Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dippers from TESS Full-frame Images. II. Spectroscopic Characterization
  of Four Young Dippers   Photometric monitoring by the Transiting Exoplanet Survey Satellite (TESS)
has discovered not only periodic signals by transiting exoplanets but also
episodic or quasi-periodic dimming around young stellar objects. The mechanisms
of the dimming of these objects, so-called "dippers", are thought to be related
to the property of the accretion or the structure of protoplanetary disks
especially in regions close to the host star. Recently, we have created the
catalog of dippers from the one year of TESS Full Frame Image (FFI) data. In
this paper, we report spectral features of four newly found dippers in that
catalog and show that they potentially shed light on the dimming mechanisms. We
found that all of the targets exhibit the H alpha emission line, which is an
indicator of an ongoing accretion. Based on its line profiles and/or their
variability, we characterized the properties of the disks of each source, which
can support the dimming mechanisms due to a dusty disk wind or an accretion
warp. Also, we found an interesting dipper (TIC 317873721), "close-in binary
dipper," showing the complex variability of the line profile and the large
radial velocity variation. Since the dimming intervals are similar to the
orbital period of the binary, we suggest that the dips are caused by dust in
the warp of accretion from a circumbinary disk onto stars. Such a close-in ($<$
0.1 au) binary dipper is rarely reported so far, further investigation will
reveal the new aspect of the disk evolution and planetary formation.

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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: physics
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The categories of this paper are: hep-ph