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IAUC 6399: GRO J1744-28; C/1996 B2

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                                                  Circular No. 6399
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)


GRO J1744-28
     R. Corbet, Goddard Space Flight Center (GSFC) and Universities Space
Research Association; and K. Jahoda, GSFC, report on behalf of the RXTE
Science Operations Facility and PCA team: "We continue to detect significant
emission from GRO J1744-28, and the following approximate quiescent flux
levels were measured in recent observations: Apr. 26, 100 mCrab, 116
min observation time; 28, 95 mCrab, 52 min; 30, 90, 100; May 3, 70, 105;
10, 60, 33; 12, 50, 58; 13, 50, 75.  During these observations the
following bursts were detected: Apr. 26.069 UT, 890 mCrab; 28.656, 120;
May 3.785, 100; 12.688, 700.  The May 12 burst had high absorption and
timing and spectral characteristics typical of a type I burst.  Owing to
the 1-deg PCA field of view we cannot yet completely rule out the
possibility that the lower-amplitude bursts might be due to another
contaminating nearby source.  Pulsations at 2.1 Hz were evident during
all observations, although since May 12 the pulsed fraction has decreased
to below 1 percent rms.  Lightcurves are available under 'TOO News' at
http://heasarc.gsfc.nasa.gov/0/docs/xte/xte_1st.html/."


COMET C/1996 B2 (HYAKUTAKE)
     Total visual magnitude estimates: Apr. 26.12 UT, 2.2 (R. Keen,
Mt. Thorodin, CO, 7 x 50 binoculars; tail 1 deg in p.a. 25 deg);
26.87, 2.5, (B. H. Granslo, Tryvann, Oslo, Norway, 10 x 50 binoculars;
tail 0.5 deg in p.a. 23 deg); 27.86, 2.0: (O. Skilbrei, Hoenefoss,
Norway, 7 x 50 binoculars; tail 1 deg in p.a. 20 deg); 28.02, 2.5-3,
(J. E. Bortle, Stormville, NY, 15 x 80 binoculars; twilight extremely
bright);  May 9.82, 3.0 (G. J. Garradd, Loomberah, N.S.W., 0.25-m
reflector; no tail visible); 10.83, 2.8: (T. Lovejoy, Jimboomba,
Queensland, 10 x 50 binoculars; tail 1 deg); 11.81, 3.3, (Lovejoy;
tail > 1 deg); 13.81, 3.5 (Garradd, 10 x 50 binoculars; tail 3 deg).
     The first postperihelic astrometric observations were made by
Garradd on May 10 and 11 and confirm the need (see IAUC 6391) to allow
for nongravitational effects in the orbit solution, the following
improvement being from MPEC 1996-J06.  Nongravitational parameters
A1 = +2.78 +/- 0.07, A2 = +0.05 +/- 0.08.  Corrections to the ephemeris
on IAUC 6391 are indicated as follows: May 12, -0.02 timemin, +0.7 arcmin;
17, -0.03, +0.8; 22, -0.06, +1.0; 27, -0.09, +1.2; June 1, -0,11, +1.3.

                    Epoch = 1996 Apr. 27.0 TT
     T = 1996 May   1.3951 TT         Peri. = 130.1780
     e = 0.999751                     Node  = 188.0453  2000.0
     q = 0.230218 AU                  Incl. = 124.9231

                      (C) Copyright 1996 CBAT
1996 May 14                    (6399)              Brian G. Marsden

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