MG11 
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Abstract

Does Sgr A* Have an Intrinsic Magnetic Moment instead of an Event Horizon?

The Low quiesecent x-ray luminosities, spectral state switches and correct radio/x-ray luminosity correlation for galactic black hole candidates (GBHC) have recently been sucessfully explained by realizing that GBHCs are magnetized eternally collapsing objects (MECO) having (1) strong intrinsic magnetic field, (2) extremely high but finite surface redshift and no (3) Event Horizon (Robertson and Leiter, ApJ, 565, 447, 2002; ApJL, 596, L203, 2003; MNRAS, 350, 391, 2004; astro-ph/0602543; Mitra, MNRAS, in press, gr-qc/0603055, astro-ph/0506183). In this paper, we show how a MECO model for Sgr A* is consistent with its observed low NIR luminosity, polarization and other properties. Thus the claim of an ``observed'' Even Horizon in Sgr A* (Broderick and Narayan, ApJ, 638, L21, 2006) is still unsubstantiated.

Physical Implications for the Uniqueness of the Value of the Integration Constant in the Vacuum Schwarzschild Solution

We consider the vacuum Schwarzschild solution both in the (1) standard Schwarzschild and (2) Eddington -Finkelstein coordinates. Since the 4-volume associated with the problem remains invariant under any curvilenear coordinate transformations, we equate the same obtained in metrics (1) and (2). It would then follow that the integration constant alpha_0 appearing in these two solutions have a unique value. We discuss the physical implications of this exact result in the light of the classic paper ``Dynamics of General Relativity'' by Arnowitt, Deser and Misner (gr-qc/0405109).

Black Holes or Eternally Collapsing Objects?

Gravitational collapse is always accompanied by radiation (Mitra, gr-qc/0605066). As the collapsing object becomes extremely compact, i.e., surface redshift z >>1, the emergent radiation quanta get gravitationally trapped. It has been shown that the heat flux associated with increased trapped radiation must change the catastrophic collapse into a secular quasistatic contraction (Mitra and Glendenning, submitted PRL, 2006). It follows then that the object becomes radiation dominated (Mitra, MNRAS, L66,367, 2006) at arbitrary low/high mass scale (Mitra, MNRAS, in press, 2006, gr-qc/0603055) before becoming true black holes. Such radiation pressure supported hot quasistatic objects having no mass upper/lower limit and radius equal to the Schwarzschild value are called Eternally Collapsing Objects(ECOs).