First X-ray source in Hydrus

The first X-ray source in Hydrus may have been any of the early detections of X-rays emanating from the constellation Hydrus.
Hydrus as a celestial X-ray source
Hydrus is a small constellation in the southern sky that ranges in latitude (declination) from -58° to -82°. If celestial X-ray sources are distributed uniformly, because of its areal portion of the celestial sphere, Hydrus would only be expected to have between four and five extrasolar astronomical X-ray sources detected by sounding rockets, balloons, or early satellites, once about 840 such sources have been found.
Astronomical X-ray source catalog
Of the 59 sources listed in "A Catalogue of Discrete Celestial X-ray Sources" observed by sounding rockets or balloons as of December 1, 1969, no X-ray source from Hydrus is detected with a published X-ray flux.
Apparently, no source in Hydrus emitted a gamma-ray burst that triggered the detectors aboard the Vela satellites during the early 70's.
Of 125 sources in the initial Uhuru catalog, none are detected in Hydrus. One source in the third Uhuru catalog of X-ray sources: 3U 0055-79, is in Hydrus.
Extrasolar X-ray source astrometry
3U 0055-79 is in equatorial coordinates for the epoch 1950 B1950.0 at right ascension (RA) declination (Dec) , with an error box area of 0.180 sq degrees. after Uhuru. The detection by OSO 7 is within the error box for 3U 0055-79.
ROSAT detected five X-ray sources within 1°.
According to SIMBAD, the Seyfert 1 galaxy ESO 12-21 is ROSAT X-ray source RX J004053-79145 at 43.4' from 3U 0055-79.
Visibly dark X-ray source
Of the first X-ray sources discovered in each constellation (126 for 89 areas), some 63% are visibly dark. These visually dark X-ray sources can be radiative cosmic dust, hydrogen gas such as an H II region (e.g. the Orion Nebula), an H I region of hydrogen, a molecular cloud, or a coronal cloud.
Astronomical gamma-ray source
The gamma-ray astronomy satellite EGRET detected one gamma-ray source (EGR J0057-7839) within 45.3' of 3U 0055-79.

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