Highlights from the INTEGRAL Spiral Arms Monitoring Program

We describe the scientific objectives and highlights from 4 years of high-cadence monitoring of the inner spiral arms of the Galaxy in X-rays (3-100 keV). The INTEGRAL Spiral Arms (ISA) program (12.8 ks per observation for a total of 1.2 Ms per year) complements the successful Galactic Bulge (GB) program by extending the monitored regions to the Inner Perseus/Norma Arm tangents on one side of the GB, and the Scutum/Sagittarius Arms on the other. These fields feature a high density of obscured high-mass X-ray binaries (HMXBs), including Supergiant Fast X-ray Transients (SFXTs), as well as other hard X-ray emitting sources (e.g. microquasars, low-mass X-ray binaries, and magnetars) that INTEGRAL is well-suited to finding thanks to its large field of view and angular resolution at high energies even in crowded regions of the sky. Mosaic images and source light curves in 2 energy bands for ISGRI and JEM-X are provided to the community at isa.gcsu.edu permitting rapid dissemination of results which enable prompt follow-up of interesting events. The ISA project represents the cornerstone of our ongoing study of transient and variable hard X-ray populations in the Milky Way.