An accurate distance to 2M1207Ab

TL;DR

This paper precisely measures the distance to the 2M1207A system, refining the physical properties and nature of its planetary companion 2M1207b, and discusses three possible scenarios for its characteristics based on the new distance.

Contribution

The study provides the first accurate trigonometric parallax measurement of 2M1207A, improving estimates of the companion’s properties and clarifying its potential formation scenarios.

Findings

Distance to 2M1207A is 52.4±1.1 pc.

Derived physical properties of 2M1207b depend on the new distance.

Three scenarios for 2M1207b's nature are discussed.

Abstract

In April 2004 the first image was obtained of a planetary mass companion (now known as 2M1207 b) in orbit around a self-luminous object different from our own Sun (the young brown dwarf 2MASSW J1207334-393254, hereafter 2M1207 A). 2M1207 b probably formed via fragmentation and gravitational collapse, offering proof that such a mechanism can form bodies in the planetary mass regime. However, the predicted mass, luminosity, and radius of 2M1207 b depend on its age, distance, and other observables such as effective temperature. To refine our knowledge of the physical properties of 2M1207 b and its nature, we obtained an accurate determination of the distance to the 2M1207 A and b system by measurements of its trigonometric parallax at the milliarcsec level. With the ESO NTT/SUSI2 telescope, in 2006 we began a campaign of photometric and astrometric observations to measure the trigonometric parallax of 2M1207 A. An accurate distance ($52.4\pm 1.1$ pc) to 2M1207A was measured. From distance and proper motions we derived spatial velocities fully compatible with TWA membership. With this new distance estimate, we discuss three scenarios regarding the nature of 2M1207 b: (1) a cool ($1150\pm150$ K) companion of mass $4\pm1$ M$_{\rm{Jup}}$, (2) a warmer ($1600\pm100$ K) and heavier ($8\pm2$ M$_{\rm{Jup}}$) companion occulted by an edge-on circum-secondary disk or (3) a hot protoplanet collision afterglow.