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IAUC 8695: P/2006 F4; RS Oph

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                                                  Circular No. 8695
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)

     R. S. McMillan, Lunar and Planetary Laboratory, reports the
Spacewatch discovery of a comet on CCD images taken by M. T. Read
and himself with the 0.9-m reflector, the object being diffuse with
a 6 deg" deg tail in p.a. 280 deg (discovery observation tabulated
below).  A. C. Gilmore reports that images taken on Mar. 30.6 UT
with the Mt. John 1.0-m f/7.7 reflector show a moderately condensed
coma about 10" in diameter with a hint of a diffuse tail on the
west side.  Astrometry and preliminary orbital elements [T = 2006
Apr. 15.1 TT, Peri. = 25.3 deg, Node = 184.4 deg, i = 12.5 deg
(equinox 2000.0), q = 2.362 AU, e = 0.349, P = 6.9 yr] appear on
MPEC 2006-F53.

     2006 UT             R.A. (2000) Decl.       Mag.
     Mar. 26.35589   14 19 57.50   - 6 55 40.7   19.9

     R. Gonzalez-Riestra, XMM-Newton Science Operation Centre,
European Space Agency; M. Orio, National Institute of Astrophysics
of Italy and University of Wisconsin; and E. Leibowitz, Tel Aviv
University, write that RS Oph was observed with XMM-Newton on Feb.
26 for 400 minutes and on Mar. 10 for 197 minutes.  At both times,
prominent emission lines were observed with the RGS gratings, due
to H-like and He-like transitions of N, O, Mg, Ne, Si, and Fe.  The
total flux was about 1.4 x 10**-10 erg/s in the first observation
and about 1.1 x 10**-10 erg/s in the second.  Some emission lines
in the range 0.6-1.6 nm decreased in strength by the second
observation, while other lines in the region 1.7-3.3 nm became much
more prominent, especially O VII (1.897 nm) and N VIII (2.478 nm),
due to a decrease of the column density of neutral hydrogen to a
value not exceeding 3 x 10**21 cm**-2 on Mar. 10.  The lines were
blueshifted by 1100-1400 km/s in the first observation and only by
a few hundred km/s in the second, and at both times, their full-
width-at-half-maximum corresponded to at least 2000 km/s.  Both
EPIC-pn spectra showed also the Fe-K-alpha complex in emission, but
it was significantly stronger in the February spectrum.  During the
second observation, after the first 2800 s, the EPIC-pn count-rate
in the range 0.15-0.50 keV quadrupled in approximately 1700 s, then
decreased by 40 percent in the following 1500 s and remained
approximately constant until the end.  During the rise and fall,
the power spectrum shows a significant signal with a period of
35.685 s.  The EPIC-pn count-rate in the range 1-10 keV had non-
correlated variations by 10 percent and no coherent oscillations.

                      (C) Copyright 2006 CBAT
2006 March 30                  (8695)            Daniel W. E. Green

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