  It is known that spinning pulsars could be source of VHE-UHE cosmic particle
acceleration. It is also conjectured that (fictitious) spinning Black Holes
(BH) could be sites of cosmic particle acceleration. However, it has been shown
by Mitra and Leiter and Robertson that General Relativity (GR) actually does
not allow the existence or formation of finite mass BHs. It was predicted that
the BH Candiadates (BHCs) have strong intrinsic magnetic fields (like pulsars)
instead of Event Horizons. And this prediction has tentatively been verified in
a series of papers by Robertson & Leiter. Thus all observed BH Candidates are
actually not BHs, and, they are expected to be MECOs. Stellar mass MECOs are GR
analogs of conventionally known isolated pulsars. While pulsars are/have (i)
COLD, i.e., not supported by radiation pressure, MECOs are HOT, i.e., supported
primarily by trapped radiation pressure, (ii) upper mass limit of 3-4 Msolar
MECOs, being HOT, have no Upper Mass Limit, (iii) surface gravitational red
shift, z ~ 0.1 -0.2, MECOs have z >> 1 so that photons can remain almost
permanently trapped inside them, (iv) magnetic field B <10^{13} G, for MECOs
the local value of B >> 10^{13} G. It may be recalled that isolated (non-
accreting) uncharged BHs are cold and dead objects without any physical
activity. On the other hand, isolated spinning MECOs are like extreme GR
pulsars.

General Physics