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IAUC 6882: 1998bm; XTE J1906+09

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                                                 Circular No. 6882
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


SUPERNOVA 1998bm IN IC 2458
     W. D. Li, M. Modjaz, R. R. Treffers, and A. V. Filippenko,
University of California at Berkeley (UCB), report their discovery
of an apparent supernova during the course of the Lick Observatory
Supernova Search (cf. IAUC 6627) with the 0.8-m Katzman Automatic
Imaging Telescope.  SN 1998bm was found and confirmed on unfiltered
CCD images obtained on Apr. 21.2 (mag about 17.6) and 22.2 UT (mag
about 17.4), respectively.  The object is located at R.A. =
9h21m30s.49, Decl. = +64o14'25".4 (equinox 2000.0), which is about
1" east and 5" north of the nucleus of IC 2458.  An image of the
same field taken on 1996 Nov. 13 (limiting mag about 18.5) by the
Beijing Astronomical Observatory Supernova Survey shows no star at
this position.
     A. V. Filippenko and D. C. Leonard, UCB, report that a
spectrum obtained on Apr. 23 with the Shane 3-m reflector at Lick
Observatory shows that SN 1998bm is of type II; the hydrogen Balmer
lines have P-Cyg profiles.


XTE J1906+09
     D. Marsden and R. Rothschild, Center for Astrophysics and
Space Sciences, University of California at San Diego, report for
the RXTE/HEXTE team:  "We report the discovery of a pulsating x-ray
source designated XTE J1906+09 during observations with RXTE of a
1 deg (FWHM) region on 1996 Aug. 16-19 containing the soft gamma-
ray repeater SGR 1900+14.  The RXTE field-of-view was centered at
R.A. = 19h05m43s, Decl. = +8o58'.8 (equinox 2000.0).  Coherent
pulsations were detected from the source by both the PCA and HEXTE
instruments at a fundamental period of 89.17 +/- 0.02 s, with
higher-order harmonics visible in the 2-10-keV power spectrum.  The
folded pulsar lightcurve is energy dependent, with a multipeaked
morphology (2-20 keV) at lower energies that becomes singly peaked
in the energy range 20-200 keV.  After correcting for instrumental,
sky, and Galactic ridge backgrounds, the pulsed fractions are 16,
6, and 4 percent in the energy ranges 2-10, 10-20, and 20-300 keV,
respectively.  The phase-averaged spectrum is well fitted over the
entire energy range by either a power law of photon index 1.9 +/-
0.1 or a thermal bremsstrahlung model of temperature kT = 20 +/- 5
keV, with a 2-10-keV flux of about 1.5 x 10E-11 erg cmE-2 sE-1.
The column density implied by the spectral fits is N_H about 1 x
10E23 cmE-2, implying a distance to the source of about 10-20 kpc.
We encourage observations at other wavelengths to refine the
position and search for a counterpart."

                      (C) Copyright 1998 CBAT
1998 April 24                  (6882)            Daniel W. E. Green

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