Feasibility of an Infrared Parallax Program Using the Fan Mountain Tinsley Reflector

TL;DR

This study evaluates the infrared astrometric capabilities of the FanCam instrument on the Tinsley reflector, demonstrating its potential for ground-based parallax measurements of low-mass stars and brown dwarfs.

Contribution

It provides the first assessment of FanCam's infrared astrometric precision, showing it can achieve parallax measurement accuracy comparable to existing infrared programs.

Findings

Achieved 0.04" +/- 0.02" precision in parallax measurements

Demonstrated feasibility of infrared parallax programs with FanCam

Infrared measurements can complement optical surveys for low-mass stars

Abstract

Despite the continuing importance of ground-based parallax measurements, few active programs remain. Because new members of the solar neighborhood tend towards later spectral types, infrared parallax programs are particularly desirable. Consequently, the astrometric quality of the new infrared camera, FanCam, developed by the Virginia Astronomical Instrumentation Laboratory (VAIL) for the 31-in (0.8-m) Tinsley reflector at Fan Mountain Observatory was assessed using 68 J-band exposures of an open cluster, NGC 2420, over a range of hour angles during 2005. Positions of 16 astrometric evaluation stars were measured and the repeatability of those positions was evaluated using the mean error in a single observation of unit weight. Overall, a precision of 1.3 +/- 0.7 microns in x (RA) and 1.3 +/- 0.8 microns in y (Dec) was attained, which corresponds to 0.04" +/- 0.02" in each axis. Although greater precision is expected from CCDs in the visual and near-infrared, this instrument can achieve precision similar to that of the ESO NTT infrared parallax program. Therefore, measuring parallaxes in the infrared would be feasible using this equipment. If initiated, such a program could provide essential distances for brown dwarfs and very low mass stars that would contribute significantly to the solar neighborhood census.