Central Bureau for Astronomical Telegrams
IAUC 7005: SGR 1900+14; 1998de, 1998dk, 1998dl
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Circular No. 7005
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SGR 1900+14
F. E. Marshall, T. Cline, and D. Palmer, Goddard Space Flight
Center, NASA; E. P. Mazets, Ioffe Physical-Technical Institute, St.
Petersburg; K. Hurley, University of California at Berkeley; and
A. P. Beardmore, Keele University, write: "The x-ray transient of
Aug. 27.432148 UT, initially reported on IAUC 7002, has been
localized using the relative arrival times at RXTE, Global Geo-
Science Wind, Near Earth Asteroid Rendezvous, and Ulysses. The six
different two-spacecraft annuli are consistent with the location of
SGR 1900+14, as expected (see IAUC 7004), with errors from about 1'
to 12'. This event appears to be the brightest soft gamma-ray
repeater in the four years of GGS-Wind operation. The maximum
intensity is difficult to determine, since this event saturated
both the RXTE PCA and the GGS-Wind detector and triggered an
automatic turn-off of the NEAR gamma-ray experiment."
M. Feroci, P. Soffitta, and E. Costa, Istituto di Astrofisica
Spaziale, CNR, Rome; and F. Frontera, Istituto Tecnologie e Studio
Radiazioni Extraterrestri, CNR, Bologna, on behalf of the
BeppoSAX/GRBM team; and M. Tavani, Istituto di Fisica Cosmica, CNR,
Milan, and Columbia Astrophysics Laboratory, report: "The Gamma-Ray
Burst Monitor (GRBM) onboard BeppoSAX was triggered by the event
reported by Cline et al. (IAUC 7002) on Aug. 27.4321259 UT. The
event showed a fast rise (< 1 s) and an exponential-like decay,
lasting > 300 s. The event was observed at an offset angle of
about 56 deg from the axis of GRBM unit 1, and showed a peak
intensity in 40-700 keV of about 64 000 counts/s. The event was
clearly detected above 100 keV. A preliminary analysis shows that
the spectrum is hard during the initial 1 s, followed by a sudden
softening. Subsequent spectral evolution shows a progressive
hardening. The near-5-s periodicity reported by Cline et al. is
evident in the GRBM data for the entire duration of the event. In
addition, starting from about 35 s after the event onset, the GRBM
clearly detected a periodic pattern of subpulses for each near-5-s
oscillation. The repetitive pattern is made of four subpulses of
period near 1 s. More detailed temporal and spectral analyses are
in progress."
SUPERNOVAE 1998de, 1998dk, 1998dl
Unfiltered CCD magnitudes by L. Boschini, Miragolo, Bergamo,
Italy, with a 0.25-m telescope (GSC comparison stars): SN 1998de
in NGC 252, Aug. 30.95 UT, 17.6; SN 1998dk in UGC 139, Aug. 30.95,
15.2; SN 1998dl in NGC 1084, Aug. 31.07, 15.1.
(C) Copyright 1998 CBAT
1998 September 1 (7005) Daniel W. E. Green
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