Infrared variability of Jupiter and Saturn

Infrared spectroscopy provides unique insights into the chemistry and dynamics of the atmospheres of Jupiter and Saturn, and of the enigmatic satellite of Saturn, Titan. The 5 micron spectral region of these objects is transparent to deep levels, and is therefore particularly useful for the identification of molecules that are present at very low (parts per billion) concentrations. In Titan, 5 micron observations probe atmospheric layers at or near the surface. Ground-based spectroscopy complements Voyager, Galileo, and Cassini measurements. The spectroscopy is sensitive to lower mixing ratios for selected molecules, while the on-board mass and infrared spectrometers probe molecules and levels that are inaccessible form the ground. The observations also provide time-based data for preparation of the upcoming missions

Rotational properties of the binary and non-binary populations in the Trans-Neptunian belt

We present results for the short-term variability of Binary Trans-Neptunian Objects (BTNOs). We performed CCD photometric observations using the 3.58 m Telescopio Nazionale Galileo, the 1.5 m Sierra Nevada Observatory telescope, and the 1.23 m Centro Astronomico Hispano Aleman telescope at Calar Alto Observatory. We present results based on five years of observations and report the short-term variability of six BTNOs. Our sample contains three classical objects: 2003MW12, or Varda, 2004SB60, or Salacia, and 2002 VT130; one detached disk object: 2007UK126; and two resonant objects: 2007TY430 and 2000EB173, or Huya. For each target, possible rotational periods and/or photometric amplitudes are reported. We also derived some physical properties from their lightcurves, such as density, primary and secondary sizes, and albedo. We compiled and analyzed a vast lightcurve database for Trans-Neptunian Objects (TNOs) including centaurs to determine the lightcurve amplitude and spin frequency distributions for the binary and non-binary populations. The mean rotational periods, from the Maxwellian fits to the frequency distributions, are 8.63+/-0.52 h for the entire sample, 8.37+/-0.58 h for the sample without the binary population, and 10.11+/-1.19 h for the binary population alone. Because the centaurs are collisionally more evolved, their rotational periods might not be so primordial. We computed a mean rotational period, from the Maxwellian fit, of 8.86+/-0.58 h for the sample without the centaur population, and of 8.64+/-0.67 h considering a sample without the binary and the centaur populations. According to this analysis, regular TNOs spin faster than binaries, which is compatible with the tidal interaction of the binaries. Finally, we examined possible formation models for several systems studied in this work and by our team in previous papers.Comment: Accepted for publication in Astronomy and Astrophysics (June 26th, 2014); minor changes with published version; 21 pages, 17 figures, 7 table

Spectroscopic Detection of Carbon Monoxide in Two Late-type T Dwarfs

M band spectra of two late-type T dwarfs, 2MASS J09373487+2931409, and Gliese 570D, confirm evidence from photometry that photospheric CO is present at abundance levels far in excess of those predicted from chemical equilibrium. These new and unambiguous detections of CO, together with an earlier spectroscopic detection of CO in Gliese 229B and existing M band photometry of a large selection of T dwarfs, suggest that vertical mixing in the photosphere drives the CO abundance out of chemical equilibrium and is a common, and likely universal feature of mid-to-late type T dwarfs. The M band spectra allow determinations of the time scale of vertical mixing in the atmosphere of each object, the first such measurements of this important parameter in late T dwarfs. A detailed analysis of the spectral energy distribution of 2MASS J09373487+2931409 results in the following values for metallicity, temperature, surface gravity, and luminosity: [M/H]~-0.3, T_eff=925-975K, log g=5.20-5.47, log L/L_sun=-5.308 +/- 0.027. The age is 3-10 Gyr and the mass is in the range 45-69 M_Jup.Comment: 36 pages incl. 12 figures and 3 tables, accepted by Ap

The Mutual Orbit, Mass, and Density of Transneptunian Binary Gknhmdm (229762 2007 UK126)

We present high spatial resolution images of the binary transneptunian object Gkn'hmdm (229762 2007 UK126) obtained with the Hubble Space Telescope and with the Keck observatory on Mauna Kea to determine the orbit of G' hG' h, the much smaller and redder satellite. G' h orbits in a prograde sense, on a circular or near-circular orbit with a period of 11.3 days and a semimajor axis of 6000 km. Tidal evolution is expected to be slow, so it is likely that the system formed already in a low-eccentricity configuration, and possibly also with the orbit plane of the satellite in or close to the plane of Gkn'hmdm's equator. From the orbital parameters we can compute the system mass to be 1.4 10(exp 20) kg. Combined with estimates of the size of Gkn'hmdm from thermal observations and stellar occultations, we can estimate the bulk density as about 1 g cm(exp 3). This low density is indicative of an ice-rich composition, unless there is substantial internal porosity. We consider the hypothesis that the composition is not unusually ice-rich compared with larger TNOs and comet nuclei, and instead the porosity is high, suggesting that mid-sized objects in the 400 to 1000 km diameter range mark the transition between small, porous objects and larger objects that have collapsed their internal void space as a result of their much higher internal pressures and temperatures

The Onset of Methane in L Dwarfs

We have detected weak absorption features produced by the strong nu(3) methane band at 3.3 microns in two L dwarfs, 2MASSW J1507476-162738 and 2MASSI J0825196+211552, classified by Kirkpatrick et al. (2000) as spectral types L5 and L7.5 respectively. These absorptions occur in objects warmer than any in which methane previously has been detected, and mark the first appearance of methane in the ultracool star-to-brown dwarf spectral sequence.Comment: 12 pages, 2 figures; accepted by ApJ Letter

The Orbit of Transneptunian Binary Manw\"e and Thorondor and their Upcoming Mutual Events

A new Hubble Space Telescope observation of the 7:4 resonant transneptunian binary system (385446) Manw\"e has shown that, of two previously reported solutions for the orbit of its satellite Thorondor, the prograde one is correct. The orbit has a period of 110.18 $\pm$ 0.02 days, semimajor axis of 6670 $\pm$ 40 km, and an eccentricity of 0.563 $\pm$ 0.007. It will be viewable edge-on from the inner solar system during 2015-2017, presenting opportunities to observe mutual occultation and eclipse events. However, the number of observable events will be small, owing to the long orbital period and expected small sizes of the bodies relative to their separation. This paper presents predictions for events observable from Earth-based telescopes and discusses the associated uncertainties and challenges.Comment: 15 pages, 3 figures, 5 table