X-Ray Sources

K. O. Mason, Mullard Space Science Laboratory, University College, London, writes that x-ray pulsations from the vicinity of 3U 1258-61 (cf. IAUC 3039) were independently discovered from data obtained with the Ariel 5 satellite. Observations made in collaboration with P. G. Murdin and N. Visvanathan on the Anglo-Australian Telescope in February reveal the presence of an early-type emission-line star near the error box of 3U 1258-61 at R.A. = 12h58m10s.7, Decl. = -61o19'53" (equinox 1950.0). H-alpha was seen in emission with an FWHM of 700 km/s and an equivalent width of 12 A. The absorption spectrum suggests a spectral type between B2 and A0. Subsequent photometry on the 102-cm telescope at Mount Stromlo gave V = 14.72 and B-V = +1.80. H. Bradt and K. Apparao, Massachusetts Institute of Technology, report that SAS-3 measurements give an x-ray position of 1' precision 30" east and 8" south of this optical position. T. Markert, F. Li, J. McClintock and S. Rappaport, Massachusetts Institute of Technology, report that the SAS-3 Group has discovered a 7s.6801 +/- 0s.0001 periodicity in the x-ray intensity of 3U 1626-67. This source was observed during Mar. 24.3-26.3 UT and was unusually bright throughout this period. The mean x-ray flux in the 3-6 keV band was ~ 0.04 that of the Crab Nebula or about 4 times as intense as reported by Uhuru. The source was also highly variable with continual intensity fluctuations on timescales of 100-400 seconds. Further optical and x-ray studies of this source should be made during this period of high intensity. M. J. Coe, A. R. Engel and J. J. Quenby, Imperial College, London, report that their Ariel 5 results suggest the existence of a hard x-ray flux from (Nova) DQ Her (1934). The measurements from the period Feb. 19-25 give a flux of (1.1 +/- 0.38) x 10**-5 ph cm**-2 s**-1 keV**-1 over the energy range 260-1200 keV. B. A. Cooke informs us that the catalogue of high galactic latitude x-ray sources, compiled from the University of Leicester sky survey instrument on Ariel 5, is now available in preprint form. Copies may be obtained from Dr. Cooke at the address: X-Ray Astronomy Group, Physics Department, The University, Leicester, U.K. Corrigendum. The zero phase quoted for 3U 1538-52 on IAUC 3039 refers to the orbital period, which Becker et al. had preliminarily estimated as 3.75 +/- 0.15 days.