Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HST/WFC3 Complete Phase-resolved Spectroscopy of White Dwarf-Brown Dwarf
  Binaries WD 0137 and EPIC 2122   Brown dwarfs in close-in orbits around white dwarfs offer an excellent
opportunity to investigate properties of fast-rotating, tidally-locked, and
highly-irradiated atmospheres. We present Hubble Space Telescope Wide Field
Camera 3 G141 phase-resolved observations of two brown dwarf-white dwarf
binaries: WD 0137-349 and EPIC 212235321. Their 1.1 to 1.7 $\mu$m phase curves
demonstrate rotational modulations with semi-amplitudes of $5.27\pm0.02$% and
$29.1\pm0.1$%; both can be well fit by multi-order Fourier series models. The
high-order Fourier components have the same phase as the first order and are
likely caused by hot spots located at the substellar points, suggesting
inefficient day/night heat transfer. Both brown dwarfs' phase-resolved spectra
can be accurately represented by linear combinations of their day- and
night-side spectra. Fitting the irradiated brown dwarf model grids to the
day-side spectra require a filling factor of ~50%, further supporting a hot
spot dominating the emission of the day-sides. The night-side spectrum of WD
0137-349B is reasonably well fit by non-irradiated substellar models and the
one of EPIC 212235321B can be approximated by a Planck function. We find strong
spectral variations in the brown dwarfs' day/night flux and brightness
temperature contrasts, which highlights the limitations of band-integrated
measurements in probing heat transfer in irradiated objects. On the
color-magnitude diagram, WD 0137-349B evolves along a cloudless model track
connecting the early-L and mid-T spectral types, demonstrating that clouds and
disequilibrium chemistry have a negligible effect on this object. A full
interpretation of these high-quality phase-resolved spectra calls for new
models that couple atmospheric circulation and radiative transfer under
high-irradiation conditions.

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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg