SIGMA-GRANAT OBSERVATIONS OF THE BRIGHT NEARBY MILLISECOND PULSAR PSRJ0437-4715

We report the first hard X-ray/soft gamma-ray observations of the rece ntly discovered bright binary millisecond pulsar PSR J0437-4715. The o bservations were performed with the French coded-mask imaging telescop e SIGMA aboard the Russian GRANAT spacecraft. More than 30 hours of us eful time were accumulated during two observations performed on May 17 th, 1993 and May 21st, 1993. No high energy emission was detected neit her in the individual sessions nor in their sum. The 2 sigma upper lim its derived in the 40 to 200 keV range correspond to a photon flux of 2.1 x 10(-3) photons cm-2 s-1 or equivalently to a luminosity of almos t-equal-to 7 x 10(32) erg s-1 for a distance of 150 pc, indicating tha t the magnetospheric efficiency of the conversion of the pulsar spin d own power into hard X-rays is less than 7.0 x 10(-2) for PSR J0437-471 5.