Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM
  Cephei   UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting
sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such
a UXor in the young ($\sim4$~Myr) open cluster Trumpler\,37, showing prominent
infrared excess, emission-line spectra, and flare activity. Our photometric
monitoring (2008--2018) detects (1)~an $\sim$3.43~day period, likely arising
from rotational modulation by surface starspots, (2)~sporadic brightening on
time scales of days due to accretion, (3)~irregular minor flux drops due to
circumstellar dust extinction, and (4)~major flux drops, each lasting for a
couple of months with a recurrence time, though not exactly periodic, of about
two years. The star experiences normal reddening by large grains, i.e., redder
when dimmer, but exhibits an unusual "blueing" phenomenon in that the star
turns blue near brightness minima. The maximum extinction during relatively
short (lasting $\leq 50$~days) events, is proportional to the duration, a
consequence of varying clump sizes. For longer events, the extinction is
independent of duration, suggestive of a transverse string distribution of
clumps. Polarization monitoring indicates an optical polarization varying
$\sim3\%$--8$\%$, with the level anticorrelated with the slow brightness
change. Temporal variation of the unpolarized and polarized light sets
constraints on the size and orbital distance of the circumstellar clumps in the
interplay with the young star and scattering envelope. These transiting clumps
are edge-on manifestations of the ring- or spiral-like structures found
recently in young stars with imaging in infrared of scattered light, or in
submillimeter of thermalized dust emission.

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The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
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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: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg