Astrophysical Parameters and Habitable Zone of the Exoplanet Hosting Star GJ 581

TL;DR

This study precisely measures the physical and stellar parameters of GJ 581 using interferometry and photometry, recalculates its habitable zone, and assesses the potential habitability of its planets.

Contribution

It provides the first direct radius measurement of GJ 581 and refines the habitable zone boundaries based on these measurements.

Findings

GJ 581's radius is 0.299 R_sun.

Effective temperature is 3498 K.

Planets d and g are within or near the habitable zone.

Abstract

GJ 581 is an M dwarf host of a multiplanet system. We use long-baseline interferometric measurements from the CHARA Array, coupled with trigonometric parallax information, to directly determine its physical radius to be $0.299 \pm 0.010 R_{\odot}$. Literature photometry data are used to perform spectral energy distribution fitting in order to determine GJ 581's effective surface temperature $T_{\rm EFF}=3498 \pm 56$ K and its luminosity $L=0.01205 \pm 0.00024 L_{\odot}$. From these measurements, we recompute the location and extent of the system's habitable zone and conclude that two of the planets orbiting GJ 581, planets d and g, spend all or part of their orbit within or just on the edge of the habitable zone.