1270010

The neutron star low-mass X-ray binary GS 1826-238 aka the Clocked Burster is currently observed in a new state change as revealed by Swift/BAT and MAXI light-curves. This is only the 4th time since the source discovery in 1989 but also already the 4th time in 15 months only indicating that these state changes seem to occur more and more frequently.As its name indicates this source is known to produce bursts at a regular recurrence time typically around 4-5 hours. We observed the source for the first time in a soft state in June 2014 (see Chenevez et al. astro-ph/1509.01248) with Swift/XRT and NuSTAR showing a much different burst behavior than usual with both much shorter bursts and recurrence times. At that time the hardness ratio of Swift/BAT to MAXI intensities was below 0.7 compared to the usual value about 1.5.The current Swift/BAT to MAXI ratio is about 0.01. Yesterday (September 26) we obtained a 1.8 ks Swift/XRT ToO to measure the actual spectrum of GS 1826-24. This observation also reveals a softer spectrum (http://www.swift.ac.uk/user_objects/tprods/USERPROD_2.110.8.170_1443271067220/spec) than in 2014 June and the best fit is obtained with a double black-body model with temperatures of 0.6 keV and 1.6 keV.Unlike the previous soft episodes GS 1826-24 is this time observable with INTEGRAL. The source was well detected by ISGRI during the Galactic Bulge (GB)observation of revolution 1587 at a significance of 29 sigmas in the 18-40 keV energy band but has remained undetected by ISGRI in the following GB observations (revs. 1589-1592). Recently GS 1826-24 has only been in JEM-X field of view in four science windows during the Galactic Center observation of rev. 1589. The source was well detected but no burst was observed during this almost 10 ksec exposure.We therefore request a ~30 ksec long observation with INTEGRAL using a couple of hexagonal patterns centered on GS 1826-24 to get an (almost) uni [truncated! Please see actual data for full text]