http://arxiv.org/abs/1908.06815
The tentative evidences for late time “echoes” in LIGO gravitational waves (GWs) have been claimed to be signatures of horizonless compact objects rather than vacuum black holes (BHs) possessing horizons. In general, in the past, many authors have considered the possibility that the so-called BHs might be only BH mimickers (BHMs). And recently it has been suggested that the true astrophysical BH having no intrinsic magnetic fields may be differentiated from magnetized BHMs by studying the radial variations of magnetic fields around pertinent compact objects (Lobanov, Nat. Astron. 2017). Here we highlight that close to the surface of BHMs, the magnetic field pattern differs significantly from the same for non-relativistic Neutron Stars (B\sim r^{-3}). In particular, we point out that for ultra-compact BHMs, the polar field is weaker than the equatorial field by an extremely large factor of \sim z_{s}/lnz_{s}, where z_{s}\gg1 is the surface gravitational redshift. We suggest that by studying the of radial variation as well as such significant asymmetry of magnetic field structure near the compact object, future observations may differentiate a theoretical black hole from a astrophysical BH mimicker (a compact object). This study also shows that even if some BHMs would be hypothesized to possess magnetic fields even stronger than that of magnetars, in certain cases, they may effectively behave as atoll type neutron stars possessing extremely low magnetic fields.
A. Mitra, C. Corda and H. Cuesta
Tue, 20 Aug 19
69/86
Comments: 15 pages, prepared for JCAP submission