Wide‐Field Millimagnitude Photometry with the HAT: A Tool for Extrasolar Planet Detection

TLDR

We discuss the system requirements for achieving millimagnitude photometric precision over a wide field with small‑aperture, short‑focal‑length telescopes used to search for transiting exoplanets. The paper describes the Hungarian‑made Automated Telescope (HAT) system designed to meet these precision requirements. HAT improves precision by executing small pointing steps during exposures to broaden the PSF for better pixel sampling, and the system is being expanded into a longitudinally spaced network of telescopes. A preliminary Spring 2003 survey with HAT‑5 optimized this PSF‑broadening technique, achieving photometric precision as good as 2 mmag on bright stars.

Abstract

We discuss the system requirements for obtaining millimagnitude photometric precision over a wide field using small aperture short focal length telescope systems, such as are being developed by a number of research groups to search for transiting extra-solar planets. We describe the Hungarian-made Automated Telescope (HAT) system which attempts to meet these requirements. The attainable precision of HAT has been significantly improved by a technique in which the telescope is made to execute small pointing steps during each exposure so as to broaden the effective point spread function of the system to a value more compatible with the pixel size of our CCD detector. Experiments during a preliminary survey (Spring 2003) of two star fields with the HAT-5 instrument allowed us to optimize the HAT photometric precision using this method of PSF broadening; in this way have been able to achieve a precision as good as 2 millimagnitudes on brighter stars. We briefly describe development of a network of HAT telescopes (HATnet) spaced in longitude.