Hubble's Variable Nebula

JD 2,451,111

142

142 - 111

Some of the subtracted images show a highly organized torus-like feature just north of (above) R Mon. It is most sharply defined and well-formed in the JD 2,451,142 minus 111 image shown above but also appears in later subtracted sets (JD 150 minus 118 , JD 171 minus 142 and JD 277 minus 253). See the animation in which it fades then reforms again around JD 223.

Before considering this as a feature of the nebula's variability, tests were undertaken to determine that it is not an artifact of the equipment or processing.

The animation referred to above uses only the JD 111 image as the basis for all subsequent changes. To test that the JD 111 image is not in some way solely responsible for the torus-like feature, the following animation is based on images from 4 different sets of dates. It shows that the torus persisted for more than a month before disappearing and that during that time it moved north-east, the same direction as the shadow transit discussed earlier.

Animation based on several different set of dates
 

Series

JD 142-111

150-118

171-142

174-160

This torus-like feature suggests that the shadows and their source are at times structured in a highly organized way. The apparent orientation of the torus is similar to that of the accretion disk around R Mon and the "throat" in the circumstellar envelope that was proposed by Close et al. (axis of rotation at P.A. 350 degrees and tilted ~20 degrees toward us.).

The profile below shows how the peak responsible for the centre of the torus, the dark trough and brighter crest to the north-east all moved northeastward in tandem between JD 111 and 142. This shifting of the peak and "trough" created the torus in the subtracted image. A look at the regular animation and false colour animation shows that the "peak" in the profile is in fact a bridge of brighter material between the envelope surrounding R Mon and the nebula to the north-west. Over the 1998-99 observing season, this bridge varied greatly in brightness, shape and position.
 

JD 2,451,142

JD 142 -111

Last modified April 18, 1999