A new symbiotic low mass X-ray binary system: 4U 1954+319

Aims. 4U 1954 + 319 was discovered 25 years ago, but only recently has a clear picture of its nature begun to emerge. We present for the first time a broad-band spectrum of the source and a detailed timing study using more than one year of monitoring data. Methods. The timing and spectral analysis was done using publicly available Swift, INTEGRAL, BeppoSAX, and RXTE/ASMdata in the 0.7 to 150 keV energy band. Results. The source spectrum is described well by a highly absorbed (N-H similar to 10(23) cm(-2)) power law with a high-energy exponential cutoff around 15 keV. An additional black body component is needed below 3 keV to account for a soft excess. The derived similar to 5 h periodicity, with a spin-up timescale of similar to 25 years, could be identified as the neutron star spin period. The spectral and timing characteristics indicate that we are dealing both with the slowest established wind-accreting X-ray pulsar and with the second confirmed member of the emerging class dubbed "symbiotic low mass X-ray binaries" to host a neutron star.