Observations of Comet b 1881 made at Monte Video

Modelling time to event with observations made at arbitrary times.

In many time-to-event studies, particularly in epidemiology, the time of the first observation or study entry is arbitrary in the sense that this is not a time of risk modification. We present a formal argument that, in these situations, it is not advisable to take the first observation as the time origin, either in accelerated failure time or proportional hazards models. Instead, we advocate u...

Comet Dust from Airborne Leonid Storm Observations

For the past five years, rare Leonid meteor storms offered unique access to cometary dust by spectacular manifestations of recently ejected dust grains, which could be observed by exceptional meteor observing techniques. The final storms, those of November 19, 2002, measured the dust distribution in a comet dust trail far from the position of the comet itself. The measured spatial and particle ...

Markov Chain Monte Carlo Simulation Made Simple

Radar observations of 8P/Tuttle: A contact-binary comet

Arecibo radar imagery of Comet 8P/Tuttle reveals a 10-km-long nucleus with a highly bifurcated shape consistent with a contact binary. A separate echo component was also detected from large (>cm-size), slow-moving grains of the type expected to contribute to the Ursid meteor stream. ! 2009 Elsevier Inc. All rights reserved.

Radar observations of Comet 2P/Encke during the 2003 apparition

The nucleus of Comet 2P/Encke was detected with the Arecibo radar during the close approach of November, 2003, making this the first comet to yield radar detections at two different apparitions. Although the measured radar cross section of 1.0 km2 was close to that obtained in 1980, the Doppler bandwidth was nearly four times larger. Most of this bandwidth difference can simply be attributed to...