arXiv subjects

Edson Otoniel

Publications and source records attributed to Edson Otoniel.

25 records · Page 2Linked to original sources

arXiv2026

Rotating strange dwarfs and their indistinguishability from white dwarfs

We investigate the structure of strange dwarfs, modeled as hybrid compact stars composed of a self bound strange quark matter core surrounded by a white dwarf like crust, within a fully relativistic framework. Static configurations are constructed by solving the Tolman Oppenheimer Volkoff equations, and uniformly rotating configurations are modeled within the Hartle Thorne slow rotation expansion (to ${\cal O}(Ω^2)$). We therefore interpret results at large fractional spins conservatively, and use the Kepler frequency mainly as a reference scale for comparing different masses and models. The stellar matter is described using a hybrid equation of state, in which the crust is modeled by a degenerate electron ion system and the core by the MIT Bag Model. By comparing strange dwarfs with conventional white dwarfs across a range of rotation rates, we show that rotation inflates the radius and can reduce (in a quantifiable way) the separation between the two families in the $(M,R)$ plane, potentially masking structural signatures associated with the presence of a quark core. Our results highlight the importance of accounting for rotational effects when interpreting mass radius measurements and other global observables in the context of searches for exotic compact objects in current and future high precision surveys.

astro-ph.SR↗

arXiv2026

Thin-Shell Wormholes from Entropy-Induced Black-Hole Geometries

Modified black-hole entropies can induce effective spacetime geometries and thereby provide a thermodynamic route for investigating thin-shell wormholes. In this work, we construct symmetric cut-and-paste wormholes from the generic entropic lapse function $F_{\mathcal S}(r)=1-4πM/\mathcal S'(r)$ and formulate the Darmois--Israel junction conditions directly in terms of the lapse and of the entropy derivatives. We derive the surface stresses, shell energy-condition combinations, conservation equation, and radial effective potential, and then apply the formalism to the Bekenstein--Hawking, Barrow, Tsallis--Cirto, Rényi, Kaniadakis, logarithmic, loop-quantum-gravity-inspired, and exponential entropy prescriptions. The analysis shows that the symmetric construction requires negative surface energy density throughout every admissible positive-lapse domain, although entropy deformations can significantly modify the horizon structure, the allowed throat region, and the localization of the surface stresses. Within the parameter domains considered here, all examined constant-barotropic branches are linearly radially unstable, despite quantitative changes in their near-horizon scales. In contrast, a variable Chaplygin shell can support stable configurations, with the stability domains determined jointly by the entropic geometry, the throat radius, and the radial exponent of the shell equation of state. These results establish a unified framework for comparing entropy-induced black-hole geometries as thin-shell wormhole seeds and show that stability is governed not by the entropy deformation alone, but by its interplay with the dynamical response of the matter localized at the throat.

gr-qc↗

arXiv2026

Double White Dwarf Mergers as Progenitors of Long-Period Transients

There is an ongoing discussion in the literature on the nature of long-period transients (LPTs), radio-emitting sources with periods ranging from hundreds to tens of thousands of seconds. Although some of these objects have been identified as white dwarf (WD) + M-dwarf binaries, this description currently does not fit the entire class. An example is GLEAM-X J162759.5-523504.3 (hereafter GLEAM-X J1627-5235), with a period of 1091 s, for which the lack of an optical counterpart disfavors the presence of such a binary system. In this case, GLEAM-X J1627-5235 could be interpreted as an isolated, massive, fast-rotating, and highly magnetized (~ 1e+9 G) WD pulsar. Its properties are consistent with a carbon-oxygen WD of mass ~1.3 Msun and radius ~2500 km, possibly supported by small-scale multipolar magnetosphere structures that keep it above the death line for WD-pulsars. We assess a double WD merger origin, modeling the post-merger rotational evolution under accretion, propeller, and magnetic braking torques. We find rotational age of ~572 Myr for GLEAM-X J1627-5235, i.e., the post-merger time required to reach its observed period. This result is consistent with current optical upper limits for GLEAM-X J1627-5235 and support the WD pulsar interpretation for this source. We also discuss how the same model can apply to other LPTs.

astro-ph.HE↗

arXiv2026

White dwarf structure in $f(R,T,L_m)$ gravity: beyond the Chandrasekhar mass limit

In this work, we investigate the relativistic structure of white dwarfs (WDs) within the framework of modified gravity theory $f(R, T, L_m) = R + αT L_m$, which introduces a non-minimal coupling between matter and curvature. Using a realistic equation of state (EoS) that includes contributions from a relativistic degenerate electron gas and ionic lattice effects, we solve the modified Tolman-Oppenheimer-Volkoff (TOV) equations for two standard choices of the matter Lagrangian density: $L_m = p$ and $L_m = -ρ$. We show that the extra $αTL_m$ term significantly alters the mass-radius relation of WDs, especially at high central densities $( ρ_c \gtrsim 10^8 - 10^9\,\rm g/cm^3)$, allowing for stable super-Chandrasekhar configurations. In particular, depending on the sign and magnitude of the parameter $α$, the maximum mass can increase or decrease, and in some regimes, the usual critical point indicating the transition from stability to instability disappears. Our findings suggest that $f(R,T,L_m)$ gravity provides a viable framework to explain the existence of massive WDs beyond the classical Chandrasekhar limit. Using Bayesian inference with WD observational data, we further constrain the coupling parameter $α$ for the two choices of the Lagrangian density $L_m$.

