Ground-Based Submillimagnitude CCD Photometry of Bright Stars Using Snapshot Observations

TL;DR

This paper presents a method for ground-based submillimagnitude photometry of bright stars using snapshot CCD imaging, enabling precise, automated monitoring suitable for planetary transit searches.

Contribution

The authors introduce a novel snapshot CCD imaging technique that achieves high-precision photometry of bright stars with minimal telescope adjustments.

Findings

Achieved photometric precision as good as 5.2x10^-4 (0.56mmag).

Demonstrated submillimagnitude precision with a 17-minute cadence for multiple stars.

Validated the method's suitability for automated planetary transit surveys.

Abstract

We demonstrate ground-based submillimagnitude (<10^-3) photometry of widely separated bright stars using snapshot CCD imaging. We routinely achieved this photometric precision by (1) choosing nearby comparison stars of a similar magnitude and spectral type, (2) defocusing the telescope to allow high signal (>10^7 electrons) to be acquired in a single integration, (3) pointing the telescope so that all stellar images fall on the same detector pixels, and (4) using a region of the CCD detector that is free of nonlinear or aberrant pixels. We describe semiautomated observations with the Supernova Integrated Field Spectrograph (SNIFS) on the University of Hawaii 2.2m telescope on Mauna Kea, with which we achieved photometric precision as good as 5.2x10^-4 (0.56mmag) with a 5 minute cadence over a 2hr interval. In one experiment, we monitored eight stars, each separated by several degrees, and achieved submillimagnitude precision with a cadence (per star) of ~17 minutes. Our snapshot technique is suitable for automated searches for planetary transits among multiple bright stars.