- ID:
- ivo://CDS.VizieR/J/ApJ/814/91
- Title:
- Comparative habitability of transiting exoplanets
- Short Name:
- J/ApJ/814/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanet habitability is traditionally assessed by comparing a planet's semimajor axis to the location of its host star's "habitable zone", the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS, and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an "eccentricity-albedo degeneracy" for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the "habitability index for transiting exoplanets" that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler objects of interest and find that planets that receive between 60% and 90% of the Earth's incident radiation, assuming circular orbits, are most likely to be habitable. Finally, we make predictions for the upcoming TESS and James Webb Space Telescope missions.
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- ID:
- ivo://CDS.VizieR/J/A+A/547/A108
- Title:
- Comparative modelling of cool giants spectra
- Short Name:
- J/A+A/547/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our ability to extract information from the spectra of stars depends on reliable models of stellar atmospheres and appropriate techniques for spectral synthesis. The corresponding paper aims to compare a wide variety of model codes and strategies for the analysis of stellar spectra that are available today. The online tables list spectral lines used during the analysis together with the basic line parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/161/265
- Title:
- Compared rotation periods for 1189 CKS host stars
- Short Name:
- J/AJ/161/265
- Date:
- 16 Mar 2022 11:58:11
- Publisher:
- CDS
- Description:
- The radius valley, a bifurcation in the size distribution of small, close-in exoplanets, is hypothesized to be a signature of planetary atmospheric loss. Such an evolutionary phenomenon should depend on the age of the star-planet system. In this work, we study the temporal evolution of the radius valley using two independent determinations of host star ages among the California-Kepler Survey (CKS) sample. We find evidence for a wide and nearly empty void of planets in the period-radius diagram at the youngest system ages (<~2-3Gyr) represented in the CKS sample. We show that the orbital period dependence of the radius valley among the younger CKS planets is consistent with that found among those planets with asteroseismically determined host star radii. Relative to previous studies of preferentially older planets, the radius valley determined among the younger planetary sample is shifted to smaller radii. This result is compatible with an atmospheric loss timescale on the order of gigayears for progenitors of the largest observed super-Earths. In support of this interpretation, we show that the planet sizes that appear to be unrepresented at ages <~2-3Gyr are likely to correspond to planets with rocky compositions. Our results suggest that the size distribution of close-in exoplanets and the precise location of the radius valley evolve over gigayears.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A16
- Title:
- Comparison of evolutionary tracks
- Short Name:
- J/A+A/560/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars is not fully understood. The relation between different types of evolved massive stars is not clear, and the role of factors such as binarity, rotation or magnetism needs to be quantified. Several groups make available the results of 1D single stellar evolution calculations in the form of evolutionary tracks and isochrones. They use different stellar evolution codes for which the input physics and its implementation varies. In this paper, we aim at comparing the currently available evolutionary tracks for massive stars. We focus on calculations aiming at reproducing the evolution of Galactic stars. Our main goal is to highlight the uncertainties on the predicted evolutionary paths. We compute stellar evolution models with the codes MESA and STAREVOL. We compare our results with those of four published grids of massive stellar evolution models (Geneva, STERN, Padova and FRANEC codes). We first investigate the effects of overshooting, mass loss, metallicity, chemical composition. We subsequently focus on rotation. Finally, we compare the predictions of published evolutionary models with the observed properties of a large sample of Galactic stars.
