The RXTE All Sky Monitor has detected an X-ray outburst in HD154791 (SAO 84844; 4U1704+24), which is an M giant that may be accreting onto a neutron star or a white dwarf. During the past two weeks, the flux at 2-10 keV has been steadily rising and is now (1997 Nov. 13) near 35 mCrab, which I believe is a historical maximum. Optical spectral observations would be very useful. This bright star may be observed briefly with northern telescopes during evening twilight. Ron Remillard, for the ASM team at MIT and GSFC (rr@space.mit.edu)