Does the gravitomagnetic monopole exist? A clue from a black hole x-ray binary

Abstract

The gravitomagnetic monopole is the proposed gravitational analogue of Dirac's magnetic monopole. However, an observational evidence of this aspect of fundamental physics was elusive. Here, we employ a technique involving three primary X-ray observational methods used to measure a black hole spin to search for the gravitomagnetic monopole. These independent methods give significantly different spin values for an accreting black hole. We demonstrate that the inclusion of one extra parameter due to the gravitomagnetic monopole not only makes the spin and other parameter values inferred from the three methods consistent with each other but also makes the inferred black hole mass consistent with an independently measured value. We argue that this first indication of the gravitomagnetic monopole, within our paradigm, is not a result of fine tuning. * Electronic address: chandra@pku.edu.cn † Electronic address: sudip@tifr.res.in

On some novel features of the Kerr–Newman-NUT spacetime

“…Thus the QPO frequencies will be affected (or, modified) by the presence of NUT charge and may lead to some interesting bound on the same when compared to observational measurements. This provides one of the astrophysical grounds to test the existence of the NUT parameter on black holes within the the Kerr-Newman-NUT family (for an attempt in a similar direction, see [77]). Besides, the special structure of ∆ appearing in the situation under consideration modifies the QPO frequencies in a significant manner, compared to the other members of the Kerr-Newman-NUT family.…”

Circular orbits in Kerr-Taub-NUT spacetime and their implications for accreting black holes and naked singularities

“…Before going into the more detail, we should first clarify that we mainly focus on the equatorial circular orbits in this paper. Therefore, we can directly use the expressions of three fundamental frequencies which have already been deduced for KTN spacetime in [24] using the general formulation derived by Ryan [32]. These are orbital frequency (Ω φ ) or the Kepler frequency…”

“…where m = M (r 2 − n 2 ) + 2 n 2 r, and the radial (Ω r ) and vertical (Ω θ ) epicyclic frequencies [24] Ω r = ± 1…”

“…Among all these solutions, the most prominent solution is Kerr spacetime, as it is astrophysically relevant. However, in a very recent paper [24], the first observational indication of the gravitomagnetic monopole has been reported and this makes the KTN spacetime astrophysically relevant. Based on the X-ray observations of an astrophysical collapsed object, black hole (BH) or naked singularity (NS), GRO J1655-40, it has been inferred there that this object contains the non-zero gravitomagnetic monopole.…”

“…Employing a new technique, Ref. [24] has demonstrated that the inclusion of one extra parameter (i.e., gravitomagnetic monopole or NUT parameter n) not only makes the spin and other parameter values inferred from the three methods consistent with each other, but also makes the inferred black hole mass consistent with an independently measured value. Therefore, it may be advantageous to use the more general KTN spacetime for accreting collapsed objects, such as GRO J1655-40.…”