Central Bureau for Astronomical Telegrams
IAUC 6874: XTE J0421+560, CI Cam; GRB 980329
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Circular No. 6874
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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XTE J0421+560 AND CI CAMELOPARDALIS
B. A. Harmon and G. J. Fishman, Marshall Space Flight Center,
NASA; and W. S. Paciesas, University of Alabama, Huntsville, report
for the BATSE team: "Hard x-rays from CI Cam have not been detected
with BATSE since Apr. 2-3. The duration of this transient event
was unusual in both its rapid rise to peak flux (about 0.1 day) and
decay (e-folding decay timescale of about 0.56 day). Both of these
timescales are much shorter than those seen from other galactic
transients observed with BATSE over the past seven years. The peak
of the hard x-ray flux occurred between Mar. 31.91-Apr. 1.04 UT at
a level of 1160 +/- 80, 950 +/- 75, 650 +/- 70, and 290 +/- 75
mCrab in the bands 20-30, 30-40, 40-50, and 50-70 keV, respectively.
BATSE detects the source only marginally in the band 70-100 keV.
The initial flux estimate given (IAUC 6856) was underestimated due
to the relatively soft spectrum of the source (power-law number
index of -3.9 +/- 0.2). No evolution of the spectral shape was
detected. The flux history of XTE J0421+560 = CI Cam and other
sources (updated daily) observed with BATSE by the Earth
occultation technique can be accessed from
http://www.batse.msfc.nasa.gov/data/occult/fluxhistories/eomon.html."
GRB 980329
M. R. Metzger, California Institute of Technology, writes:
"Near-infrared K-band images of the area surrounding the variable
radio source detected by Taylor et al. (GCN 40; cf. IAUC 6872),
possibly associated with GRB 980329 (IAUC 6853, 6854), were
obtained on Apr. 6.27 and 8.28 UT with the Keck-I 10-m telescope.
The source reported by Larkin et al. (GCN 51, coincident with the
galaxy reported by Djorgovski et al. on GCN 41) was detected on
both nights, at K = 21.4 +/- 0.2 and 21.9 +/- 0.4, respectively.
Comparison with the magnitudes reported by Larkin et al. indicates
that the source has faded by about 1 mag between Apr. 2.3 and 8.28.
This suggests that part of the K flux may be infrared afterglow of
GRB 980329; this is consistent with fading, detections, and upper
limits reported previously (GCN 41, 46, 48; IAUC 6864, 6866, 6868).
Further measurements are suggested to estimate the infrared
brightness of any underlying host."
(C) Copyright 1998 CBAT
1998 April 13 (6874) Daniel W. E. Green
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