ann-marie-madigan-on-the-origin-of-young-stars-in-the-galactic-center.html

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         title="Permalink to Ann-Marie Madigan: On the Origin of Young Stars in the Galactic Center">Ann-Marie Madigan: On the Origin of Young Stars in the Galactic Center</a></h2>
 
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    <abbr class="published" title="2013-10-01T15:05:00-06:00">
      2013/10/01
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    <address class="vcard author">
      By <a class="url fn" href="https://keflavich.github.io/blog/author/adam-ginsburg.html">Adam Ginsburg</a>
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<dl class="docutils">
<dt>Central pc cluster</dt>
<dd><ul class="first last simple">
<li>orbital parameters</li>
<li>disk of O/WR stars
+ distinct from S stars: circular-ish orbits</li>
<li>binary disruption formation of S-stars
+ hypervelocity ejected star
+ other star has eccentricity &gt; 0.98</li>
<li>further stars?
+ &quot;memory&quot; of initial eccentricity &quot;stored&quot; at large radii
+ relaxation times increase
+ can't measure eccentricity directly because of long orbital timescales</li>
<li>Simulations of young stars orbiting
+ initial high eccentricity (disruption formation)
+ initial low eccentricity (disk formation)</li>
<li>Depending on the stellar mass, both origins are possible.
+ lower masses better fit for disruption mechanism</li>
<li>IMF in disk
+ different formation mechanism would imply they should not be included in IMF measurements</li>
<li>start in eccentric, relax into circular
+ depends on density profile
+ can infer density profile</li>
<li>&quot;h-statistic&quot;
+ angular momentum vector = ±1 if circular orbit, 0 on plunging &quot;orbit&quot;
+ degeneracy between inclination and eccentricity</li>
<li>&quot;special purpose&quot; n-body code
+ high-mass stars consistent with disk
+ low-mass stars more like binary disruption</li>
<li>implies top-heavier IMF</li>
</ul>
</dd>
</dl>
<div class="section" id="questions">
<h2>Questions</h2>
<blockquote>
<ul class="simple">
<li>Q Cuadra: What tells you about the cuspiness?  Precession?</li>
<li>A: Yes.  Orbits closer to black hole have long precession scales.  Leads to
more rapid change in eccentricity (and less precession).</li>
<li>Q: What is timescale for thermalization to eccentricity?</li>
<li>A: Depends on radius.  S-stars, already relaxed.  &gt;0.02 pc, takes Myrs</li>
<li>Q Farhad: Radial profile of the S-cluster B-stars?</li>
<li>A: Haven't looked at that; similar to O and WR stars.</li>
<li>A: R^-2?  Poisson limited.  R^-1.5?</li>
</ul>
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