Cooling of dark-matter admixed neutron stars with density-dependent equation of state

Abstract

We propose a dark-matter (DM) admixed density-dependent equation of state where the fermionic DM interacts with the nucleons via Higgs portal. Presence of DM can hardly influence the particle distribution inside neutron star (NS) but can significantly affect the structure as well as equation of state (EOS) of NS. Introduction of DM inside NS softens the equation of state. We explored the effect of variation of DM mass and DM Fermi momentum on the NS EOS. Moreover, DM-Higgs coupling is constrained using dark matter direct detection experiments. Then, we studied cooling of normal NSs using APR and DD2 EOSs and DM admixed NSs using dark-matter modified DD2 with varying DM mass and Fermi momentum. We have done our analysis by considering different NS masses. Also DM mass and DM Fermi momentum are varied for fixed NS mass and DM-Higgs coupling. We calculated the variations of luminosity and temperature of NS with time for all EOSs considered in our work and then compared our calculations with the observed astronomical cooling data of pulsars namely Cas A, RX J0822-43, 1E 1207-52, RX J0002+62, XMMU J17328, PSR B1706-44, Vela, PSR B2334+61, PSR B0656+14, Geminga, PSR B1055-52 and RX J0720.4-3125. It is found that APR EOS agrees well with the pulsar data for lighter and medium mass NSs but cooling is very fast for heavier NS. For DM admixed DD2 EOS, it is found that for all considered NS masses, all chosen DM masses and Fermi momenta agree well with the observational data of PSR B0656+14, Geminga, Vela, PSR B1706-44 and PSR B2334+61. Cooling becomes faster as compared to normal NSs in case of increasing DM mass and Fermi momenta. It is infered from the calculations that if low mass super cold NSs are observed in future that may support the fact that heavier WIMP can be present inside neutron stars.

Effects of dark matter on the nuclear and neutron star matter

“…From this, we conclude that one can constraint the DM percentage inside the NS. If the DM percentage is more than canonical star, it forms a mini black hole at the core and destroys the NS ( The cooling of NS is also faster with the increasing of DM mass (Ding et al 2019;Bhat & Paul 2020). That means the positive B may have a relation with the cooling properties of the NS or in other words; it may accelerate the urca process.…”

“…The detailed discussions can be found in our previous calculations (Das et al 2020). As we know that the addition of DM softens the EoS, reduce mass-radius of the NS (Li et al 2012;Das et al 2019;Bhat & Paul 2020;Quddus et al 2020;Das et al 2020).…”

Dark Matter Effects on the Compact Star Properties

“…After accretion of the DM, this affects properties of the NS. If the DM is self-annihilating in nature, it heats the NS and fastens the cooling rate [51,52], while the non-self-annihilating DM is deposited in the star core and influences the structural properties [40,53,54]. The effects of bosonic DM on the gravitational wave signals were studied in Ref.…”

Impacts of dark matter on the $f$-mode oscillation of hyperon star

“…With the addition of DM, the EOS of the NS becomes softer and M , R and dimensionless tidal deformability (Λ) decreases [25,26]. Different phenomena such as the cooling rate becomes faster for DM admixed NS [28]. If the self-gravitating DM particle having a mass more than the Chandrasekhar limit, it forms a mini black hole, and destroys the NS [22].…”