Abstract
ABSTRACTWe present results of analyses of observations of the X‐ray source 2A 1704+241 with the ROSAT Position Sensitive Proportional Counter (PSPC) and the High Resolution Imager (HRI). The source 2A 1704+241 was first associated with the M giant star HD 154791 based on observations with the HEAO 1 scanning modulation collimator and the Einstein IPC and analysis of a spectrum of HD 154791 obtained with the International Ultraviolet Explorer. This identification was unusual because there are few bright X‐ray binaries associated with an M giant star. We observed 2A 1704+241 with the PSPC and the HRI in order to determine more accurately the position of the X‐ray source and in order to study the previously seen 900 s variability in the Einstein data. Based on the previous identification and determination of the position of MS 1703.7+2417, an active galactic nucleus in the field, and the position of three previously unreported X‐ray sources that we have associated with stars in the USNO‐A2.0 catalog, we have greatly reduced the X‐ray positional error of 2A 1704+241. HD 154791 remains the prime candidate as the optical counterpart of the X‐ray source. While the 50% modulation in the X‐ray flux seen by the Einstein IPC is apparent in the ROSAT data, it appears to be at a slightly different frequency.
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