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IAUC 7350: 2000D; 1E 161348-5055

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                                                  Circular No. 7350
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)

     G. M. Hurst, Basingstoke, England, reports the discovery by
Tom Boles, Wellingborough, of an apparent supernova (mag 16.2) on
unfiltered CCD images taken on Jan. 22.928 and 24.806 UT in the
course of the U.K. Nova/Supernova Patrol.  SN 2000D is located at
R.A. = 2h18m04s.84, Decl. = +38o04'27".4 (equinox 2000.0; mean of
two measures), which is 6" west and 11" south of the center of UGC
1767.  Confirming images of SN 2000D were obtained by R. Arbour,
South Wonston, on Jan. 24 and by M. Armstrong, Rolvenden, on Jan.
25.83.  An image taken on 1999 Sept. 18.212 by Boles does not show
the new object to a limit of mag about 18.  SN 2000D is not present
on the second Palomar Sky Survey (limiting mag about 19), where
Hurst notes that the new star is slightly northwest of an H II

1E 161348-5055
     G. P. Garmire, G. G. Pavlov, and A. B. Garmire, Pennsylvania
State University; and V. E. Zavlin, Max-Planck-Insitut fur
Extraterrestrische Physik, write:  "The Chandra X-ray Observatory
observed the supernova remnant (SNR) RCW 103 (G332.4-0.4) for 5.55
hr on 1999 Sept. 26.  We have determined the following position of
the pointlike source 1E 161348-5055 seen near the center of RCW
103:  R.A. = 16h17m36s.26, Decl. = -51o02'25".0 (equinox 2000.0;
uncertainty about 0".2).  No obvious optical counterpart (to mag R
= 24) is seen closer than 3".95 from the source.  The observed flux
is 9.6 x 10**-13 erg cm**-2 s**-1 in the band 0.4-10 keV, which
corresponds to a luminosity of at least 1 x 10**33 erg s**-1 for a
distance of 3300 pc.  The light curve is compatible with a fragment
of a sinusoid with period 5.97 (+0.47, -0.44) hr (90-percent
confidence) and pulsed fraction about 60 percent.  We reanalyzed
the ASCA archival data of this source obtained during a 16-hr
period in Aug. 1993, and we found variations with period 6.05
(+0.28, -0.35) hr, the maximum of the first of the three observed
peaks being at Aug. 18 +/- 0.04 UT.  The observed pulse fraction,
20-40 percent, is smaller than that found with Chandra, likely due
to a larger contribution from the SNR background.  The light curve
of a 36-hr ASCA observation in Sept. 1997, when the source's flux
was an order of a magnitude lower, is consistent with a sinusoid
with period 6.3 +/- 0.6 hr.  The 6-hr periodicity hints that the
source may be a low-mass binary with an underluminous secondary
component and unusually low x-ray luminosity.  This is the first
observation of such a long periodicity of a compact supernova

                      (C) Copyright 2000 CBAT
2000 January 27                (7350)            Daniel W. E. Green

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