- ID:
- ivo://CDS.VizieR/J/MNRAS/408/827
- Title:
- Simulations of supernova explosions
- Short Name:
- J/MNRAS/408/827
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radiation-hydrodynamic simulations of core-collapse supernova (SN) explosions, artificially generated by driving a piston at the base of the envelope of a rotating or non-rotating red-supergiant progenitor star. We search for trends in ejecta kinematics in the resulting Type II-Plateau (II-P) SN, exploring dependencies with explosion energy and pre-SN stellar-evolution model.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/786/33
- Title:
- Simulations of the late stage of planet formation
- Short Name:
- J/ApJ/786/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M_{earth}_ to 1 M_J_) in Jupiter's orbit at ~5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A84
- Title:
- Slowly diffusing planetary solutions freq. analysis
- Short Name:
- J/A+A/628/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Over short time-intervals, planetary ephemerides have traditionally been represented in analytical form as finite sums of periodic terms or sums of Poisson terms that are periodic terms with polynomial amplitudes. This representation is not well adapted for the evolution of planetary orbits in the solar system over million of years which present drifts in their main frequencies as a result of the chaotic nature of their dynamics. We aim to develop a numerical algorithm for slowly diffusing solutions of a perturbed integrable Hamiltonian system that will apply for the representation of chaotic planetary motions with varying frequencies. By simple analytical considerations, we first argue that it is possible to exactly recover a single varying frequency. Then, a function basis involving time-dependent fundamental frequencies is formulated in a semi-analytical way. Finally, starting from a numerical solution, a recursive algorithm is used to numerically decompose the solution into the significant elements of the function basis. Simple examples show that this algorithm can be used to give compact representations of different types of slowly diffusing solutions. As a test example, we show that this algorithm can be successfully applied to obtain a very compact approximation of the La2004 solution of the orbital motion of the Earth over 40Myr ([-35Myr,5Myr]). This example was chosen because this solution is widely used in the reconstruction of the past climates.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/147
- Title:
- Slug analysis of star clusters in NGC 628 & 7793
- Short Name:
- J/ApJ/812/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/27
- Title:
- SNe IIP progenitors. I. LMC giant comparison sample
- Short Name:
- J/ApJ/886/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the evolution of massive star progenitors of supernovae of type IIP. We take the example of the nearby and well-studied SN2013ej. We explore how convective overshoot affects the stellar structure, surface abundances, and effective temperature of massive stars, using the Modules for Experiments in Stellar Astrophysics. In particular, models with moderate overshoot (f=0.02-0.031) show the presence of blue loops in the Hertzsprung-Russell diagram with a red to blue excursion (log_10_[Teff/K] from <3.6 to >4.0) and transition back to red, during the core helium-burning phase. Models with overshoot outside this range of f values kept the star in the red supergiant state throughout the post-helium-ignition phases. The surface CNO abundance shows enrichment post-main-sequence and again around the time when helium is exhausted in the core. These evolutionary changes in surface CNO abundance are indistinguishable in the currently available observations due to large observational uncertainties. However, these observations may distinguish between the ratio of surface nitrogen to oxygen at different evolutionary stages of the star. We also compare the effects of convective overshoot on various parameters related to likelihood of explosion of a star as opposed to collapse to a black hole. These parameters are the compactness parameter, M_4_, and {mu}_4_. The combination {mu}_4_xM_4_, and {mu}_4_ have similar variations with f and both peak at f=0.032. We find that all of our 13M_{sun}_ models are likely to explode.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/105
- Title:
- SNe progenitor masses probability distribution
- Short Name:
- J/ApJ/791/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using resolved stellar photometry measured from archival Hubble Space Telescope imaging, we generate color-magnitude diagrams of the stars within 50 pc of the locations of historic core-collapse supernovae (SNe) that took place in galaxies within 8 Mpc. We fit these color-magnitude distributions with stellar evolution models to determine the best-fit age distribution of the young population. We then translate these age distributions into probability distributions for the progenitor mass of each SN. The measurements are anchored by the main-sequence stars surrounding the event, making them less sensitive to assumptions about binarity, post-main-sequence evolution, or circumstellar dust. We demonstrate that, in cases where the literature contains masses that have been measured from direct imaging, our measurements are consistent with (but less precise than) these measurements. Using this technique, we constrain the progenitor masses of 17 historic SNe, 11 of which have no previous estimates from direct imaging. Our measurements still allow the possibility that all SN progenitor masses are <20 M_{sun}_. However, the large uncertainties for the highest-mass progenitors also allow the possibility of no upper-mass cutoff.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A61
- Title:
- SN Ib nebular phase properties
- Short Name:
- J/A+A/656/A61
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Following our recent work on Type II supernovae (SNe), we present a set of 1D nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase Type Ibc SNe starting from state-of-the-art explosion models with detailed nucleosynthesis. Our grid of progenitor models is derived from He stars that were subsequently evolved under the influence of wind mass loss. These He stars, which most likely form through binary mass exchange, synthesize less oxygen than their single-star counterparts with the same zero-age main sequence (ZAMS) mass. This reduction is greater in He-star models evolved with an enhanced mass loss rate. We obtain a wide range of spectral properties at 200 d. In models from He stars with an initial mass >6M_{sun}_ the [OI] {lambda}{lambda}6300, 6364 is of comparable or greater strength than [CaII] {lambda}{lambda}7291, 7323 - the strength of [OI] {lambda}{lambda}6300, 6364 increases with He-star initial mass. In contrast, models from lower mass He stars exhibit a weak [OI] {lambda}{lambda}6300, 6364, strong [CaII] {lambda}{lambda}7291, 7323, but also strong NII lines and FeII emission below 5500{AA}. The ejecta density, modulated by the ejecta mass, the explosion energy, and clumping, has a critical impact on the gas ionization, line cooling, and the spectral properties. FeII dominates the emission below 5500{AA} and is stronger at earlier nebular epochs. It ebbs as the SN ages, while the fractional flux in [OI] {lambda}{lambda}6300, 6364 and [CaII] {lambda}{lambda}7291, 7323 increases, with a similar rate, as the ejecta recombine. Although the results depend on the adopted wind mass loss rate and pre-SN mass, we find that He-stars of 6-8M_{sun}_ initially (ZAMS mass of 23-28M_{sun}_) match adequately the properties of standard SNe Ibc. This finding agrees with the oset in progenitor masses inferred from the environments of SNe Ibc relative to SNe II. Our results for less massive He stars are more perplexing, since the predicted spectra are not seen in nature. They may be missed by current surveys or associated with Type Ibn SNe in which interaction dominates over decay power.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/33
- Title:
- SOFIA Massive (SOMA) Star Formation Survey. I.
