SETI public: Systematic Analysis of 22 Microlensing Parallax Candidates

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Paper: astro-ph/0506183
Date: Thu, 9 Jun 2005 19:16:03 GMT (140kb)

Title: Systematic Analysis of 22 Microlensing Parallax Candidates

Authors: Shawn Poindexter (1), Cristina Afonso (2), David P. Bennett (3),
  Jean-Francois Glicenstein (4), Andrew Gould (1), Michal K. Szymanski (5),
and
  Andrzej Udalski (5) ((1) Ohio State, (2) Max-Planck fuer Astronomie, (3)
  Notre Dame, (4) CEA Saclay, (5) Warsaw University Observatory)
Comments: 69 Pages, 10 Figures, 24 Tables, Submitted to ApJ
\\
  We attempt to identify all microlensing parallax events for which the
parallax fit improves \Delta\chi^2 > 100 relative to a standard microlensing
model. We outline a procedure to identify three types of discrete
degeneracies
(including a new one that we dub the ``ecliptic degeneracy'') and find many
new
degenerate solutions in 16 previously published and 6 unpublished events.
Only
four events have one unique solution and the other 18 events have a total of
44
solutions. Our sample includes three previously identified black-hole (BH)
candidates. We consider the newly discovered degenerate solutions and
determine
the relative likelihood that each of these is a BH. We find the lens of
event
MACHO-99-BLG-22 is a strong BH candidate (78%), event MACHO-96-BLG-5 is a
marginal BH candidate (37%), and MACHO-98-BLG-6 is a weak BH candidate
(2.2%).
The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating
planet
candidate based on a weak 3 sigma detection of finite-source effects. We
find
that event MACHO-179-A is a brown dwarf candidate within ~100 pc of the Sun,
mostly due to its very small projected Einstein radius, \tilde r_E =
0.23+-0.05
AU. As expected, these microlensing parallax events are biased toward lenses
that are heavier and closer than average. These events were examined for
xallarap (or binary-source motion), which can mimic parallax. We find that
23%
of these events are strongly affected by xallarap.

\\ ( http://arXiv.org/abs/astro-ph/0506183 , 140kb)

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