- ID:
- ivo://CDS.VizieR/J/ApJ/724/341
- Title:
- Nucleosynthesis of massive metal-free stars
- Short Name:
- J/ApJ/724/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution and explosion of metal-free stars with masses 10-100M_{sun}_ are followed, and their nucleosynthetic yields, light curves, and remnant masses determined. Such stars would have been the first to form after the big bang and may have left a distinctive imprint on the composition of the early universe. When the supernova yields are integrated over a Salpeter initial mass function (IMF), the resulting elemental abundance pattern is qualitatively solar, but with marked deficiencies of odd-Z elements with 7<=Z<=13. Neglecting the contribution of the neutrino wind from the neutron stars that they form, no appreciable abundances are made for elements heavier than germanium. The computed pattern compares favorably with what has been observed in metal-deficient stars with [Z]<~-3. For the lower mass supernovae considered, the distribution of remnant masses clusters around typical modern neutron star masses, but above 20-30M-{sun}_, with the value depending on explosion energy, black holes are copiously formed by fallback, with a maximum hole mass of ~40M_{sun}_. A novel automated fitting algorithm is developed for determining optimal combinations of explosion energy, mixing, and IMF in the large model database to agree with specified data sets. The model is applied to the low-metallicity sample of Cayrel et al. (Cat. J/A+A/416/1117) and the two ultra-iron-poor stars HE0107-5240 and HE1327-2326. Best agreement with these very low metallicity stars is achieved with very little mixing, and none of the metal-deficient data sets considered show the need for a high-energy explosion component. In contrast, explosion energies somewhat less than 1.2B seem to be preferred in most cases.
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- ID:
- ivo://CDS.VizieR/J/ApJ/854/18
- Title:
- Nucleosynthesis of p nuclides
- Short Name:
- J/ApJ/854/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The production of the heavy stable proton-rich isotopes between ^74^Se and ^196^Hg-the p nuclides-is due to the contribution from different nucleosynthesis processes, activated in different types of stars. Whereas these processes have been subject to various studies, their relative contributions to Galactic chemical evolution (GCE) are still a matter of debate. Here we investigate for the first time the nucleosynthesis of p nuclides in GCE by including metallicity and progenitor mass-dependent yields of core-collapse supernovae (ccSNe) into a chemical evolution model. We used a grid of metallicities and progenitor masses from two different sets of stellar yields and followed the contribution of ccSNe to the Galactic abundances as a function of time. In combination with previous studies on p-nucleus production in thermonuclear supernovae (SNIa), and using the same GCE description, this allows us to compare the respective roles of SNeIa and ccSNe in the production of p-nuclei in the Galaxy. The {gamma} process in ccSN is very efficient for a wide range of progenitor masses (13M_{sun}_-25M_{sun}_) at solar metallicity. Since it is a secondary process with its efficiency depending on the initial abundance of heavy elements, its contribution is strongly reduced below solar metallicity. This makes it challenging to explain the inventory of the p nuclides in the solar system by the contribution from ccSNe alone. In particular, we find that ccSNe contribute less than 10% of the solar p nuclide abundances, with only a few exceptions. Due to the uncertain contribution from other nucleosynthesis sites in ccSNe, such as neutrino winds or {alpha}-rich freeze out, we conclude that the light p-nuclides ^74^Se, ^78^Kr, ^84^Sr, and ^92^Mo may either still be completely or only partially produced in ccSNe. The {gamma}-process accounts for up to twice the relative solar abundances for ^74^Se in one set of stellar models and ^196^Hg in the other set. The solar abundance of the heaviest p nucleus ^196^Hg is reproduced within uncertainties in one set of our models due to photodisintegration of the Pb isotopes ^208,207,206^Pb. For all other p nuclides, abundances as low as 2% of the solar level were obtained.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/99
- Title:
- Nucleosynthetic yields for stars >12M{sun}
- Short Name:
