Phase Closure at 691 GHz using the Submillimeter Array

TL;DR

This paper reports the first successful phase closure observations at around 690 GHz using the SMA, including astronomical detections of planets and galactic sources, and presents the first high-resolution images at this frequency.

Contribution

It demonstrates the first phase closure at nearly 690 GHz with the SMA, enabling high-resolution imaging in this challenging frequency band.

Findings

First phase closure at ~690 GHz achieved.

Detected CO(6-5) line in planets and galactic sources.

Produced first arcsecond-scale images at this frequency.

Abstract

Phase closure at 682 GHz and 691 GHz was first achieved using three antennas of the Submillimeter Array (SMA) interferometer located on Mauna Kea, Hawaii. Initially, phase closure was demonstrated at 682.5 GHz on Sept. 19, 2002 using an artificial ground-based "beacon" signal. Subsequently, astronomical detections of both Saturn and Uranus were made at the frequency of the CO(6-5) transition (691.473 GHz) on all three baselines on Sept. 22, 2002. While the larger planets such as Saturn are heavily resolved even on these short baselines (25.2m, 25.2m and 16.4m), phase closure was achieved on Uranus and Callisto. This was the first successful experiment to obtain phase closure in this frequency band. The CO(6-5) line was also detected towards Orion BN/KL and other Galactic sources, as was the vibrationally-excited 658 GHz water maser line toward evolved stars. We present these historic detections, as well as the first arcsecond-scale images obtained in this frequency band.