PSF-based Analysis for Detecting Unresolved Wide Binaries

TL;DR

This paper introduces a deep learning method to detect unresolved wide binaries in space telescope images by analyzing PSF morphology, achieving high accuracy on simulated and real data, and revealing their distribution in star clusters.

Contribution

The paper presents a novel PSF-based deep learning approach for identifying unresolved wide binaries, improving detection accuracy over traditional methods.

Findings

Achieved 97.2% accuracy on simulated data from the Chinese Space Station Telescope.

Identified 18 wide binary candidates in NGC 6121 with separations of 7 to 140 au.

Most candidates are outside the cluster core, indicating they are likely first-generation stars.

Abstract

Wide binaries play a crucial role in analyzing the birth environment of stars and the dynamical evolution of clusters. When wide binaries are located at greater distances, their companions may overlap in the observed images, becoming indistinguishable and resulting in unresolved wide binaries, which are difficult to detect using traditional methods. Utilizing deep learning, we present a method to identify unresolved wide binaries by analyzing the point-spread function (PSF) morphology of telescopes. Our trained model demonstrates exceptional performance in differentiating between single stars and unresolved binaries with separations ranging from 0.1 to 2 physical pixels, where the PSF FWHM is ~2 pixels, achieving an accuracy of 97.2% for simulated data from the Chinese Space Station Telescope. We subsequently tested our method on photometric data of NGC 6121 observed by the Hubble Space Telescope. The trained model attained an accuracy of 96.5% and identified 18 wide binary candidates with separations between 7 and 140 au. The majority of these wide binary candidates are situated outside the core radius of NGC 6121, suggesting that they are likely first-generation stars, which is in general agreement with the results of Monte Carlo simulations. Our PSF-based method shows great promise in detecting unresolved wide binaries and is well suited for observations from space-based telescopes with stable PSF. In the future, we aim to apply our PSF-based method to next-generation surveys such as the China Space Station Optical Survey, where a larger-field-of-view telescope will be capable of identifying a greater number of such wide binaries.