- J/ApJ/769/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the sensitivity of nucleosynthesis in massive stars to the truncation of supernova explosions above a certain mass. It is assumed that stars of all masses contribute to nucleosynthesis by their pre-explosive winds, but above a certain limiting main sequence mass, M_BH_, the presupernova star becomes a black hole and ejects nothing more. The solar abundances from oxygen to atomic mass 90 are fit quite well assuming no cutoff at all, i.e., by assuming all stars up to 120M_{sun}_ make successful supernovae. Little degradation in the fit occurs if M_BH_ is reduced to 25M_{sun}_. If this limit is reduced further however, the nucleosynthesis of the s-process declines precipitously and the production of species made in the winds, e.g., carbon, becomes unacceptably large compared with elements made in the explosion, e.g., silicon and oxygen. By varying uncertain physics, especially the mass loss rate for massive stars and the rate for the ^22^Ne({alpha},n)^25^Mg reaction rate, acceptable nucleosynthesis might still be achieved with a cutoff as low as 18M_{sun}_. This would require, however, a supernova frequency three times greater than the fiducial value obtained when all stars explode in order to produce the required ^16^O. The effects of varying M_BH_ on the nucleosynthesis of ^60^Fe and ^26^Al, the production of helium as measured by {Delta}Y/{Delta}Z, and the average masses of compact remnants are also examined.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/24
- Title:
- NuGrid stellar data set I. Yields from H to Bi
- Short Name:
- J/ApJS/225/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide a set of stellar evolution and nucleosynthesis calculations that applies established physics assumptions simultaneously to low- and intermediate-mass and massive star models. Our goal is to provide an internally consistent and comprehensive nuclear production and yield database for applications in areas such as presolar grain studies. Our non-rotating models assume convective boundary mixing (CBM) where it has been adopted before. We include 8 (12) initial masses for Z=0.01 (0.02). Models are followed either until the end of the asymptotic giant branch phase or the end of Si burning, complemented by simple analytic core-collapse supernova (SN) models with two options for fallback and shock velocities. The explosions show which pre-SN yields will most strongly be effected by the explosive nucleosynthesis. We discuss how these two explosion parameters impact the light elements and the s and p process. For low- and intermediate-mass models, our stellar yields from H to Bi include the effect of CBM at the He-intershell boundaries and the stellar evolution feedback of the mixing process that produces the ^13^C pocket. All post-processing nucleosynthesis calculations use the same nuclear reaction rate network and nuclear physics input. We provide a discussion of the nuclear production across the entire mass range organized by element group. The entirety of our stellar nucleosynthesis profile and time evolution output are available electronically, and tools to explore the data on the NuGrid VOspace hosted by the Canadian Astronomical Data Centre are introduced.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A96
- Title:
- Number counts produced by the EGG
- Short Name:
- J/A+A/602/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper introduces egg, the Empirical Galaxy Generator, a tool designed within the ASTRODEEP collaboration to generate mock galaxy catalogs for deep fields with realistic fluxes and simple morphologies. The simulation procedure is based exclusively on empirical prescriptions - rather than first principles - to provide the most accurate match with current observations at 0<z<7. We considered that galaxies can be either quiescent or star-forming, and used their stellar mass (M*) and redshift (z) as the fundamental properties from which all the other observables can be statistically derived. Drawing z and M* from the observed galaxy stellar mass functions, a star-formation rate (SFR) is attributed to each galaxy from the tight SFR-M* main sequence, while dust attenuation, optical colors and simple disk plus bulge morphologies are obtained from empirical relations that we established from the high quality Hubble and Herschel observations from the CANDELS fields. Random scatter was introduced in each step to reproduce the observed distributions of each parameter. Based on these observables, an adequate panchromatic spectral energy distribution (SED) is selected for each galaxy and synthetic photometry is produced by integrating the redshifted SED in common broad-band filters. Finally, the mock galaxies are placed on the sky at random positions with a fixed angular two-point correlation function to implement basic clustering. The resulting flux catalogs reproduce accurately the observed number counts in all broad bands from the ultraviolet up to the sub-millimeter, and can be directly fed to image simulators such as SkyMaker. The images can then be used to test source extraction softwares and image-based techniques such as stacking. egg is open-source, and is made available to the community on behalf of the ASTRODEEP collaboration, together with a set of pre-generated catalogs and images.
