An accurate distance to 2M1207Ab

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 ($1150\pm 150$ K) companion of mass $4\pm 1$ M${}_{\mathrm{Jup}}$, (2) a warmer ($1600\pm 100$ K) and heavier ($8\pm 2$ M${}_{\mathrm{Jup}}$) companion occulted by an edge-on circum-secondary disk or (3) a hot protoplanet collision afterglow.

5 pages, 3 figures, accepted for publication as letter in A&A, 6/11/2007

References in corpus (7)

• Discovery of Two T Dwarf Companions with the Spitzer Space Telescope
• The Planetary Mass Companion 2MASS1207-3932 B: Temperature, Mass and Evidence for an Edge-On Disk
• HD 203030B: an Unusually Cool Young Sub-Stellar Companion near the L/T Transition
• Discovery of a Bipolar Outflow from 2MASSW J1207334-393254, A 24 Jupiter Mass Brown Dwarf
• An Improbable Solution to the Underluminosity of 2M1207B: A Hot Protoplanet Collision Afterglow
• The Trigonometric Parallax of the Brown Dwarf Planetary System 2MASSW J1207334-393254
• The First Direct Distance and Luminosity Determination for a Self-Luminous Giant Exoplanet: The Trigonometric Parallax to 2MASS1207334-393254Ab

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