- ID:
- ivo://CDS.VizieR/J/A+A/627/A28
- Title:
- beta Pic BRITE, bRing, SMEI light curves
- Short Name:
- J/A+A/627/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanet properties crucially depend on the parameters of their host stars: more accurate stellar parameters yield more accurate exoplanet characteristics. When the exoplanet host star shows pulsations, asteroseismology can be used for an improved description of the stellar parameters. We aim to revisit the pulsational properties of {beta} Pic and identify its pulsation modes from normalized amplitudes in five different passbands. We also investigate the potential presence of a magnetic field. We conducted a frequency analysis using three seasons of BRITE-Constellation observations in the two BRITE filters, the about 620-day-long bRing light curve, and the nearly 8-year-long SMEI photometric time series. We calculated normalized amplitudes using all passbands and including previously published values obtained from ASTEP observations. We investigated the magnetic properties of {beta} Pic using spectropolarimetric observations conducted with the HARPSpol instrument. Using 2D rotating models, we fit the normalized amplitudes and frequencies through Monte Carlo Markov chains. We identify 15 pulsation frequencies in the range from 34 to 55d^-1^, where two, F13 at 53.6917d^-1^ and F11 at 50.4921d^-1^, display clear amplitude variability. We use the normalized amplitudes in up to five passbands to identify the modes as three l=1, six l=2, and six l=3 modes. {beta} Pic is shown to be non-magnetic with an upper limit of the possible undetected dipolar field of 300 Gauss. Multiple fits to the frequencies and normalized amplitudes are obtained, including one with a near equator-on inclination for {beta} Pic, which corresponds to our expectations based on the orbital inclination of {beta} Pic b and the orientation of the circumstellar disk. This solution leads to a rotation rate of 27% of the Keplerian breakup velocity, a radius of 1.497+/-0.025R_{sun}_, and a mass of 1.797+/-0.035M_{sun}_. The ~2% errors in radius and mass do not account for uncertainties in the models and a potentially erroneous mode-identification.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/719/L79
- Title:
- BH spin-orbit misalignment in Galactic XRBs
- Short Name:
- J/ApJ/719/L79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In black hole (BH) X-ray binaries (XRBs), a misalignment between the spin axis of the BH and the orbital angular momentum can occur during the supernova explosion that forms the compact object. In this Letter, we present population synthesis (PS) models of Galactic BH XRBs and study the probability density function of the misalignment angle and its dependence on our model parameters. In our modeling, we also take into account the evolution of the misalignment angle due to accretion of material onto the BH during the XRB phase. The major factor that sets the misalignment angle for XRBs is the natal kick that the BH may receive at its formation. However, large kicks tend to disrupt binaries, while small kicks allow the formation of XRBs and naturally select systems with small misalignment angles. Our calculations predict that the majority (>67%) of Galactic field BH XRBs have rather small (<~10{deg}) misalignment angles, while some systems may reach misalignment angles as high as ~90{deg} and even higher. These results are robust among all PS models. The assumption of small misalignment angles is extensively used to observationally estimate BH spin magnitudes, and for the first time we are able to confirm this assumption using detailed PS calculations.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/615
- Title:
- Binary compact object coalescence rates
- Short Name:
- J/ApJ/716/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we estimate binary compact object merger detection rates for LIGO, including the potentially significant contribution from binaries that are produced in elliptical galaxies near the epoch of peak star formation. Specifically, we convolve hundreds of model realizations of elliptical- and spiral-galaxy population syntheses with a model for elliptical- and spiral-galaxy star formation history as a function of redshift. Our results favor local merger rate densities of 4x10^-3^Mpc^-3^/Myr for binary black holes (BHs), 3x10^-2^Mpc^-3^/Myr for binary neutron stars (NSs), and 10^-2^Mpc^-3^/Myr for BH-NS binaries. Assuming a detection signal-to-noise ratio threshold of 8 for a single detector (in practice as part of a network, to reduce its noise), corresponding to radii Dbns of the effective volume inside of which a single LIGO detector could observe the inspiral of two 1.4M_{sun}_ NSs of 14Mpc and 197Mpc, for initial and advanced LIGO, we find event rates of any merger type of 2.9x10^-2^-0.46 and 25-400yr^-1^ (at 90% confidence level), respectively.
54. Binary evolution
- ID:
- ivo://CDS.VizieR/J/MNRAS/319/215
- Title:
- Binary evolution
- Short Name:
- J/MNRAS/319/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Eggleton's stellar evolution code, we carry out 150 runs of Population I binary evolution calculations with the initial primary mass between 1 and 8 solar masses, the initial mass ratio q=M_1/M_2 between 1.1 and 4, and the onset of Roche lobe overflow (RLOF) at an early, middle or late Hertzsprung-gap stage. We assume that the RLOF is conservative in the calculations. We list characteristics for binaries with different initial parameters at the beginning of RLOF, minimum luminosity during RLOF, the end of the last episode of RLOF and the end of the evolutionary calculations. The characteristics includes the age of the primary, its mass, mass transfer rate, its effective temperature, its luminosity, its radius, its helium core mass, its carbon-oxygen core mass, the hydrogen abundance at its surface, the mass ratio of the binary, and the orbital period.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/183
- Title:
- Binary stellar evolution data for Kepler systems
- Short Name:
- J/ApJ/832/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope (CE) stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and CE stage (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the CE phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-CE, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and nonadiabatic) if their host binaries undergo more than one CE stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same CE stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semimajor axis can survive the CE evolution of a close binary star with a total mass of 1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+AS/122/51
- Title:
- B to G stars calibration in Geneva photometry
- Short Name:
- J/A+AS/122/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used recent Kurucz models and many standard stars to revise previous calibrations of the Geneva photometric parameters in terms of Teff, logg, and [M/H]. In addition, new parameters pT and pG were defined, which are the Geneva equivalents of Stromgren's a and r parameters and allow to estimate Teff and logg for stars with intermediate temperature (spectral type A0-A3). A fortran code (calib.f) has been written, which applies our calibration to stars measured in the Geneva system. A conspicuous change in slope appears in the grid d vs B2-V1. It seems to be linked with the onset of convection in the superficial layers of the star's envelope.
- ID:
- ivo://CDS.VizieR/J/ApJS/196/11
- Title:
- Bulge+disk decompositions of SDSS galaxies
- Short Name:
- J/ApJS/196/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform two-dimensional, point-spread-function-convolved, bulge+disk decompositions in the g and r bandpasses on a sample of 1123718 galaxies from the Legacy area of the Sloan Digital Sky Survey Data Release Seven. Four different decomposition procedures are investigated which make improvements to sky background determinations and object deblending over the standard SDSS procedures that lead to more robust structural parameters and integrated galaxy magnitudes and colors, especially in crowded environments. We use a set of science-based quality assurance metrics, namely, the disk luminosity-size relation, the galaxy color-magnitude diagram, and the galaxy central (fiber) colors to show the robustness of our structural parameters. The best procedure utilizes simultaneous, two-bandpass decompositions. Bulge and disk photometric errors remain below 0.1mag down to bulge and disk magnitudes of g~19 and r~18.5. We also use and compare three different galaxy fitting models: a pure Sersic model, an n_b_=4 bulge+disk model, and a Sersic (free n_b_) bulge+disk model. The most appropriate model for a given galaxy is determined by the F-test probability. All three catalogs of measured structural parameters, rest-frame magnitudes, and colors are publicly released here.
- ID:
- ivo://CDS.VizieR/J/A+A/402/425
- Title:
- BVIJHK properties of Single Stellar Populations
- Short Name:
- J/A+A/402/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a large grid of photometric properties of single stellar populations that focuses on the near infrared properties of intermediate age populations. The underlying model was presented in recent articles, where we compared its predictions with observations of properties of star clusters and of asymptotic giant branch populations of Local Group galaxies. The grid is made available in tabular form. We present the time evolution of optical and near-infrared broadband colours in the BVIJHK passbands, with ages ranging from 50Myr to 15Gyr, and for initial chemical compositions [Z=0.0004, Y=0.23], [Z=0.004, Y=0.24], [Z=0.008, Y=0.25], [Z=0.02, Y=0.28], and [Z= 0.05, Y=0.352]. The evolution of the stellar mass-to-light ratio in the V and K passbands is also provided. All the stellar models are followed from the zero age main sequence (ZAMS) to the central carbon ignition for massive stars, or to the end of the thermally pulsing regime of the asymptotic giant branch phase (TP-AGB) for low and intermediate mass stars.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/513
- Title:
- Calcium triplet synthesis
- Short Name:
- J/A+AS/130/513
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present theoretical equivalent widths for the sum of the two strongest lines of the calcium triplet, CaT index, in the near-IR ({lambda}{lambda} 8542, 8662{AA}), using evolutionary synthesis techniques and the most recent models and observational data for this feature in individual stars. We compute the CaT index for Single Stellar Populations (instantaneous burst, standard Salpeter-type IMF at four different metallicities, Z=0.004, 0.008, 0.02 (solar) and 0.05, and ranging in age from very young bursts of star formation (few Myr) to old stellar populations, up to 17Gyr, representative of galactic globular clusters, elliptical galaxies and bulges of spirals. The interpretation of the observed equivalent widths of CaT in different stellar systems is discussed. Composite-population models are also computed as a tool to interpret the CaT detections in star-forming regions, in order to disentangle between the component due to Red Supergiant stars, RSG, and the underlying, older, population. CaT is found to be an excellent metallicity-indicator for populations older than 1 Gyr, practically independent of the age. We discuss its application to remove the age-metallicity degeneracy, characteristic of all studies of galaxy evolution based on the usual integrated indices (both broad band colors and narrow band indices). The application of the models computed here to the analysis of a sample of elliptical galaxies will be discussed in a forthcoming paper Gorgas et al. 1997).
- ID:
- ivo://CDS.VizieR/J/AZh/82/437
- Title:
- Calculated chemical composition of galactic PN
- Short Name:
- J/AZh/82/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a study of the chemical compositions of Galactic planetary nebulae taking into account two types of inhomogeneity in the nebular gas density in their envelopes are reported. New analytical expressions for the ionization correction factors have been derived and are used to determine the chemical compositions of the nebular gas in Galactic planetary nebulae. The abundances of He, N, O, Ne, S, and Ar have been found for 193 objects. The Y-Z diagrams for various He abundances are analyzed for type II planetary nebulae separately and jointly with HII regions. The primordial helium abundance Yp and enrichment ratio dY/dZ are determined, and the resulting values are compared with the data of other authors. Radial abundance gradients in the Galactic disk are studied using type II planetary nebulae.
