- ID:
- ivo://CDS.VizieR/J/AJ/156/292
- Title:
- Effect of close companions on exoplanetary radii
- Short Name:
- J/AJ/156/292
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the distribution and occurrence rate of small planets was a fundamental goal of the Kepler transiting exoplanet mission, and could be improved with K2 and Transiting Exoplanet Survey Satellite (TESS). Deriving accurate exoplanetary radii requires accurate measurements of the host star radii and the planetary transit depths, including accounting for any "third light" in the system due to nearby bound companions or background stars. High-resolution imaging of Kepler and K2 planet candidate hosts to detect very close (within ~0.5") background or bound stellar companions has been crucial for both confirming the planetary nature of candidates, and the determination of accurate planetary radii and mean densities. Here we present an investigation of the effect of close companions, both detected and undetected, on the observed (raw count) exoplanet radius distribution. We demonstrate that the recently detected "gap" in the observed radius distribution (also seen in the completeness-corrected distribution) is fairly robust to undetected stellar companions, given that all of the systems in the sample have undergone some kind of vetting with high-resolution imaging. However, while the gap in the observed sample is not erased or shifted, it is partially filled in after accounting for possible undetected stellar companions. These findings have implications for the most likely core composition, and thus formation location, of super-Earth and sub-Neptune planets. Furthermore, we show that without high-resolution imaging of planet candidate host stars, the shape of the observed exoplanet radius distribution will be incorrectly inferred, for both Kepler- and TESS-detected systems.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/156/83
- Title:
- Effect of stellar companions on planetary systems
- Short Name:
- J/AJ/156/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler light curves used to detect thousands of planetary candidates are susceptible to dilution due to blending with previously unknown nearby stars. With the automated laser adaptive optics instrument, Robo-AO, we have observed 620 nearby stars around 3857 planetary candidates host stars. Many of the nearby stars, however, are not bound to the KOI. We use galactic stellar models and the observed stellar density to estimate the number and properties of unbound stars. We estimate the spectral type and distance to 145 KOIs with nearby stars using multi-band observations from Robo-AO and Keck-AO. Most stars within 1" of a Kepler planetary candidate are likely bound, in agreement with past studies. We use likely bound stars and the precise stellar parameters from the California Kepler Survey to search for correlations between stellar binarity and planetary properties. No significant difference between the binarity fraction of single and multiple-planet systems is found, and planet hosting stars follow similar binarity trends as field stars, many of which likely host their own non-aligned planets. We find that hot Jupiters are ~4x more likely than other planets to reside in a binary star system. We correct the radius estimates of the planet candidates in characterized systems and find that for likely bound systems, the estimated planetary radii will increase on average by a factor of 1.77, if either star is equally likely to host the planet. Lastly, we find the planetary radius gap is robust to the impact of dilution.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/10
- Title:
- Effects of a {kappa}-distribution in HII regions
- Short Name:
- J/ApJS/208/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recently, Nicholls et al. (2012ApJ...752..148N), inspired by in situ observations of solar system astrophysical plasmas, suggested that the electrons in H II regions are characterized by a {kappa}-distribution of energies rather than a simple Maxwell-Boltzmann distribution. Here, we have collected together new atomic data within a modified photoionization code to explore the effects of both the new atomic data and the {kappa}-distribution on the strong-line techniques used to determine chemical abundances in H II regions. By comparing the recombination temperatures (T_rec_) with the forbidden line temperatures (T_FL_), we conclude that {kappa}~20. While representing only a mild deviation from equilibrium, this result is sufficient to strongly influence abundances determined using methods that depend on measurements of the electron temperature from forbidden lines. We present a number of new emission line ratio diagnostics that cleanly separate the two parameters determining the optical spectrum of H II regions--the ionization parameter q or {} and the chemical abundance, 12+log(O/H). An automated code to extract these parameters is presented. Using the homogeneous data set from van Zee et al. 1998, Cat. J/AJ/116/2805, we find self-consistent results between all of these different diagnostics. The systematic errors between different line ratio diagnostics are much smaller than those found in the earlier strong-line work. Overall, the effect of the {kappa}-distribution on the strong-line abundances derived solely on the basis of theoretical models is rather small.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A126
- Title:
- Effects of a revised ^7^Be e^-^-capture rate
- Short Name:
