Evidence that the Directly-Imaged Planet HD 131399 Ab is a Background Star
Abstract
We present evidence that the recently discovered, directly-imaged planet HD 131399 Ab is a background star with non-zero proper motion. From new JHK1L' photometry and spectroscopy obtained with the Gemini Planet Imager, VLT/SPHERE, and Keck/NIRC2, and a reanalysis of the discovery data obtained with VLT/SPHERE, we derive colors, spectra, and astrometry for HD 131399 Ab. The broader wavelength coverage and higher data quality allow us to re-investigate its status. Its near-infrared spectral energy distribution excludes spectral types later than L0 and is consistent with a K or M dwarf, which are the most likely candidates for a background object in this direction at the apparent magnitude observed. If it were a physically associated object, the projected velocity of HD 131399 Ab would exceed escape velocity given the mass and distance to HD 131399 A. We show that HD 131399 Ab is also not following the expected track for a stationary background star at infinite distance. Solving for the proper motion and parallax required to explain the relative motion of HD 131399 Ab, we find a proper motion of 12.3 mas/yr. When compared to predicted background objects drawn from a galactic model, we find this proper motion to be high, but consistent with the top 4% fastest-moving background stars. From our analysis we conclude that HD 131399 Ab is a background K or M dwarf.
Cite
@article{arxiv.1705.06851,
title = {Evidence that the Directly-Imaged Planet HD 131399 Ab is a Background Star},
author = {Eric L. Nielsen and Robert J. De Rosa and Julien Rameau and Jason J. Wang and Thomas M. Esposito and Maxwell A. Millar-Blanchaer and Christian Marois and Arthur Vigan and S. Mark Ammons and Etienne Artigau and Vanessa P. Bailey and Sarah Blunt and Joanna Bulger and Jeffrey Chilcote and Tara Cotten and René Doyon and Gaspard Duchêne and Daniel Fabrycky and Michael P. Fitzgerald and Katherine B. Follette and Benjamin L. Gerard and Stephen J. Goodsell and James R. Graham and Alexandra Z. Greenbaum and Pascale Hibon and Sasha Hinkley and Li-Wei Hung and Patrick Ingraham and Rebecca Jensen-Clem and Paul Kalas and Quinn Konopacky and James E. Larkin and Bruce Macintosh and Jerome Maire and Franck Marchis and Stanimir Metchev and Katie M. Morzinski and Ruth A. Murray-Clay and Rebecca Oppenheimer and David Palmer and Jennifer Patience and Marshall Perrin and Lisa Poyneer and Laurent Pueyo and Roman R. Rafikov and Abhijith Rajan and Fredrik T. Rantakyrö and Jean-Baptiste Ruffio and Dmitry Savransky and Adam C. Schneider and Anand Sivaramakrishnan and Inseok Song and Remi Soummer and Sandrine Thomas and J. Kent Wallace and Kimberly Ward-Duong and Sloane Wiktorowicz and Schuyler Wolff},
journal= {arXiv preprint arXiv:1705.06851},
year = {2017}
}
Comments
35 pages, 20 figures, Published in AJ