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 squeezar.tex 2003, ApJL, 590, L25
Date: Tue, 3 Jun 2003 01:46:36 +0300
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\documentclass[12pt,preprint]{aastex}

\title{Squeezars: Tidally powered stars orbiting a massive black hole}

\author{Tal Alexander}

\affil{Faculty of Physics, The Weizmann Institute of Science, POB 26, Rehovot
76100, Israel}

\author{\and}

\author{Mark Morris}

\affil{Division of Astronomy and Astrophysics, University of California,
Los Angeles, CA 90095-1562, USA}

\begin{abstract}
We propose that there exists a class of transient sources,
"squeezars", which are stars caught in highly eccentric orbits around
a massive (m<10^8 Mo) black hole (MBH), whose atypically high
luminosity (up to a significant fraction of their Eddington
luminosity) is powered by tidal interactions with the MBH. Their
existence follows from the presence of a mass sink, the MBH, in the
galactic center, which drives a flow of stars into nearly radial
orbits to replace those it has destroyed. We consider two limits for
the stellar response to tidal heating: surface heating with radiative
cooling ("hot squeezars") and bulk heating with adiabatic expansion
("cold squeezars"), and calculate the evolution of the squeezar orbit,
size, luminosity and effective temperature. The squeezar formation
rate is only ~0.05 that of tidal disruption flares, but squeezar
lifetimes are many orders of magnitude longer, and so future
observations of squeezars in nearby galaxies can probe the tidal
process that feeds MBHs and the effects of extreme tides on stars. The
mean number of squeezars orbiting the Galactic MBH is estimated at
0.1-1.