- ID:
- ivo://CDS.VizieR/J/A+A/333/231
- Title:
- O-M stars model atmospheres
- Short Name:
- J/A+A/333/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broad band colors and bolometric corrections in the Johnson-Cousins-Glass system (Bessell, 1990PASP..102.1181B; Bessell & Brett, 1988PASP..100.1134B) have been computed from synthetic spectra from new model atmospheres of Kurucz (1995a, priv. comm.), Castelli (1997, priv. comm.), Plez, Brett & Nordlund (1992A&A...256..551P), Plez (1995-97, priv. comm.), and Brett (1995A&A...295..736B, 1995A&AS..109..263B). These atmospheres are representative of larger grids that are currently being completed. We discuss differences between the different grids and compare theoretical color-temperature relations and the fundamental color temperature relations derived from: (a) the infrared-flux method (IRFM) for A-K stars (Blackwell & Lynas-Gray 1994A&A...282..899B; Alonso et al. 1996A&AS..117..227A) and M dwarfs (Tsuji et al. 1996A&A...305L...1T); (b) lunar occultations (Ridgway et al. 1980ApJ...235..126R) and (c) Michelson interferometry (Di Benedetto & Rabbia 1987A&A...188..114D; Dyck et al. 1996AJ....111.1705D; Perrin et al. 1998A&A...331..619P) for K-M giants, and (d) eclipsing binaries for M dwarfs. We also compare color-color relations and color-bolometric correction relations and find good agreement except for a few colors. The more realistic fluxes and spectra of the new model grids should enable accurate population synthesis models to be derived and permit the ready calibration of non-standard photometric passbands. As well, the theoretical bolometric corrections and temperature-color relations will permit reliable transformation from observed color magnitude diagrams to theoretical HR diagrams.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/572/A69
- Title:
- Opacities of magnetized neutron stars
- Short Name:
- J/A+A/572/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is observational evidence that central compact objects (CCOs) in supernova remnants have moderately strong magnetic fields B~10^11^G. Meanwhile, available models of partially ionized hydrogen atmospheres of neutron stars with strong magnetic fields are restricted to B>~10^12^G. Extension of the applicability range of the photosphere models to lower field strengths is complicated by a stronger asymmetry of decentered atomic states and by the importance of excited bound states. We extend the equation of state and radiative opacities, as presented in previous papers for 10^12^G<~B<~10^15^G, to weaker fields. We constructed analytical fitting formulae for binding energies, sizes, and oscillator strengths for different bound states of a hydrogen atom moving in moderately strong magnetic fields and calculate an extensive database for photoionization cross sections of such atoms. Using these atomic data, in the framework of the chemical picture of plasmas we solved the ionization equilibrium problem and calculated thermodynamic functions and basic opacities of partially ionized hydrogen plasmas at these field strengths. Then plasma polarizabilities were calculated from the Kramers-Kronig relation, and the radiative transfer equation for the coupled normal polarization modes was solved to obtain model spectra. An equation of state and radiative opacities for a partially ionized hydrogen plasma are obtained at magnetic fields B, temperatures T, and densities {rho} typical for atmospheres of CCOs and other isolated neutron stars with moderately strong magnetic fields. The first- and second-order thermodynamic functions, monochromatic radiative opacities, and Rosseland mean opacities are calculated and tabulated, considering partial ionization, for 3x10^10G<~B<~10^12^G, 10^5^K<~T<~10^7^K, and a wide range of densities. Atmosphere models and spectra are calculated to verify the applicability of the results and to determine the range of magnetic fields and effective temperatures where the incomplete ionization of the hydrogen plasma is important.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/114
- Title:
- Opacity-sampling models of Mira variables
- Short Name:
- J/MNRAS/418/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four model series of the CODEX dynamical opacity-sampling models of Mira variables with solar abundances, designed to have parameters similar to {omicron} Cet, R Leo and R Cas. We demonstrate that the CODEX models provide a clear physical basis for the molecular shell scenario used to explain interferometric observations of Mira variables. We show that these models generally provide a good match to photometry and interferometry at wavelengths between the near-infrared and the radio, and make the model outputs publicly available. These models also demonstrate that, in order to match visible and infrared observations, the Fe-poor silicate grains that form within 3 continuum radii must have small grain radii and therefore cannot drive the winds from O-rich Mira variables.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/3757
- Title:
- Open-cluster density profiles
- Short Name:
- J/MNRAS/456/3757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Surface and spatial radial density profiles in open clusters are derived using a kernel estimator method. Formulae are obtained for the contribution of every star into the spatial density profile. The evaluation of spatial density profiles is tested against open-cluster models from N-body experiments with N=500. Surface density profiles are derived for seven open clusters (NGC 1502, 1960, 2287, 2516, 2682, 6819 and 6939) using Two-Micron All-Sky Survey data and for different limiting magnitudes. The selection of an optimal kernel half-width is discussed. It is shown that open-cluster radius estimates hardly depend on the kernel half-width. Hints of stellar mass segregation and structural features indicating cluster non-stationarity in the regular force field are found. A comparison with other investigations shows that the data on open-cluster sizes are often underestimated. The existence of an extended corona around the open cluster NGC 6939 was confirmed. A combined function composed of the King density profile for the cluster core and the uniform sphere for the cluster corona is shown to be a better approximation of the surface radial density profile.The King function alone does not reproduce surface density profiles of sample clusters properly. The number of stars, the cluster masses and the tidal radii in the Galactic gravitational field for the sample clusters are estimated. It is shown that NGC 6819 and 6939 are extended beyond their tidal surfaces.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A12
- Title:
- Optical light curves of {gamma}-ray bursts
- Short Name:
- J/A+A/557/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive analysis of the optical and X-ray light curves (LCs) and spectral energy distributions (SEDs) of a large sample of gamma-ray burst (GRB) afterglows to investigate the relationship between the optical and X-ray emission after the prompt phase. We consider all data available in the literature, which where obtained with different instruments. We collected the optical data from the literature and determined the shapes of the optical LCs. Then, using previously presented X-ray data we modeled the optical/X-ray SEDs. We studied the SED parameter distributions and compared the optical and X-ray LC slopes and shapes.
- ID:
- ivo://CDS.VizieR/J/ApJS/113/121
- Title:
- Optically thick winds from degenerate dwarfs. I.
- Short Name:
- J/ApJS/113/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Twenty-six sequences of optically thick wind solutions have been calculated which mimic the time-dependent evolution of classical novae of populations I and II. The peak of the new opacity around log T=5.2 due to iron lines is found to be strong enough to accelerate the winds even in very low iron abundance such as Z=0.001 for massive white dwarfs (>=0.8M_{sun}_). The old population novae show the slow light curve, the long X-ray turn-off time, the small expansion velocity and the small wind mass-loss rate. The X-ray turn-off time is a good indicator of the white dwarf mass because of its strong dependence on the white dwarf mass and weak dependence on the populations. The white dwarf mass is estimated to be ~0.6M_{sun}_ for GQ Mus and ~1.0M_{sun}_ for V1974 Cyg. The systematic difference of the wind velocity is predicted between novae in globular clusters and in galactic disk. Twenty-six tables are presented in the computer readable form of CD-ROM that consists of solutions of the optically thick wind and the static for the decay phase of classical novae with composition of X=0.35, C=0.1 and O=0.2 and heavy elements content Z=0.001, 0.004, 0.02, 0.05 and 0.1 for the white dwarf masses of 0.4, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 and 1.35M_{sun}_. These tables list the characteristic values of the envelope such as the photospheric temperature, the velocity, the wind mass-loss rate and fluxes of four wavelength bands. The updated OPAL opacity (Iglesias & Rogers, 1996ApJ...464..943I) is used.
