An Optical Interferometer with Wavelength Dispersion

TL;DR

This paper introduces MAPPIT, an optical interferometer that combines non-redundant masking with wavelength dispersion, enabling high-resolution observations of stars, including binary systems and red giants, over a broad spectral bandwidth.

Contribution

The paper presents the design, data processing methods, and initial results of MAPPIT, a novel interferometer that achieves simultaneous wide-band fringe recording with high spectral resolution.

Findings

Sigma Sgr identified as a close binary with 11.5 mas separation.

First-time resolution of beta Gru with a 27 mas diameter.

Angular diameters measured for alpha Sco and beta Gru.

Abstract

MAPPIT is an optical interferometer installed at the coude focus of the 3.9-m Anglo-Australian Telescope. The instrument combines non-redundant masking with wavelength dispersion and is able to record fringes simultaneously over a wide bandwidth. For typical observations centred near 600 nm, the bandwidth is 55 nm and the spectral resolution is 3 nm. This paper describes the instrument and the data processing methods and presents some results. We find the star sigma Sgr to be a close binary; the system is only partially resolved, with a separation of (11.5 +/- 2) milliarcsec (assuming the components to have equal magnitudes). We also give angular diameter measurements of two red giant stars, alpha Sco and beta Gru. The observations of beta Gru (spectral type M5 III) resolve the star for the first time and give an equivalent uniform-disk diameter of (27 +/- 3) milliarcsec.