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IAUC 6510: Cyg X-1; SNe

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                                                  Circular No. 6510
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     S. N. Zhang and C. R. Robinson, Universities Space Research
Association; and W. Cui, Massachusetts Institute of Technology
(MIT), report:  "We have detected the 5.6-day orbital period of the
blackhole candidate Cyg X-1 in the ASM/RXTE data, confirming a
similar detection with the Ginga ASM in its low-energy band during
the x-ray hard state (Kitamoto et al., submitted to Ap.J.).  The
modulation is only detectable in the hard state (before around 1996
May 17 and after around Aug. 10) and is strongest in the lowest ASM
energy band (1.3-3.0 keV), with a full amplitude of around 10
percent and x-ray flux minimum near superior conjunction of the
compact object.  This seems to indicate that the modulation is due
to an asymmetry in the photoelectric absorption.  However, the lack
of any significant orbital modulation in the soft state suggests
that another effect may be responsible for the detected modulation,
unless the power-law component is much more heavily absorbed than
the blackbody component, since the ASM 1.3-3.0-keV detector
counting rate is dominated by the power-law component in the hard
state and by the blackbody component in the soft state."

     G. V. Williams, Smithsonian Astrophysical Observatory, reports
his measures of the positions of seven supernovae discovered by
Jean Mueller.  Given below are the supernova designation, position
(internal uncertainty < 0".4) as measured from the Digital Sky
Survey (based on original Palomar Sky Survey), offset from host
galaxy's center, and reference to the discovery report.  The
nucleus of the host galaxy (UGC 465) for SN 1954ac is ill-defined.

SN            R.A.  (2000)  Decl.            Offset           IAUC
1950O      16 15 09.39   +18 57 14.4     10".0 E, 12".8 S     5536
1953J       0 44 55.66   +16 56 10.8     14".5 E,  4".5 S     5140
1953L       5 15 46.52   +71 27 41.6      3".6 W,  8".6 N     5466
1954ac      0 43 50.78   +32 50 32.9      0".5 W, 38".2 S     5140
1954ad      8 32 46.37   + 0 13 33.7      7".2 W,  5".9 S     5175
1955R      12 34 42.49   +49 19 54.8      3".8 E, 26".0 N     5525
1955S      15 36 40.61   +43 32 38.0     16".2 W, 15".8 N     5761

                      (C) Copyright 1996 CBAT
1996 November 23               (6510)            Daniel W. E. Green

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