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Published May 1, 2013 | Published
Journal Article Open

Reconnaissance of the HR 8799 Exosolar System. I. Near-infrared Spectroscopy


We obtained spectra in the wavelength range λ = 995-1769 nm of all four known planets orbiting the star HR 8799. Using the suite of instrumentation known as Project 1640 on the Palomar 5 m Hale Telescope, we acquired data at two epochs. This allowed for multiple imaging detections of the companions and multiple extractions of low-resolution (R ~ 35) spectra. Data reduction employed two different methods of speckle suppression and spectrum extraction, both yielding results that agree. The spectra do not directly correspond to those of any known objects, although similarities with L and T dwarfs are present, as well as some characteristics similar to planets such as Saturn. We tentatively identify the presence of CH_4 along with NH_3 and/or C_2H_2, and possibly CO_2 or HCN in varying amounts in each component of the system. Other studies suggested red colors for these faint companions, and our data confirm those observations. Cloudy models, based on previous photometric observations, may provide the best explanation for the new data presented here. Notable in our data is that these presumably co-eval objects of similar luminosity have significantly different spectra; the diversity of planets may be greater than previously thought. The techniques and methods employed in this paper represent a new capability to observe and rapidly characterize exoplanetary systems in a routine manner over a broad range of planet masses and separations. These are the first simultaneous spectroscopic observations of multiple planets in a planetary system other than our own.

Additional Information

© 2013 American Astronomical Society. Received 2012 November 12; accepted 2013 March 8; published 2013 April 10. We are especially grateful for our two referees, both of whom were particularly meticulous, thorough, and fair. Their reports resulted in significant improvements in the paper. A portion of this work is or was supported by the National Science Foundation under award Nos. AST-0215793, 0334916, 0520822, 0619922, 0804417, 0908497, 1039790 and EAGER grant 1245018. A portion of the research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and was funded by internal Research and Technology Development funds. A portion of this work was supported by NASA Origins of the Solar System grant No. NMO7100830/102190, and NASA APRA grant No. 08-APRA08-0117. B.R.O. acknowledges continued support from Paco. Our team is also grateful to the Plymouth Hill Foundation, and an anonymous donor, as well as the efforts of Mike Werner, Paul Goldsmith, Jacob van Zyl, and Stephanie Hunt. E.L.R. acknowledges support from NASA through the American Astronomical Society's Small Research Grant Program. R.N. performed this work with funding through a grant from Helge Ax:son Johnson's foundation. L.P. performed this work in part under contract with the California Institute of Technology funded by NASA through the Sagan Fellowship Program. S.H. is supported by a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under award No. AST-1203023. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. R.F. and D.W.H. were partially supported by the National Science Foundation under award No. IIS-1124794. B.R.O. thanks Didier Saumon and Mark Marley, as well as Bruce Macintosh, Gilles Chabrier and Isabelle Baraffe, as well as Jackie Faherty and Statia Cook, for comments and discussion of a draft prior to submission. We thank the Raymond and Beverly Sacker Foundation whose generous donation allowed the purchase of the original Project 1640 detector. We also thank Teledyne Imaging Sensors for their help and support throughout this project. We thank the dedication and assistance of Andy Boden, Shrinivas Kulkarni and Anna Marie Hetman at Caltech Optical Observatories. Finally, the entire team expresses sincere gratitude and appreciation for the hard work of the Palomar mountain crew, especially by Bruce Baker, Mike Doyle, Carolyn Heffner, John Henning, Greg van Idsinga, Steve Kunsman, Dan McKenna, Jean Mueller, Kajsa Peffer, Kevin Rykowski, and Pam Thompson. This project would be impossible without the flexibility, responsiveness and dedication of such an effective and motivated staff. A description of the contributions of each author can be found at http://www.amnh.org/project1640.

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