gr-qc↗

arXiv2025

Quantum improved wormholes in the Dekel-Zhao dark matter halo

This work presents and investigates novel traversable wormhole solutions within the framework of Asymptotically Safe Gravity (ASG), sourced by a dark matter halo modeled by the Dekel--Zhao density profile. The scale-dependent gravitational coupling $G(k)$, derived from the ASG renormalization group flow in the infrared regime, is incorporated directly into the field equations, providing a consistent description of quantum gravitational corrections even at astrophysical scales. The combined effects of the running coupling (parameterized by $ξ$) and the dark matter characteristics determine the geometric structure and physical viability of the wormhole. The solutions satisfy the flare-out and asymptotic flatness conditions within restricted parameter domains, exhibiting enhanced curvature near the throat due to ASG corrections. Null Energy Conditions are necessarily violated at the throat, and stability analysis based on the adiabatic sound speed as well as the modified Tolman--Oppenheimer--Volkoff equation reveal that quantum effects from ASG counteract the destabilizing influence of dark matter. Phenomenologically, the wormhole shadow radius increases nearly linearly with $ξ$, lying within the Event Horizon Telescope bounds for Sgr~A$^*$ when $ξ/M \simeq 0.8--0.9$, thus suggesting that ASG-corrected wormholes may represent observable signatures of quantum gravity in the strong-field regime.

gr-qc↗

arXiv2021

Mass limits of the extremely fast-spinning white dwarf CTCV J2056-3014

CTCV J2056--3014 is a nearby cataclysmic variable with an orbital period of approximately $1.76$ hours at a distance of about $853$ light-years from the Earth. Its recently reported X-ray properties suggest that J2056-3014 is an unusual accretion-powered intermediate polar that harbors a fast-spinning white dwarf (WD) with a spin period of $29.6$ s. The low X-ray luminosity and the relatively modest accretion rate per unit area suggest that the shock is not occurring near the WD surface. It has been argued that, under these conditions, the maximum temperature of the shock cannot be directly used to determine the mass of the WD (which, under the abovementioned assumptions, would be around $0.46$ $M_\odot$). Here, we explore the stability of this rapidly rotating WD using a modern equation of state (EoS) that accounts for electron--ion, electron--electron, and ion--ion interactions. For this EoS, we determine the mass density thresholds for the onset of pycnonuclear fusion reactions and study the impact of microscopic stability and rapid rotation on the structure and stability of WDs, considering them with helium, carbon, oxygen, and neon. From this analysis, we obtain a minimum mass for CTCV J2056--3014 of $0.56~M_\odot$ and a maximum mass of around $1.38~M_\odot$. If the mass of CTCV J2056--3014 is close to the lower mass limit, its equatorial radius would be on the order of $10^4$~km due to rapid rotation. Such a radius is significantly larger than that of a nonrotating WD of average mass ($0.6\, M_\odot$), which is on the order of $7\times 10^3$~km. The effects on the minimum mass of J2056-3014 due to changes in the temperature and composition of the stellar matter were found to be negligibly small.

astro-ph.SR↗

arXiv2017

Very Magnetized White Dwarfs with Axisymmetric Magnetic Field and the Importance of the Electron Capture and Pycnonuclear Fusion Reactions for their Stability

In this work, we study the properties of magnetized white dwarfs taking into account possible instabilities due to electron capture and pycnonuclear fusion reactions in the cores of such objects. The structure of white dwarfs is obtained by solving the Einstein-Maxwell equations with a poloidal magnetic field in a fully general relativistic approach. The stellar interior is composed of a regular crystal lattice made of carbon ions immersed in a degenerate relativistic electron gas. The onsets of electron capture reactions and pycnonuclear reactions are determined with and without magnetic fields. We find that magnetized white dwarfs violate the standard Chandrasekhar mass limit significantly, even when electron capture and pycnonuclear fusion reactions are present in the stellar interior. We obtain a maximum white dwarf mass of around $2.14\,M_{\odot}$ for a central magnetic field of $\sim 3.85\times 10^{14}$~G, which indicates that magnetized white dwarfs may play a role for the interpretation of superluminous type Ia supernovae. Furthermore, we show that the critical density for pycnonuclear fusion reactions limits the central white dwarf density to $9.35\times 10^9$ g/cm$^3$. As a result, equatorial radii of white dwarfs cannot be smaller than $\sim 1100$~km. Another interesting feature concerns the relationship between the central stellar density and the strength of the magnetic field at the core of a magnetized white dwarf. For high magnetic fields, we find that the central density increases (stellar radius decrease) with magnetic field strength, which makes ultramagnetized white dwarfs more compact. The opposite is the case, however, if the central magnetic field is less than $\sim 10^{13}$~G. In the latter case, the central density decreases (stellar radius increases) with central magnetic field strengths.

astro-ph.SR↗