Transition to the soft-intermediate state of MAXI J1659-152

ATel #2927; T. Belloni, S. Motta, T. Muñoz-Darias (INAF - Brera Observatory, Italy)
on 12 Oct 2010; 21:42 UT
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Credential Certification: Tomaso Belloni (belloni@merate.mi.astro.it)

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MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) was observed by RXTE on 2010 Oct 12 16:37 to 17:17. The power density spectrum showed a power-law component with a strong type-B QPO at a frequency of 3.91 +/- 0.01 Hz with a quality factor of 8.5. The total 0.1-64 Hz fractional rms was 6.5%, within the expected range for the soft-intermediate state (see Muñoz-Darias et al., 2010, arXiv:1008.0558). The PCA energy spectrum was well fitted with a model consisting of a disk blackbody and a power law, without need for an emission line or high-energy cutoff. Only an upper limit of 3 10^21 cm^-2 (3 sigma) could be established for the value of the interstellar absorption. The best fit parameters were: photon index gamma = 2.32 +/- 0.02 and disk inner temperature kT = 0.97 +/- 0.02 keV. The 3-25 keV flux was 6.7 10^-9 erg/cm^2/s. The previous observation on the same day at 00:37-01:34 UT showed strong band-limited noise and a type-C QPO at a centroid frequency of 6.68 +/- 0.04 Hz (Q=10), with a total fractional rms of 14.2%. The PCA energy spectrum was fitted with the same two-component model and yielded gamma = 2.28 +/- 0.10 and kT = 0.89 +/- 0.02 keV. The 3-25 keV flux was 5.2 10^-9 erg/cm^2/s. Observations at all wavelengths are encouraged, as this transition has been associated to the ejection of relativistic jets.

Light curve and hardness-intensity diagram for the current outburst of MAXI J1659-152