The Gemini NICI Planet-Finding Campaign: Discovery of a Close Substellar Companion to the Young Debris Disk Star PZ Tel

摘要

We report the discovery of a tight substellar companion to the young solaranalog PZ Tel, a member of the Beta Pictoris moving group observed with highcontrast adaptive optics imaging as part of the Gemini NICI Planet-FindingCampaign. The companion was detected at a projected separation of 16.4 +/- 1.0AU (0.33 +/- 0.01") in April 2009. Second-epoch observations in May 2010demonstrate that the companion is physically associated and shows significantorbital motion. Monte Carlo modeling constrains the orbit of PZ Tel B toeccentricities > 0.6. The near-IR colors of PZ Tel B indicate a spectral typeof M7+/-2 and thus this object will be a new benchmark companion for studies ofultracool, low-gravity photospheres. Adopting an age of 12 +8 -4 Myr for thesystem, we estimate a mass of 36 +/- 6 Mjup based on the Lyon/DUSTYevolutionary models. PZ Tel B is one of few young substellar companionsdirectly imaged at orbital separations similar to those of giant planets in ourown solar system. Additionally, the primary star PZ Tel A shows a 70 umemission excess, evidence for a significant quantity of circumstellar dust thathas not been disrupted by the orbital motion of the companion.