htof: A new open-source tool for analyzing Hipparcos, Gaia, and future astrometric missions

TL;DR

htof is an open-source software tool designed for interpreting and fitting intermediate astrometric data from Hipparcos, Gaia, and future missions, enabling advanced analysis of stellar systems and potential exoplanets.

Contribution

The paper introduces htof, a versatile tool supporting high-order astrometric solutions for multiple missions, and demonstrates its application in data correction, orbital analysis, and exoplanet detection predictions.

Findings

Identified data corruption in Hipparcos 2007 IAD for 6617 sources.

Reconciled corrupted IAD with catalog solutions using htof.

Predicted potential exoplanets in the $eta$~Pic system.

Abstract

We present htof, an open-source tool for interpreting and fitting the intermediate astrometric data (IAD) from both the 1997 and 2007 reductions of Hipparcos, the scanning-law of Gaia, and future missions such as the Nancy Grace Roman Space Telescope (NGRST). htof solves for the astrometric parameters of any system for any arbitrary combination of absolute astrometric missions. In preparation for later Gaia data releases, htof supports arbitrarily high-order astrometric solutions (e.g. five-, seven-, nine-parameter fits). Using htof, we find that the IAD of 6617 sources in Hipparcos 2007 might have been affected by a data corruption issue. htof integrates an ad-hoc correction that reconciles the IAD of these sources with their published catalog solutions. We developed htof to study masses and orbital parameters of sub-stellar companions, and we outline its implementation in one orbit fitting code (orvara, https://github.com/t-brandt/orvara). We use htof to predict a range of hypothetical additional planets in the $\beta$~Pic system, which could be detected by coupling NGRST astrometry with Gaia and Hipparcos. htof is pip installable and available at https://github.com/gmbrandt/htof .