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1
Castelli, Fiorella, and Robert L. Kurucz. "Models for Vega." International Astronomical Union Colloquium 138 (1993): 496–501. http://dx.doi.org/10.1017/s0252921100020959.
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AbstractBy using the ATLAS9 code which requires the new opacity data from Kurucz (1992), we derived a new atmospheric model for Vega with parameters Teff=9500 K, log g=3.95, [M/H]=−0.5, ξ=2 kms s−1. The model was fixed by comparing observed and computed energy distributions and Balmer profiles.
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Kurucz, Robert L. "Computation of Opacities for Diatomic Molecules." International Astronomical Union Colloquium 146 (1994): 282–95. http://dx.doi.org/10.1017/s0252921100021400.
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In this section I briefly describe my efforts to improve the atomic and molecular line data. This work is described in more detail in Kurucz (1992a). In subsequent sections I briefly describe three methods for computing opacity and the models and spectra that result from using them.My model calculations in the 1970s used the distribution-function line opacity computed by Kurucz (1979a,b) from the line data of Kurucz & Peytremann (1975). We had computedgfvalues for 1.7 million atomic lines for sequences up through nickel using scaled-Thomas-Fermi-Dirac wavefunctions and eigenvectors determined from least squares Slater parameter fits to the observed energy levels. We also collected all published data ong fvalues and included them in the line list whenever they appeared to be more reliable than the computed data (that work is ongoing, but I am running behind).
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Cugier, H. "Asteroseismology with the new opacity bump at log T ≈ 5.06." Proceedings of the International Astronomical Union 9, S301 (August 2013): 401–2. http://dx.doi.org/10.1017/s1743921313014750.
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AbstractAlthough the κ mechanism of pulsations is known for early-type stars, opacities and the equation of state are still uncertain. Stellar models calculated for the OP data implemented with the new Kurucz opacities at log T < 5.2 were investigated for different chemical compositions of elements. The additional metallic opacity bump at log T ≈ 5.06 that occurs in the Kurucz data changes markedly the oscillation spectra of unstable modes. Basic properties of the new opacity bump and examples of seismic models are shown. B-type stars observed in the Galaxy, LMC and SMC were considered. The problem was studied using Dziembowski's computing codes for linear, non-adiabatic and non-radial oscillations.
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Morel, P., C. Van’t Veer, G. Berthomieu, R. Cayrel, F. Castelli, M. J. Goupil, Y. Lebreton, and J. Provost. "Restoration of the Atmosphere in Solar Models." International Astronomical Union Colloquium 137 (1993): 57–59. http://dx.doi.org/10.1017/s0252921100017449.
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AbstractFrom models of the Sun atmosphere obtained with ATLAS 9 (Kurucz 1992) it appears that the diffusion limit of the transfer equation becomes valid only at depths larger than TR ~ 10. Even with physics as consistent as possible one restores the atmosphere with an accuracy not better than ~ 40%, but with small consequences on solar calibrated models. Despite the eigenmodes have turning points located in the atmosphere, the study of the oscillations reveals differences less than 2μHz when the atmosphere is restored with various assumptions.
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Kurucz, Robert L. "Synthetic Template Spectra." Highlights of Astronomy 10 (1995): 407–10. http://dx.doi.org/10.1017/s1539299600011552.
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I will compute representative spectra for all spectral types for which my model calculations (Kurucz 1992; 1993a; 1994a) are valid. High-resolution zero-rotation fluxes and intensities will be distributed on CD-ROMS together with programs (Kurucz 1993B) for broadening the spectra to arbitrary rotation velocities, macroturbulent velocities, and instrumental profiles, and for transmitting the spectrum through an atmosphere.Since the line data are still not well determined, I actually have to make two calculations, one with only the lines with good wavelengths to preserve wavelength detail, and one with all lines, including predicted, to preserve the energy distribution for photometric calibration. In the first case the spectrum is usable as a radial velocity, abundance, or classification template. Even though the line list is incomplete, its signal-to-noise can be higher than that of observed spectra for cross-correlating.The models are plane parallel, LTE, in hydrostatic equilibrium, and have no triatomic opacities. Therefore, M stars and supergiants cannot be computed realisticly. The abundances available now are scaled-solar and alpha-enhanced scaled-solar. Individual abundances can be changed for the spectrum calculation. My new model atmosphere program, ATLAS 12 (Kurucz 1993c), which does not yet work, will allow arbitrary abundances.I have made test calculations for Arcturus, the sun, Vega, Sirius, and a17000K B. star. Figure 1 shows the effect of resolution on the appearance of the spectrum. Figure 2 shows the effect of rotation. The spectrum for Arcturus is displayed in Kurucz (1994b) with the molecular bands labelled.
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Evans, Nancy Remage, Terry J. Teays, Lyla L. Taylor, John B. Lester, and Robert B. Hindsley. "The Temperature of the Supergiant α Per." International Astronomical Union Colloquium 155 (1995): 393–94. http://dx.doi.org/10.1017/s0252921100037660.
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AbstractWe compare observed fluxes from the ultraviolet (IUE) through J and K with recent Kurucz model atmospheres to determine a temperature for the F5 lb supergiant α Per. The two most important advances in this study as compared with previous work are the use of well calibrated ultraviolet fluxes and the use of models with an appropriate microturbulence.
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Gulati, R. K., and M. Chavez. "Synthesis of Lick Spectral Indices With Overshooting and No-Overshooting Model Atmospheres." Symposium - International Astronomical Union 192 (1999): 356–62. http://dx.doi.org/10.1017/s007418090020435x.
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Using Lester's version of the Kurucz codes, we have computed a set of models with and without “approximate overshooting”. Based on the new models, we have synthesized the spectra in the wavelength range 4800–5400 Å in order to investigate the role of overshooting and no-overshooting models on the Lick indices. Preliminary results show that the differences between the indices are significant in the case of Hβ and Mgb. We need to investigate further the importance of this convection parameter, by comparing model spectra with observed spectra.
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Peters, Geraldine J., and Ronald S. Polidan. "A New Analysis of the Abundance Standards ι Herculis and τ Scorpii." Symposium - International Astronomical Union 111 (1985): 417–21. http://dx.doi.org/10.1017/s0074180900079110.
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Recent continuum and line data in the far ultraviolet for ι Her (B3IV) and τ Sco (BOV) have been combined with published observations in the near uv and visible spectral regions and interpreted with the aid of the Kurucz (1979) line-blanketed model atmospheres. For ι Her and τ Sco, respectively, interpolated models of (Teff/log g) 17500±500K/3.75±0.15, and 31500±1500K/4.3±0.2 fit the observed continua from 900–6500Å and the profiles of Hγ and Hδ. Adopting these models, solar abundances are suggested for both stars.
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Meléndez, J., L. Casagrande, I. Ramírez, and M. Asplund. "Precise Li abundances in metal-poor stars: depletion in the Spite plateau." Proceedings of the International Astronomical Union 5, S265 (August 2009): 71–72. http://dx.doi.org/10.1017/s1743921310000220.
