The Beta Pic dataset was obtained on 3 February 2023, in the course of the ESO-led development of a new GRA4MAT narrow off-axis mode. This new mode allows an observer to specify small offsets where to point MATISSE, with respect to the fringe tracking target. This mode is very similar to the dual on-axis mode of GRAVITY that was successfully applied to exoplanet spectroscopy. It will be offered to the community in the Call for Proposals for Period 112.

The dataset consists of two observations of science target beta Pic and calibrator HD 39918. Each dataset contains an observation sequence with MATISSE being moved on sky with the following pattern: star, planet, anti-planet, planet, where planet corresponds to the position of β Pictoris b, at an offset from the star, predicted at (ΔRA, ΔDEC) = (284, 462) mas, at the time of observation. The anti-planet position is an observation at the same offset on the opposite side of the star, i.e. at  (ΔRA, ΔDEC) = (-284, -462) mas. The current offset position is available in the primary FITS header keywords of each released file under SEQ.OFFSET.ALPHA and SEQ.OFFSET.DELTA.

The relevant data files of the star and the calibrator can be found in the MATISSE Commissioning web page. If any of these data are used in a publication, please acknowledge that the results are based on public data released from the MATISSE commissioning observations at the VLT Interferometer under Programme ID 60.A-9257(H).