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Norio Narita, Takahiro Nagayama, Takuya Suenaga, Akihiko Fukui, Masahiro Ikoma, Yasushi Nakajima, Shogo Nishiyama, Motohide Tamura, IRSF SIRIUS JHKs Simultaneous Transit Photometry of GJ 1214b, Publications of the Astronomical Society of Japan, Volume 65, Issue 2, 25 April 2013, 27, https://doi.org/10.1093/pasj/65.2.27
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Abstract
We report on the high-precision transit photometry of GJ 1214b in JHK|$ _{\rm s}$| bands simultaneously taken with the SIRIUS camera on the Infrared Survey Facility 1.4 m telescope located in Sutherland, South Africa. Our Markov-Chain Monte Carlo analysis shows that observed planet-to-star radius ratios in the JHK|$ _{\rm s}$| bands are |$ R_{\rm p}/R_{{\rm s},J}$||$ =$| 0.11833 |$ \pm$| 0.00077, |$ R_{\rm p}/R_{{\rm s},H}$||$ =$| 0.11522 |$ \pm$| 0.00079, and |$ R_{\rm p}/R_{{\rm s},K_{\rm s}}$||$ =$| 0.11459 |$ \pm$| 0.00099, respectively. The radius ratios are very consistent with previous studies by Bean et al. (2011, ApJ, 743, 92) within 1 |$ \sigma$| , while our ratio in the K|$ _{\rm s}$| band is shallower than previous measurements in the same band by Croll et al. (2011, ApJ, 736, 78) and inconsistent even at the 4 |$ \sigma$| level with them. We have no satisfactory explanation for this discrepancy at this point. Our overall results support a flat transmission spectrum in the observed bands, which can be explained by a water-dominated atmosphere or an atmosphere with extensive high-altitude clouds or haze. To explain the discrepancy of the radius ratios, and to determine a definitive atmosphere model for GJ 1214b in the future, more extended transit observations in around the K|$ _{\rm s}$| band would be especially important.