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AbstractWe present Li abundances for 73 stars in the metallicity range −3.5 < [Fe/H] < −1.0 using improved IRFM temperatures (Casagrande et al. 2009) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality equivalent widths (σEW ~ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 2.72) from standard BBN.
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Moya, A., R. Garrido, and M. A. Dupret. "Nonadiabatic observables in main sequence δ Scuti stars." International Astronomical Union Colloquium 193 (2004): 271–74. http://dx.doi.org/10.1017/s0252921100010770.
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AbstractUsing a theoretical nonadiabatic pulsation model, phase differences and amplitude ratios between the relative effective temperature variation and the relative radial displacement have been calculated. These quantities, when compared with photometric observations in different colours, provide an efficient instrument for mode identification, the first step to understand the internal structure of the stars. The theoretical results presented in this paper show a dependence for δ Scuti stars on the mixing length parameter α used to treat the convection using the standard Mixing Length Theory. The nonadiabatic pulsational code developed here includes the pulsation-atmosphere interaction as described by Dupret et al. (2002). The equilibrium models are provided by the CESAM evolutionary code, where a complete reconstruction of non-grey atmospheres (Kurucz models) is included.
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Meléndez, Jorge, Luca Casagrande, Iván Ramírez, Martin Asplund, and William J. Schuster. "Observational signatures for depletion in the Spite plateau: solving the cosmological Li discrepancy?" Proceedings of the International Astronomical Union 5, S268 (November 2009): 211–14. http://dx.doi.org/10.1017/s174392131000414x.
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AbstractWe present Li abundances for 73 stars in the metallicity range −3.5 < [Fe/H] < −1.0 using improved IRFM temperatures (Casagrande et al. 2010) with precise E(B-V) values obtained mostly from interstellar NaI D lines, and high-quality equivalent widths (σEW ~ 3%). At all metallicities we uncover a fine-structure in the Li abundances of Spite plateau stars, which we trace to Li depletion that depends on both metallicity and mass. Models including atomic diffusion and turbulent mixing seem to reproduce the observed Li depletion assuming a primordial Li abundance ALi = 2.64 dex (MARCS models) or 2.72 (Kurucz overshooting models), in good agreement with current predictions (ALi = 2.72) from standard BBN. We are currently expanding our sample to have a better coverage of different evolutionary stages at the high and low metallicity ends, in order to verify our findings.
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Castelli, F., P. Gouttebroze, J. Beckman, L. Crivellari, and B. Foing. "A Method for Calibrating, in Absolute Flux Units, Ca II H Profiles of Late Type Stars Observed at ESO." Symposium - International Astronomical Union 132 (1988): 153–61. http://dx.doi.org/10.1017/s0074180900034951.
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In this paper we have applied to the Sun a method for calibrating, in absolute flux units, Ca II H profiles of late-type stars. After comparing, in the region 3948-3882 A, an LTE synthetic spectrum with the data of the solar flux Atlas by Kurucz et al. (1984), we have defined the wavelength ranges where observations agree with computations, based on specific radiative equilibrium models and collisional broadening parameters. By fitting in these regions the spectrum of the moon observed at ESO with the corresponding synthetic spectrum, we derived a calibration factor that enables us to calibrate, in absolute flux units, the whole observed range.
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Buser, Roland, and Robert L. Kurucz. "Line-Blanketing in Theoretical Model Atmospheres for F, G, and K-Type Stars." Symposium - International Astronomical Union 132 (1988): 531–36. http://dx.doi.org/10.1017/s0074180900035622.
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We have computed improved flux distributions from Gustafsson et al.'s extensive grids of theoretical model atmospheres for late-type (F-K) giant and dwarf stars. In order to enhance the realism of the computed fluxes throughout the optical and the ultraviolet wavelength ranges, the massive list of atomic opacity sources used for the hotter Kurucz models was also employed in calculating the cooler spectra. For both the giant and the dwarf models, the resulting synthetic UBVRI photometry provides excellent matches to the spectroscopic calibrations of the observed metallicity and temperature scales based on the ultraviolet excesses, δ (U-B), and the BVRI colors, respectively. We conclude that atomic line-blanketing due to known, rather than “missing”, opacity sources accounts for the largest fraction of the systematic UV discrepancy existing between observations and earlier model calculations.
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Gimenez, A., and A. Claret. "A Study of the Irradiation of Secondaries of Algol Binaries." International Astronomical Union Colloquium 107 (1989): 343. http://dx.doi.org/10.1017/s025292110008800x.
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In order to investigate the effects of irradiation on the spectra of the cooler components of Algol binaries, a modified version of the Upsalla Model Atmosphere code (U.M.A.) has been used. The upper boundary condition was changed to take into account the external radiation field and an automatic procedure to prevent numerical oscillations was introduced. In order to simulate the external flux from the hot component we have used the Kurucz grid interpolated for the wavelenghts adopted in U.M.A. code. Since secondary stars of Algoltype binaries normally have deep convective layers, we impose the condition that the entropy of these zones must be the same in the irradiated and in the non-irradiated models.
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Lorenzo-Gutiérrez, A., E. J. Alfaro, J. Maíz Apellániz, R. H. Barbá, A. Marín-Franch, A. Ederoclite, D. Cristóbal-Hornillos, et al. "Deriving stellar parameters from GALANTE photometry: bias and precision." Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 9, 2020): 3342–57. http://dx.doi.org/10.1093/mnras/staa892.
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ABSTRACT In this paper, we analyse how to extract the physical properties from the GALANTE photometry of a stellar sample. We propose a direct comparison between the observational colours (photometric bands normalized to the 515 nm central wavelength) and the synthetic colours derived from different stellar libraries. We use the reduced χ2 as the figure of merit for selecting the best fitting between both colour sets. The synthetic colours of the Next Generation Spectral Library (NGSL) provide a valuable sample for testing the uncertainty and precision of the stellar parameters derived from observational data. Reddening, as an extrinsic stellar physical parameter becomes a crucial variable for accounting for the errors and bias in the derived estimates: the higher the reddenings, the larger the errors and uncertainties in the derived parameters. NGSL colours also enable us to compare different theoretical stellar libraries for the same set of physical parameters, where we see how different catalogues of models can provide very different solutions in a, sometimes, non-linear way. This peculiar behaviour makes us to be cautious with the derived physical parameters obtained from GALANTE photometry without previous detailed knowledge of the theoretical libraries used to this end. In addition, we carry out the experiment of deriving physical stellar parameters from some theoretical libraries, using some other libraries as observational data. In particular, we use the Kurucz and Coelho libraries, as input observational data, to derive stellar parameters from Coelho + TLUSTY and Kurucz + TLUSTY stellar libraries, respectively, for different photometric errors and colour excesses.
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Barcza, S. "Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models - I. Theory and practical implementation." Monthly Notices of the Royal Astronomical Society 406, no. 1 (May 5, 2010): 486–92. http://dx.doi.org/10.1111/j.1365-2966.2010.16676.x.
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Demarque, P., B. Chaboyer, D. B. Guenther, and M. H. Pinsonneault. "Helioseismology, solar evolution and other physics." Highlights of Astronomy 10 (1995): 332–34. http://dx.doi.org/10.1017/s1539299600011424.
