- ID:
- ivo://CDS.VizieR/J/ApJS/179/451
- Title:
- Predicted IR excesses for protoplanetary disks
- Short Name:
- J/ApJS/179/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe calculations for the formation of icy planets and debris disks at 30-150AU around 1-3M_{sun}_ stars. Debris disk formation coincides with the formation of planetary systems. As protoplanets grow, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. Stellar lifetimes and the collisional cascade limit the growth of protoplanets. The maximum radius of icy planets, r_max_~1750km, is remarkably independent of initial disk mass, stellar mass, and stellar age. These objects contain <=3%-4% of the initial mass in solid material. Collisional cascades produce debris disks with maximum luminosity ~2x10^-3^ times the stellar luminosity. The peak 24um excess varies from ~1% times the stellar photospheric flux for 1M_{sun}_ stars to ~50 times the stellar photospheric flux for 3M_{sun}_ stars. The peak 70-850um excesses are ~30-100 times the stellar photospheric flux. For all stars, the 24-160um excesses rise at stellar ages of 5-20Myr, peak at 10-50Myr, and then decline. The decline is roughly a power law, f{propto}t^-n^ with n~0.6-1.0. This predicted evolution agrees with published observations of A-type and solar-type stars. The observed far-IR color evolution of A-type stars also matches model predictions.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/494/209
- Title:
- Pre-main sequence evolutionary tracks
- Short Name:
- J/A+A/494/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In close binary systems, the axial rotation and the mutual tidal forces of the component stars deform each other and destroy their spherical symmetry by means of the respective disturbing potentials. We present new models for low-mass, pre-main sequence stars that include the combined distortion effects of tidal and rotational forces on the equilibrium configuration of stars. Using our theoretical results, we aim at investigating the effects of interaction between tides and rotation on the stellar structure and evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A46
- Title:
- Pre-main sequence evolutionary tracks
- Short Name:
- J/A+A/510/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields are at the heart of the observed stellar activity in late-type stars, and they are presumably generated by a dynamo mechanism at the interface layer (tachocline) between the radiative core and the base of the convective envelope. Since dynamo models are based on the interaction between differential rotation and convective motions, the introduction of rotation in the ATON 2.3 stellar evolutionary code allows for explorations regarding a physically consistent treatment of magnetic effects in stellar structure and evolution, even though there are formidable mathematical and numerical challenges involved.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A49
- Title:
- Pre-main sequence stars evolutionary models
- Short Name:
- J/A+A/599/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Protostars grow from the first formation of a small seed and subsequent accretion of material. Recent theoretical work has shown that the pre-main-sequence (PMS) evolution of stars is much more complex than previously envisioned. Instead of the traditional steady, one-dimensional solution, accretion may be episodic and not necessarily symmetrical, thereby affecting the energy deposited inside the star and its interior structure. Given this new framework, we want to understand what controls the evolution of accreting stars. We use the MESA stellar evolution code with various sets of conditions. In particular, we account for the (unknown) efficiency of accretion in burying gravitational energy into the protostar through a parameter, ksi, and we vary the amount of deuterium present. We confirm the findings of previous works that, in terms of evolutionary tracks on an Hertzprung-Russell (H-R) diagram, the evolution changes significantly with the amount of energy that is lost during accretion. We find that deuterium burning also regulates the PMS evolution. In the low-entropy accretion scenario, the evolutionary tracks in the H-R diagram are significantly different from the classical tracks and are sensitive to the deuterium content. A comparison of theoretical evolutionary tracks and observations allows us to exclude some cold accretion models (ksi~0) with low deuterium abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A132
- Title:
- Pre-main sequence stars evolutionary models. II
- Short Name:
- J/A+A/618/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to investigate how planet formation is imprinted on stellar surface composition using up-to-date stellar evolution models. We simulate the evolution of pre-main-sequence stars as a function of the efficiency of heat injection during accretion, the deuterium mass fraction, and the stellar mass, M*. For simplicity, we assume that planet formation leads to the late accretion of zero-metallicity gas, diluting the surface stellar composition as a function of the mass of the stellar outer convective zone. We estimate that in the solar system, between 97 and 168 Mearth of condensates formed planets or were ejected from the system. We adopt 150 M_earth_(M*/M_sun_)(Z/Z_sun_) as an uncertain but plausible estimate of the mass of heavy elements that is not accreted by stars with giant planets, including our Sun. By combining our stellar evolution models to these estimates, we evaluate the consequences of planet formation on stellar surface compositions. We show that after the first ~0.1 million years (Myr) during which stellar structure can differ widely from the usually assumed fully-convective structure, the evolution of the convective zone follows classical pre-main-sequence evolutionary tracks within a factor of two in age. We find that planet formation should lead to a scatter in stellar surface composition that is larger for high-mass stars than for low-mass stars. We predict a spread in [Fe/H] of approximately 0.05dex for stars of temperature Teff~6500K, to 0.02dex for Teff~5500K, marginally compatible with differences in metallicities observed in some binary stars with planets. Stars with Teff>=7000K may show much larger [Fe/H] deficits, by 0.6dex or more, in the presence of efficient planet formation, compatible with the existence of refractory-poor lambda Boo stars. We also find that planet formation may explain the lack of refractory elements seen in the Sun as compared to solar twins, but only if the ice-to-rock ratio in the solar-system planets is less than ~0.4 and planet formation began less than ~1.3Myr after the beginning of the formation of the Sun.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/38
- Title:
- Presupernova evolution
- Short Name:
- J/ApJS/199/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new set of zero metallicity models in the range 13-80M_{sun}_ together to the associated explosive nucleosynthesis. These models are fully homogeneous with the solar metallicity set we published in Limongi & Chieffi (2006ApJ...647..483L) and will be freely available at the Online Repository for the FRANEC Evolutionary Output (ORFEO) Web site. A comparison between these yields and an average star that represents the average behavior of most of the very metal-poor stars in the range -5.0<[Fe/H]<-2.5 confirms previous findings that only a fraction of the elemental [X/Fe] may be fitted by the ejecta of standard core collapse supernovae.