- Short Name:
- J/ApJ/843/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an overview and first results of the Stratospheric Observatory For Infrared Astronomy Massive (SOMA) Star Formation Survey, which is using the FORCAST instrument to image massive protostars from ~10 to 40{mu}m. These wavelengths trace thermal emission from warm dust, which in Core Accretion models mainly emerges from the inner regions of protostellar outflow cavities. Dust in dense core envelopes also imprints characteristic extinction patterns at these wavelengths, causing intensity peaks to shift along the outflow axis and profiles to become more symmetric at longer wavelengths. We present observational results for the first eight protostars in the survey, i.e., multiwavelength images, including some ancillary ground-based mid- infrared (MIR) observations and archival Spitzer and Herschel data. These images generally show extended MIR/FIR emission along directions consistent with those of known outflows and with shorter wavelength peak flux positions displaced from the protostar along the blueshifted, near-facing sides, thus confirming qualitative predictions of Core Accretion models. We then compile spectral energy distributions and use these to derive protostellar properties by fitting theoretical radiative transfer models. Zhang and Tan models, based on the Turbulent Core Model of McKee and Tan, imply the sources have protostellar masses m*~10-50M_{sun}_ accreting at ~10^-4^-10^-3^M_{sun}_/yr inside cores of initial masses Mc~30-500M_{sun}_ embedded in clumps with mass surface densities {Sigma}_cl_~0.1-3g/cm^2^. Fitting the Robitaille et al. models typically leads to slightly higher protostellar masses, but with disk accretion rates ~100x smaller. We discuss reasons for these differences and overall implications of these first survey results for massive star formation theories.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A51
- Title:
- Solar evolutionary and structure models
- Short Name:
- J/A+A/655/A51
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In protoplanetary disks, the growth and inward drift of dust lead to the generation of a temporal "pebble wave" of increased metallicity. This phase must be followed by a phase in which the exhaustion of the pebbles in the disk and the formation of planets lead to the accretion of metal-poor gas. At the same time, disk winds may lead to the selective removal of hydrogen and helium from the disk. Hence, stars grow by accreting gas that has an evolving composition. In this work, we investigated how the formation of the Solar System may have affected the composition and structure of the Sun, and whether it plays any role in solving the so-called solar-abundance problem, that is, the fact that standard models with up-to-date lower-metallicity abundances reproduce helioseismic constraints significantly more poorly than those with old higher-metallicity abundances. We simulated the evolution of the Sun from the protostellar phase to the present age and attempted to reproduce spectroscopic and helioseismic constraints. We performed chi-squared tests to optimize our input parameters, which we extended by adding secondary parameters. These additional parameters accounted for the variations in the composition of the accreted material and an increase in the opacities. We confirmed that, for realistic models, planet formation occurs when the solar convective zone is still massive; thus, the overall changes due to planet formation are too small to significantly improve the chi-square fits. We found that solar models with up-to-date abundances require an opacity increase of 12% to 18% centered at T=10^6.4^K to reproduce the available observational constraints. This is slightly higher than, but is qualitatively in good agreement with, recent measurements of higher Fe opacities. These models result in better fits to the observations than those using old abundances; therefore, they are a promising solution to the solar abundance problem. Using these improved models, we found that planet formation processes leave a small imprint in the solar core, whose metallicity is enhanced by up to 5%. This result can be tested by accurately measuring the solar neutrino flux. In the improved models, the protosolar molecular cloud core is characterized by a primordial metallicity in the range Zproto=0.0127-0.0157 and a helium mass fraction in the range Yproto=0.268-0.274.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/L27
- Title:
- Solar flares predictors
- Short Name:
- J/ApJ/774/L27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on several magnetic nonpotentiality parameters obtained from the vector photospheric active region magnetograms obtained with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station over two solar cycles, a machine learning model has been constructed to predict the occurrence of flares in the corresponding active region within a certain time window. The Support Vector Classifier, a widely used general classifier, is applied to build and test the prediction models. Several classical verification measures are adopted to assess the quality of the predictions. We investigate different flare levels within various time windows, and thus it is possible to estimate the rough classes and erupting times of flares for particular active regions. Several combinations of predictors have been tested in the experiments. The True Skill Statistics are higher than 0.36 in 97% of cases and the Heidke Skill Scores range from 0.23 to 0.48. The predictors derived from longitudinal magnetic fields do perform well, however, they are less sensitive in predicting large flares. Employing the nonpotentiality predictors from vector fields improves the performance of predicting large flares of magnitude >=M5.0 and >=X1.0.
