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Circular No. 7399 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304 Phone 617-495-7244/7440/7444 (for emergency use only) XTE J1550-564 D. A. Smith, A. M. Levine, R. Remillard, and D. Fox, Massachusetts Institute of Technology; and R. Schaefer, Goddard Space Flight Center, NASA, on behalf of the RXTE/ASM Team, report: "Observations over Apr. 6-10 with the RXTE All-Sky Monitor show a clear detection of a source with maximum likelihood position 1' +/- 3' from the position of XTE J1550-564 (IAUC 7009, 7197, etc.). It is therefore highly likely that we have detected renewed activity of XTE J1550-564. A 2-12-keV light curve from this location shows an approximately linear flux increase at a rate of about 15 +/- 2 mCrab/day. Extrapolation of this rate indicates zero flux on Apr. 2. The energy spectrum is slightly harder than that of the Crab, and there is as yet no evidence for spectral evolution." N. Masetti, Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Bologna; and R. Soria, Mullard Space Science Laboratory, University College, London, communicate: "We observed the optical counterpart of the soft-x-ray transient XTE J1550-564 on Apr. 10.58 UT, using the CCD imager on the 1.02-m telescope at Siding Spring Observatory. From a preliminary analysis of the data, we find B = 19.73 +/- 0.05, V = 18.14 +/- 0.03, R = 17.16 +/- 0.05. This shows that XTE J1550-564 is again in an outburst phase. Further multiwavelength observations of the source are encouraged." Soria and Masetti add that further CCD images of the optical counterpart, centered on Apr. 10.79 UT, show that the source is brightening at a rate of 0.30 +/- 0.05 mag/day in the B band, 0.25 +/- 0.05 mag/day in the V band, and 0.20 +/- 0.03 mag/day in the R band. SUPERNOVA 2000bi IN ANONYMOUS GALAXY Further to his report on IAUC 7398, M. M. M. Santangelo adds that SN 2000bi is slightly brighter than the faint star that lies a few arcsec north of the galaxy nucleus. SUPERNOVAE 2000B, 2000I, 2000K, 2000Q Unfiltered CCD magnitude estimates by K. Sarneczky, K. Sziladi, and L. Kiss, Piszkesteto station, Konkoly Observatory: SN 2000B in NGC 2320, Mar. 13.82 UT, 18.0 +/- 0.3; SN 2000I in NGC 2958, Mar. 15.91, 18.2 +/- 0.3; SN 2000K in MCG +9-19-191, Mar. 13.89, 18.7 +/- 0.3; SN 2000Q, Mar. 16.12, 17.3 +/- 0.2. (C) Copyright 2000 CBAT 2000 April 10 (7399) Daniel W. E. Green
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