Search for extrasolar planets with high-precision relative astrometry

TL;DR

This paper describes a high-precision relative astrometry method using innovative observational techniques to detect unseen substellar companions by measuring star wobble, achieving micro-arcsecond precision.

Contribution

The authors introduce a new observation mode and statistical approach to improve astrometric measurement precision for detecting exoplanets.

Findings

Achieved 100-150 micro-arcsecond precision in separation measurements.

Demonstrated the effectiveness of the cube-mode and statistical analysis.

Applied method to the binary star HD 19994 with a known planet candidate.

Abstract

We present our search program for substellar companions using high-precision relative astronomy. Due to its orbital motion around the star, an unseen substellar companion would produce a periodic "wobble" of the host star, which is the astrometric signal of the unseen companion. By measuring the separation between the components of stellar double and triple systems, we want to measure this astrometric signal of a possible unseen companion indirectly as a relative and periodic change of these separations. Using a new observation mode (the "cube-mode") where the frames were directly saved in cubes with nearly no loss of time during the readout, an adaptive optics system to correct for atmospheric noise and an infrared narrow band filter in the near infrared to suppress differential chromatic refraction (DCR) effects we achive for our first target (the double star HD 19994) a relative precision for the separation measurements of about 100...150 micro-arsecond per epoch. To reach a precision in the micro-arcsec-regime, we use a statistical approach. We take several thousand frames per target and epoche and after a verification of a Gaussian distribution the measurement precision can be calculated as the standard deviation of our measurements divided by the square root of the number of Gaussian distributed measurements. Our first observed target is the stellar binary HD 19994 A & B, where the A component has a known radial velocity planet candidate.