- J/A+A/623/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The electron-capture rate on ^7^Be is the main production channel for ^7^Li in several astrophysical environments. Theoretical evaluations have to account for not only the nuclear interaction, but also the processes in the plasma where ^7^Be ions and electrons interact. In the past decades several estimates were presented, pointing out that the theoretical uncertainty in the rate is in general of few percents. In the framework of fundamental solar physics, we consider here a recent evaluation for the ^7^Be+e^-^ rate, not used up to now in the estimate of neutrino fluxes. We analysed the effects of the new assumptions on Standard Solar Models (SSMs) and compared the results obtained by adopting the revised ^7^Be+e^-^ rate to those obtained by the one reported in a widely used compilation of reaction rates (ADE11). We found that new SSMs yield a maximum difference in the efficiency of the ^7^Be channel of about -4% with respect to what is obtained with the previously adopted rate. This fact affects the production of neutrinos from ^8^B, increasing the relative flux up to a maximum of 2.7%. Negligible variations are found for the physical and chemical properties of the computed solar models. The agreement with the SNO measurements of the neutral current component of the ^8^B neutrino flux is improved
- ID:
- ivo://CDS.VizieR/J/ApJ/719/996
- Title:
- Effects of binarity in SEGUE pipeline
- Short Name:
- J/ApJ/719/996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the effects that unresolved binaries have on the determination of various stellar atmospheric parameters for targets from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) using numerical modeling, a grid of synthetic spectra, and the SEGUE Stellar Parameter Pipeline (SSPP). The SEGUE survey, a component of the Sloan Digital Sky Survey-II (SDSS-II) project focusing on Galactic structure, provides medium resolution spectroscopy for over 200000 stars of various spectral types over a large area on the sky. To model undetected binaries that may be in this sample, we use a variety of mass distributions for the primary and secondary stars in conjunction with empirically determined relationships for orbital parameters to determine the fraction of G-K dwarf stars, defined by SDSS color cuts as having 0.48<=(g-r)_0_<=0.75, that will be blended with a secondary companion. We focus on the G-K dwarf sample in SEGUE as it records the history of chemical enrichment in our galaxy. To determine the effect of the secondary on the spectroscopic parameters, specifically effective temperature, surface gravity, metallicity, and [{alpha}/Fe], we synthesize a grid of model spectra from 3275 to 7850K and [Fe/H]=-0.5 to -2.5 from MARCS model atmospheres using TurboSpectrum. These temperature and metallicity ranges roughly correspond to a stellar mass range of 0.1-1.0M_{sun}_. We assume that both stars in the pair have the same metallicity. We analyze both "infinite" signal-to-noise ratio (S/N) models and degraded versions of the spectra, at median S/N of 50, 25, and 10.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A203
- Title:
- Effects of IMG on Galactic chemical enrichment
- Short Name:
- J/A+A/650/A203
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We have been seeing mounting evidence that the stellar initial mass function (IMF) might extend far beyond the canonical Mi~100M_{sun}_ limit, but the impact of such a hypothesis on the chemical enrichment of galaxies is yet to be clarified. We aim to address this question by analysing the observed abundances of thin- and thick-disc stars in the Milky Way with chemical evolution models that account for the contribution of very massive stars dying as pair instability supernovae. We built new sets of chemical yields from massive and very massive stars up to Mi~350M_{sun}_ by combining the wind ejecta extracted from our hydrostatic stellar evolution models with explosion ejecta from the literature. Using a simple chemical evolution code, we analysed the effects of adopting different yield tables by comparing predictions against observations of stars in the solar vicinity. After several tests, we set our focus on the [O/Fe] ratio that best separates the chemical patterns of the two Milky Way components. We nd that with a standard IMF, truncated at Mi~100M_{sun}_, we can reproduce various observational constraints for thin-disc stars; however, the same IMF fails to account for the [O/Fe] ratios of thick-disc stars. The best results are obtained by extending the IMF up to Mi=350M_{sun}_; while including the chemical ejecta of very massive stars in the form of winds and pair instability supernova (PISN) explosions. Our study indicates that PISN may have played a significant role in shaping the chemical evolution of the thick disc of the Milky Way. Including their chemical yields makes it easier to reproduce not only the level of the a-enhancement, but also the observed slope of thick-disc stars in the [O/Fe] versus [Fe/H] diagram. The bottom line is that the contribution of very massive stars to the chemical enrichment of galaxies is potentially quite important and should not be neglected in models of chemical evolution.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/34
- Title:
- Effects of preionization in radiative shocks
- Short Name:
