Statistics of Titan's South Polar Tropospheric Clouds

We present the first long-term study of the behavior of the sporadically observed tropospheric clouds recently discovered near Titan's south pole. We find that one or more small individual cloud systems is present in the 70°-80° south region during every night of observation. These clouds account for 0.5%-1% of Titan's 2.0 μm flux, consistent with a global cloud cover fraction of 0.2%-0.6%. Clouds observed over multiple-night observing periods remained nearly fixed in brightness and position with respect to Titan's surface. The continual presence of south polar clouds is consistent with the hypothesis that surface heating during the long period of continuous polar sunlight at the time of Titan's southern summer solstice drives seasonal convection and cloud formation at the pole

The Mass, Orbit, and Tidal Evolution of the Quaoar-Weywot System

Here we present new adaptive optics observations of the Quaoar-Weywot system. With these new observations we determine an improved system orbit. Due to a 0.39 day alias that exists in available observations, four possible orbital solutions are available with periods of $\sim11.6$, $\sim12.0$, $\sim12.4$, and $\sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5\pm0.1\times10^{21}$ kg are found. These observations provide an updated density for Quaoar of 2.7-5.0{g cm^{-3}}. In all cases, Weywot's orbit is eccentric, with possible values $\sim0.13-0.16$. We present a reanalysis of the tidal orbital evolution of the Quoaor-Weywot system. We have found that Weywot has probably evolved to a state of synchronous rotation, and have likely preserved their initial inclinations over the age of the Solar system. We find that for plausible values of the effective tidal dissipation factor tides produce a very slow evolution of Weywot's eccentricity and semi-major axis. Accordingly, it appears that Weywot's eccentricity likely did not tidally evolve to its current value from an initially circular orbit. Rather, it seems that some other mechanism has raised its eccentricity post-formation, or Weywot formed with a non-negligible eccentricity.Comment: Accepted to Icarus, Nov. 8 201

Comet Shoemaker‐Levy 9: No effect on the Io plasma torus

Observations of the Io plasma torus made before, during, and after the impact of Comet Shoemaker‐Levy 9 with Jupiter reveal no comet‐induced changes. Three weeks of high spectral‐resolution ground‐based visible spectroscopy show no changes larger than typical day‐to‐day variations in the torus densities, ion temperatures, or rotation velocities. Comparison with six months of identically obtained data from 1991 and 1992 also shows no differences

A high-Resolution Catalog of Cometary Emission Lines

Using high-resolution spectra obtained with the Hamilton echelle spectrograph at Lick Observatory, we have constructed a catalog of emission lines observed in comets Swift-Tuttle and Brorsen-Metcalf. The spectra cover the range between 3800 Å and 9900 Å with a spectral resolution of λ/Δλ~42000. In the spectra, we catalog 2997 emission lines of which we identify 2438. We find cometary lines due to H, O, C_2, CN, NH_2, C_3, H_2O^+, CH, and CH^+. We list 559 unidentified lines compiled from the two spectra and comment on possibilities for their origins

Discovery of Temperate Latitude Clouds on Titan

Until now, all the clouds imaged in Titan's troposphere have been found at far southern latitudes (60°-90° south). The occurrence and location of these clouds is thought to be the result of convection driven by the maximum annual solar heating of Titan's surface, which occurs at summer solstice (2002 October) in this south polar region. We report the first observations of a new recurring type of tropospheric cloud feature, confined narrowly to ~40° south latitude, which cannot be explained by this simple insolation hypothesis. We propose two classes of formation scenario, one linked to surface geography and the other to seasonally evolving circulation, which will be easily distinguished with continued observations over the next few years

Non-detection of the OH Meinel system in comet P/Swift-Tuttle

We report a search for emissions from the OH Meinel system in high-resolution near-infrared spectra of comet P/Swift-Tuttle. Because of the large cometary heliocentric velocity and high resolution of the spectrograph, the cometary lines should be well separated from the bright OH sky lines. Contrary to the findings of Tozzi et al. (1994) - who report seeing cometary OH at intensities comparable to the sky emissions in their low-resolution spectra - we find no OH in these spectra with an upper limit of 5% the value of the night sky lines. The non-detection of these cometary lines is consistent with theoretical calculations of expected emission strengths from prompt and fluorescent emission from cometary OH

A Slowly Precessing Disk in the Nucleus of M31 as the Feeding Mechanism for a Central Starburst

We present a kinematic study of the nuclear stellar disk in M31 at infrared wavelengths using high spatial resolution integral field spectroscopy. The spatial resolution achieved, FWHM = 0."12 (0.45 pc at the distance of M31), has only previously been equaled in spectroscopic studies by space-based long-slit observations. Using adaptive optics-corrected integral field spectroscopy from the OSIRIS instrument at the W. M. Keck Observatory, we map the line-of-sight kinematics over the entire old stellar eccentric disk orbiting the supermassive black hole (SMBH) at a distance of r<4 pc. The peak velocity dispersion is 381+/-55 km/s , offset by 0.13 +/- 0.03 from the SMBH, consistent with previous high-resolution long-slit observations. There is a lack of near-infrared (NIR) emission at the position of the SMBH and young nuclear cluster, suggesting a spatial separation between the young and old stellar populations within the nucleus. We compare the observed kinematics with dynamical models from Peiris & Tremaine (2003). The best-fit disk orientation to the NIR flux is [$\theta_l$, $\theta_i$, $\theta_a$] = [-33 +/- 4$^{\circ}$, 44 +/- 2$^{\circ}$, -15 +/- 15$^{\circ}$], which is tilted with respect to both the larger-scale galactic disk and the best-fit orientation derived from optical observations. The precession rate of the old disk is $\Omega_P$ = 0.0 +/- 3.9 km/s/pc, lower than the majority of previous observations. This slow precession rate suggests that stellar winds from the disk will collide and shock, driving rapid gas inflows and fueling an episodic central starburst as suggested in Chang et al. (2007).Comment: accepted by Ap

Microscopic approach to large-amplitude deformation dynamics with local QRPA inertial masses

We have developed a new method for determining microscopically the fivedimensional quadrupole collective Hamiltonian, on the basis of the adiabatic self-consistent collective coordinate method. This method consists of the constrained Hartree-Fock-Bogoliubov (HFB) equation and the local QRPA (LQRPA) equations, which are an extension of the usual QRPA (quasiparticle random phase approximation) to non-HFB-equilibrium points, on top of the CHFB states. One of the advantages of our method is that the inertial functions calculated with this method contain the contributions of the time-odd components of the mean field, which are ignored in the widely-used cranking formula. We illustrate usefulness of our method by applying to oblate-prolate shape coexistence in 72Kr and shape phase transition in neutron-rich Cr isotopes around N=40.Comment: 6pages, talk given at Rutherford Centennial Conference on Nuclear Physics, 8 - 12 August 2011, The University of Mancheste

A new 1.6-micron map of Titan’s surface

We present a new map of Titan's surface obtained in the spectral 'window' at ∼1.6 μm between strong methane absorption. This pre-Cassini view of Titan's surface was created from images obtained using adaptive optics on the W.M. Keck II telescope and is the highest resolution map yet made of Titan's surface. Numerous surface features down to the limits of the spatial resolution (∼200–300 km) are apparent. No features are easily identifiable in terms of their geologic origin, although several are likely craters