We report on a series of Swift /XRT observations , performed between February and 22 March 2012 , during the quiescent state of the neutron-star X-ray binary SAX J1750.8–2900 .
In these observations , the source was either just detected or undetected , depending on the exposure length ( which ranged from \sim 0.3 to \sim 3.8 ks ) .
The upper limits for the non-detections were consistent with the detected luminosities ( when fitting a thermal model to the spectrum ) of \sim 10 ^ { 34 } erg s ^ { -1 } ( 0.5–10 keV ) .
This level is consistent with what has been measured previously for this source in quiescence .
However , on March 17 the source was found to have an order of magnitude larger count rate .
When fitting the flare spectrum with an absorbed power-law model , we obtained a flare luminosity of ( 3 - 4 ) \times 10 ^ { 34 } erg s ^ { -1 } ( 0.5–10 keV ) .
Follow-up Swift observations showed that this flare lasted < 16 days .
This event was very likely due to a brief episode of low-level accretion onto the neutron star and provides further evidence that the quiescent state of neutron-star X-ray transients might not be as quiet as is generally assumed .
The detection of this low-level accretion flare raises the question whether the quiescent emission of the source ( outside the flare ) could also be due to residual accretion , albeit continuous instead of episodic .
However , we provide arguments which would suggest that the lowest intensity level might instead represent the cooling of the accretion-heated neutron star .