Discovery of X-ry pulsations in the Be/X-ray binary LS992/ RX J0812.4-3114

We report on the discovery of X-ray pulsations from the Be/X-ray system LS 992/RX J0812.4--3114 during an RXTE observation. From a timing analysis of the source we obtained a barycentric pulse period of 31.8851 \pm 0.0004 s. The pulse profile is highly structured and departs from a pure sinusoidal shape. It shows a sharp dip that may indicate absorption by the accretion flow. The energy spectrum from 3-30 keV can be fitted by a power-law model with an exponential cut-off in accordance with other X-ray pulsars. The X-ray luminosity is estimated to be $\sim 1.1 \times 10^{36} erg/s$ in the energy range 3-30 keV, assuming a distance of $\sim 9 kpc$.