Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variable structure in the PDS70 disc and uncertainties in
  radio-interferometric image restoration   The compact mm-wavelength signal in the central cavity of the PDS70 disc,
revealed by deep ALMA observations, is aligned with unresolved Halpha emission,
and is thought to stem from a circum-planetary disc (CPD) around PDS70c. We
revisit the available ALMA data on PDS70c with alternative imaging strategies,
and with special attention to uncertainties and to the impact of the so-called
"JvM correction", which is thought to improve the dynamic range of restored
images. We also propose a procedure for the alignment and joint imaging of
multi-epoch visibility data. We find that the JvM correction exaggerates the
peak signal-to-noise of the data, by up to a factor of 10. In the case of
PDS70, we recover the detection of PDS70c from the July 2019 data, but only at
8sigma. However, its non-detection in Dec. 2017 suggests that PDS70c is
variable by at least 42%+-13% over a 1.75yr time-span, so similar to models of
the Halpha variability. We also pick up fine structure in the inner disc, such
that its peak is offset by ~ 0.04" from the disc centre. The inner disc is
variable too, which we tentatively ascribe to Keplerian rotation as well as
intrinsic morphological changes.

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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga