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IAUC 6507: 4U 1820-30; C/1995 O1

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                                                  Circular No. 6507
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)


4U 1820-30
     A. P. Smale, Goddard Space Flight Center (GSFC), NASA and
Universities Space Research Association; and W. Zhang and N. E.
White, GSFC, report:  "RXTE observations of the low-mass x-ray
binary 4U 1820-30 performed on Oct. 15 and Oct. 26-30 reveal the
presence of high-frequency quasiperiodic oscillations (QPOs) when
the source is in its low state (160-200 mCrab).  The centroid
frequency of the main peak varies between 546 +/- 2 and 796 +/- 6
Hz, and is tightly correlated with source intensity.  The QPO width
is typically 20-30 Hz, with rms amplitude 5.0 +/- 0.5 percent.
When the source is at the upper end of this range, a second
significant QPO peak appears with frequency 1066 +/- 5 Hz, width 46
+/- 12 Hz, and rms amplitude 3.2 +/- 0.5 percent.  When the source
brightens above 200 mCrab, neither QPO is detected."


COMET C/1995 O1 (HALE-BOPP)
     Extension to the ephemeris on IAUC 6440, from orbital elements
by B. G. Marsden on MPC 28052:

1996/97     R. A. (2000) Decl.   Delta     r    Elong. Phase    m1
Nov. 23    17 56.41   - 1 30.5   2.981   2.245   35.0   14.6    3.9
     28    18 01.13   - 0 58.1   2.948   2.182   32.6   14.1    3.7
Dec.  3    18 06.18   - 0 22.0   2.909   2.120   30.5   13.7    3.6
      8    18 11.58   + 0 18.3   2.864   2.057   28.9   13.4    3.4
     13    18 17.31   + 1 03.1   2.812   1.994   27.7   13.3    3.2
     18    18 23.40   + 1 53.2   2.755   1.930   27.0   13.4    3.1
     23    18 29.86   + 2 49.0   2.691   1.867   26.9   13.8    2.9
     28    18 36.71   + 3 51.3   2.621   1.804   27.2   14.4    2.7
Jan.  2    18 43.99   + 5 00.8   2.546   1.740   28.0   15.4    2.4
      7    18 51.74   + 6 18.4   2.466   1.677   29.2   16.6    2.2
     12    19 00.02   + 7 45.2   2.381   1.614   30.6   18.1    2.0
     17    19 08.92   + 9 22.4   2.291   1.551   32.3   19.8    1.7
     22    19 18.54   +11 11.0   2.198   1.489   34.1   21.7    1.4
     27    19 29.01   +13 12.7   2.102   1.428   36.0   23.9    1.2
Feb.  1    19 40.54   +15 28.7   2.004   1.368   37.9   26.3    0.9
      6    19 53.38   +18 00.8   1.906   1.309   39.7   28.8    0.6
     11    20 07.85   +20 50.1   1.807   1.251   41.4   31.5    0.3

                      (C) Copyright 1996 CBAT
1996 November 19               (6507)            Daniel W. E. Green

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