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The last few years have seen rapid progress in solar interior modeling, and standard solar models (SSM) now predict a p-mode oscillation spectrum which agrees, within the estimated uncertainties in the physical input, with the observed oscillation spectrum of the Sun (Guenther et al., 1992a, 1992b; Guzik & Cox, 1993). This is the result of a number of improvements in the input physics, most notably the advances in opacities for the solar interior (Rogers & Iglesias, 1994) and the low temperature regions of the Sun (Kurucz, 1991). The agreement between the observed solar p-mode frequencies and the frequencies predicted by the SSM is not yet perfect, however, and understanding these discrepancies has become a focus of our research.
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Kurucz, Robert L. "A new opacity-sampling model atmosphere program for arbitrary abundances." Symposium - International Astronomical Union 176 (1996): 523–26. http://dx.doi.org/10.1017/s0074180900083546.
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I have developed a new opacity-sampling version of my model atmosphere program called ATLAS12. It recognizes more than 1000 atomic and molecular species, each in up to 10 isotopic forms. It can treat all ions of the elements up through Zn and the first 5 ions of heavier elements up through Es. The elemental and isotopic abundances are treated as variables with depth. At present ATLAS12 reads atomic line data from Kurucz CD-ROM 1 and diatomic molecular data from Kurucz CD-ROM 15. For each line the wavelength, identification, lower energy level, gf, radiative, Stark, and van der Waals damping constants are packed into 16 bytes. At each wavelength point in a frequency integration the Voigt profiles of all the significant nearby lines are computed and summed. The H, He, and auto-ionizing lines are treated with the appropriate profile functions.The fluxes predicted by ATLAS12 are not accurate in intermediate or narrow bandpass intervals because the sample size is too small. A special stripped version of the spectrum synthesis program SYNTHE is used to generate the surface flux for the converged model using the line data on CD-ROMs 1 and 15. That high resolution spectrum can be used directly or can be instrumentally broadened to compare to low resolution observations.ATLAS12 can be used to produce improved models for Am and Ap stars. It should be very useful for investigating diffusion effects in atmospheres. It can be used to model exciting stars for H II regions with abundances consistent with those of the H II region. These programs and line files will be distributed on CD-ROMs.
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Vince, Oliver, and Istvan Vince. "Determination of metallicity of the HR7914 solar-like star." Serbian Astronomical Journal, no. 167 (2003): 69–74. http://dx.doi.org/10.2298/saj0367069v.
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By using the Blackwell program package by R.O. Gray, the metallicity of the HR7914 solar-like star was determined. The program package utilizes measured equivalent widths of several chosen neutral iron spectral lines from the observed spectra, appropriate atomic and spectral line parameters and adequate Kurucz?s stellar atmosphere models. The method is based on determination of the minimum dispersion of the iron abundance versus microturbulent velocity functions for the selected neutral iron spectral lines. The spectra were observed at National Astronomical Observatory Rozhen (NAO Rozhen), Bulgaria, using the 2m-telescope and Coude spectrograph. They were reduced with the IRAF program package. The measurement of the spectral line parameters was done with the SPE program package. The metallicity of the HR7914 solar-like star was determined to be 0.02.
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Antonello, E., and S. Cermiti. "Amplitude of RR Lyrae Star Light Curves: Comparison between Observations and One—Zone Model Predictions." International Astronomical Union Colloquium 139 (1993): 339. http://dx.doi.org/10.1017/s0252921100117798.
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Stellingwerf's one–zone model is a simple and useful tool for reproducing the main observed pulsational characteristics of RR Lyrae and high amplitude δScuti stars, in particular their light and color curves (Stellingwerf et al., 1987, Ap.J.313, L75; Antonello, 1990, Astr. Ap.230, 127). In the present poster we show in better detail a comparison of the observed amplitudes of the light curve at various wavelengths with those predicted by the one–zone model; a preliminary result on this subject was reported in the short note by Grieco and Antonello (1990, in Confrontation between Stellar Pulsation and Evolution p. 101). As in the previous applications, here we use the published grids of atmospheric models (Kurucz, 1979, Ap.J.Suppl. 40, 1) and we do not consider possible shock effects.
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Cacciari, C., G. Clementini, and L. Prevot. "The Absolute Luminosity of RR Lyrae Variables." Symposium - International Astronomical Union 126 (1988): 587–88. http://dx.doi.org/10.1017/s0074180900043205.
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We have taken UBVRI photoelectric photometry and CORAVEL radial velocities for 6 field RR Lyraes, i.e. SW And, YZ Cap, SW Dra, SS For, RV Phe and V440 Sgr, with the purpose of applying the Baade-Wesselink (B-W) method and determining their absolute magnitudes. The present improvements with respect to previous applications of the method are: a) the use of the (V-I) color, which shows the smallest sensitivity to gravity and metal abundance in the color-visual surface brightness plane. b) the use of a new grid of model atmospheres by Buser and Kurucz (1986), which include an improved treatment of opacity and convection. They provide a complete set of models for the relevant values of effective temperatures, gravities and metal abundances, thus avoiding the need of inaccurate interpolations or extrapolations.
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Barcza, S., and J. M. Benkő. "Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models - II. Adaptation to double-mode stars." Monthly Notices of the Royal Astronomical Society 419, no. 4 (November 24, 2011): 2774–82. http://dx.doi.org/10.1111/j.1365-2966.2011.19920.x.
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Rossi, Silvia, Roberto Ortiz, Ronald Wilhelm, Roberto Costa, and Timothy C. Beers. "A spectroscopic survey of FHB stars near the south galactic pole." Proceedings of the International Astronomical Union 5, S262 (August 2009): 422–23. http://dx.doi.org/10.1017/s1743921310003522.
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AbstractWe present the results of a medium-resolution spectroscopic survey of 43 field horizontal-branch (FHB) candidates carried out near the south galactic pole, selected from the original list of FHB candidates compiled by Beers et al. (2007). The observation list includes only stars classified as “high-probability” candidates, according to their 2MASS infrared colours. Atmospheric parameters of some stars have been obtained by comparing some spectral features with theoretical models provided by Kurucz (1993). A comparison between the grid of model atmospheres with some parameters of the Hδ line allowed the determination of log g, whilst [Fe/H] was estimated by the equivalent widths of the MgII 4481 and Caii lines. About 77% of the sample have been classified as FHB stars, 10% as subdwarfs, whilst the remaining 13% are probably main-sequence A-type stars far from the Galactic plane.
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Mazzitelli, Italo, and Francesca D’Antona. "Main Sequence Structures Including The Overadiabatic CM Convection Model." International Astronomical Union Colloquium 137 (1993): 457–60. http://dx.doi.org/10.1017/s0252921100018248.
