L-band nulling interferometry at the VLTI with Asgard/NOTT: status and plans

TL;DR

The paper reports on the current status and plans for NOTT, an L'-band nulling interferometer at VLTI, focusing on recent laboratory results, design updates, and ongoing development activities aimed at exoplanet characterization.

Contribution

It provides an update on NOTT's development, including laboratory testing, design improvements, and software development for exoplanet science applications.

Findings

First fringes and null measurements with GLS photonic chip

Successful testing of photonic chip at cryogenic temperatures

Progress in integration and software development for exoplanet detection

Abstract

NOTT (formerly Hi-5) is the L'-band (3.5-4.0~microns) nulling interferometer of Asgard, an instrument suite in preparation for the VLTI visitor focus. The primary scientific objectives of NOTT include characterizing (i) young planetary systems near the snow line, a critical region for giant planet formation, and (ii) nearby main-sequence stars close to the habitable zone, with a focus on detecting exozodiacal dust that could obscure Earth-like planets. In 2023-2024, the final warm optics have been procured and assembled in a new laboratory at KU Leuven. First fringes and null measurements were obtained using a Gallium Lanthanum Sulfide (GLS) photonic chip that was also tested at cryogenic temperatures. In this paper, we present an overall update of the NOTT project with a particular focus on the cold mechanical design, the first results in the laboratory with the final NOTT warm optics, and the ongoing Asgard integration activities. We also report on other ongoing activities such as the characterization of the photonic chip (GLS, LiNbO3, SiO), the development of the exoplanet science case, the design of the dispersion control module, and the progress with the self-calibration data reduction software.