The Directly Imaged Planet Around the Young Solar Analog 1RXS J160929.1 – 210524: Confirmation of Common Proper Motion, Temperature, and Mass

• Published in: The Astrophysical journal Vol. 719; no. 1; p. 497
• Main Authors: Lafrenière, David, Jayawardhana, Ray, van Kerkwijk, Marten H
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 10.08.2010
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; Estimates; EVOLUTION; LUMINOSITY; MASS; MEASURING INSTRUMENTS; MOTION; OPTICAL PROPERTIES; Orbitals; PHOTOMETRY; PHYSICAL PROPERTIES; Planetary mass; PLANETS; PROPER MOTION; Separation; Spectra; SPECTROSCOPY; STAR EVOLUTION; STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/719/1/497

Giant planets are usually thought to form within a few tens of AU of their host stars, and hence it came as a surprise when we found what appeared to be a planetary mass (~0.008 M ) companion around the 5 Myr old solar mass star 1RXS J160929.1 -- 210524 in the Upper Scorpius association. At the time, we took the object's membership in Upper Scorpius--established from near-infrared, H- and K-band spectroscopy--and its proximity (22 or 330 AU) to the primary as strong evidence for companionship, but could not verify their common proper motion. Here, we present follow-up astrometric measurements that confirm that the companion is indeed comoving with the primary star, which we interpret as evidence that it is a truly bound planetary mass companion. We also present new J-band spectroscopy and 3.0-3.8 Delta *mm photometry of the companion. Based on a comparison with model spectra, these new measurements are consistent with the previous estimate of the companion effective temperature of 1800 plus or minus 200 K. We present a new estimate of the companion mass based on evolution models and the calculated bolometric luminosity of the companion; we obtain a value of 0.008+0.003 --0.002 M , again consistent with our previous result. Finally, we present angular differential imaging observations of the system allowing us to rule out additional planets in the system more massive than 1 M Jup, 2 M Jup, and 8 M Jup at projected separations larger than 3'' (~440 AU), 07 (~100 AU), and 035 (~50 AU), respectively. This companion is the least massive known to date at such a large orbital distance; it shows that objects in the planetary mass range exist at orbital separations of several hundred AU, posing a serious challenge for current formation models.