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AbstractWe computed the main sequence structure of masses from 2 to 0.7 M⊙ for two choices of helium (Y) and metal (Z) mass fractions. Models are given for solar composition (Y=0.285, Z=0.018) and for a composition appropriate to a younger population I (Y=0.32, Z=0.03). We took particular care both in the choice of the most recent opacities presently available and in the treatment of the input physics and numerics (see also D’Antona et al, 1992).Opacities from Rogers and Iglesias (1992) were adopted where available, complemented with those by Kurucz (1991) at T≤10000 K and, elsewhere, by the Los Alamos opacities (Huebner et al. 1977). The equation of state by Mihalas et al. (1988) was used at ρ ≤ 0.01, and elsewhere the relation P = P(ρ,T) was taken from Magni and Mazzitelli (1979), while the adiabatic gradient was obtained from a Saha type e.o.s..
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Cohen, Martin, R. G. Walker, M. J. Barlow, J. R. Deacon, F. C. Witteborn, D. F. Carbon, and G. C. Augason. "Absolute Spectrally Continuous Stellar Irradiance Calibration in the Infrared." International Astronomical Union Colloquium 136 (1993): 59–65. http://dx.doi.org/10.1017/s0252921100007387.
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AbstractWe present first efforts to establish a network of absolutely calibrated continuous infrared spectra of standard stars across the 1-35μm range in order to calibrate arbitrary broad and narrow passbands and low-resolution spectrometers from ground-based, airborne, balloon, and satellite-borne sensors. The value to photometry of such calibrated continuous spectra is that one can integrate arbitrary filters over the spectra and derive the stellar in-band flux, monochromatic flux density, and hence the magnitude, for any site. This work is based on new models of Sirius and Vega by Kurucz which were calculated by him, for the first time, with realistic stellar metallicities and a customized finely-gridded infrared wavelength scale. We have absolutely calibrated these two spectra and have calculated monochromatic flux densities for both stars, and isophotal wavelengths, for a number of infrared filters. Preliminarily, the current IRAS point source flux calibration is too high by 2, 6, 3, and 12% at 12, 25, 60, and 100μm, respectively.
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Gerbaldi, M., J. Zorec, F. Castelli, and R. Faraggiana. "Parameters Teff and L/L⊙ for a Group of λ Bootis Candidate Stars and their Evolutionary Status." International Astronomical Union Colloquium 138 (1993): 413–17. http://dx.doi.org/10.1017/s0252921100020820.
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AbstractThe Teff value, according to the definition of this parameter, is computed with the procedure described; the observations are then compared with the flux distribution from Kurucz’ LTE blanketed models for various values of the metallicity parameter [Z/H].Then we derive the bolometric luminosity L/L⊙ by combining the stellar bolometric flux with the values of the trigonometric parallaxes and of the colour excess found in the literature. These luminosities are then plotted on evolutionary sequences; from the position of some λ Boo stars (ρ Vir and π1 Ori), we argue that their evolutionary stage, if interpreted as that of stars having left the main sequence, is too late to keep the λ Boo abundance anomalies.These same λ Boo stars, plotted on pre-main sequence evolutionary tracks, would indicate increasing λ Boo character when the stars are approaching the main sequence showing the strongest character in λ Boo and 29 Cyg, the two stars nearest the ZAMS.
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Frinchaboy, P. M., and D. Nielsen. "The WIYN Open Cluster Study Photometric Binary Survey: Initial Findings for NGC 188." Proceedings of the International Astronomical Union 3, S246 (September 2007): 109–10. http://dx.doi.org/10.1017/s174392130801541x.
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AbstractThe WIYN open cluster study (WOCS) has been working to yield precise optical (UBRVI) photometry for all stars in the field of a selection of “prototypical” open clusters. Additionally, WOCS has been using radial velocities to obtain orbit solutions for cluster member hard-binary stars (with period less than 1000 days). Recently, WOCS has been expanded to include the near-infrared (JHKs; 2MASS plus new deep ground-based) and mid-infrared ([3.6], [4.5], [5.8], [8.0] micron) photometry from Spitzer/IRAC observations. This multi-wavelength data (0.3–8.0 microns) allows us to identify binaries photometrically, with mass ratios from 1.0–0.3, across a wide range of primary masses. The spectral energy distribution (SED) fitter by Robitaille et al. (2007) is used to fit the fluxes of 10–12 bands to Kurucz stellar models. This technique allows us to explore the soft binary population for the first time. Using this photometric technique, we find that NGC 188 has a binary fraction of 36-49% and provide a star-by-star comparison to the WOCS radial velocity-based hard binary study.
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Molaro, P. "Lithium Abundance of Halo Stars With New Teff." Highlights of Astronomy 10 (1995): 441–42. http://dx.doi.org/10.1017/s1539299600011655.
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The lithium observed in the atmospheres of unevolved halo stars is believed to be an essentially unproccessed element which reflects the primordial yields. The primordial nature of Li is inferred from the presence of a constant Li abundance for all the halo dwarfs where convection is not effective (Teff ≥ 5600 K). Such an uniformity is taken as evidence for the absence of any stellar depletion during the formation and the long life of the halo stars and also as evidence for the absence of any production mechanism acting either before or at the same time of the formation of the halo population. The existence of a real plateau has been recently questioned by Thorburn (1994), Norris et al (1994) and Deliyannis et al (1993). These results open the possibility of substantial depletion by rotational mixing where a certain degree of dispersion is foreseen for different initial angular momenta of the stars and/or to a significant Galactic Li enrichment within the first few Gyrs.Lithium abundances in a sample (39) of halo dwarfs have been redetermined by using the new Teff derived by Fuhrmann et al (1994) from modelling of the Balmer lines. These Teff are reddening independent, homogeneous and of higher quality than those based on broad band photometry. The sample represent a significant fraction of the presently available Li determinations, and form an unique sample with a good and homogeneous Teff Fuhrmann et al are also able to provide errors in the Teff for individual stars and in most cases they are as good as ± 50 K, which is a factor 2 smaller than the grossly estimated errors for photometric-based Teff. The Li equivalent widths have been taken from the literature and the theoretically derived random errors from Deliyannis et al (1993) or computed following their prescriptions. Abundances have been derived by generating new atmospheric models by using the ATLAS-9 code by Kurucz (1993) with enhanced α-elements and without the overshooting option. If we use the Kurucz 1993 grid which includes overshooting the Li abundance is increased by ≈ 0.08 dex.
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Barcza, S., and J. M. Benkő. "Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models – III. SW And, DH Peg, CU Com and DY Peg." Monthly Notices of the Royal Astronomical Society 442, no. 2 (June 16, 2014): 1863–76. http://dx.doi.org/10.1093/mnras/stu978.
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Alonso, A., S. Arribas, and C. Martínez-Roger. "Colours and Teff of Main Sequence Stars Covering the Galactic Metallicity Range." Symposium - International Astronomical Union 164 (1995): 368. http://dx.doi.org/10.1017/s0074180900108873.
