Improving Interferometric Null Depth Measurements using Statistical Distributions: Theory and First Results with the Palomar Fiber Nuller

TL;DR

This paper introduces a novel statistical analysis method for nulling interferometry that significantly improves measurement accuracy of astrophysical null depths by leveraging the distributions of fluctuating signals, demonstrated with the Palomar Fiber Nuller.

Contribution

The paper presents a self-calibrated statistical approach that enhances null depth measurement precision, reducing reliance on calibrator observations and applicable to various interferometers.

Findings

Achieved null depth measurement errors as low as a few 10^-4.

Measured null depths below 10^-3 without calibrator data.

Demonstrated method's effectiveness on Palomar Hale telescope data.

Abstract

A new "self-calibrated" statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast atmospheric fluctuations. The approach yields an accuracy much better (about an order of magnitude) than is presently possible with standard data reduction methods, because the astrophysical null depth accuracy is no longer limited by the magnitude of the instrumental phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone-and no observations of calibrators-we find that error bars on the astrophysical null depth as low as a few 10-4 can be obtained in the near-infrared, which means that null depths lower than 10-3 can be reliably measured. This statistical analysis is not specific to our instrument and may be applicable to other interferometers.