- J/ApJS/229/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we treat the preionization problem in shocks over the velocity range 10<v_s_<1500km/s in a self-consistent manner. We identify four distinct classes of solutions controlled by the value of the shock-precursor parameter, {Psi}=Q/v_s_, where Q is the ionization parameter of the UV photons escaping upstream. This parameter determines both the temperature and the degree of ionization of the gas entering the shock. In increasing velocity, the shock solution regimes are cold neutral precursors (v_s_<~40km/s), warm neutral precursors (40<~v_s_<~75km/s), warm partly ionized precursors (75<~v_s_<~120km/s), and fast shocks in which the preshock gas is in photoionization equilibrium and is fully ionized. The main effect of a magnetic field is to push these velocity ranges to higher values and to limit the postshock compression. In order to facilitate comparison with observations of shocks, we provide a number of convenient scaling relationships for parameters, such as postshock temperature, compression factors, cooling lengths, and H{beta} and X-ray luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A74
- Title:
- EFIGI catalogue of 4458 nearby galaxies
- Short Name:
- J/A+A/532/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Now that large databases of resolved galaxy images are provided by modern imaging surveys, advanced morphological studies can be envisioned, urging for well defined calibration samples. We present the EFIGI catalogue, a multiwavelength database specifically designed for a dense sampling of all Hubble types. The catalogue merges data from standard surveys and catalogues (Principal Galaxy Catalogue, Sloan Digital Sky Survey, Value-Added Galaxy Catalogue, HyperLeda, and the NASA Extragalactic Database) and provides detailed morphological information. Imaging data are obtained from the SDSS DR4 release in the u, g, r, i, and z bands for a sample of 4458 PGC galaxies, whereas photometric and spectroscopic data are obtained from the SDSS DR5 catalogue. Point-Spread Function models are derived in all five bands. Composite colour images of all objects are visually examined by a group of astronomers, and galaxies are staged along the Hubble sequence and classified according to 16 morphological attributes describing their structure, texture, as well as environment and appearance on a five-level scale. The EFIGI Hubble sequence shows remarkable agreement with the RC3 Revised Hubble Sequence. The main characteristics and reliability of the catalogue are examined, including photometric completeness, type mix, systematic trends and correlations. The final EFIGI database is a large sub-sample of the local Universe, with a dense sampling of Sd, Sdm, Sm and Im types compared to magnitude-limited catalogues. We estimate the photometric catalogue to be more than ~80% complete for galaxies with 10<g<14. More than 99.5% of EFIGI galaxies have a known redshift in the HyperLeda and NED databases.
4909. EFOSC photometry of M3-2
- ID:
- ivo://CDS.VizieR/J/A+A/619/A84
- Title:
- EFOSC photometry of M3-2
- Short Name:
- J/A+A/619/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow detecting post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre of PN M3-2 and found it to be an eclipsing binary with an orbital period of 1.88 days. However, the components of the binary appear to be two A or F stars, of almost equal masses, and are thus too cold to be the source of ionisation of the nebula. Using deep images of the central star obtained in good seeing, we confirm a previous result that the central star is more likely a much fainter star, located 2 arcsec away from the bright star. The eclipsing binary is thus a chance alignment on top of the planetary nebula. We also studied the nebular abundance and confirm it to be a Type I PN.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A116
- Title:
- EG And Halpha line fluxes and radial velocities
- Short Name:
- J/A+A/646/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Structure of the wind from the cool giants in symbiotic binaries carries important information for understanding the wind mass transfer to their white dwarf companions, its fuelling, and thus the path to different phases of symbiotic-star evolution. In this paper we indicate a non-spherical distribution of the neutral wind zone around the red giant (RG) in the symbiotic binary star EG And. In particular, its focusing towards the orbital plane and the asymmetry alongside the orbital motion of the RG. We achieved this aim by analysing the periodic orbital variations of fluxes and radial velocities of individual components of the H_alpha and [OIII] lambda 5007 lines observed on our high-cadence medium (R~11000) and high-resolution (R~38000) spectra. The asymmetric shaping of the neutral wind zone at the near-orbital-plane region is indicated by: (i) the asymmetric course of the Halpha core emission fluxes along the orbit, (ii) the presence of their secondary maximum around the orbital phase phi=0.1 possibly caused by the refraction effect, and (iii) the properties of the H_alpha broad wing emission originating by Raman scattering on H^0^ atoms. The wind is substantially compressed from polar directions to the orbital plane as constrained by the location of the [OIII] lambda 5007 line emission zones in the vicinity of the RG at/around its poles. The corresponding mass-loss rate from the polar regions of <~10^-8^M_{sun}_/yr is a factor of >~10 lower than the average rate of ~10^-7^M_{sun}_/yr derived from nebular emission of the ionized wind from the RG, and it is two orders of magnitude lower than that measured in the near-orbital-plane region from Rayleigh scattering. The startling properties of the nebular [OIII] lambda 5007 line in EG And provides an independent indication of the wind focusing towards the orbital plane -- the key to understanding the efficient wind mass transfer in symbiotic binary stars.