Discovery of a similar to 1 Hz quasi-periodic oscillation in the low-mass X-ray binary 4U 1746-37

have discovered a similar to 1 Hz quasi-periodic oscillation (QPO) present in the persistent X-ray emission of the globular cluster source, dipper, an d low-mass X-ray binary (LMXB) 4U 1746-37. The QPO was also observed during type I X-ray bursts. The QPO properties resemble those of QPOs found recen tly in the LMXB dippers 4U 1323-62 and EXO 0748-676, which makes 4U 1746-37 the third source known to exhibit this type of QPO. We present evidence fo r X-ray spectral changes in this source similar to those observed in LMXBs referred to as atoll sources. We detect two states, a lower intensity and s pectrally hard state and a higher intensity and spectrally soft state. This may explain the different spectral characteristics reported for 4U 1746-37 earlier. The high-intensity state resembles the banana branch state of ato ll sources. The QPOs are seen only in the low-intensity state and are absen t when the source is in the banana branch. This strongly suggests that eith er the accretion disk or an extended central source changes shape between t he low-intensity state and the banana branch. Twelve bursts were detected, of which five took place while the source was on the banana branch and seve n while the source was in the low-intensity state. The bursts occurring on the banana branch had an e-folding time similar to 3 times longer than thos e that occurred in the low-intensity state. Whereas previously detected dip s showed a decrease in count rate of only similar to 15%, we found a dip in one observation for which the count rate dropped from similar to 200 count s s(-1) to similar to 20 counts s(-1). This dip lasted only similar to 250 s, during which clear spectral hardening occurred. This is the first time s trong evidence for spectral changes during a dip have been reported for thi s source.