[BAA Comets] Approx. 3.7 magnitude outburst of Comet 17P/Holmes

[Richard Miles]

I can confirm thanks to observations by Nick James (Chelmsford, UK, IAU 970) and Denis Buczynski (Tarbatness, UK, IAU I81) that 17P/Holmes has indeed outburst. 

Prior to this event happening, the magnitude of the comet in a 30 arcsec aperture was R=18.0 and its appearance during Jan 22 - Jan 26 (3 epochs) was entirely quiescent with only a faint coma and strong central condensation. After outburst on 2015 January 26.7+/-0.4, a value of R=14.3 (V=14.6) has been determined from both observers' image data. The present outburst is of the order of 4 magnitudes in amplitude, i.e. its largest outburst since 2007.

There appears to be significant asymmetry in the expanding coma, which now exceeds 20 arcsec in diameter in stacked images.

Observations are continuing.

Richard Miles
BAA

  ----- Original Message ----- 
  From: rmiles.btee at btinternet.com [comets-ml] 
  To: comets-ml at yahoogroups.com 
  Sent: Wednesday, January 28, 2015 6:06 PM
  Subject: [comets-ml] Significant outburst of Comet 17P/Holmes





  It appears that Comet 17P/Holmes has undergone a significant outburst on 2015 January 26 possibly reaching 14th magnitude. If confirmed, this outburst will be the most energetic event of its kind since this comet's mega-outburst of 2007 October 23.

  Two 120-sec exposures through an SDSS-r' filter taken by the 2.0-m Faulkes Telescope North on January 28.25 show an extended coma some 10-12 arcsec in diameter with possible outflows at p.a. 20 deg and 270 deg. Seeing in the images is estimated to be in the range 1.0-1.4 arcsec. The FITS images are not yet available (these require 24 hours to come online) and so accurate photometry cannot yet be performed.Two previous 120-sec exposures through an SDSS-r' filter taken with the same 2.0-m Faulkes Telescope North on January 26.29 show 17P to be entirely quiescent at around 17-18th magnitude.
  Further results to follow.

  Observations of 17P are strongly encouraged.The results reported here are made possible thanks to the Las Cumbres Observatory Global Telescope Network (LCOGT).

  Richard Miles, British Astronomical Association