INTEGRAL TOO observations of MAXI J1659-152

ATel #2888; E. Kuulkers (ESA/ESAC), C. Kouveliotou (NASA/MSFC), J. Chenevez (DTU Space), A. J. van der Horst (NASA/MSFC/ORAU), on behalf of a larger collaboration
on 30 Sep 2010; 12:09 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Erik Kuulkers (ekuulker@rssd.esa.int)

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INTEGRAL observed the recently discovered X-ray transient MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) from UT 27 September 19:04 to 29 September 2010 09:04 (i.e., simultaneous with the XMM-Newton observations, Kuulkers et al. 2010, ATel #2887) for a total exposure of 100 ksec.

During the first ~58 ksec exposure the source was about 180 mCrab (20-40 keV) and 110 mCrab (40-80 keV) as seen with IBIS/ISGRI. The intensity does not show a strong trend during the observations. Variations up to about 10% (20-40 keV) are seen in the hard X-ray flux on time scales of down to the pointing exposure time (about half an hour). In the same time period JEM-X records an X-ray flux of about 180 mCrab (3-10 keV) and 220 mCrab (10-35 keV).

The above indicates a slow decline in the hard X-ray flux of the source with respect to previous INTEGRAL observations, obtained 2 days earlier (Vovk et al. 2010, ATel #2875). The soft X-ray (<20 keV) flux is consistent with the RXTE/PCA observations taken during the INTEGRAL TOO observations (Kalamkar et al. 2010, ATel #2881). The decline in hard X-rays is in contrast to the rise seen in soft X-rays (<20 keV) flux over the last days (Kennea et al. 2010, ATel #2877; Kuulkers et al. 2010, ATel #2887), and supports the source being in a transitional stage from the hard state to the soft state (Kalamkar et al. 2010, ATel #2881) during the XMM-Newton and INTEGRAL observations.

We note that a second INTEGRAL TOO will start today, 30 September 2010 at UT 12:51. We encourage any simultaneous observations at all wavelengths with the INTEGRAL one.

We thank the INTEGRAL Science Operations Centre for their extremely prompt scheduling of our TOO and the ISDC Data Centre for Astrophysics for their help in the ISGRI quick-look analysis.