- ID:
- ivo://CDS.VizieR/I/348
- Title:
- Orbital parameters in Milky-Way-like potentials
- Short Name:
- I/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbital parameters, such as eccentricity and maximum vertical excursion, of stars in the Milky Way are an important tool for understanding its dynamics and evolution, but calculation of such parameters usually relies on computationally-expensive numerical orbit integration. We present and test a fast method for estimating these parameters using an application of the Sackel fudge, used previously for the estimation of action-angle variables. We show that the method is highly accurate, to a level of <1% in eccentricity, over a large range of relevant orbits and in different Milky Way-like potentials, and demonstrate its validity by estimating the eccentricity distribution of the RAVE-TGAS data set and comparing it to that from orbit integration. Using the method, the orbital characteristics of the ~7 million Gaia DR2 stars with radial velocity measurements are computed with Monte Carlo sampled errors in ~116 hours of parallelised cpu time, at a speed that we estimate to be ~3 to 4 orders of magnitude faster than using numerical orbit integration. We demonstrate using this catalogue that Gaia DR2 samples a large range of orbits in the solar vicinity, down to those with r_peri_<~2.5kpc, and out to r_ap_>~13kpc. We also show that many of the features present in orbital parameter space have a low mean zmax, suggesting that they likely result from disk dynamical effects.
- ID:
- ivo://CDS.VizieR/J/AJ/158/88
- Title:
- Oscillations in KOI-976's Kepler photometry
- Short Name:
- J/AJ/158/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the bulk system parameters of the seismically active, rapidly rotating {delta}-Scuti KOI-976 and constrain the orbit geometry of its transiting binary companion using a combined approach of asteroseismology and gravity-darkening light curve analysis. KOI-976 is a 1.62+/-0.2 M_{sun}_ star with a measured v sin(i) of 120+/-2 km/s and seismically induced variable signal that varies by ~0.6% of the star's total photometric brightness. We take advantage of the star's oblate shape and seismic activity to perform three measurements of its obliquity angle relative to the plane of the sky. We first apply a rotational splitting theory to the star's variable signal observed in short-cadence Kepler photometry to constrain KOI-976's obliquity angle, and then subtract off variability from that data set using the linear algorithm for significance reduction software LASR. We perform gravity-darkened fits to Kepler variability-subtracted short-cadence photometry and to Kepler's phase-folded long-cadence photometry to obtain two more measurements of the star's obliquity. We find that the binary system transits in a grazing configuration with measured obliquity values of 36{deg}+/-17{deg}, 46{deg}+/-16{deg}, and 43{deg}+/-20{deg}, respectively, for the three measurements. We perform these analyses as a way to demonstrate overcoming the challenges high-mass stars can present to transit light curve fitting and to prepare for the large number of exoplanets that the Transiting Exoplanet Survey Satellite will discover orbiting A/F stars.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A119
- Title:
- Outer boundary conditions for evolving cool WD
- Short Name:
- J/A+A/546/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarf evolution is essentially a gravothermal cooling process, which, for cool white dwarfs, depends on the treatment of the outer boundary conditions. We provide detailed outer boundary conditions that are appropriate to computing the evolution of cool white dwarfs by employing detailed nongray model atmospheres for pure hydrogen composition. We also explore the impact on the white dwarf cooling times of different assumptions for energy transfer in the atmosphere of cool white dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1998
- Title:
- Outer planetary systems
- Short Name:
- J/AJ/116/1998
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to better understand the range of dynamically long-lived giant planet systems, we present the results of a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos. Our simulations produced systems that are stable for at least a billion years and that exhibit a wide range of characteristics. Some of these systems are reminiscent of the outer solar system. The number of planets ranged from one to seven. Many systems contained only Uranus-mass objects. We constructed systems that were more compact than the outer solar system and systems that were much sparser, with planets on very eccentric orbits. Perhaps most surprisingly, some of the systems that we constructed were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales.
