Two short lived X-ray transients at high galactic latitude

Abstract

UNTIL recently, sources known to exhibit transient behaviour were restricted to a region close to the galactic plane. Now, extended observations at high galactic latitudes by the Ariel V, ANS and SAS-3 X-ray detectors have revealed transients with an impressive variety of temporal behaviour. Reporting the first such transient Ricketts et al.¹ described how A1103+38 (b^II ≃ 65°) increased in intensity by an order of magnitude over a period of between 10 and 28 d with an additional ‘flare’ which lasted ∼ 1 d. In contrast Rappaport et al.¹² observed a spectrally hard transient MX2346–65 (b^II ≃ −51°) which lasted between 45 s and 2,200 s (ref. 2) and was about as intense as the Crab Nebula. In the error box of A1103–38 the radio source B2 1101+38, whose optical counterpart MK421 may be a BL Lacertae object, could be responsible for the X-ray transient. As there are no obvious optical candidates with which to associate MX2346−65, Rappaport et al. suggest sporadic mass transfer on to a white dwarf from a faint, variable dM class star. We here report two transients at high galactic latitudes observed by the Leicester sky survey experiment on Ariel V whose time scales, of the order of hundreds of minutes, are intermediate between those discussed above.