OBSERVATIONS OF THE LOW-MASS X-RAY SYSTEM-4U 1626-67 KZ TRA BY THE GRANAT-ASTROPHYSICAL-OBSERVATORY/

We present the results of observations of the x-ray pulsar 4U 1626-67 in the 4-40 keV energy band by the Granat Observatory ART-P telescope. The source has a power-law energy spectrum with slope alpha congruent -to 0.3 up to E(cut) congruent-to 13.6 keV. We found that the pulsar's spin-up rate (P/P = - 2.10(-4) yr-1), observed since the time of the pulsar's discovery in 1977, has changed sign to become a quasistationa ry spindown (P/P = + 2.5.10(-4) yr-1). In addition, the source luminos ity in the 4-20 keV band has decreased by a factor of two (L(X) congru ent-to 4.10(36) (D/10 kpc)2 erg sec-1). The pulse shape has become tri ple-peaked in the 4-10 keV energy band, almost sinusoidal in the 10-28 keV band, and irregular in the 28-40 keV band. The phase of global mi nimum of the pulse profile is the same for all energy bands. During th e observations, we detected none of the powerful outbursts that are ch aracteristic of this source.