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Published online by Cambridge University Press: 25 May 2016
On 1993 August 20, we observed the Rho-Oph dark cloud and detected hard X-rays from Class I sources (Koyama et al.(1994), Kamata et al.(1997)). One of the sources (EL29) showed a flare-like variability, while another (WL6) exhibited sinusoidal variation with no large spectral change. The later would be due to a spin of the protostar. The sinusoidal period of about 1 day is shorter than spin periods of TTSs of ~3-7 day.