-------------------------------------------------------------------
THE ASTRONOMER Electronic Circular No 2430      2008 Mar 10 10.10UT
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
-------------------------------------------------------------------
COMET 17P/HOLMES
Mark Kidger and Richard Miles have sent the following report:

Images and photometry by several observers, including Ramón Naves and 
Montse Campàs (MPC 213), Martin Mobberley (MPC 480, reduced by Montse 
Campàs), Faustino García (MPC J38), Gustavo Muler (MPC J47) and Richard 
Miles (J77), suggest that comet 17P/Holmes has shown a further 
mini-outburst, which appears to have initiated on 2008 March 7.  The 
three events detected so far have taken place at 44.6+/-0.6, 89.5+/-0.6 
and 135.1+/-0.8 days after the initial outburst on 2007 October 23.7, 
giving a mean interval of 45.0 +/-0.5 days determined from a least 
squares fit.  The correlation coefficient of the fit is r2=0.99997.  It 
is likely that this periodicity corresponds to the rotation period of 
the nucleus whereby the same area is activated when receiving insolation 
and thus it is concluded that 17P/Holmes is a very slow rotator, 
comparable to 29P/Schwassmann-Wachmann 1, which from Spitzer
observations of its jets (Stansberry J.A., et al., 2004, ApJ Suppl.
Ser., 154, 463) appears to rotate with a period of 60 days or more.

The following analysis by Richard Miles adjusted to constant 
heliocentric distance; delta and phase angle (rel. March 7 20:00 UT) 
shows the development of the current outburst. Photometry is for a 10 
arcsec square aperture, equivalent to a physical aperture of 22000 km at 
the comet.  The amplitude of the brightening is currently about 0.4 
magnitudes.

Date     Time        R Mag.    Outburst amplitude  MPC Code
March 4  21:21 UT   16.05  -0.02 mag.  J77
March 5  21:00 UT   16.02  -0.03 mag.  J47
March 5  21:10 UT   16.06  +0.01 mag.  J38
March 7  19:56 UT   15.88  -0.21 mag.  213
March 7  20:00 UT   15.97  -0.12 mag.  480
March 7  23:15 UT   15.77  -0.32 mag.  J47
March 8  21:55 UT   15.72  -0.38 mag.  J47
March 8  22:03 UT   15.70  -0.40 mag.  J47

Guy M Hurst