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IAUC 6680: GK Per; S/1997 (3671) 1

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                                                 Circular No. 6680
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/cfa/ps/cbat.html
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     S. Balman, H. B. Ogelman, and M. Orio, University of Wisconsin
at Madison, report:  "In a pointed observation with the High
Resolution Imager onboard the satellite ROSAT, the nova shell of
the classical nova Per 1901 (GK Per) has been detected in the x-ray
energy band 0.1-2.4 keV with an effective exposure of 53646.4 s.
This is the first detection of a nova shell in x-rays.  The x-ray
nebula extends 46" southwest, 60" northwest, 52" southeast, and 43"
northeast of GK Per, with an elliptical shape.  The shell shows a
clumpy morphology with several knots that are centrally bright and
limb-darkened.  The size of the knots vary between 4" and 8".  The
x-ray knots are not coincident with the optical knots; however,
there is x-ray emission coincident with the radio maxima and a
ridge in the southwestern part of the nebula.  The surface
brightness of the nebula is 703.4 +/- 54.5 counts arcminE-2 (0.01
+/- 0.001 counts/s), and the HRI countrate ratio for the point
source and the shell indicates that only 20 percent of the x-ray
flux is coming from the shell.  ROSAT PSPC data show that the
spectrum of the shell is thermal in origin."

S/1997 (3671) 1
     S. Mottola and G. Hahn, Institute of Planetary Exploration,
German Aerospace Research, Berlin; and P. Pravec and L. Sarounova,
Ondrejov Observatory, report: "Our photometric observations of this
Apollo object from the European Southern Observatory (La Silla) and
Ondrejov on nine nights during May 30.9-June 8.1 UT revealed the
presence of attenuations of the object's brightness of about 0.08
mag lasting for about 2 hr, superimposed on its normal rotational
lightcurve (P = 2.705 hr, amplitude 0.14 mag).  The attenuation
events were detected on May 30.985, June 1.131, 6.918, and 8.071; a
period of 1.155 days was derived from the observations.  We
interpret these features as occultations/eclipses of a satellite
orbiting (3671) Dionysus.  The observed lightcurve characteristics
are similar to those of 1994 AW_1 (Pravec and Hahn 1997, Icarus
127, 431) and 1991 VH (IAUC 6607), suggesting that a binary nature
may be relatively common among certain classes of near-earth
asteroids.  Further observations of the occultation/eclipse events
are needed to model the dynamics of this system, and interested
observers are encouraged to participate in a monitoring campaign.
For updated information, see http://earn.dlr.de/dionysus."

                      (C) Copyright 1997 CBAT
1997 June 10                   (6680)            Daniel W. E. Green

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