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IAUC 6350: GRS 1739-278 AND GRO J1744-28; C/1996 B2

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                                                  Circular No. 6350
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)


GRS 1739-278 AND GRO J1744-28
     K. Borozdin, N. Alexandrovich, and R. Sunyaev, Space Research
Institute, Moscow, report on behalf of MIR-KVANT-TTM team:  "The
TTM experiment onboard the Mir-Kvant Space Station has detected GRS
1739-278 (IAUC 6348) as a very bright and soft x-ray source.  The
2- to 27-keV flux was equal to 200 +/- 50 mCrab on Feb. 28, rising
to 500 +/- 50 mCrab on Mar. 1.  The TTM position (R.A. = 17h42m40s,
Decl. = -27o45'.8, equinox 2000.0; uncertainty +/- 1'), is inside
the SIGMA/Granat error box.  The source was weaker than 100 mCrab
during previous TTM sessions of GC observation (Feb. 6-7).  The
spectrum in the band 2-27 keV can be roughly fitted by a power law
with spectral index 2.7 +/- 0.1 and hydrogen absorption column
density (4.1 +/- 0.7) x 10E22 cmE-2.  However, the two-component
(soft component plus hard power law) model with smaller absorption
provides better agreement with data obtained on Mar. 1.  Such x-ray
spectra are typical for accreting blackhole candidates.  GRO
J1744-28 was observed simultaneously during galactic field
observations.  The 2- to 27-keV flux was 1650 +/- 70 mCrab on Feb.
7, 515 +/- 30 mCrab on Feb. 28, and 1220 +/- 50 mCrab on Mar. 1.
The TTM localized the source at R.A. = 17h44m34s, Decl. = -28o45'.2
(uncertainty +/- 1'); this source has a much harder spectrum in the
band 2-27 KeV than does GRS 1739-278."


COMET C/1996 B2 (HYAKUTAKE)
     C. Lisse, Goddard Space Flight Center; and K. Dennerl and J.
Schmitt, Max-Planck-Institut fur Extraterrestrische Physik,
Garching, communicate:  "Comet C/1996 B2 will be observed with the
x-ray satellite ROSAT.  The scheduled observing intervals are as
follows:  Mar. 26.493-26.529 UT, 26.626-26.634, 26.638-26.662,
26.708-26.729, 26.89-26.902, 27.554-27.591, 27.687-27.695, 27.703-
27.724, 27.772-27.789, 27.841-27.856, 28.417-28.44.  Simultaneous
observations at other wavelengths are encouraged."
     Naked-eye m1, coma-diameter, and tail-length estimates:
Mar. 21.93 UT, 0.8, 67', -- (K. Cernis, Rukainiai, Lithuania);
22.41, 0.9, 1.5 deg, 31 deg (R. Keen, Mt. Thorodin, CO); 22.60,
1.0, 90', 30 deg (S. J. O'Meara, Volcano, HI); 22.68, 0.3, 70', 40
deg (P. Camilleri, Cobram, Vic., Australia); 23.30, 0.5, 2 deg, 30
deg (D. W. E. Green, near S. Carver, MA); 23.45, 0.2, --, 45 deg
(C. S. Morris, Whitaker Peak, CA).

                      (C) Copyright 1996 CBAT
1996 March 23                  (6350)            Daniel W. E. Green

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