- ID:
- ivo://CDS.VizieR/J/AJ/155/162
- Title:
- Comparison of IUE and CALSPEC SEDs for 6 WDs
- Short Name:
- J/AJ/155/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A collection of spectral energy distributions (SEDs) is available in the Hubble Space Telescope (HST) CALSPEC database that is based on calculated model atmospheres for pure hydrogen white dwarfs (WDs). A much larger set (~100000) of UV SEDs covering the range (1150-3350 {AA}) with somewhat lower quality are available in the IUE database. IUE low-dispersion flux distributions are compared with CALSPEC to provide a correction that places IUE fluxes on the CALSPEC scale. While IUE observations are repeatable to only 4%-10% in regions of good sensitivity, the average flux corrections have a precision of 2%-3%. Our re-calibration places the IUE flux scale on the current UV reference standard and is relevant for any project based on IUE archival data, including our planned comparison of GALEX to the corrected IUE fluxes. IUE SEDs may be used to plan observations and cross-calibrate data from future missions, so the IUE flux calibration must be consistent with HST instrumental calibrations to the best possible precision.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/165
- Title:
- Comparison of Lick indexes
- Short Name:
- J/MNRAS/406/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar population models of absorption-line indices are an important tool for the analysis of stellar population spectra. They are most accurately modelled through empirical calibrations of absorption-line indices with the stellar parameters such as effective temperature, metallicity and surface gravity, which are the so-called fitting functions. Here we present new empirical fitting functions for the 25 optical Lick absorption-line indices based on the new stellar library Medium resolution INT Library of Empirical Spectra (MILES). The major improvements with respect to the Lick/IDS library are the better sampling of stellar parameter space, a generally higher signal-to-noise ratio and a careful flux calibration. In fact, we find that errors on individual index measurements in MILES are considerably smaller than in Lick/IDS. Instead, we find the rms of the residuals between the final fitting functions and the data to be dominated by errors in the stellar parameters. We provide fitting functions for both Lick/IDS and MILES spectral resolutions and compare our results with other fitting functions in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/511/612
- Title:
- Comparison of Radio-loud and Quiet Quasars
- Short Name:
- J/ApJ/511/612
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made radio observations of 87 optically selected quasars at 5 GHz with the VLA in order to measure the radio power for these objects and hence determine how the fraction of radio-loud quasars varies with redshift and optical luminosity. The sample has been selected from the recently completed Edinburgh Quasar Survey and covers a redshift range of 0.3{<=}z{<=}1.5 and an optical absolute magnitude range of (-26.5){<=}M_B_{<=}(-23.5) (h=1/2, q_o_=1/2). We have also matched other existing surveys with the Faint Images of the Radio Sky at Twenty Centimeters and NRAO VLA Sky Survey radio catalogs and combined these data so that the optical luminosity-redshift plane is now far better sampled than before. We have fitted a model to the probability of a quasar being radio-loud as a function of absolute magnitude and redshift, and from this model we infer the radio-loud and radio-quiet optical luminosity functions. The radio-loud optical luminosity function is featureless and flatter than the radio-quiet one. It evolves at a marginally slower rate if quasars evolve by density evolution, but the difference in the rate of evolutions of the two different classes is much less than was previously thought.
- ID:
- ivo://CDS.VizieR/J/ApJS/178/280
- Title:
- Compendium of ISO far-IR extragalactic data
- Short Name:
- J/ApJS/178/280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Far-infrared line and continuum fluxes are presented for a sample of 227 galaxies observed with the Long Wavelength Spectrometer on the Infrared Space Observatory (ISO, Kessler et al., 1996A&A...315L..27K). The galaxy sample includes normal star-forming systems, starbursts, and active galactic nuclei covering a wide range of colors and morphologies. The data set spans some 1300 line fluxes, 600 line upper limits, and 800 continuum fluxes. Several fine-structure emission lines are detected that arise in either photodissociation or HII regions: [OIII] 52um, [NIII] 57um, [OI] 63um, [OIII] 88um, [NII] 122um, [OI] 145um, and [CII] 158um. Molecular lines such as OH at 53, 79, 84, 119, and 163um, and H_2_O at 58, 66, 75, 101, and 108um are also detected in some galaxies. In addition to those lines emitted by the target galaxies, serendipitous detections of Milky Way [CII] 158um and an unidentified line near 74um in NGC 1068 are also reported. Finally, continuum fluxes at 52, 57, 63, 88, 122, 145, 158, and 170um are derived for a subset of galaxies in which the far-infrared emission is contained within the ~75" ISO LWS beam. The statistics of this large database of continuum and line fluxes, including trends in line ratios with the far-infrared color and infrared-to-optical ratio, are explored.
- ID:
- ivo://CDS.VizieR/VIII/56
- Title:
- Compendium of Radio Measurements of Bright Galaxies
- Short Name:
- VIII/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains all radio measurements of optically bright 'normal' galaxies available up until publication of this compendium in 1975. The compendium was originally intended to simplify statistical analysis of radio properties of these normal galaxies. No data processing was carried out (except to bring the data into a consistent format) and no identification was attempted. These data were originally published as Haynes R.F., Huchtmeier W.K.H., Siegman B., and Wright A.E., CSIRO Publication, 1975. The electronic version of this catalog has made small changes to the original version in an attempt to better identify positions with their source names. Where there was no entry on a line for the source name or position in the published version, data from the previous line was repeated.
- ID:
- ivo://CDS.VizieR/J/ApJS/81/83
- Title:
- Compendium of Radio Spectra and Luminosities
- Short Name:
- J/ApJS/81/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog is a complete sample of 256 powerful extragalactic radio sources. The catalog includes source identification, redshift, luminosities and spectral indices at standard rest frequencies as well as bolometric luminosities between emitted frequencies of 10 MHz and 100 GHz. The paper also includes fits to the measured radio spectra which have not been included in this catalog.
