Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Coordinated X-ray and Optical Campaign of the Nearest Massive
  Eclipsing Binary, delta Orionis Aa: III. Analysis of Optical Photometric MOST
  and Spectroscopic (Ground Based) Variations   We report on both high-precision photometry from the MOST space telescope and
ground-based spectroscopy of the triple system delta Ori A consisting of a
binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7d, and a more distant tertiary
(O9 IV P > 400 yrs). This data was collected in concert with X-ray spectroscopy
from the Chandra X-ray Observatory. Thanks to continuous coverage for 3 weeks,
the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first
time in non-phased data. From the spectroscopy we have a well constrained
radial velocity curve of Aa1. While we are unable to recover radial velocity
variations of the secondary star, we are able to constrain several fundamental
parameters of this system and determine an approximate mass of the primary
using apsidal motion. We also detected second order modulations at 12 separate
frequencies with spacings indicative of tidally influenced oscillations. These
spacings have never been seen in a massive binary, making this system one of
only a handful of such binaries which show evidence for tidally induced
pulsations.

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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex