Soft-to-Hard transition in MAXI J1659-152
ATel #2999; T. Muñoz-Darias, H. Stiele, T. M. Belloni, S. Motta (INAF-Osservatorio Astronomico di Brera)
on 2 Nov 2010; 06:30 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Teo Muñoz-Darias (tmd@brera.inaf.it)
Subjects: X-ray, Request for Observations, Binary, Black Hole, Transient
Recent RXTE observations of MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) show that MAXI J1659-152 performed a transition from soft states to the hard intermediate state between Oct 31 (07:51 UT; observation 95118-01-16-00) and Nov 01 (05:15; observation 95118-01-16-01). A timing analysis of these two observations shows that fractional rms increases from 8% to 15% during the above period, being now consistent with the typical values observed in the hard intermediate state (Muñoz-Darias et al., 2010, arXiv:1008.0558). A weak type C QPO at ~6 Hz, typical of this state, appears in the power density spectra. Hardness (PCA channels 7-13 (2.87-5.71 keV)/14-23 (5.71-9.51 keV)) also increases from ~0.3 to ~0.5. A disk-blackbody + power law fit of the PCU spectra shows an increase of the power law contribution.
This transition is confirmed by the last RXTE observation of the source (95118-01-17-00) on Nov 02 00:03 UT where we measure a fractional rms of 19 % and a QPO frequency of ~ 5 Hz.
The systems was discovered on Sep 25, 2010 (ATel #2873; GCN #11296). It was in the hard-intermediate state in Sep 28 (ATEL #2881) and transitions to the soft-intermediate (ATEL #2927) and soft (ATEL #2951) states were observed on Oct 12 and Oct 18. We note that this fast outburst evolution is in principle consistent with MAXI J1659-152 having a short orbital period as proposed in ATEL #2926 and ATEL #2912. Observations at all wavelengths are encouraged.
See light curve and hardness-intensity diagram for the whole outburst MAXI J1659-152
