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IAUC 7482: 2000dh; EXO 1745-248; CI Aql

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                                                  Circular No. 7482
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 617-495-7440/7244/7444 (for emergency use only)

SUPERNOVA 2000dh IN IC 5374
     T. Puckett, Mountain Town, GA; and D. George, Ottawa, ON,
report the discovery of an apparent supernova (mag 19.4) on an
unfiltered CCD frame (limiting mag 20.5) taken with the Puckett
Observatory 0.60-m automated supernova patrol telescope on Aug.
24.22 UT.  SN 2000dh is located at R.A. = 0h01m03s.94, Decl. =
+4 30'05".4 (equinox 2000.0), which is 8".7 west and 4".7 north of
the center of IC 5374.  The new object was also present on an
unfiltered CCD frame taken on Aug. 25.29, but it does not appear on
Palomar Sky Survey images taken on 1991 Sept. 13 (limiting mag
about 21.0), 1992 Aug. 27 (limiting mag about 21.0), or 1955 Nov.
11 (limiting mag about 20.0).

EXO 1745-248
     C. B. Markwardt, University of Maryland and Goddard Space
Flight Center (GSFC), NASA; and T. E. Strohmayer, J. H. Swank, and
W. Zhang, GSFC, write:  "The transient EXO 1745-248 in the globular
cluster Terzan 5 (cf. IAUC 7454) has recently increased in
intensity.  RXTE PCA pointed and scanning observations from July
13-Aug. 15 show that the persistent intensity has varied
erratically, increasing to 600 mCrab (2-10 keV) on Aug. 21.8 UT,
which is near the Eddington limit for a source at 7600 pc.  Dipping
activity is also present, but no eclipse events have been seen.
Fifteen x-ray bursts were detected, with peak fluxes between 200
and 350 mCrab and an average separation of 25 min.  The x-ray
spectrum of the bursts at the peak was consistent with blackbody
emission with kT = 2.4-2.8 keV and radii of 2-4 km.  Only modest
cooling is suggested in the tails of the bursts.  The short burst
recurrence time, the range of peak luminosities, and the weak
cooling suggest that the bursts may be of type II (accretion
instability), but we cannot exclude a thermonuclear origin.  The
persistent emission of Aug. 13 is best fitted by a blackbody and
power law with exponential cut-off plus an iron emission feature
near 6.6 keV, typical of bright, low-mass x-ray binaries.  Two
quasiperiodic features were present on Aug. 13, with centroids of
65 and 134 mHz, the fundamental having a fractional r.m.s.
amplitude of 10 percent.  Optical observations are encouraged."

     Visual magnitude estimates by M. Lehky, Hradec Kralove,
Czech Republic:  June 7.875 UT, 11.0; 10.968, 11.7; July 25.958,
12.9; 30.954, 12.8; Aug. 1.916, 12.8; 19.909, 12.9; 20.899, 12.9.

                      (C) Copyright 2000 CBAT
2000 August 25                 (7482)            Daniel W. E. Green

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