------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 1507 2000 Mar 31 14.30UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK GMH at AST.STAR.RL.AC.UK WORLD WIDE WEB http://www.demon.co.uk/astronomer ------------------------------------------------------------------- XTE J1118+480 (=Q2000/175) R. Remillard, E. Morgan, D. Smith, and E. Smith report for the RXTE ASM team at the Massachusetts Institute of Technology and at Goddard Space Flight Center, NASA: "The RXTE All-Sky Monitor has detected x-ray emission from a new source, XTE J1118+480. The ASM position is centred at R.A. = 11h18m17s, Decl. = +48o03'.0 (2000; 90-percent-confidence radius 6'). The average x-ray intensity (2-12 keV) was 39(8) mCrab on Mar. 29. Retrospective ASM analysis indicates that the x-ray flux has been slowly rising since Mar. 5. Another modest outburst had previously occurred during Jan. 2-29, peaking at 37(3) mCrab on Jan. 6. The SIMBAD database lists only an unremarkable guide star (V about 11) near the x-ray position. The source was confirmed in an 800-s RXTE pointed observation beginning on Mar. 29.968 UT. Rapid flares (e.g., 10 s) were seen, reaching a factor of 5 above the baseline flux near 25 mCrab and suggesting a Galactic x-ray source. No pulsations were detected. The x-ray spectrum does not vary appreciably during intense flares. Preliminary spectral analysis indicates a power law visible to 30 keV. The photon index is roughly 1.8, which is similar to Cyg X-1 in its hard state. The high galactic latitude (+62 deg) and x-ray properties present a puzzling combination, and observations at other wavelengths are urgently needed." Makoto Uemura and Taichi Kato report that there is an object brighter than 15 mag located at 1' from RXTE detected position R.A. = 11h 18m 17s, Decl. = +48o 03'.0 (2000). In the DSS images, there are only faint objects near the position of this possible optical counterpart of XTE J1118+480. Denis Buczynski reports: I have observed the field of XTE1118+480 at 2000 March 30 20:43:04 UT with the 33cm F/3 automatic reflector+SXL8 CCD unfiltered+90s exp at Conder Brow Observatory (iau978) and have imaged a bright object at the the location indicated by Uemura and have derived the follwing results: XTE1118+480 12.91 GSC3451-1542 comparision star 12.8 GSC3451-974 check star 12.22 Guy M Hurst