Search for photometric variability in the vicinity of SGR 1900+14 and discovery of a high-mass cluster

A pair of spectroscopically nearly identical M supergiant stars were proposed [1] as possible counterparts to SGR 1900+14 based on positional coincidences with gamma-ray and x-ray localizations. Whether these stars or the nearby fading radio source [9] are associated with SGR 1900+14 is not yet clear. We obtained I- and J-band photometric observations of the M stars with 10 to 120 second time resolution obtained on 16 nights before and during the active phase of SGR 1900+14 beginning in June 1998. Despite more than 54,000 seconds of integration time, no observations were obtained within an hour of a gamma-ray burst event. No short term variability was found for any object within the ROSAT error circle to I less than or equal to 24.5, although an unrelated eclipsing binary was discovered just outside the ROSAT circle. PSF subtraction of the bright M stars reveals a previously hidden compact star cluster.