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IAUC 6659: GS 1843+00; C/1997 J2; C/1997 J1

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                                                 Circular No. 6659
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)


GS 1843+00
     A. Santangelo, S. Giarrusso, S. Del Sordo, G. Cusumano, S.
Piraino, and A. Segreto, Istituto di Fisica Cosmica e Applicazioni
Informatica, Palermo; D. Dal Fiume and M. Orlandini, Istituto
Tecnologie e Studio Radiazioni Extraterrestri, Bologna; A. N.
Parmar and T. Oosterbroek, Space Science Department, European Space
Agency, ESTEC; and L. Piro and M. Feroci, Istituto di Astrofisica
Spaziale, Frascati, report:  "A BeppoSAX Narrow Field Instrument
observation of the transient x-ray pulsar GS 1843+00 was carried
out on Apr 4.0798-4.6250 UT.  MECS and LECS observed the source at
R.A. = 18h45m34s, Decl. = +0o52'.5 (equinox 2000.0).  The estimated
error, which is mainly due to systematic uncertainty, is 30".  A
search for the unidentified optical counterpart is urged.
Pulsations of about 29.5 s were clearly detected from the source.
The source fluxes measured were as follows (in units of 10E-10 erg
cmE-2 sE-1):  2-10 keV (LECS and MECS), 4.44; 4-40 keV (HPGSPC),
22.1; 20-200 keV (PDS), 15.3.  The energy spectrum is well fitted
at higher energies (HPGSPC/PDS) by a cutoff power law with photon
index 0.39 +/- 0.09 and cut-off energy 20.2 +/- 1 keV, while at low
energies the spectrum shows strong photoelectric absorption with
n_H = (2.61 +/- 0.13) x 10E22 cmE-2.  Inspection of the XTE ASM
lightcurves reveals that the source was still active at a 2-10-keV
flux of 12 mCrab as of May 1."


COMET C/1997 J2 (MEUNIER-DUPOUY)
     Total magnitude estimates (visual unless otherwise noted): May
7.99 UT, 13.3 (G. Comello, Roden, The Netherlands, 0.30-m reflector;
initially thought to be C/1997 J1); 9.91, 12.6 (M. Meyer,
Frauenstein, Germany, 0.25-m reflector); 10.03, 12.8 (R. J. Bouma,
Groningen, The Netherlands, 0.25-m reflector); 10.89, 13.3 (H.
Mikuz, Crni Vrh Observatory, Slovenia, 0.20-m f/2 Baker-Schmidt
camera + V filter + CCD; tail about 2' long in p.a. 350 deg); 10.94,
12.7 (Meyer).


COMET C/1997 J1 (MUELLER)
     Total magnitude estimates (visual unless otherwise noted): May
7.92 UT, 12.9 (Meyer); 9.95, 13.0 (Bouma); 10.85, 13.5 (K. Hornoch,
Lelekovice, Czech Republic, 0.35-m reflector); 10.87, 12.6 (Mikuz,
CCD + V filter); 10.94, 12.2 (Meyer).

                      (C) Copyright 1997 CBAT
1997 May 12                    (6659)            Daniel W. E. Green

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