Grant Christie

VERTICAL STRUCTURE IN PLUTO'S ATMOSPHERE FROM THE 2006 JUNE 12 STELLAR OCCULTATION

Pluto occultations are historically rare events, having been observed in 1988, 2002, 2006, and, as Pluto moves into the crowded Galactic plane, on several occasions in 2007. Here we present six results from our observations of the 2006 June 12 event from several sites in Australia and New Zealand. First, we show that Plutos 2006 bulk atmospheric column abundance, as in 2002, is over twice the value measured in 1988, implying that nitrogen frost on Plutos surface is 1.2-1.7 K warmer in 2006 than 1988 despite a 9% drop in incident solar flux. We measure a half-light shadow radius of 1216 ± 8.6 km in 2006, nominally larger than published values of 1213 ± 16 km measured in 2002. Given the current error bars, this latest half-light radius cannot discriminate between continued atmospheric growth or shrinkage, but it rules out several of the volatile transport scenarios modeled by Hansen & Paige. Second, we resolve spikes in the occultation light curve that are similar to those seen in 2002 and model the vertical temperature fluctuations that cause them. Third, we show that Plutos upper atmosphere appears to hold a steady temperature of ~100 K, as predicted from the methane thermostat model, even at latitudes where the methane thermostat is inoperative. This implies that energy transport rates are faster than radiational cooling rates. Fourth, this occultation has provided the first significant detection of a non-isothermal temperature gradient in Plutos upper atmosphere also reported by Elliot et al., possibly the result of CO gas in Plutos upper atmosphere. Fifth, we show that a haze-only explanation for Plutos light curve is extremely unlikely; a thermal inversion is necessary to explain the observed light curve. And sixth, we derive an upper limit for the haze optical depth of 0.0023 in the zenith direction at average CCD wavelengths.

A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

Fermi Guest Investigator grants [NNX14AQ36G, NNG16PX24I, NNX15AU77G, NNX16AR73G]; National Science Foundation [AST-1615084]; Research Corporation for Science Advancement Scialog Fellows Program [RCSA 23810]; NSF; NASA

Operating a global network of autonomous observatories

We discuss our experiences operating a heterogeneous global network of autonomous observatories. The observatories are presently situated on four continents, with a fifth expected during the summer of 2010. The network nodes are small to intermediate diameter telescopes (<= 150 cm) owned by different institutions but running the same observatory control software. We report on the experience gained during construction, commissioning and operation of the observatories, as well as future plans. Problems encountered in the construction and operation of the nodes are summarised. Operational statistics as well as scientific results from the observatories are also presented.