ASM 2000+25

F. Makino and the Ginga Team, Sagamihara, Kanagawa, communicate the following measurements (which include revision of the data on IAUC 4587) of the x-ray intensity at 3-6 keV (in units of 10**-8 erg cm**-2 s**-1): Apr. 26.03 UT, 7.28; 26.90, 7.80; 28.41, 8.34; 29.51, 8.14; May 1.71, 7.94; 2.78, 7.71; 3.92, 7.33; 5.86, 6.35; 6.73, 6.41; 9.67, 6.03; 10.49, 5.98; 11.74, 5.86; 13.34, 5.73. R. M. Wagner, A. A. Henden and R. Bertram, Ohio State University; and S. G. Starrfield, Arizona State University, write: "Spectroscopic observations (range 450-720 nm, nominal spectral resolution 1.5 nm) of candidates A and B for ASM 2000+25 (IAUC 4589) were obtained on May 14 and 16, respectively, with the Ohio State University CCD spectrograph on the Perkins 1.8-m telescope. The spectrum of candidate A is that of a late M-type star, since it shows strong TiO and VO bands; no emission features were present in the spectrum, contrary to the report on IAUC 4598, which was based on low-dispersion objective-prism spectra obtained on the same day and in the same spectral region. The spectrum of candidate B shows a featureless, slightly reddened continuum. No strong emission or absorption lines are present. This spectrum is completely analogous to that of V616 Mon = A0620-00 obtained at maximum in 1975 (Gull et al. 1976, Ap.J. 206, 260). The lack of an optical object on archival plates, the presence of a new optical object that might be associated with the abrupt appearance of a new x- ray source, the detection of soft x-ray emission and the featureless appearance of the optical spectrum strongly suggest that candidate B is the optical counterpart of the x-ray source."