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We present the results of a general programme aimed to study the effects of metallicity on the temperature scale of late main sequence stars (F0-K5). A sample of approximately 400 stars with published UBV(RI) and ubvy – β photometry has been collected from the literature. A three years campaign of observations (Alonso et al. 1994b) was carried out to obtain JHK photometry in order to apply the InfraRed Flux Method (IRFM) to derive effective temperatures. The effect of metallicity on Colour-Colour IR diagrams is discussed. The absolute flux calibration in the IR was revised in Alonso et al. (1994a). The effect of metallicity on the bolometric correction has been studied in Alonso et al. (1995) in order to derive bolometric fluxes. The temperatures have been derived by applying the IRFM using new Kurucz models. Teff = f(Colours, [Fe/H], log(g)) relations are obtained for dwarfs covering the ranges 4000K ≤ Teff ≤ 8000K, 3.5 ≤ logg ≤ 5.00, +0.5 ≤ [Fe/H] ≤ −3.00 which expands considerably the database of previous works. These relations are used to check atmosphere models through the analysis of UBV RIJH Kubvy – β synthetic photometry in combination with the IRFM. The transformation from the theoretical HR diagram into an observational one is analyzed with the new relations. The influence of these points on the study of the evolution of the Galaxy is briefly discussed.
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Al-Wardat, M. "Physical Parameters of the Visually Close Binary Systems Hip70973 and Hip72479." Publications of the Astronomical Society of Australia 29, no. 4 (2012): 523–28. http://dx.doi.org/10.1071/as12004.
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AbstractAtmospheric modelling of the components of the visually close binary systems Hip70973 and Hip72479 was used to estimate the individual physical parameters of their components. The model atmospheres were constructed using a grid of Kurucz solar metalicity blanketed models and used to compute a synthetic spectral energy distribution for each component separately, and hence for the combined system. The total observational spectral energy distributions of the systems were used as a reference for comparison with the synthetic ones. We used the feedback modified parameters and iteration method to obtain the best fit between synthetic and observational spectral energy distributions. The physical parameters of the components of the system Hip70973 were derived as = 5700 ± 75 K, = 5400 ± 75 K, log ga = 4.50 ± 0.05, log gb = 4.50 ± 0.05, Ra = 0.98 ± 0.07 R⊙, Rb = 0.89 ± 0.07 R⊙, and π = 26.25 ± 1.95 mas, with G4 and G9 spectral types, and those of the system Hip72479 as = 5400 ± 50 K, = 5180 ± 50 K, log ga = 4.50 ± 0.05, log gb = 4.60 ± 0.05, Ra = 0.89 ± 0.07 R⊙, Rb = 0.80 ± 0.07 R⊙, and π = 23.59 ± 1.00 mas, with G9 and K1 spectral types.
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Butler, Keith. "Atmospheres and Winds of Hot Stars - Impacts of New Opacity Calculations and Continuing Needs." Highlights of Astronomy 10 (1995): 585–87. http://dx.doi.org/10.1017/s1539299600012168.
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In this paper I review some recent advances in the use of large amounts of atomic data in the modelling of atmospheres and winds of hot stars. The review is highly selective but representative of current developments. A more general overview is to be found in Kudritzki and Hummer (1990) although the field is changing so rapidly that much has happened since then. The paper breaks down into three parts: work on line formation, in which the atmospheric structure is known and held fixed, is described first, then follows a description of the inclusion of line opacities in non-LTE in the atmosphere problem itself, and finally recent developments in the theory of radiatively driven stellar winds are summarized. Here special emphasis is given to a novel distance determination method based entirely on spectroscopie quantities. I close with a brief shopping list.In a series of papers, Becker and Butler (1992,1994a, b,c) have investigated iron and nickel spectra in sub-dwarfs using the complete linearization method of Auer and Heasley (1976). The method scales linearly with the number of frequency points so they were able to use well over 10000 frequencies to adequately describe the line opacities. Several thousand lines were treated explicitly and the resultant computed spectra gave execellent fits to observed Hubble spectra in the wavelength ranges dominated by the ions concerned.The different ionization stages gave consistent results for the iron and nickel abundances but only after line-blocking from millions of spectral lines in the far UV had been included. This was done using the Kurucz (1988) line lists coupled with line grouping as suggested by Anderson (1989) and described briefly in the next section.The line-blanketed atmospheres of Kurucz (1991) are the best available up to about 30000K, where non-LTE effects start to become important. Non-LTE line-blanketed atmospheres have become feasible because the computational requirements of the accelerated lambda iteration (ALI) method (Werner and Husfeld, 1985) also scale linearly with the number of frequency points. On the other hand, Anderson (1989) suggested grouping energetically adjacent atomic levels together to form pseudo-levels on the basis that although they might, as a group, be in non-LTE, they should be in LTE with respect to one another due to the large number of collisions between them. This greatly reduces the number of levels to be considered but instead gives rise to highly complicated pseudo line-profiles. Grigsby et al (1992), who did not use ALI, constructed the first grid of line-blanketed non-LTE models by using a variation on the Opacity Distribution Function concept to group line opacities into blocks thereby reducing the number of frequency points required. Dreizler and Werner (1993) on the other hand were able to sample the opacity as they used ALI in their models.
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Mathys, G. "Link to the Physical Modelling with an Emphasis on Chemical Peculiarities." Highlights of Astronomy 10 (1995): 415–18. http://dx.doi.org/10.1017/s1539299600011576.
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Frequently, the atmospheres of stars of spectral types B to F, on which the attention is particularly focussed in this Joint Discussion, are characterized by non-standard physical conditions: non-solar abundance patterns, surface in homogeneities, strong magnetic fields. The most extreme anomalies are found in the chemically peculiar (CP) stars but more moderate departures from standard atmospheres are observed in many stars in the considered temperature range. This can affect the derivation of fundamental stellar parameters in a number of ways, some of which will be presented in this contribution. The emphasis is set on those physical processes which are specific to CP stars. Due to lack of space, this review is necessarily incomplete: a selection of recent results of interest will be pointed out and some directions of investigation will be suggested.CP stars have an anomalous continuous energy distribution. Fitting this distribution by standard model atmospheres can only be achieved using models corresponding to different effective temperatures to represent different spectral ranges (e.g., Leone & Catalano 1991). This is obviously not physically meaningful: the effective temperature characterizes the total flux of a star, thus is unique. “Realistic” models must incorporate the anomalous elemental abundances. Such models are presently being developed by Kurucz (ATLAS12) and by the Vienna group (Weiss 1994, private communication). The latter is adapted from Muthsam’s (1979) code. One important result obtained by Muthsam is that the relation T(τ) appears steeper in magnetic Ap stars than in normal stars. This view recently received support from observations of rapid oscillations (Matthews et al. 1990). But even such realistic models may not represent satisfactorily CP star atmospheres, as some potentially important opacity sources may still be unknown. For instance, the broad continuum depressions observed in many magnetic CP stars have not been fully explained yet.
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Peña, J. H., R. Peniche, and R. Garrido. "Strömgren Photoelectric Photometry of the Dwarf Cepheid Stars DY Peg and BP Peg." International Astronomical Union Colloquium 139 (1993): 429. http://dx.doi.org/10.1017/s0252921100118184.
