THE transient X-ray source Ariel 1118 - 61 has been discovered by Ariel V (refs 1, 2) and the best estimate for the position is (1950.0) α = 11 h 18 min 59s δ = -61° 35.3′. We point out here the presence in the error box of the long period Mira-type variable RS Cen (1950.0) α = 11 h 18 min 16.5 s δ = -61° 36.0′. It has been suggested that in the Mira-type variables o Ceti (Mira) and SY For the blue variable companion is a white dwarf illuminated by infalling material accreted from the strong wind of the M-type star3-5. The similarity between these systems and the (recurrent) nova T CrB has also been stressed5. We propose that some transient X-ray sources are binary systems consisting of a compact object in orbit around a long period variable. The accretion rate of material on to the compact object in such a system4 is ≲ 10-8 M ȯyr-1 which is just the rate required to produce X rays from a compact object. We note too the proposed identification6 of another transient X-ray source (2U1543 - 47) with a variable late-type giant.
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