- ID:
- ivo://CDS.VizieR/J/A+A/339/123
- Title:
- PSR J1012+5307 evolutionary tracks
- Short Name:
- J/A+A/339/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of evolutionary tracks for white dwarfs with helium cores in the mass range from 0.179 to 0.414M_{sun}_. The tracks are based on a 1M_{sun}_ model sequence extending from the pre-main sequence stage up to the tip of the red-giant branch. Applying large mass loss rates at appropriate positions forced the models to move off the giant branch.The further evolution was then followed across the Hertzsprung-Russell diagram and down the cooling branch.
- ID:
- ivo://CDS.VizieR/J/A+A/366/565
- Title:
- Radial oscillations of relativistic stars
- Short Name:
- J/A+A/366/565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new survey of the radial oscillation modes of neutron stars. This study complements and corrects earlier studies of radial oscillations. We present an extensive list of frequencies for the most common equations of state and some more recent ones. In order to check the accuracy, we use two different numerical schemes which yield the same results. The stimulation for this work comes from the need of the groups that evolve the full nonlinear Einstein equations to have reliable results from perturbation theory for comparison.
- ID:
- ivo://CDS.VizieR/J/A+A/466/641
- Title:
- Reaction rates of NeNa-MgAl chains in AGB stage
- Short Name:
- J/A+A/466/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test the effect of proton-capture reaction rate uncertainties on the abundances of the Ne, Na, Mg and Al isotopes processed by the NeNa and MgAl chains during hot bottom burning (HBB) in asymptotic giant branch (AGB) stars of intermediate mass between 4 and 6M_{sun}_ and metallicities between Z=0.0001 and 0.02. We provide uncertainty ranges for the AGB stellar yields, for inclusion in galactic chemical evolution models, and indicate which reaction rates are most important and should be better determined.
- ID:
- ivo://CDS.VizieR/J/AJ/156/33
- Title:
- Resonance sticking in the population of scattering TNOs
- Short Name:
- J/AJ/156/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A substantial fraction of our solar system's trans-Neptunian objects (TNOs) are in mean-motion resonance with Neptune. Many of these objects were likely caught into resonances by planetary migration-either smooth or stochastic- approximately 4 Gyr ago. Some, however, gravitationally scattered off of Neptune and became transiently stuck in more recent events. Here we use numerical simulations to predict the number of transiently stuck objects, captured from the current actively scattering population, that occupy 111 resonances at semimajor axes a=30-100 au. Our source population is an observationally constrained model of the currently scattering TNOs. We predict that, integrated across all resonances at these distances, the current transient-sticking population comprises 40% of the total transiently stuck+scattering TNOs, suggesting that these objects should be treated as a single population. We compute the relative distribution of transiently stuck objects across all p:q resonances with 1/6=<q/p=<1, p<40, and q<20, providing predictions for the population of transient objects with H_r_<8.66 in each resonance. We find that the relative populations are approximately proportional to each resonance's libration period and confirm that the importance of transient sticking increases with semimajor axis in the studied range. We calculate the expected distribution of libration amplitudes for stuck objects and demonstrate that observational constraints indicate that both the total number and the amplitude distribution of 5:2 resonant TNOs are inconsistent with a population dominated by transient sticking from the current scattering disk. The 5:2 resonance hence poses a challenge for leading theories of Kuiper Belt sculpting.