- ID:
- ivo://CDS.VizieR/J/AJ/157/235
- Title:
- Observations of the Kepler field with TESS
- Short Name:
- J/AJ/157/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the ability of the Transiting Exoplanet Survey Satellite (TESS) to detect and improve our understanding of planetary systems in the Kepler field. By modeling the expected transits of all confirmed and candidate planets detected by Kepler as expected to be observed by TESS, we provide a probabilistic forecast of the detection of each Kepler planet in TESS data. We find that TESS has a greater than 50% chance of detecting 260 of these planets at the 3{sigma} level in one sector of observations and an additional 120 planets in two sectors. Most of these are large planets in short orbits around their host stars, although a small number of rocky planets are expected to be recovered. Most of these systems have only one known transiting planet; in only ~5% of known multiply transiting systems do we anticipate more than one planet to be recovered. When these planets are recovered, we expect TESS to be a powerful tool to characterize transit timing variations. Using Kepler-88 (KOI-142) as an example, we show that TESS will improve measurements of planet-star mass ratios and orbital parameters, and significantly reduce the transit timing uncertainty in future years. Because TESS will be most sensitive to hot Jupiters, we research whether TESS will be able to detect tidal orbital decay in these systems. We find two confirmed planetary systems (Kepler-2 b and Kepler-13 b) and five candidate systems that will be good candidates to detect tidal decay.
- ID:
- ivo://CDS.VizieR/J/AJ/155/205
- Title:
- Occurrence rates for Q1-Q16 KOI catalog planet cand.
- Short Name:
- J/AJ/155/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new framework to characterize the occurrence rates of planet candidates identified by Kepler based on hierarchical Bayesian modeling, approximate Bayesian computing (ABC), and sequential importance sampling. For this study, we adopt a simple 2D grid in planet radius and orbital period as our model and apply our algorithm to estimate occurrence rates for Q1-Q16 planet candidates orbiting solar-type stars. We arrive at significantly increased planet occurrence rates for small planet candidates (R_p_<1.25 R_{Earth}_) at larger orbital periods (P>80 day) compared to the rates estimated by the more common inverse detection efficiency method (IDEM). Our improved methodology estimates that the occurrence rate density of small planet candidates in the habitable zone of solar-type stars is 1.6_-0.5_^+1.2^ per factor of 2 in planet radius and orbital period. Additionally, we observe a local minimum in the occurrence rate for strong planet candidates marginalized over orbital period between 1.5 and 2 R_{Earth}_ that is consistent with previous studies. For future improvements, the forward modeling approach of ABC is ideally suited to incorporating multiple populations, such as planets, astrophysical false positives, and pipeline false alarms, to provide accurate planet occurrence rates and uncertainties. Furthermore, ABC provides a practical statistical framework for answering complex questions (e.g., frequency of different planetary architectures) and providing sound uncertainties, even in the face of complex selection effects, observational biases, and follow-up strategies. In summary, ABC offers a powerful tool for accurately characterizing a wide variety of astrophysical populations.
- ID:
- ivo://CDS.VizieR/J/AJ/162/216
- Title:
- Occurrence rates for systems with a Venus-like planet
- Short Name:
- J/AJ/162/216
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Population studies of Kepler's multiplanet systems have revealed a surprising degree of structure in their underlying architectures. Information from a detected transiting planet can be combined with a population model to make predictions about the presence and properties of additional planets in the system. Using a statistical model for the distribution of planetary systems, we compute the conditional occurrence of planets as a function of the period and radius of Kepler-detectable planets. About half (0.52{+/-}0.03) of the time, the detected planet is not the planet with the largest semi-amplitude (K) in the system, so efforts to measure the mass of the transiting planet with radial velocity (RV) follow up will have to contend with additional planetary signals in the data. We simulate RV observations to show that assuming a single-planet model to measure the K of the transiting planet often requires significantly more observations than in the ideal case with no additional planets, due to systematic errors from unseen planet companions. Our results show that planets around 10 day periods with K close to the single-measurement RV precision ({sigma}1,obs) typically require ~100 observations to measure their K to within 20% error. For a next generation RV instrument achieving {sigma}1,obs =10cm/s, about ~200 (600) observations are needed to measure the K of a transiting Venus in a Kepler-like system to better than 20% (10%) error, which is ~2.3 times as many as would be necessary for a Venus without any planetary companions.
