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IAUC 7681: 2001dn; C/2001 A2

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                                                  Circular No. 7681
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)

     G. M. Hurst, Basingstoke, England, reports the discovery by T.
Boles (Coddenham, Suffolk) of an apparent supernova (mag 15.5) on
an unfiltered CCD image (limiting mag 18.5) obtained on Aug. 14.069
UT with a 0.36-m reflector.  The following averaged astrometry was
measured from six exposures:  R.A. = 1h44m35s.32, Decl. =
+37o41'49".7 (equinox 2000.0), which is 4" west and 3" north of the
center of NGC 662.  SN 2001dn is also present on unfiltered CCD
images taken on Aug. 14.870 (by Boles; mag about 15.5) and 15.003
(by M. Armstrong, Rolvenden, Kent).  SN 2001dn was not present on a
Boles image taken on 1999 Oct. 16 (limiting mag 18.5) or on Palomar
Sky Survey photographs taken on 1989 Nov. 18 and 1988 Sept. 13.

     P. D. Feldman, H. A. Weaver, and E. B. Burgh, Johns Hopkins
University, report observations of comet C/2001 A2 with the Far
Ultraviolet Spectroscopic Explorer beginning July 12.58 UT and
coinciding with the photometric event reported on IAUC 7679:
"Spectra (range 91-118 nm; spectral resolution 0.03 nm) were
obtained using the 30" x 30" aperture.  Several new cometary
emissions were identified, particularly the (0,0) bands of the CO
Birge-Hopfield systems (C-X and B-X) at 108.8 and 115.1 nm,
respectively; O I [(**1)D-(**1)D] at 115.2 nm; and three lines of the
H_2 Lyman system at 107.16, 111.86, and 116.68 nm, pumped by solar
Lyman-beta fluorescence.  Also detected were O I multiplets at
98.9, 102.7, and 104.0 nm, and several lines of the H I Lyman
series.  The rotational envelopes of the CO bands are resolved and
appear to consist of both cold and warm components, the cold
component accounting for 80 percent of the flux and having a
rotational temperature of 60 K.  The warm component may be
indicative of a CO_2 source.  Both the CO bands and the O I
115.2-nm emission (an indicator of H_2O production) decreased by a
factor of two over the 7.5 hr observation.  Preliminary estimates
of the production rates at the beginning of the observation are
Q(CO) = 4 x 10**(27) s**(-1) and Q(H_2O) = 3 x 10**(29) s**(-1)
(vectorial model).  These values may be uncertain by as much as a
factor of two, due to uncertainties in the solar flux.  No emission
is detected from Ar I at 104.8 and 106.7 nm and He I at 58.4 nm (in
second order).  We derive Q(Ar) </= 6 x 10**(25) s**(-1) (5-sigma
upper limit), which implies that Ar/O is more than a factor of ten
less than solar.  In addition to the features listed above, more
than two dozen other emissions remain unidentified."

                      (C) Copyright 2001 CBAT
2001 August 15                 (7681)            Daniel W. E. Green

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