Exo-NINJA at Subaru: fiber-fed spectro-imaging of exoplanets and circumstellar disks at R$\sim$4000

TL;DR

Exo-NINJA is a planned fiber-fed spectro-imaging instrument for the Subaru Telescope that will enable high-resolution, spatially-resolved characterization of exoplanets and circumstellar disks in the near-infrared, with significantly improved throughput.

Contribution

It introduces a novel fiber-fed spectro-imaging system linking high contrast imaging and medium-resolution spectroscopy at Subaru, enhancing throughput and spatial resolution for exoplanet studies.

Findings

Design and integration plan for Exo-NINJA at Subaru.

Laboratory tests of fiber bundle throughput and focal ratio degradation.

Expected on-sky performance and trade-offs for fiber choices.

Abstract

Exo-NINJA will realize nearIR R$\sim$4000 diffraction-limited narrow-field spectro-imaging for characterization of exoplanets and circumstellar disk structures. It uniquely combines mid-R spectroscopy, high throughput, and spatial resolution, in contrast to CHARIS, which does spectro-imaging, and REACH, which is single-point (no spatial resolution). Exo-NINJA's spectro-imaging at the telescope diffraction limit will characterize exoplanet atmospheres, detect and map (spatially and spectrally) gas accretion on protoplanets, and also detect exoplanets at small angular separation ($\lambda$/D) from their host star by spectro-astrometry. Exo-NINJA will link two instruments at the Subaru Telescope using a high-throughput hexagonal multi-mode fiber bundle (hexabundle). The fiber coupling resides between the high contrast imaging system SCExAO, which combines ExAO and coronagraph, and the medium-resolution spectrograph NINJA (R$=$4000 at JHK bands). Exo-NINJA will provide an end-to-end throughput of 20% compared to the 1.5% obtained with REACH. Exo-NINJA is scheduled for implementation on the Subaru Telescope's NasIR platform in 2025; we will present a concise overview of its future installation, laboratory tests such as the throughput and focal ratio degradation (FRD) performance of optical fiber imaging hexabundles, in the NIR and the trade-offs for fiber choices for the NINJA-SCExAO hexabundle fiber cable, and the expected on sky performance.