Rotating strange dwarfs and their indistinguishability from white dwarfs

TL;DR

This paper models rotating strange dwarfs with hybrid quark matter cores and white dwarf crusts, showing rotation effects can make them resemble white dwarfs in mass-radius observations, complicating their identification.

Contribution

It provides a relativistic framework for modeling rotating strange dwarfs and demonstrates how rotation influences their observable properties, potentially masking their exotic nature.

Findings

Rotation inflates the radius of strange dwarfs.

Rotation can reduce the mass-radius separation between strange dwarfs and white dwarfs.

Accounting for rotation is crucial in interpreting observational data for exotic compact objects.

Abstract

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 ${\cal O}(\Omega^2)$). 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.