arXiv subjects

L. Bartolomeo Koninckx

Publications and source records attributed to L. Bartolomeo Koninckx.

3 recordsLinked to original sources

arXiv2025

Stellar Evolution in Close Binaries: Processes and Outcomes

We discuss some aspects of stellar evolution in binary systems. While single stars can swell following the chemical evolution of their interior, stars belonging to binary systems cannot overflow the size of the Roche lobe and hydrostatic equilibrium is strictly impossible. The system is forced to exchange mass between its members through the inner Lagrangian point. In the first part of the paper, we discuss the standard evolution of binaries that have a non-degenerate donor star and a compact companion. We show that the model fails when to account for the occurrence of binary pulsars when they predict a long-standing mass transfer episode. Models including irradiation feedback and evaporation in close binaries are examined next. Following these sections, we discuss the case of systems with a black hole (BH). We show that if BHs are born non-rotating, binary interaction seems insufficient to speed them up, an indication that BH rotation is a feature present at birth. Finally, we discuss Blue Straggler Stars detected in open and globular clusters. Since they cannot be understood as single-born stars, we evaluate one of the proposed channels is mass transfer in close binaries, and discuss its viability and the limitations of the present models.

astro-ph.SR↗

arXiv2025

Understanding the evolution of black hole spin in X-ray binary systems: Case study of XTE~J1550-564

We present a comprehensive study of the X-ray binary system XTE~J1550-564, with the primary objective of analyzing the evolution of the black hole's spin parameter. To achieve this objective, we embarked on the necessary step of identifying a plausible progenitor for the system. Using a set of models covering various parameter combinations, we were able to replicate the system's observed characteristics within acceptable error margins, including fundamental parameters such as component masses, orbital period, donor luminosity, and effective temperature. The model results indicate the possibility of diverse evolutionary pathways for the system, highlighting the significant role played by the initial mass of the donor star and the efficiency of mass transfer episodes. While some models are well-aligned with estimates of the mass transfer rate, they all fall short of explaining the black hole's observed moderate spin ($a^* = 0.49$). We also explored alternative magnetic braking prescriptions, finding that only an extreme and fully conservative scenario, based on the convection and rotation boosted prescription, can reproduce the observed spin and only in a marginal way. Our study attempts to shed light on the complex dynamics of black hole X-ray binaries and the challenges of explaining their observed properties with theoretical models.

astro-ph.HE↗

arXiv2023

An evolutionary model for V404 Cyg system

V404 Cyg is a Low Mass X-Ray Binary (LMXB) system that has undergone outbursts in 1938, 1989, and 2015. During these events, it has been possible to determine relevant data of the system; such as the masses of the compact object (a black hole, BH) and its companion, the orbital period, the companion spectral type, and luminosity class, among others. Remarkably, the companion star has a metallicity appreciably higher than solar. All these data allow us to construct theoretical models to account for its structure, looking for its initial configuration and predicting its final fate. Assuming that the BH is already formed when the primary star reaches the Zero Age Main Sequence, we used our binary evolution code for such a purpose. We obtained that the present characteristics of the system are nicely accounted for by a model with initial masses of 9 solar masses for the BH, 1.5 solar masses for the companion star, an initial orbital period of 1.5 d and considering that at most 30% of the mass transferred by the donor is accreted by the BH. The metallicity of the donor for our best fit was Z = 0.028 (twice solar metallicity). We also studied the evolution of the BH spin parameter assuming that initially, it is not rotating. Remarkably, the spin of the BHs in our models is far from reaching the available observational determination. This may indicate that the BH in V404 Cyg is initially spinning, a result that may be relevant for understanding the formation BHs in the context of LMXB systems.

astro-ph.SR↗