GRO J1735-27

S. Grebenev, K. Borozdin, and R. Sunyaev, Space Research Institute, Moscow, on behalf of the Mir-Kvant/TTM and Granat/ART-P teams, communicate: "The ROSAT position of a new x-ray pulsar GRO J1735-27 (= RX J1735.9-2726; cf. IAUC 6207, 6212) is within the 1' error circle for KS 1732-273, the source discovered by Mir-Kvant/ TTM on 1989 Mar. 20 and Sept. 4 (in't Zand et al. 1991, Adv. Space Res. 11, (8)187); the mean flux from the source was about 22 mCrab in the band 3-10 keV during both 1989 observations. The source was marginally detected with Granat/ART-P on 1990 Apr. 4, when its flux at 3-10 keV was 13.4 +/- 2.2 mCrab, but it was not found (at the flux level of 26 mCrab, 3-sigma upper limit) on 1990 Oct. 11. Thus, the 1989 and 1990 observations noted above, together with those on 1990 Sept. 5-7 by ROSAT and on 1995 Aug. 14 by GRO, are likely due to episodic accretion during the periastron passage (by an accreting neutron star in the binary system) and provide us with an estimate of the binary period (5-6 months)."