SOXS at the NTT: completion and first on-sky performance of the new transient spectroscopic facility
Abstract
The Son Of X-Shooter (SOXS) instrument is a new spectroscopic facility designed to equip the ESO's New Technology Telescope (NTT) with broad-band spectroscopic capabilities optimized for time-domain and transient astrophysics. Covering the 0.35–2.0 μm wavelength range with two spectrographic arms working simultaneously, complemented by an acquisition and imaging channel, SOXS is engineered to deliver efficient target acquisition, wide spectral coverage, and high throughput for studying all kinds of transients Over the past years, the project has progressed through several major milestones leading to the instrument’s installation at La Silla Observatory. The Assembly, Integration, and Verification (AIV) phase was completed in Italy, followed by the instrument’s successful Preliminary Acceptance in Europe (PAE). After final validation, SOXS was shipped to Chile, where the team carried out reassembly, alignment, and full functional verification at the NTT, completing the AIV in Chile and the commissioning phase. The on-site integration process included verifying the instrument, interfacing with the telescope, debugging and validating the instrument software and pipeline using real data collected on the sky. First-light observations confirm that SOXS meets or exceeds its design specifications in spectral resolution. Early verification data demonstrate SOXS's capability to obtain rapid, high-quality spectra of transient sources across its full wavelength range, validating its role as a key facility for time-domain programmes and multi-messenger follow-up. The instrument is ready for regular observations and has been officially offered to the ESO community. The paper will present an overview of these activities, discuss the lessons learned and highlight representative on-sky results from the commissioning phase.