We investigate the stability and $e^{+}{e}^{-}$ pair creation of supercritically charged superheavy nuclei, $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets based on the Thomas-Fermi approximation. The model parameters are fixed by reproducing masses and charge properties of these supercritically charged objects reported in earlier publications. It is found that $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets may be more stable than ${}^{56}\mathrm{Fe}$ at the baryon number $A\gtrsim 315$, $5\times {10}^4$, and $1.2\times {10}^8$, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $\sim 965$, while $ud\mathrm{QM}$ nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than 39, 433, and $2.7\times {10}^5$. The $e^{+}{e}^{-}$ pair creation will inevitably start for superheavy nuclei with charge numbers $Z\ge 177$, for $ud\mathrm{QM}$ nuggets with $Z\ge 163$, for strangelets with $Z\ge 192$, and for strangeon nuggets with $Z\ge 212$. A universal relation $Q/R_e=(m_e-{\overline{\mu }}_e)/\alpha$ is obtained at a given electron chemical potential ${\overline{\mu }}_e$, where $Q$ is the total charge and $R_e$ the radius of electron cloud. The maximum number of $Q$ without causing $e^{+}{e}^{-}$ pair creation is then fixed by taking ${\overline{\mu }}_e=-m_e$. For supercritically charged objects with ${\overline{\mu }}_e<-m_e$, the decay rate for $e^{+}{e}^{-}$ pair production is estimated based on the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. It is found that most positrons are emitted at $t\lesssim {10}^{-15}\mathrm{s}$, while a long lasting positron emission can be observed for large objects with $R\gtrsim 1000\mathrm{fm}$. The emission of positrons and electron-positron annihilation from supercritically charged objects may be partially responsible for the short $\gamma$-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in x-ray spectra from galaxies and galaxy clusters.

• Received 4 February 2020
• Accepted 6 May 2020

DOI:https://doi.org/10.1103/PhysRevD.101.103031