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AbstractA study of short period high amplitude Dwarf Cepheid stars has been undertaken in order to discriminate between the two possible models, namely Bessel's (1969) proposal of low mass Pop. II or old Pop. I. The telecsope utilized was the 1.5 m at the SPM Observatory. The Danish spectrophotometer that allows the simultaneous acquisition of data in the uvby filters and almost simultaneously in the Hβ narrow and wide niters was attached. With this advantage of simultaneous observations, no phasing adjustment was needed, eliminating the risks of losing information due to amplitude varition explained either by multiple periodicity or by the Blazhko effect. We have restricted our discussion to the descending branch and light minimum phase interval between 0.175 to 0.725. For this interval the unreddened indices (b – y)0 and (cl)0 were calculated as in Nissen (1988), which will serve to determine the effective gravity and temperature variation of both stars, through the model atmsphere calibrations by Breger (1974), based on the ATLAS and Kurucz model atmospheres. Mean log g values of 4.0 and 4.33, and mean temperatures of 7500 and 7700 K were determined for DY Her and BP Peg, respectively. It can be concluded that both pulsating stars DY Her and BP Peg are Pop.I, normal Dwarf Cepheid stars.
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Rola, C., L. Tresse, G. Stasińska, and F. Hammer. "The Nature of the Emission Galaxies in the Canada France Redshift Survey (CFRS)." Symposium - International Astronomical Union 164 (1995): 462. http://dx.doi.org/10.1017/s0074180900109726.
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The nature of the emission-line galaxies up to z ≈ 0.3 in the CFRS was analysed. The (4500–8500Å) spectral range allowed us to measure the Hα line intensity until z ≈ 0.3 and to correct for reddening. This permitted us to examine the physical properties of these galaxies in the light of a new grid of photoionisation models, obtained with the code PHOTO (Stasińska 1990). This grid was used to define the loci for photoionisation by hot main sequence stars in two diagnostic diagrams. As ionisation source we used the Kurucz (1992) log g = 5 stellar model atmospheres with abundances consistent with those of the model nebulae. The photoionisation models reproduce the separation zone between the objects thermally and non-thermally excited in the [S II] λ6725/Hα versus [O III]λ5007/Hβ diagnostic diagram, which Veilleux and Osterbrock (1987) determined empirically. A equivalent separation zone was defined for the [O III] λ5007/Hβ versus [O II] λ3727/Hβ diagram. In spite of its reddening dependence, this diagram is useful to separate the H II region-like galaxies from the non-thermally excited ones. Using both diagrams the analysis of the CFRS data allowed us to obtain the following statistics about the nature of the objects: about 20 % of all the galaxies with z ≤ 0.3 have spectra with properties intermediate between Seyfert 2 galaxies and LINERs (compared to 2 % found in the local Universe; Huchra & Burg 1992). More details of this work are given in Tresse et al. (1994). A full version will be submitted to MNRAS.
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Pollard, Karen, P. L. Cottrell, and W. A. Lawson. "A spectroscopic study of RCB stars in the Galaxy and the LMC." International Astronomical Union Colloquium 139 (1993): 215. http://dx.doi.org/10.1017/s0252921100117415.
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AbstractHigh resolution échelle spectra have been obtained of two Large Magellanic Cloud (LMC) and one galactic R Coronae Borealis (RCB) star with the Anglo-Australian Telescope. An analysis of these data using He- and C-rich models and the model atmosphere code WIDTH6 of Kurucz indicates that the galactic RCB star SU Tau and the two LMC stars, W Men and HV12842, have similar atmospheric parameters to the warmer galactic RCB and hydrogen-deficient Carbon (HdC) stars e.g., R CrB and XX Cam. Specifically, the new stars have Teff ∼7000 K, log g = 0.5-1.0, microturbulent velocities between 6 and 8 km.s-1 and C/He ratios from 0.004 to 0.006.An abundance analysis has been performed on these stars for a wide range of species. Special emphasis has been placed on particular elements H, He, Li, C, N, O, & Fe (see figure 1), which are key indicators of the extent and relative importance of nuclear processes such as the CNO cycle and triple-alpha process, and also of the physical processes such as convective mixing and mass loss. Specific values for the abundances of [H/He], [Li/Fe] and [Fe/total] (expressed relative to the total abundance of all species) in SU Tau and HV12842 are -5.4 & -6.4, +2.5 & +2.4, -0.4 & -0.8.
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Van Hamme, W., R. E. Wilson, and R. M. Branly. "Multiple Probes of the AS Cam Dynamical Problem." International Astronomical Union Colloquium 187 (2002): 155–60. http://dx.doi.org/10.1017/s0252921100001342.
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AbstractAS Camelopardalis is notorious for its apparent disregard for the theory of apsidal motion. The orbit of this 3.43-day double-lined eclipsing binary (B8V + B9.5V) rotates approximately 15° per century, which is only 0.3 to 0.4 as fast as predicted (classical + relativistic). Our dynamical program explores, as have others, the suggestion that a third star perturbs the orbit of the eclipsing pair and slows its apsidal motion, dω/dt. On the observational side, we unify the process of extracting apsidal motion and light-time effect parameters from eclipse minima by directly including a third body light-time effect along with the usual ephemeris parameters. By numerical experiment we identify third body parameters consistent with the eclipse timings and with the dynamics of third body perturbations. Results include the minimum third body mass required to produce the given retrograde apsidal rate. Finally, we use a general binary star light curve program that includes a light-time effect to solve for dω/dt and ephemeris parameters together with other quantities, combining 21 years of radial velocities and light curves within one coherent analysis. The program has an improved stellar atmosphere routine based on Legendre polynomials that have been fitted to Kurucz atmosphere models. By analyzing whole light curves, the program has access to more information than only times of minima. Results agree well with those from eclipse timings over 100 years and attain smaller standard errors despite utilizing only one-fifth of the traditional method’s baseline in time.
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Sbordone, Luca, Piercarlo Bonifacio, and Fiorella Castelli. "ATLAS 9 and ATLAS 12 under GNU-Linux." Proceedings of the International Astronomical Union 2, S239 (August 2006): 71–73. http://dx.doi.org/10.1017/s1743921307000142.
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AbstractWe successfully ported the suite of codes developed by R. L. Kurucz for stellar atmosphere modelling, abundance determination and synthetic spectra calculation, to run under GNU-Linux. The ported codes include ATLAS 9 and ATLAS 12 for 1-D plane-parallel atmosphere model calculation, DFSYNTHE, which calculates the Opacity Distribution Functions (ODF) to be used with ATLAS 9, WIDTH to derive chemical abundances from measured line Equivalent Widths (EW) and SYNTHE to calculate synthetic spectra. The codes input and output files remain fully compatible with the VMS versions, while the computation speed has been greatly increased due to the high efficiency of modern PC CPUs. As an example, ATLAS 9 model calculations and the computation of large (e.g. 10 nm) synthetic spectra can be executed in a matter of minutes on any mainstream laptop computer. Arbitrary chemical compositions can be used in calculations (by using ATLAS 12 through opacity sampling or by calculating ad-hoc ODFs for ATLAS 9). The large set of scripting languages existing under Linux (shell, perl, python. . .) and the availability of low-cost multiprocessor Linux architectures (such as Beowulf) makes the port highly effective to build model farms to produce large quantities of atmosphere models or synthetic spectra (e.g. for the production of integrated light synthetic spectra). The port is hosted on a dedicated website including a download section for source codes, precompiled binaries, needed data (opacities, line lists and so on), sample launch scripts and documentation.
