Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Apodization in high-contrast long-slit spectroscopy. II. Concept
  validation and first on-sky results with VLT/SPHERE   Spectral characterization of young, giant exoplanets detected by direct
imaging is one of the tasks of the new generation of high-contrast imagers. For
this purpose, the VLT/SPHERE instrument includes a unique long-slit
spectroscopy (LSS) mode coupled with Lyot coronagraphy in its infrared
dual-band imager and spectrograph (IRDIS). The performance of this mode is
intrinsically limited by the use of a non-optimal coronagraph, but in a
previous work we demonstrated that it could be significantly improved at small
inner-working angles using the stop-less Lyot coronagraph (SLLC). We now
present the development, testing, and validation of the first SLLC prototype
for VLT/SPHERE. Based on the transmission profile previously proposed, the
prototype was manufactured using microdots technology and was installed inside
the instrument in 2014. The transmission measurements agree well with the
specifications, except in the very low transmissions (<5% in amplitude). The
performance of the SLLC is tested in both imaging and spectroscopy using data
acquired on the internal source. In imaging, we obtain a raw contrast gain of a
factor 10 at 0.3" and 5 at 0.5" with the SLLC. Using data acquired with a
focal-plane mask, we also demonstrate that no Lyot stop is required to reach
the full performance, which validates the SLLC concept. Comparison with a
realistic simulation model shows that we are currently limited by the internal
phase aberrations of SPHERE. In spectroscopy, we obtain a gain of ~1 mag in a
limited range of angular separations. Simulations show that although the main
limitation comes from phase errors, the performance in the non-SLLC case is
very close to the ultimate limit of the LSS mode. Finally, we obtain the very
first on-sky data with the SLLC, which appear extremely promising for the
future scientific exploitation of an apodized LSS mode in SPHERE.

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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: chao-dyn
36
The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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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: stat
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph