Mergers and Tidal Breakups of Binary Systems of Primordial DM Planets with Baryon Admixture and Emission of Gravitational Waves

Abstract

Here, we discuss the possibility of the admixture of baryons to the DM primordial planets, with the DM particles varying in mass from 20 GeV to 100 GeV. We have considered different fractions of admixture particles to form the planet. The mass of the primordial planet made completely of DM ranges from asteroid mass to Neptune mass. However, the mass of primordial planets (admixed with DM and baryonic matter) is found to increase with the fraction of baryonic matter in the planets, and the mass of these objects can go well beyond the mass of Jupiter (around 40 times Jupiter’s mass) and can also approach sub-stellar mass (brown dwarf mass). So far, thousands of exoplanets have been discovered by the Kepler mission and more will be found by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, which is observing the entire sky to locate planets orbiting the nearest and brightest stars. Many exoplanets, such as exo-Jupiter, discovered so far fall in this mass range, and unsure whether these exoplanets are entirely made of baryons. Some of the exoplanets with a mass several times Jupiter’s mass could be possible signatures of the presence of primordial planets with an admixture of baryonic and DM particles. It is also found that some of these planets could reach even sub-stellar mass (1032 g), such as that of a brown dwarf. Additionally, even if a small fraction of DM particles is trapped in these objects, the flux of ambient DM particles would be reduced significantly. This could be one of the many reasons for not detecting the DM particles in various experiments, such as XENON1T, etc., as suggested earlier. If two such primordial planets (in a binary system) merge, they will release a lot of energy. The energy released in gravitational waves, as well as the time scale of the merger of these objects, is found to increase with the mass of primordial objects. The frequency of gravitational waves emitted in these systems is matching within the range of LIGO. The objects near the galactic center could consist of such primordial objects, planets, comets, etc. We also discuss the possibility of the tidal break up of these primordial objects in the presence of a BH. The mass of BH required for tidal break up is calculated, and it is found that the mass of BH required for tidal break up increases with the DM particle mass and also with the increase in the fraction of baryons in these objects. The energy released during tidal breakup will be emitted as gravitational waves. The energy released, as well as the frequency of waves, is tabulated, and the frequency is in the sensitivity range of LIGO.

Keywords

• primordial planets
• dark matter
• DM
• baryonic admixture
• early universe