Astrophys. J., 818, 176 (2016/February-3)
Discovery of rotational modulations in the planetary-mass companion 2M1207b: intermediate rotation period and heterogeneous clouds in a low gravity atmosphere.
ZHOU Y., APAI D., SCHNEIDER G.H., MARLEY M.S. and SHOWMAN A.P.
Abstract (from CDS):
Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves directly probe the rotational periods of ultra-cool objects. We present here, for the first time, time-resolved high-precision photometric measurements of a planetary-mass companion, 2M1207b. We observed the binary system with Hubble Space Telescope/Wide Field Camera 3 in two bands and with two spacecraft roll angles. Using point-spread function-based photometry, we reach a nearly photon-noise limited accuracy for both the primary and the secondary. While the primary is consistent with a flat light curve, the secondary shows modulations that are clearly detected in the combined light curve as well as in different subsets of the data. The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters, respectively. By fitting sine waves to the light curves, we find a consistent period of 10.7–0.6+1.2 hr and similar phases in both bands. The J- and H-band amplitude ratio of 2M1207b is very similar to a field brown dwarf that has identical spectral type but different J-H color. Importantly, our study also measures, for the first time, the rotation period for a directly imaged extra-solar planetary-mass companion.
brown dwarfs - planets and satellites: atmospheres - planets and satellites: individual: 2M1207b - techniques: photometric
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<Available at CDS (J/ApJ/818/176): table1.dat table2.dat>
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