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IAUC 6597: SAX J1750.8-2900; 81P

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                                                 Circular No. 6597
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SAX J1750.8-2900
     A. Bazzano, Istituto di Astrofisica Spaziale (IAS), CNR,
Frascati; J. Heise, Space Research Organization of the Netherlands
(SRON), Utrecht; P. Ubertini, M. Cocchi, and L. Natalucci, IAS; J.
M. Muller, SRON and BeppoSAX, Rome; R. Jager and J. in 't Zand,
SRON; and L. Di Ciolo, G. Celidonio, A. Coletta, P. Giommi, D.
Ricci, M. Capalbi, and S. Rebecchi, BeppoSAX, Rome, report the
detection of a new weak x-ray source in the galactic-center region
with the Wide Field Camera onboard the BeppoSAX satellite:  "The
source, SAX J1750.8-2900, was initially detected on Mar. 18.032 UT,
in the range 1.6-8.3 keV with an intensity of about 50 mCrab, at
R.A. = 17h50m48s, Decl. = -29o00'.0 (equinox 2000.0; preliminary
error radius 5').  The nearest known x-ray source is the ROSAT
Point Source Catalogue object 1RXP J175029-2859.9 (flux 1.75 x
10E-13 erg sE-1 cmE-2), located 4' away, at the edge of the SAX
J1750.8-2900 error box.  No optical, ultraviolet, or gamma-ray
sources are known within a 5' radius.  At radio wavelengths, three
sources are listed in the NRAO/VLA Sky Survey database (cf.
http://www.cv.nrao.edu/~jcondon/nvss.html) at R.A. = 17h50m29s.9,
Decl. = -28o59'07"; 17h50m50s.9, -29o03'11"; and 17h51m03s.6,
-29o00'37".  In the infrared, the IRAS 17477-2900 (from the Point-
Source Catalogue) is nearby.  During follow-up monitoring, a burst
was detected on Mar. 20.38795 from the same position of the newly
detected source, with a peak intensity of 0.7 Crab (1-s time bin)
and duration 20 s."

     T. Farnham and D. Schleicher, Lowell Observatory, report on
narrow-band photometry of comet 81P with the 0.79-m telescope on
Mar. 5.4 UT, at r = 1.70:  "Haser-model production rates were log
Q(OH) = 27.77, log Q(CN) = 25.25, and log Q(C2) = 24.92, and the
dust-production rate was log (Af rho) = 2.63; combining these
results with those previously obtained with the Hall telescope on
Feb. 12.2 and 15.2 (r = 1.78-1.77 AU) implies that gas and dust
production are essentially unchanged over this three-week interval."
     Further total visual magnitude estimates:  Mar. 4.78 UT, 9.5
(K. Hornoch, Lelekovice, Czech Rep., 0.35-m reflector); 7.76, 9.6
(V. Znojil, Brno, Czech Rep., 25x100 binoculars); 11.92, 9.9 (A.
Pereira, Cabo da Roca, Portugal, 0.25-m reflector); 13.09, 9.7 (J.
E. Bortle, Stormville, NY, 0.41-m reflector); 16.91, 9.7 (B. H.
Granslo, Fjellhamar, Norway, 0.20-m reflector).

                      (C) Copyright 1997 CBAT
1997 March 20                  (6597)            Daniel W. E. Green

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