During a 50 ks monitoring observation of the Galactic bulge performed in September 1999 by the Wide Field Cameras on board the BeppoSAX satellite , an X-ray burst was detected from a sky position \sim 3 \degr off the Galactic centre .
No previously known X-ray sources are located within the position error circle of the observed burst .
The new burster , SAX J1752.3 - 3138 , did not show any persistent emission during the whole observation .
No other bursting events , as well as steady emission , were reported so far by other instruments or detected in the WFC archive , which covers \sim 6 Ms and \sim 4 Ms for burst and persistent luminosity detection , respectively , starting from August 1996 .
Unless the source is a very weak transient , this could indicate SAX J1752.3 - 3138 is an atypical burster , a member of a possibly new class of sources characterised by very low steady luminosities and accretion rates ( L _ { { X } } \la 10 ^ { 35 } { ergs } ^ { -1 } ) and extremely rare bursting activity .
The characteristics of the detected burst are consistent with a type I event , identifying the source as a weakly magnetised neutron star in a low-mass X-ray binary system .
Evidence for photospheric radius expansion due to Eddington-limited burst luminosity allows to estimate the distance to the source ( \sim 9 kpc ) .