- ID:
- ivo://CDS.VizieR/J/AJ/158/109
- Title:
- Occurrence rates of planets orbiting FGK stars
- Short Name:
- J/AJ/158/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the occurrence rate of planets, ranging in size from 0.5 to 16 R_{Earth}_, orbiting FGK stars with orbital periods from 0.5 to 500 days. Our analysis is based on results from the "DR25" catalog of planet candidates produced by NASA's Kepler mission and stellar radii from Gaia "DR2" (Cat. I/345). We incorporate additional Kepler data products to accurately characterize the efficiency of planets being recognized as "threshold crossing events" by Kepler's Transiting Planet Search pipeline and labeled as planet candidates by the robovetter. Using a hierarchical Bayesian model, we derive planet occurrence rates for a wide range of planet sizes and orbital periods. For planets with sizes 0.75-1.5 R_{Earth}_ and orbital periods of 237-500 days, we find a rate of planets per FGK star of <0.27 (84.13th percentile). While the true rate of such planets could be lower by a factor of ~2 (primarily due to potential contamination of planet candidates by false alarms), the upper limits on the occurrence rate of such planets are robust to ~10%. We recommend that mission concepts aiming to characterize potentially rocky planets in or near the habitable zone of Sun-like stars prepare compelling science programs that would be robust for a true rate in the range f_R,P_=0.03-0.40 for 0.75-1.5 R_{Earth}_ planets with orbital periods in 237-500 days, or a differential rate of {Gamma}_{Earth}_=(d^2^f)/[d(lnP)d(lnR_p_)]=0.06-0.76.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/30
- Title:
- OGLE LMC-T2CEP-211 eclipsing binary LCs and RVs
- Short Name:
- J/ApJ/868/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a peculiar W Virginis (pWVir) type II Cepheid, OGLE-LMC-T2CEP-211 (P_puls_=9.393d), in a double-lined binary system (P_orb_=242d), which shed light on virtually unknown evolutionary status and structure of pWVir stars. The dynamical mass of the Cepheid (first ever for a type II Cepheid) is 0.64+/-0.02M_{sun}_, and the radius R=25.1+/-0.3R_{sun}_. The companion is a massive (5.67M_{sun}_) main-sequence star obscured by a disk. Such a configuration suggests a mass transfer in the system history. We found that originally the system (P_orb_^init^=12d) was composed of 3.5 and 2.8M_{sun}_ stars, with the current Cepheid being more massive. The system age is now ~200Myr, and the Cepheid is almost completely stripped of hydrogen, with helium mass of ~92% of the total mass. It finished transferring the mass 2.5Myr ago and is evolving toward lower temperatures passing through the instability strip. Comparison with observations indicates a reasonable 2.7x10^-8^M_{sun}_/yr mass loss from the Cepheid. The companion is most probably a Be main-sequence star with T=22000K and R=2.5R_{sun}_. Our results yield a good agreement with a pulsation theory model for a hydrogen-deficient pulsator, confirming the described evolutionary scenario. We detected a two-ring disk (R_disk_~116R_{sun}_) and a shell (R_shell_~9R_{sun}_) around the companion, which is probably a combination of the matter from the past mass transfer, the mass being lost by the Cepheid owing to wind and pulsations, and a decretion disk around a rapidly rotating secondary. Our study, together with observational properties of pWVir stars, suggests that the majority of them are products of a similar binary evolution interaction.
