Practical Coherent Integration with the NPOI

TL;DR

This paper discusses the current methods and advancements in coherent integration using the NPOI, enabling highly precise stellar measurements through phase referencing and complex visibilities.

Contribution

It introduces a generalized group-delay approach and demonstrates high-precision stellar and binary star measurements with the NPOI.

Findings

Measured stellar diameters with a precision of 1 part in 350.

Demonstrated binary star property measurements.

Highlighted advantages of complex phase data products.

Abstract

In this paper we will discuss the current status of coherent integration with the Navy Prototype Optical Interferometer (NPOI) (Armstrong et al. 2008). Coherent integration relies on being able to phase reference interferometric measurements, which in turn relies on making measurements at multiple wavelengths. We first discuss the generalized group-delay approach, then the meaning of the resulting complex visibilities and then demonstrate how coherent integration can be used to perform very precision measurement of stellar properties. For example, we demonstrate how we can measure the diameter of a star to a precision of one part in 350, and measure properties of binary stars. The complex phase is particularly attractive as a data product because it is not biased in the same way as visibility amplitudes.