| Abstract : | Recently, several neutron stars (NSs), particularly pulsars, with mass > 2 solar mass have been observed from gravitational wave mergers as well as pulsar timing studies. On the other hand, the existence of massive white dwarfs (WDs), even violating the Chandrasekhar mass limit, was inferred from the peak luminosities of type Ia supernovae. Hence, there is a generic question of the origin of massive compact objects. Here we explore the existence of massive, magnetized, rotating compact objects using GRMHD code XNS. We visualize the deformation due to magnetic field (toroidal and/or poloidal) and rotation, by solving the Einstein equation (describing space-time metric) and Magneto-Hydrostatic Equilibrium (providing distribution of matter/energy) simultaneously for stationary stellar equilibria. Our aim here is to understand the detection possibility of isolated, massive, magnetized NSs and WDs, which are difficult to detect in electromagnetic surveys, such as SDSS, Kepler, Gaia. Such isolated rotating objects with magnetic field and rotation axes misaligned, hence (triaxial system) having non-zero obliquity angle, can emit continuous gravitational waves (GWs), which can be detected by upcoming detectors.. We discuss the decays of magnetic field, angular velocity, and obliquity angle with time, due to Hall, Ohmic, ambipolar diffusion and angular momentum extraction by GW and dipole radiation, which determine the timescales related to the GW emission. These explorations suggest that the detection of massive compact objects is challenging and sets a timescale for detection. We calculate the signal-to-noise ratio of GW emission, which confirms that many detector cannot detect them immediately, but may be detectable by Einstein Telescope, Cosmic Explorer and BBO, DECIGO over months of integration time, leading to direct detection of NSs and WDs respectively.
Reference: ApJ, 955 (2023) 1, 19
doi: 10.3847/1538-4357/aceb63 |
