Traversable wormholes inside anisotropic magnetized neutron stars: physical properties and potential observational imprints

TL;DR

The paper develops a ghost-free model of WH+NS systems by coupling GR to two nondynamical scalar fields in the presence of anisotropic neutron-fluid matter and chaotic magnetic fields. It demonstrates that NEC violation near the wormhole throat—and thus traversability—persists regardless of anisotropy or magnetic fields, while the scalar sector drives the exotic behavior. Through two construction approaches, it shows WH+NS configurations can be extremely massive (surpassing several solar masses) and ultracompact, with large surface redshifts and potential gravitational-wave echoes whose properties depend on the magnetic-field configuration. The study provides quantitative predictions for ADM mass, throat size, redshift, and echo-time, offering observational imprints that could guide future gravitational-wave and electromagnetic searches for exotic compact objects.

Abstract

In this paper, we formulate wormhole-plus-neutron-star (WH+NS) systems supported by two scalar fields, allowing for both pressure anisotropy and magnetic fields. In general, such WH+NS systems contain ghosts; however, these ghosts can be eliminated. We find that neither anisotropy nor magnetic fields affect the traversability of the wormhole. In particular, the null energy condition (NEC) remains violated in the vicinity of the wormhole throat, ensuring the traversable nature of the geometry. For magnetized configurations, the resulting WH+NS systems can become extremely massive, with ADM masses exceeding $8\,M_\odot$, and can exhibit large surface redshifts exceeding $z \simeq 1.5$. Furthermore, we analyze the gravitational-wave echo time of the systems, which serves as a potential observational imprint. Our results indicate that the echo time can vary depending on the magnetic field configuration, suggesting that WH+NS systems may provide distinctive signals of gravitational echo.

Figures (12)

• Figure 1: Mass–radius relation of the pure NSs and the WH+NS systems for different values of $h$. Panels (a) and (b) correspond to Approach 1 and Approach 2, respectively.
• Figure 2: Radii of the stellar surface and the wormhole throat in the WH+NS configurations as functions of the ADM mass for different values of $h$. Panels (a) and (b) correspond to Approach 1 and Approach 2, respectively.
• Figure 3: Compactness of the WH+NS systems as a function of the ADM mass for different values of $h$. Panels (a) and (b) correspond to Approach 1 and Approach 2, respectively.
• Figure 4: Surface redshift of the WH+NS systems as a function of the ADM mass for different values of $h$. Panels (a) and (b) correspond to Approach 1 and Approach 2, respectively.
• Figure 5: Echo time of the WH+NS systems as a function of the ADM mass for different values of $h$. Panels (a) and (b) correspond to Approach 1 and Approach 2, respectively.