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ATEL # 2951; Nikolai Shaposhnikov (UMD/CRESST/NASA/GSFC), Kazutaka Yamaoka (Aoyama Gakuin University)
on 18 Oct 2010; 15:28 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Nikolai Shaposhnikov (email@example.com)
Subjects: X-ray, Black Holes, Transients
Referred to by ATEL #: 2999
The last two RXTE observations of the new galactic black hole candidate MAXI J1659-152 (Atels #2873,#2877,#2881) performed on October 17, 2010, 04:16 UT and 18:52 UT have clearly shown changes in the source spectral and variability properties consistent with a transition to the high soft state. Specifically, the power density spectrum have shown the rms variability level of about 5% presented by the low frequency red noise only. No quasi-periodic features are observed. Our spectral analysis have shown that the source spectrum has softened significantly. Namely, the Comptonized fraction has decreased sharply from 0.3 to 0.2, while the index stayed at the value of 2.35 for both observations. The spectral hardness (9-20 keV/ 2-9 keV flux ratio) have correspondingly decreased from 0.85 to 0.7. The observed evolution strongly suggests that the source has completed the transition through the soft intermediate state (Atel #2927) and has entered the high soft state. RXTE team plans to continue the MAXI J1659-152 monitoring program throughout the active phase of the current outburst.