Atlas of H-Band Spectra of Southern Symbiotic Stars

Symbiotic stars are interacting binary systems composed of an evolved star (generally a late-type red giant) and a degenerate or dwarf companion in orbit close enough for mass transfer to occur. Understanding the status of the late-type star is important for developing binary models for the symbiotic systems as it affects the transfer of matter needed to activate the hot component. Infrared observations have been very useful in probing the nature of late-type stars in symbiotic systems. This work presents a set of symbiotic stars observed with SOAR/OSIRIS (R∼3000) in the H-band. We aimed to search for possible molecular circumstellar emission, to characterize the cool companion in these systems, and to confront the new findings with those obtained from the previous K-band classifications. We detected molecular emission from just one object, BI Cru, which displays the second-overtone CO-bands. To fit the observed photospheric CO absorption bands, we used the MARCS atmosphere models. We present our results as a mini atlas of symbiotic stars in the near-infrared region to facilitate the comparison among different observed symbiotic systems.Fil: Marchiano, Paula Esther. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Arias, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Kraus, Michaela. Czech Academy of Sciences; República ChecaFil: Kourniotis, Michalis. Czech Academy of Sciences; República ChecaFil: Torres, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Cidale, Lydia Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Borges Fernandes, Marcelo. Observatorio Nacional de Rio de Janeiro; Brasi

The spectroscopic orbits and physical parameters of GG car

GG Car is a peculiar B type star with emission lines classified as a B[e] supergiant star. In this work we present a spectral analysis of this system based on spectra obtained at Casleo. We fit the spectral energy distribution adopting a model for the gas and dust circumstellar components and thus we obtain the physical parameters of the star and its environment.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat