J/A+A/706/A275 Detection limits in the SHINE F150 survey (Sabalbal+, 2026)
Enhanced detection limits in the SHINE F150 survey through the regime switching
model. Optimizing thresholds and investigating environmental noise.
Sabalbal M., Absil O., Dahlqvist C.-H., Delorme P.
<Astron. Astrophys. 706, A275 (2026)>
=2026A&A...706A.275S 2026A&A...706A.275S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Optical
Keywords: atmospheric effects - methods: data analysis -
techniques: image processing - surveys -
planets and satellites: detection
Abstract:
In high-contrast imaging, a novel detection algorithm for angular
differential imaging (ADI) sequences has recently been introduced: the
Regime Switching Model (RSM). This advanced statistical tool enhances
the distinction between planetary signals and bright speckles by
simultaneously combining multiple ADI-based post-processing
techniques.
In this study, we apply the RSM algorithm to analyze the F150 sample
from the SHINE high-contrast imaging survey carried out with
VLT/SPHERE, aiming to enhance detection limits and identify new
exoplanet candidates. Additionally, we investigate how environmental
conditions influence post-processed noise distributions and detection
thresholds.
We generate detection maps and contrast curves for 213 observations in
the F150 SHINE sample using the RSM algorithm. A clustering approach
based on environmental parameters is used to group observations with
similar noise characteristics. We propose two methods for defining
radial detection thresholds in the RSM maps: fitting a log-normal
distribution to the post-processed noise and maximizing the F1 score.
We also assess the performance of various combinations of
post-processing techniques within the RSM framework to identify
optimal configurations.
This study demonstrates the utility of clustering based on
observational parameters, effectively distinguishing features like
wind-driven halos and low-wind effects. Detection thresholds vary
significantly across clusters, differing by up to a factor of 10,
highlighting the importance of considering observational environments.
Log-normal thresholds provide conservative, noise-aware limits, while
F1 score-based thresholds offer observation-specific results, both
showing compatibility overall. RSM improves detection limits by an
average factor of two at arcsec and five at inner working angles
compared to standard PCA processing. This study reports more than 30
newly detected signals, including one promising candidate awaiting
second-epoch confirmation.
Description:
Table with observing conditions of all F150 SHINE sample used in the
paper. Values derived from the HC-DC profucts header files.
Name of the star, observation date, total parallactic angle range
(Delta PA), seeing, wind speed, Strehl ratio, coherence time, number
of frames, raw contrast at 500mas, and associated cluster number, and
the corresponding cluster center are provided for each F150 target.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 78 213 Observing conditions of all F150 SHINE sample
used in the paper
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- Star SIMBAD star name
23- 32 A10 "date" Date Observation date
34- 39 F6.2 deg DPA Total parallactic angle range
41- 44 F4.2 arcsec Seeing Seeing
46- 50 F5.2 m/s WS Wind Speed
52- 55 F4.1 ms CT Coherence Time
57- 59 I3 --- Nframes [32/800] Number of frames
61- 69 E9.7 --- RC Raw contrast at 500mas
71- 74 F4.2 --- SRatio Strehl Ratio
76 I1 --- Cluster [1/6] Associated cluster number
78 I1 --- Center [0/1] Center or not (1)
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Note (1): Flag as follows:
0 = not center
1 = center
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Acknowledgements:
From Mariam Sabalbal, mariam.sabalbal(at)uliege.be
This work has made use of the High Contrast Data Centre, jointly
operated by OSUG/IPAG (Grenoble), PYTHEAS/LAM/CeSAM (Marseille),
OCA/Lagrange (Nice), Observatoire de Paris/LESIA (Paris), and
Observatoire de Lyon/CRAL, and supported by a grant from Labex
OSUG@2020 (Investissements d'avenir - ANR10 LABX56).
(End) Patricia Vannier [CDS] 10-Dec-2025