New Constraint on the Atmosphere of (50000) Quaoar from a Stellar Occultation
Kobayashi, Naoto; Maehara, Hiroyuki; Matsunaga, Noriyuki; Nakada, Yoshikazu; Ita, Yoshifusa; Usui, Fumihiko; Arimatsu, Ko; Tominaga, Nozomu; Itoh, Yoichi; Takahashi, Hidenori; Kokubo, Mitsuru; Morokuma, Tomoki; Doi, Mamoru; Miyata, Takashi; Ohsawa, Ryou; Motohara, Kentaro; Morii, Mikio; Takahashi, Jun; Tozuka, Miyako; Sako, Shigeyuki; Sarugaku, Yuki; Konishi, Masahiro; Yoshikawa, Makoto; Shigeyama, Toshikazu; Ikeda, Shiro; Urakawa, Seitaro; Watanabe, Jun-ichi; Hashimoto, George L.; Kasuga, Toshihiro; Yamashita, Takuya; Okumura, Shin-ichiro; Aoki, Tsutomu; Arima, Noriaki; Yamashita, Misato; Ichiki, Makoto; Sato, Mikiya; Soyano, Takao; Tarusawa, Ken'ichi
Japan
Abstract
We report observations of a stellar occultation by the classical Kuiper Belt object (50000) Quaoar that occurred on 2019 June 28. A single-chord high-cadence (2 Hz) photometry data set was obtained with the Tomo-e Gozen CMOS camera mounted on the 1.05 m Schmidt telescope at Kiso Observatory. The obtained ingress and egress data do not show any indication of atmospheric refraction and allow new 1σ and 3σ upper limits of 6 and 16 nbar, respectively, to be set for the surface pressure of a pure methane atmosphere. These upper limits are lower than the saturation vapor pressure of methane at Quaoar’s expected mean surface temperature (T ∼ 44 K) and imply the absence of a ∼10 nbar-level global atmosphere formed by methane ice on Quaoar’s surface.