RECONNAISSANCE OF THE HR 8799 EXOSOLAR SYSTEM. I. NEAR-INFRARED SPECTROSCOPY

Abstract

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