Article: Nielsen, EL; De Rosa, RJ; Rameau, J; Wang, JJ; Esposito, TM; Millar-Blanchaer, MA; Marois, C; Vigan, A; Ammons, SM; Artigau, E; Bailey, VP; Blunt, S; Bulger, J; Chilcote, J; Cotten, T; Doyon, R; Duchene, G; Fabrycky, D; Fitzgerald, MP; Follette, KB; Gerard, BL; Goodsell, SJ; Graham, JR; Greenbaum, AZ; Hibon, P; Hinkley, S; Hung, LW; Ingraham, P; Jensen-Clem, R; Kalas, P; Konopacky, Q; Larkin, JE; Macintosh, B; Maire, J; Marchis, F; Metchev, S; Morzinski, KM; Murray-Clay, RA; Oppenheimer, R; Palmer, D; Patience, J; Perrin, M; Poyneer, L; Pueyo, L; Rafikov, RR; Rajan, A; Rantakyro, FT; Ruffio, JB; Savransky, D; Schneider, AC; Sivaramakrishnan, A; Song, I; Soummer, R; Thomas, S; Wallace, JK; Ward-Duong, K; Wiktorowicz, S; Wolff, S; “Evidence That the Directly Imaged Planet HD 131399 Ab Is a Background Star”, Astronomical Journal, 154 (5)
Abstract: We present evidence that the recently discovered, directly imaged planet HD 131399 Ab is a background star with nonzero 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 reinvestigate 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(-1). 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.
Funding Acknowledgement: W.M. Keck Foundation; European Organization for Astronomical Research in the Southern Hemisphere under ESO program [098.C-0864(A)]; European Commission Sixth and Seventh Framework Programmes as part of the Optical Infrared Coordination Network for Astronomy (OPTICON) [RII3-Ct-2004-001566, 226604, 312430]; Fonds de Recherche du Quebec; NASA through the Sagan Fellowship Program; NASA through Hubble Fellowship grant – Space Telescope Science Institute [51378.01-A, NAS5-26555]; NSF [AST-1411868, AST-141378, AST-1518332]; NASA [NNX14AJ80G, NNX15AC89G, NNX15AD95G, NNX16AD44G]; NRAO Student Observing Support Award [SOSPA3-007]; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]; NASA Science Mission Directorate; ESO
Funding Text: This work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina), and Ministerio da Ciencia, Tecnologia e Inovacao (Brazil). Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO program 098.C-0864(A) and based on data obtained from the ESO Science Archive Facility. SPHERE is an instrument designed and built by a consortium consisting of IPAG (Grenoble, France), MPIA (Heidelberg, Germany), LAM (Marseille, France), LESIA (Paris, France), Laboratoire Lagrange (Nice, France), INAFOsservatorio di Padova (Italy), Observatoire de Genve (Switzerland), ETH Zurich (Switzerland), NOVA (Netherlands), ONERA (France), and ASTRON (Netherlands) in collaboration with ESO. SPHERE was funded by ESO, with additional contributions from CNRS (France), MPIA (Germany), INAF (Italy), FINES (Switzerland), and NOVA (Netherlands).SPHERE also received funding from the European Commission Sixth and Seventh Framework Programmes as part of the Optical Infrared Coordination Network for Astronomy (OPTICON) under grant number RII3-Ct-2004-001566 for FP6 (20042008), grant number 226604 for FP7 (20092012), and grant number 312430 for FP7 (20132016).J.R., R.D., and D.L. acknowledge support from the Fonds de Recherche du Quebec. J.R.M.’s work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Support for M.M.B.’s work was provided by NASA through Hubble Fellowship grant #51378.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Researchers were supported by NSF grants AST-1411868 (K.B.F., B.M., and J.P.), AST-141378 (G.D.), and AST-1518332 (R.D.R., J.J.W., T.M.E., J.R.G., P.G.K.). Researchers were supported by NASA grants NNX14AJ80G (E.L.N., S.C.B., B.M., F.M., and M.P.), NNX15AC89G and NNX15AD95G (B.M., J.E.W., T.M.E., R.J.D.R., G.D., J.R.G., P.G.K.) and NNX16AD44G (K.M.M.). K.W.D. is supported by an NRAO Student Observing Support Award SOSPA3-007. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work benefited from the NASA Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by the NASA Science Mission Directorate.