  The spreading layer (SL) on neutron star surface of GX 9+9 during the upper
banana state was studied using INTEGRAL and RXTE observations. The SL-area
becomes larger with increasing accretion rate while the SL-temperature remains
close to the critical Eddington value, confirming predictions by Inogamov and
Sunyaev (1999) and Suleimanov and Poutanen (2006). However, at low accretion
rate the observed temperature is higher and SL-belt shallower than those
predicted, requiring confirmation and theoretical explananation.
