The Atmospheres of Other Worlds: Atmosperhic Components of the Worlds of HR 8799

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

Authors:

1. B. R. Oppenheimer (a)
2. C. Baranec (b)
3. C. Beichman (a,c)
4. D. Brenner (a)
5. R. Burruss (d)
6. E. Cady (d)
7. J. R. Crepp (e,m)
8. R. Dekany (b)
9. R. Fergus (f)
10. D. Hale (b)
11. L. Hillenbrand (e)
12. S. Hinkley (e)
13. David W. Hogg (g)
14. D. King (h)
15. E. R. Ligon (d)
16. T. Lockhart (d)
17. R. Nilsson (a)
18. I. R. Parry (a,h)
19. L. Pueyo (i)
20. E. Rice (a,j)
21. J. E. Roberts (d)
22. L. C. Roberts, Jr (d)
23. M. Shao (d)
24. A. Sivaramakrishnan (a,k)
25. R. Soummer (a,k)
26. T. Truong (d)
27. G. Vasisht (d)
28. A. Veicht (a)
29. F. Vescelus (d)
30. J. K. Wallace (d)
31. C. Zhai (d)
32. N. Zimmerman (a,m)

Affiliations:

a. Astrophysics Department, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA; bro@amnh.org

b. Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USA

c. NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125, USA

d. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena CA 91109, USA

e. Department of Astronomy, California Institute of Technology, 1200 E. California Blvd, MC 249-17, Pasadena, CA 91125, USA

f. Department of Computer Science, Courant Institute of Mathematical Sciences, New York University, 715 Broadway, New York, NY 10003, USA

g. Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003, USA

h. Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, UK

i. Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA

j. Department of Engineering Science & Physics, College of Staten Island, 2800 Victory Blvd., Staten Island, NY 10314, USA

k. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

l. unknown, not included in paper.

m. unknown, not included in paper

Abstract:

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 5mHale 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 CH4 along with NH3 and/or C2H2, and possibly CO2 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.