IAUC 7253: GM Sgr, SAX J1819.3-2525 = XTE J1819-254; P/1999 RO_28 The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site). ------------------------------------------------------------------------ Read IAUC 7252 [ SEARCH ] Read IAUC 7254 View IAUC 7253 in .dvi or .ps format. IAUC number ------------------------------------------------------------------------ Circular No. 7253 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) GM SAGITTARII AND SAX J1819.3-2525 = XTE J1819-254 R. Stubbings, Drouin, Vic., Australia, reports that GM Sgr is undergoing a very bright outburst after showing recent rapid variations, his visual magnitude estimates being: Aug. 11.488 UT, 12.3; 14.436, 12.5; 29.424, 12.7; 31.496, 13.0; Sept. 9.462, 11.2; 11.599, 11.9; 12.409, 11.1; 13.397, 11.9; 14.491, 11.4; 15.395, 8.8; 15.408, 8.8. Additional m_v estimates by A. Pearce, Nedlands, W. Australia: Sept. 15.550, 9.5; 15.571, 9.6. D. A. Smith, A. M. Levine, and E. H. Morgan, Massachusetts Institute of Technology (MIT), on behalf of the RXTE All-Sky Monitor (ASM) team at MIT and Goddard Space Flight Center, report that, in response to the visual observations of GM Sgr, SAX J1819.3-2525 (an x-ray transient likely to be associated with GM Sgr; cf. IAUC 7119, 7120) was measured by the ASM on Sept. 15.420 UT to have an intensity of 1.55 +/- 0.04 Crab (2-12 keV; estimated error based solely on counting statistics). Subsequent measurements showed a rapid increase in x-ray intensity: Sept. 15.422, 1.32 +/- 0.04 Crab; 15.423, 1.43 +/- 0.04; 15.488, 2.41 +/- 0.04; 15.489, 3.74 +/- 0.05; 15.701, 10.0 +/- 0.2; 15.703, 12.2 +/- 0.2. The spectrum is harder than that of the Crab nebula. The star attributed by Goranskij (1990, IBVS 3464) to GM Sgr has been measured on the Digital Sky Survey by G. V. Williams, Smithsonian Astrophysical Observatory, to be at R.A. = 18h19m21s.61, Decl. = -25o24'26".3 (equinox 2000.0; uncertainty +/- 1".0 in both coordinates); this is 1' north of the GCVS position from Luyten (1927, HCO Bull. No. 852). COMET P/1999 RO_28 (LONEOS) C. Hergenrother, Lunar and Planetary Laboratory, reports that a co-added 600-s CCD exposure with the Steward Observatory 2.3-m reflector on Sept. 13 of 1999 RO_28 (discovered by LONEOS; cf. MPEC 1999-R23; discovery position given below) shows a stellar condensation with a faint 20" tail in p.a. 310 deg. M. Tichy and J. Ticha, Klet, later reported a faint coma of diameter 8" and 7" on images taken on Sept. 8.93 and 10.02 UT, respectively. Observations by J. V. Scotti with the Spacewatch telescope at Kitt Peak on Sept. 15.4 show a coma diameter of 9" (m_1 = 18.6-18.7, m_2 = 20.6-21.0) and a 0'.72 tail in p.a. 308 deg. New orbital elements on MPEC 1999-R47 include T = 1999 Oct. 2.35 TT, q = 1.2302 AU, P = 6.46 yr. 1999 UT R.A. (2000) Decl. m2 Sept. 7.32994 23 41 39.78 -14 32 00.5 18.4 (C) Copyright 1999 CBAT 1999 September 15 (7253) Daniel W. E. Green ------------------------------------------------------------------------ Read IAUC 7252 [ SEARCH ] Read IAUC 7254 View IAUC 7253 in .dvi or .ps format. ------------------------------------------------------------------------ Our Web policy. Index to the CBAT/MPC/ICQ pages. CBAT