arXiv subjects

M. L. Novarino

Publications and source records attributed to M. L. Novarino.

5 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

Formation and nature of "Huntsman" binary pulsars

Spider systems are a class of close binaries in which a neutron star first accretes from a normal companion, and later ablates it in some cases. New observations have expanded this category, with the addition of a Huntsman group, tentatively linked to a short donor phase along the red bump in the secondary evolutionary track. We present explicit evolutionary tracks that support the Huntsman nature recently suggested, and discuss how the whole class of spiders emerges from the full consideration of irradiation and ablating winds. We address the irradiation feedback (IFB) effects and the hydrogen-shell burning detachment (HSBD) simultaneously, and show that they act independently and do not interfere with each other, supporting a physical picture of the Huntsman group. We employ our binary evolution code to compute a suite of binary systems formed by a donor star and a neutron star for different initial orbital periods, assuming solar composition and Z=0.01. Although many models do not consider IFB, we also present the evolution with IFB for one system as an example. We found that the recently suggested association of Huntsman pulsar with the evolutionary stage where (as a consequence of the dynamics of HSBD) the system remains detached for a few million years is plausible. However, this feature alone is unable to account for the occurrence of Redback spider pulsars. Meanwhile, models including IFB, with pulsed mass transfer, display detachment episodes that can be naturally associated with the Redback stage. Irradiation feedback does not preclude or modify HSBD and in fact, Huntsman systems were already present as an implicit prediction in our earlier calculations. We conclude that Huntsman is an expected stage of the spider systems under quite general conditions. This is another step towards a unified picture of spider pulsars as a group.

astro-ph.SR↗

arXiv2024

The impact of different magnetic braking prescriptions on the evolution of LMXBs

We revisit the evolution of low-mass close binary systems under different magnetic braking (MB) prescriptions. We study binaries with a neutron star accretor. During mass transfer episodes, these systems emit X-rays and are known as Low Mass X-ray Binaries (LMXBs). When mass transfer stops, they can be observed as binary pulsars. Additionally, some of these systems can experience mass transfer while having orbital periods of less than 1 hr, thus evolving into ultracompact X-ray binaries (UCXBs). The evolution of LMXBs depends on their capability to lose angular momentum and maintain stable mass transfer. Among the angular momentum loss mechanisms, MB is one important, and still uncertain phenomenon. The standard MB prescription faces some problems when calculating LMXB evolution, leading to, e.g., a fine-tuning problem in the formation of UCXBs. Recent studies proposed new MB prescriptions, yielding diverse outcomes. Here, we investigate the effects of three novel MB prescriptions on the evolution of LMXBs using our stellar code. We found that all MB prescriptions considered allow the formation of binaries with orbital periods spanning from less than one hour to more than tens of days. Remarkably, our results enable the occurrence of wide systems even for the MB law that causes the strongest angular momentum losses and very high mass transfer rates. We found that models computed with the strongest MB prescription reach the UCXB state starting from a wider initial orbital period interval. Finally, we discuss and compare our results with observations and previous studies performed on this topic.

astro-ph.HE↗

arXiv2021

Effect of tides on the orbital evolution of the redback system PSR 1723-2837

The standard model of stellar evolution in Close Binary Systems assumes that during mass transfer episodes the system is in a synchronised and circularised state. Remarkably, the redback system PSR J1723-2837 has an orbital period derivative $\dot{P}_{orb}$ too large to be explained by this model. Motivated by this fact, we investigate the action of tidal forces in between two consecutive mass transfer episodes for a system under irradiation feedback, which is a plausible progenitor for PSR J1723-2837. We base our analysis on Hut's treatment of equilibrium tidal evolution, generalised by considering the donor as a two layers object that may not rotate as a rigid body. We also analyse three different relations for the viscosity with the tidal forcing frequency. We found that the large value measured for $\dot{P}_{orb}$ can be reached by systems where the donor star rotates slower (by few percent) than the orbit just after mass transfer episodes. Van Staden & Antoniadis have observed this object and reported a lack of synchronism, opposite to that required by the Hut's theory to account for the observed $\dot{P}_{orb}$. Motivated by this discrepancy, we analyse photometric data obtained by the spacecraft Kepler second mission K2, with the purpose of identifying the periods present in PSR J1723-2837. We notice several periods close to those of the orbit and the rotation. The obtained periods pattern reveals the presence of a more complex phenomenology, which would not be well described in the frame of the weak friction model of equilibrium tides.

astro-ph.SR↗

arXiv2020

Binary evolution leading to the formation of the very massive neutron star in the J0740+6620 binary system

We study the evolution of close binary systems in order to account for the existence of the recently observed binary system containing the most massive millisecond pulsar ever detected, PSR J0740+6620, and its ultra-cool helium white dwarf companion. In order to find a progenitor for this object we compute the evolution of several binary systems composed by a neutron star and a normal donor star employing our stellar code. We assume conservative mass transfer. We also explore the effects of irradiation feedback on the system. We find that irradiated models also provide adequate models for the millisecond pulsar and its companion, so both irradiated and non irradiated systems are good progenitors for PSR J0740+6620. Finally, we obtain a binary system that evolves and accounts for the observational data of the system composed by PSR J0740+6620 (i.e. orbital period, mass, effective temperature and inferred metallicity of the companion, and mass of the neutron star) in a time scale smaller than the age of the Universe. In order to reach an effective temperature as low as observed, the donor star should have an helium envelope as demanded by observations.

astro-ph.SR↗