0970001

MAXI J1305-704 is a new X-ray transient recently discovered by MAXI (ATel #4024 #4035). On April 10 the Swift/BAT flux was ~25 mCrab (15-50 keV ATel #4034). Since then it rose up to ~50 mCrab and it isnow seen at a plateau at ~30 mCrab. A Swift/XRT spectrum on April 11 could be described by either a power-law with photon index ~2 or an absorbed thermal disk model with kT~1.2 keV. The large optical amplitude the blue optical SED and the initial hard X-ray spectrum point to a black hole being the compact object (ATel #4030). A hard-to-soft state transition occurred on April 9/10 alsosuggestive of a black hole (ATel #4044). The non-detection of strong X-ray variability on April 11 supports the current soft-state interpretation. However as noted in ATels #4035 and 4044 a neutron star can still not be ruled out. Swift/XRT observations on April 14 also revealed absorption dips possibly at a period of ~1.5 hours which would be the shorterst orbital period seen so far for a black hole candidate. In order to verify the nature of the compact object we request 2 TOO observations of 50 ksec each to be executed asap. These observations provide the high energy coverage (IBIS and SPI) to allow the detection of a potential hard energy tail. The long uninterrupted observations allow us to verify with JEM-X the presence of X-ray dips if observed they will help in scrutinizing the orbital period. The long observation will also maximize the chance to detect any type I X-ray burst which would rule out a black hole but point to a neutron star. We therefore request the observations to be done in the HEX pattern. We are aware that INTEGRAL TOO proposals do exist in the AO9 proposal database. However these are for objects for which the compact object nature has been established. Since it is uncertain at the moment they cannot be triggered. As waiting to get a firm answer on that could be too late we suggest to observe [truncated! Please see actual data for full text]