Thermal radiation of thin accretion disk around Taub-NUT black hole

Abstract

The effects of a gravitomagnetic charge on the thermal radiation properties of a thin accretion disk surrounding a non-rotating black hole are studied. The studied system consists of a non-rotating black hole with a non-zero gravitomagnetic charge and a Novikov–Thorne disk that is thin and optically thick. It is found that the gravitomagnetic charge enhances the gravitational field of the central black hole, resulting in an increase in the event horizon and innermost stable circular orbit (ISCO) radii. However, the maximum flux of radiant energy from the accretion disk is reduced and shifted outward from the central object due to the effect of the gravitomagnetic charge. The thermal profile of the accretion disk also exhibits a similar dependence on the radial coordinate and the gravitomagnetic charge of the black hole. The radiative efficiency of the accretion disk decreases from around 6% to approximately 2% with an increase in the value of the gravitomagnetic charge by [Formula: see text]. The thermal spectra of the accretion disk are also shifted towards lower frequencies, corresponding to the gravitational redshift of electromagnetic radiation coming from the disk, with an increase in the value of the gravitomagnetic charge. One may conclude that the effect of the gravitomagnetic charge is opposite to the effect of black hole spin.