Stellar Cartography

Efficiently Searching for Close-in Companions Around Young M Dwarfs Using a Multi-year PSF Library

By Keith Cowing

Press Release

August 28, 2024

Filed under astronomy, imaging, Keck, M-dwarf, Stellar Cartography, Super-RDI

Efficiently Searching for Close-in Companions Around Young M Dwarfs Using a Multi-year PSF Library — Left: Final PSF-subtracted images of LO Peg obtained with Super-RDI. North is up and east is to the left. The image and color bar are depicted in linear scale in normalized analog to digital units and have been smoothed using a Gaussian kernel with a 1.5 pixel standard deviation (40% of the width of the instrumental PSF) to average out high-frequency noise. Right: Parallactic angle of individual frames obtained across the entire observation sequence. Presented as insets are three representative de-rotated pre-processed frames (north is up and east is to the left) in the sequence showing that the point source in our final PSF-subtracted image rotates across the sequence as expected for a speckle. — astro-ph.EP

We present Super-RDI, a unique framework for the application of reference star differential imaging (RDI) to Keck/NIRC2 high-contrast imaging observations with the vortex coronagraph.

Super-RDI combines frame selection and signal-to-noise ratio (S/N) optimization techniques with a large multi-year reference point spread function (PSF) library to achieve optimal PSF subtraction at small angular separations.

We compile a ∼7000 frame reference PSF library based on a set of 288 new Keck/NIRC2 L′ sequences of 237 unique targets acquired between 2015 and 2019 as part of two planet-search programs, one focusing on nearby young M dwarfs and the other targeting members of the Taurus star-forming region.

For our dataset, synthetic companion injection-recovery tests reveal that frame selection with the mean-squared error (MSE) metric combined with KLIP-based PSF subtraction using 1000-3000 frames and <500 principal components yields the highest average S/N for injected synthetic companions.

We uniformly reduce targets in the young M-star survey with both Super-RDI and angular differential imaging (ADI). For the typical parallactic angle rotation of our dataset (∼10∘), Super-RDI performs better than a widely used implementation of ADI at separations ≲0.4″ (≈5 λ/D) gaining an average of 0.25 mag in contrast at 0.25″ and 0.4 mag in contrast at 0.15″.

This represents a performance improvement in separation space over RDI with single-night reference star observations (∼100 frame PSF libraries) applied to a similar Keck/NIRC2 dataset in previous work. We recover two known brown dwarf companions and provide detection limits for 155 targets in the young M-star survey.

Our results demonstrate that increasing the PSF library size with careful selection of reference frames can improve the performance of RDI with the Keck/NIRC2 vortex coronagraph in L′.

Aniket Sanghi, Jerry Xuan, Jason Wang, Dimitri Mawet, Brendan Bowler, Henry Ngo, Marta Bryan, Garreth Ruane, Olivier Absil, Elsa Huby

Comments: Accepted to AJ. 41 pages, 13 figures, 4 tables. Data presented in this work: this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2408.14268 [astro-ph.EP] (or arXiv:2408.14268v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2408.14268
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Submission history
From: Aniket Sanghi
[v1] Mon, 26 Aug 2024 13:44:17 UTC (14,651 KB)
https://arxiv.org/abs/2408.14268

Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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