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Valegård, P. G., L. B. F. M. Waters, and C. Dominik. "What happened before?" Astronomy & Astrophysics 652 (August 2021): A133. http://dx.doi.org/10.1051/0004-6361/202039802.
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Context. Planets form in circumstellar disks around pre-main-sequence stars. A key question is, how do the formation and evolution of protoplanetary disks depend on stellar mass? Studies of circumstellar disks at infrared and submillimeter wavelengths around intermediate-mass Herbig Ae/Be stars have revealed disk structures such as cavities, gaps, and spiral arms. The Herbig Ae/Be stars represent an older population of intermediate-mass pre-main-sequence stars. Since these evolve toward the main sequence on timescales comparable to those of typical disk dissipation, a full picture of disk dispersal in intermediate-mass pre-main-sequence stars must include the intermediate-mass T Tauri (IMTT) stars. Aims. We seek to find the precursors of the Herbig Ae/Be stars in the solar vicinity within 500 pc from the Sun. We do this by creating an optically selected sample of IMTT stars from the literature, here defined as stars of masses 1.5 M⊙≤ M*≤ 5 M⊙ and with a spectral type between F and K3. Methods. We used literature optical photometry (0.4–1.25 μm) and distances determined from Gaia DR2 parallax measurements together with Kurucz stellar model spectra to place the stars in a HR diagram. We employed Siess evolutionary tracks to identify IMTT stars from the literature and derived masses and ages. We used Spitzer spectra to classify the disks around the stars into Meeus Group I and Group II disks based on their [F30/F13.5] spectral index. We also examined the 10 μm silicate dust grain emission and identified emission from polycyclic aromatic hydrocarbons (PAH). From this, we built a qualitative picture of the disks around the IMTT stars and compared this with available spatially resolved images at infrared and submillimeter wavelengths to confirm our classification. Results. We find 49 IMTT stars with infrared excess. The identified disks are similar to the older Herbig Ae/Be stars in disk geometries and silicate dust grain population. The detection frequency of PAHs is higher than from disks around lower mass T Tauri stars but less frequent than from Herbig Ae/Be disks. Spatially resolved images at infrared and submillimeter wavelengths suggest gaps, and spirals are also present around the younger precursors to the Herbig Ae/Be stars. Conclusions. Comparing the timescale of stellar evolution toward the main sequence and current models of protoplanetary disk evolution, the similarity between Herbig Ae/Be stars and the IMTT stars points toward an evolution of Group I and Group II disks that are disconnected and represent two different evolutionary paths.
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Zhou, Youzhou. "Ergodic Inequality of a Two-Parameter Infinitely-Many-Alleles Diffusion Model." Journal of Applied Probability 52, no. 01 (March 2015): 238–46. http://dx.doi.org/10.1017/s0021900200012316.
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In this paper three models are considered. They are the infinitely-many-neutral-alleles model of Ethier and Kurtz (1981), the two-parameter infinitely-many-alleles diffusion model of Petrov (2009), and the infinitely-many-alleles model with symmetric dominance Ethier and Kurtz (1998). New representations of the transition densities are obtained for the first two models and the ergodic inequalities are provided for all three models.
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Zhou, Youzhou. "Ergodic Inequality of a Two-Parameter Infinitely-Many-Alleles Diffusion Model." Journal of Applied Probability 52, no. 1 (March 2015): 238–46. http://dx.doi.org/10.1239/jap/1429282618.
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In this paper three models are considered. They are the infinitely-many-neutral-alleles model of Ethier and Kurtz (1981), the two-parameter infinitely-many-alleles diffusion model of Petrov (2009), and the infinitely-many-alleles model with symmetric dominance Ethier and Kurtz (1998). New representations of the transition densities are obtained for the first two models and the ergodic inequalities are provided for all three models.
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GÜNDÜZ, Şafak. "VEKÂLET TEORİSİNİN PERDE ARKASINDAKİ KURUCU SENDROMU: KURUMSAL YÖNETİŞİM VE KURUMSAL SOSYAL SORUMLULUĞA BİR TEHDİT UNSURU." Business & Management Studies: An International Journal 6, no. 1 (April 25, 2018): 1–16. http://dx.doi.org/10.15295/bmij.v6i1.124.
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Vekâlet teorisi çalışmalarında asil-vekil sorununun arkasında yatan asıl sebebi araştıran çalışmalara neredeyse yer verilmemiştir. Mükemmel işleyen bir kurumsal yönetişim modeli üzerinde henüz bir görüş birliğine varılamadığından bu çalışma ile asil-vekil sorununun ardında yatan gizli sebebe dikkat çekilerek kurumsal sosyal sorumluluk ile birlikte yürütülmesi gereken daha sağlıklı bir kurumsal yönetişim önerisi sunulacaktır. Çalışmanın amacı vekâlet sorununun ardındaki sebeplerden bir tanesinin Kurucu Sendromu olabileceğinin ve bunun da kurumsal yönetişim ve kurumsal sosyal sorumluluk için bir tehdit unsuru olduğunun ortaya konulmasıdır. Çalışma, Vekalet Teorisinin psikolojik ve davranışsal tetikleyicilerini bir sendrom ile açıklamaya çalışması bakımından ilk olma ve bu anlamda literatürdeki bir boşluğu doldurma özelliğine sahiptir. Örgütlerin kurumsal sosyal sorumluluk odaklı olma özelliğini arttırmak için Kurucu Sendromundan kurtulmaları gerekliliği üzerinde teorik bir perspektif sunan bu çalışma özellikle örgütsel davranış bilimcilerine de ışık tutar niteliktedir.
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Pardoux, Etienne, and Brice Samegni-Kepgnou. "Large deviation principle for epidemic models." Journal of Applied Probability 54, no. 3 (September 2017): 905–20. http://dx.doi.org/10.1017/jpr.2017.41.
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Abstract We consider a general class of epidemic models obtained by applying the random time changes of Ethier and Kurtz (2005) to a collection of Poisson processes and we show the large deviation principle for such models. We generalise the approach followed by Dolgoarshinnykh (2009) in the case of the SIR epidemic model. Thanks to an additional assumption which is satisfied in many examples, we simplify the recent work of Kratz and Pardoux (2017).
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TEMİZ, Hüseyin, Elçin DALKILIÇ, and Tansel HACIHASANOĞLU. "YÖNETİM KURULU YAPISI VE KÂR YÖNETİMİ UYGULAMALARI: BIST İMALAT SEKTÖRÜ ÖRNEĞİ." Business & Management Studies: An International Journal 5, no. 4 (January 7, 2018): 119–36. http://dx.doi.org/10.15295/bmij.v5i4.185.
