#FRUITY TRACKS 2.04 UPGRADE#

Consequently, the physical conditions for triggering He burning in the He intershell are reached earlier during the AGB phase compared to models with lower initial masses. In particular, their larger initial masses produce more compact cores, and thus larger temperatures can be obtained in their interiors. The evolution of those objects resembles that of their low-mass counterparts, even if noticeable differences exist. In this paper, we present a new set of AGB models with larger initial masses (4 в‰¤ M/ M в‰¤ 6). To date, FRUITY only includes low-mass stars (i.e., stars with initial masses M в‰¤ 3 ). Through a web interface, we provide tables of the isotopic and elemental compositions as well as the stellar yields of AGB stars.

For the past several years, we have made our AGB yields available on the FRUITY database (Cristallo et al. Sets of AGB stars need uniform (i.e., computed with the same code) and complete (i.e., containing a large number of masses) information in order to properly describe the chemical evolution of the host systems. The interested reader can find a vast body of literature on AGB stars (Iben & Renzini 1983 Herwig 2005 Straniero et al.

AGB stars efficiently synthesize both light (C, N, F, and Na) and heavy elements (those created via the slow neutron capture process, the s-process). During AGB, a strong stellar wind erodes the convective envelope, thus polluting the interstellar medium. Meanwhile, the products of internal nucleosynthesis appear on the stellar surface. If the expansion has been large enough, then the H-shell switches off and the convective envelope can penetrate the H-exhausted and chemically enriched He-intershell (this phenomenon is known as Third Dredge Up, TDU). Then, the layers above expand and cool until the convective shell is quenched. The rate of nuclear energy is too large to be carried away by radiation, and thus a convective shell develops which makes the He-intershell chemically homogenous. This situation is repeatedly interrupted by the growth of thermonuclear runaway thermal pulses (TPs) in the He-intershell, triggered by the activation of 3 О± reactions. The surface luminosity is mainly sustained by the H-burning shell. During the AGB, the structure consists of a partially degenerate CO core, an He-shell, and an H-shell separated by a thin helium-rich layer (the so-called He-intershell) and an expanded and cool convective envelope. The evolution of such objects is characterized by a sequence of burning and mixing episodes which carry the nuclear products synthesized in the internal layers to the stellar surface.

#FRUITY TRACKS 2.04 UPGRADE#

Finally, we present the upgrade of the FRUITY web interface, which now also includes the physical quantities of the TP-AGB phase for all of the models included in the database (ph-FRUITY).ДЄsymptotic giant branch (AGB) stars are ideal laboratories to test our understanding of stellar interiors. Moreover, we quantify the influence intermediate-mass models have on the carbon star luminosity function. We compare our theoretical final core masses to available white dwarf observations. At low metallicities, our models undergo hot bottom burning and hot third dredge up. In particular, the s-process distributions of the more massive models are dominated by the 22Ne( О±,n) 25Mg reaction, which is efficiently activated during TPs.

Depending on the initial stellar mass, the heavy element nucleosynthesis is dominated by different neutron sources. Moreover, the high temperature at the base of the convective envelope prevents it from deeply penetrating the underlying radiative layers. This effect is due to the fact that the interpulse phases are short and, therefore, thermal pulses (TPs) are weak. Due to less efficient third dredge up episodes, models with large core masses show modest surface enhancements. We describe the physical and chemical evolution of the computed models from the main sequence up to the end of the AGB phase. This set integrates the existing models for low-mass AGB stars (1.3 в‰¤ M/ M вЉ™ в‰¤ 3.0) already included in the FRUITY database. We present a new set of models for intermediate-mass asymptotic giant branch (AGB) stars (4.0, 5.0, and 6.0 M вЉ™) at different metallicities (в€’2.15 в‰¤ в‰¤ +0.15).

Fruity tracks 2.04