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THE ASTRONOMER Electronic Circular No 2405      2007 Dec 24 14.23UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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SUPERNOVA 2007sr (=OPTICAL TRANSIENT NEAR ANTENNAE GALAXIES)
Further to the note on TA E-Circular 2402, A. J. Drake et. al., have 
also reported their discovery on CBET 1172
The new object has now been designated 2007sr and appears on one
of the arms (or "antennae") emanating from NGC 4038 (which is
interacting with the galaxy NGC 4039). Nothing appears at this position 
in co-added CSS images from 2006 Dec. 21 (limiting mag about 21.5); 
also, nothing definite appears on multiple exposures obtained on 1999 
Feb. 22 with the Hubble Space Telescope though
it is possible that a precursor as bright as I-band mag about 23 is
present therein.

Martin Nicholson, Daventry responded to TA E-Circular 2042 by reporting 
that he imaged the object under rather unfavourable conditions and 
obtained the following position:
RA 12h 01m 52.81s DEC -18 58' 21.6"(2000)
The following magnitudes were derived:
JD             Mag
2454454.97117 12.83B
2454454.97036 13.03G
2454454.96953 12.99R
He used a Takahashi Epsilon 250mm F/3.8 astrograph and an ST-8XE CCD 
camera mounted on a Paramount GT1100ME mount housed at an Observatory 
near Mahill, New Mexico.

Ernesto Guido and Giovanni Sostero, Italy have reported to TAHQ that co 
adding five frames (60 seconds each) in each filter, B, V and R, 
obtained remotely (near Mayhill, NM) through a 0.25m, f/3.4 reflector + 
CCD on 2007 Dec 19.42, confirms the presence of an optical transient at 
coordinates:
RA 12h 01m 52.80s DEC -18 58' 21.8" (2000) which is not present in the 
Palomar Sky Survey archive plates. Their photometry indicates the 
following magnitudes: B=13.20, V= 12.85 and R= 12.80 (accuracy +/- 0.05 
magnitudes in each colour).

Dan Green, Central Bureau, notes that SNe 1921A, 1974E, and 2004gt
also appeared in NGC 4038.

G. Umbriaco, Dipartimento di Astronomia, Universita' di Padova et. al., 
report that a spectrogram obtained on Dec. 20.22 UT at Asiago with the 
Galileo 1.22-m telescope shows it to be a type-Ia supernova with good 
fits to spectra of SNe 1996Z and 2002bo at five and four days after 
B-maximum light, respectively.

COMET 17P/HOLMES
M. R. Combi, University of Michigan et. al., report on IAUC 8905 that 
the SWAN camera on the SOHO spacecraft, located at the earth-sun L1 
Lagrange point, makes daily full-sky images of hydrogen Lyman_alpha. 
SWAN detected comet 17P/Holmes beginning with the rapid rise of activity 
on Oct. 24 UT.  The Lyman_alpha coma was observed to expand and brighten 
over the next few days, as water -- and subsequently OH -- were 
photodissociated to produce hydrogen. An initial expansion velocity in 
the range between 17 and 20 km/s was deduced from a preliminary analysis 
of the images, which is consistent with the initial production of H 
atoms from the photo-dissociation of water.  A preliminary time-series 
analysis of the images yields daily averages of the global 
water-production rate. This indicates that there was a rapid rise in the 
water-production rate by Oct. 25, resembling the visual light curve.
Guy M Hurst