Here we present additional photometry of targets observed as part of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System. 12 targets were re-observed with the Wide Field Camera 3 in optical and NIR wavebands designed to complime
nt those used during the first visit. Additionally, all observations originally presented by Fraser and Brown (2012) were reanalyzed through the same updated photometry pipeline. A reanalysis of the optical and NIR colour distribution reveals a bifurcated optical colour distribution and only two identifiable spectral classes, each of which occupies a broad range of colours and have correlated optical and NIR colours, in agreement with our previous findings. We report the detection of significant spectral variations on 5 targets which cannot be attributed to photometry errors, cosmic rays, point spread function or sensitivity variations, or other image artifacts capable of explaining the magnitude of the variation. The spectrally variable objects are found to have a broad range of dynamical classes, absolute magnitudes, exhibit a broad range of apparent magnitude variations, and are found in both compositional classes. The spectrally variable objects with sufficiently accurate colours for spectral classification maintain their membership, belonging to the same class at both epochs. 2005 TV189 exhibits a sufficiently broad difference in colour at the two epochs that span the full range of colours of the neutral class. This strongly argues that the neutral class is one single class with a broad range of colours, rather than the combination of multiple overlapping classes.
Here we measure the absolute magnitude distributions (H-distribution) of the dynamically excited and quiescent (hot and cold) Kuiper Belt objects (KBOs), and test if they share the same H-distribution as the Jupiter Trojans. From a compilation of all
useable ecliptic surveys, we find that the KBO H-distributions are well described by broken power-laws. The cold population has a bright-end slope, $alpha_{textrm{1}}=1.5_{-0.2}^{+0.4}$, and break magnitude, $H_{textrm{B}}=6.9_{-0.2}^{+0.1}$ (r-band). The hot population has a shallower bright-end slope of, $alpha_{textrm{1}}=0.87_{-0.2}^{+0.07}$, and break magnitude $H_{textrm{B}}=7.7_{-0.5}^{+1.0}$. Both populations share similar faint end slopes of $alpha_2sim0.2$. We estimate the masses of the hot and cold populations are $sim0.01$ and $sim3times10^{-4} mbox{ M$_{bigoplus}$}$. The broken power-law fit to the Trojan H-distribution has $alpha_textrm{1}=1.0pm0.2$, $alpha_textrm{2}=0.36pm0.01$, and $H_{textrm{B}}=8.3$. The KS test reveals that the probability that the Trojans and cold KBOs share the same parent H-distribution is less than 1 in 1000. When the bimodal albedo distribution of the hot objects is accounted for, there is no evidence that the H-distributions of the Trojans and hot KBOs differ. Our findings are in agreement with the predictions of the Nice model in terms of both mass and H-distribution of the hot and Trojan populations. Wide field survey data suggest that the brightest few hot objects, with $H_{textrm{r}}lesssim3$, do not fall on the steep power-law slope of fainter hot objects. Under the standard hierarchical model of planetesimal formation, it is difficult to account for the similar break diameters of the hot and cold populations given the low mass of the cold belt.
Here we present high cadence photometry taken by the Acquisition Camera on Gemini South, of a close passage by the $sim540$ km radius Kuiper Belt Object, (50000) Quaoar, of a r=20.2 background star. Observations before and after the event show that t
he apparent impact parameter of the event was $0.019pm0.004$, corresponding to a close approach of $580pm120$ km to the centre of Quaoar. No signatures of occultation by either Quaoars limb or its potential atmosphere are detectable in the relative photometry of Quaoar and the target star, which were unresolved during closest approach. From this photometry we are able to put constraints on any potential atmosphere Quaoar might have. Using a Markov chain Monte Carlo and likelihood approach, we place pressure upper limits on sublimation supported, isothermal atmospheres of pure N$_2$, CO, and CH$_4$. For N$_2$ and CO, the upper limit surface pressures are 1 and 0.7 $mu{bar}$ respectively. The surface temperature required for such low sublimation pressures is $sim33$ K, much lower than Quaoars mean temperature of $sim44$ K measured by others. We conclude that Quaoar cannot have an isothermal N$_2$ or CO atmosphere. We cannot eliminate the possibility of a CH$_4$ atmosphere, but place upper surface pressure and mean temperature limits of $sim138$ nbar and $sim44$ K respectively.