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Bu çalışmanın amacı firmaların yönetim kurulu yapısı (bağımsız üye, denetim komitesi, kadın üye ve yönetim kurulu büyüklüğü) ve kâr yönetimi uygulamaları arasındaki ilişkinin incelenmesidir. Söz konusu ilişkinin incelenmesi amacıyla dört farklı kâr yönetimi tahmin modeli kullanılmış ve dört hipotez test edilmiştir. Çalışma kapsamında BIST İmalat Sektöründe faaliyet gösteren firmalara ait 2011 – 2016 yıllarını kapsayan veriler kullanılmıştır. Elde edilen sonuçlara göre; yönetim kurulu içindeki bağımsız üye oranının tahakkuk ve gelir manipülasyonu temelli kâr yönetimi uygulamaları ile ilişkili olduğu ve yönetim kurulundaki kadın üye oranının artmasının nakit akışı ve gelir manipülasyonu temelli kâr yönetimi uygulamalarını azalttığı görülmüştür. Yönetim kurulu büyüklüğünün artmasının da nakit akışı ve gelir manipülasyonu temelli kâr yönetimi uygulamalarını azalttığı tespit edilmiştir. Çalışma kapsamında elde edilen bulguların denetim komitesi üye oranının kâr yönetimi uygulamalarını azalttığı hipotezini desteklemediği sonucuna ulaşılmıştır.
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Cugier, H. "Seismic models of O and B stars with Kurucz’s opacity data." Astronomy & Astrophysics 565 (May 2014): A76. http://dx.doi.org/10.1051/0004-6361/201220507.
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Cunha, M. S., J. M. M. B. Fernandes, and M. J. P. F. G. Monteiro. "Seismic Tests of Theoretical Models of HR 1217." International Astronomical Union Colloquium 185 (2002): 302–3. http://dx.doi.org/10.1017/s0252921100016316.
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A way in which we might learn about the physics of the interior of roAp stars is by studying their oscillations. To that aim we have initiated a study in order to investigate what additional constraints might be imposed to the physics of the interior of roAp stars from the study of their oscillation spectra. We have chosen to start this work by studying the well known multi-periodic roAp star HR 1217. The observed data used for HR1217 were L/L⊙=7.8±0.7 and Teff=7400±100 K, from Matthews et al. (1999), Zs=0.009 estimated from Ryabchikova et al. (1997), and Δv=67.91±0.12μHz from Kurtz et al. (1989).
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Engin;CEVGER, SAKARYA. "ET VE BALIK KURUMU KOMBiNALAR ARASI ET TAŞIMASINDA ULAŞTIRMA MODELİ UYGULAMASI." Ankara Üniversitesi Veteriner Fakültesi Dergisi 43, no. 2 (1996): 1. http://dx.doi.org/10.1501/vetfak_0000000702.
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ŞAMİL, Serhat, and Onur TOK. "DENETİM RAPORU GECİKMESİ ve KURUMSAL YÖNETİM GÖSTERGELERİ ARASINDAKİ İLİŞKİ: BİST İMALAT ŞİRKETLERİ ÜZERİNE BİR ARAŞTIRMA." Business & Management Studies: An International Journal 8, no. 4 (December 10, 2020): 159–76. http://dx.doi.org/10.15295/bmij.v8i4.1712.
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Kurumsal yönetimin amaçlarından birisi olan güvenilir finansal bilgi sağlamada, en kritik rol bağımsız denetime düşmektedir. Bağımsız denetimin kurumsal yönetim yapısının bir bileşeni olmakla birlikte diğer kurumsal yönetim uygulamalarıyla öngörülen ilişkisi bu çalışmanın çıkış noktasıdır. Bu bağlamda çalışmada, finansal bilgi kullanıcılarının da önem atfettikleri bağımsız denetim raporlarının onaylanma süresi (Denetim Raporu Gecikmesi, DRG) ile diğer kurumsal yönetim uygulamalarının ilişkisi araştırılmaktadır. Araştırma 2018 yılında BİST İMALAT sektöründe yer alan firmalardan elde edilen verilerle yapılmaktadır. Söz konusu firmalara ait veriler kesitsel olarak toplanmış ve çoklu regresyon modeli ile analize tabi tutulmuştur. Elde edilen sonuçlara göre, yönetim kurulunun toplanma sıklığının, yönetim kurulu büyüklüğünün, kurumsal yönetim kurulunun etkinliğinin ve iç kontrol etkinliğinin denetim raporu gecikmesindeki değişimi istatistiksel olarak anlamlı bir şekilde açıklayabilmektedir. Bununla birlikte, iç kontrol etkinliğine gösterge olarak kabul edilen iç kontrol biriminin yönetim kurulu komitelerine sunduğu rapor sayısı ile DRG arasındaki ilişki öngörülen yönde değildir. Ayrıca yönetim kurulu bağımsız üye oranı ve yönetim kurulunda muhasebe/finans/denetim alanında tecrübeli kişilerin varlığının, denetim raporundaki gecikmedeki değişimi açıklayacağına ilişkin hipotezler istatistiksel olarak desteklenememiştir.
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Eloy Rodríguez, Angel Rolland, and Pilar López de Coca. "The m1 Index in RR Lyrae Stars." International Astronomical Union Colloquium 139 (1993): 421. http://dx.doi.org/10.1017/s0252921100118123.
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AbstractWe have carried out simultaneous uvbyβ photometry for several RR Lyrae stars. For each of these stars, the observed m1 index variation along the pulsation cycle is compared with that expected variation from the (Δm1*,β) grids of Rodriguez et al. (1991) for the corresponding temperatures, gravities and metallicities. The m1 index variations are also calculated using the Kurucz's models. Good agreement is found
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Al-WARDAT, M. A., A. TAANI, and M. ASPLUND. "A METHOD FOR ESTIMATING PARALLAXES OF VCBS: MODIFICATION TO HIPPARCOS PARALLAX MEASUREMENTS." International Journal of Modern Physics: Conference Series 23 (January 2013): 64–73. http://dx.doi.org/10.1142/s2010194513011082.
Full textAbstract:
We presented a method useful for estimating parallaxes of visually close binary stars (VCBS). The method depends on atmospheric modeling of the components of the VCBS. We construct model atmospheres by using a grid of Kurucz solar metalicity blanketed models1, which can be applied to calculate the synthetic spectral energy distribution for each component of the binary separately. In addition to study the entire system. However, the entire observational spectral energy distribution of the system was used as a reference for the comparison with the synthetic ones. We choose Hip4809 system to investigate the method, and we also study its physical and geometrical parameters. The new parallax of the system was estimated as π = 40.32 ± 5.00 mas, which disagrees with the Hipparcos parallax measurement (13.94 ± 0.90 mas). Furthermore the model atmosphere parameters of the components of the system were derived as: [Formula: see text], [Formula: see text], log ga = 4.50 ± 0.13, log gb = 4.50 ± 0.13, Ra = 0.94 ± 0.12R⊙, Rb = 0.93 ± 0.12R⊙, Depending on the derived parameters, the masses of the system's components were estimated as 1.03 ± 0.02M⊙ and 1.01 ± 0.02M⊙ for the primary and secondary components respectively, and their spectral types were concluded as G6V for both of them.