Here we present observations of 7 large Kuiper Belt Objects. From these observations, we extract a point source catalog with $sim0.01$ precision, and astrometry of our target Kuiper Belt Objects with $0.04-0.08$ precision within that catalog. We have
developed a new technique to predict the future occurrence of stellar occultations by Kuiper Belt Objects. The technique makes use of a maximum likelihood approach which determines the best-fit adjustment to cataloged orbital elements of an object. Using simulations of a theoretical object, we discuss the merits and weaknesses of this technique compared to the commonly adopted ephemeris offset approach. We demonstrate that both methods suffer from separate weaknesses, and thus, together provide a fair assessment of the true uncertainty in a particular prediction. We present occultation predictions made by both methods for the 7 tracked objects, with dates as late as 2015. Finally, we discuss observations of three separate close passages of Quaoar to field stars, which reveal the accuracy of the element adjustment approach, and which also demonstrate the necessity of considering the uncertainty in stellar position when assessing potential occultations.
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 availa
ble with periods of $sim11.6$, $sim12.0$, $sim12.4$, and $sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5pm0.1times10^{21}$ kg are found. These observations provide an updated density for Quaoar of $2.7-5.0{g cm$^{-3}$}$. In all cases, Weywots 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 Weywots eccentricity and semi-major axis. Accordingly, it appears that Weywots 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.
We present the first results of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was to measure the surface properties of a large number of Kuiper belt objects and attempt to infer compo
sitional and dynamical correlations. We find that the Centaurs and the low-perihelion scattered disk and resonant objects exhibit virtually identical bifurcated optical colour distributions and make up two well defined groups of object. Both groups have highly correlated optical and NIR colours which are well described by a pair of two component mixture models that have different red components, but share a common neutral component. The small, $H_{606}gtrsim5.6$ high-perihelion excited objects are entirely consistent with being drawn from the two branches of the mixing model suggesting that the colour bifurcation of the Centaurs is apparent in all small excited objects. On the other hand, objects larger than $H_{606}sim5.6$ are not consistent with the mixing model, suggesting some evolutionary process avoided by the smaller objects. The existence of a bifurcation amongst all excited populations argues that the two separate classes of object existed in the primordial disk before the excited Kuiper belt was populated. The cold classical objects exhibit a different type of surface which has colours that are consistent with being drawn from the red branch of the mixing model, but with much higher albedos.
Here we report WFPC2 observations of the Quaoar-Weywot Kuiper belt binary. From these observations we find that Weywot is on an elliptical orbit with eccentricity of 0.14 {pm} 0.04, period of 12.438 {pm} 0.005 days, and a semi-major axis of 1.45 {pm}
0.08 {times} 104 km. The orbit reveals a surpsingly high Quaoar-Weywot system mass of 1.6{pm}0.3{times}10^21 kg. Using the surface properties of the Uranian and Neptunian satellites as a proxy for Quaoars surface, we reanalyze the size estimate from Brown and Trujillo (2004). We find, from a mean of available published size estimates, a diameter for Quaoar of 890 {pm} 70 km. We find Quaoars density to be rho = 4.2 {pm} 1.3 g cm^-3, possibly the highest density in the Kuiper belt.
We present here HST NICMOS F110W and F160W observations of Haumea, and its two satellites Hiiaka and Namaka. From the measured (F110W-F160W) colours of -1.209 +/-0.004, -1.48 +/- 0.06, and -1.4 +/- 0.2 mag for each object, respectively, we infer that
the 1.6 imcron water-ice absorption feature depths on Hiiaka and Namaka are at least as deep as that of Haumea. The light-curve of Haumea is detected in both filters, and we find that the infrared colour is bluer by approximately 2-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family.
We have performed a survey of the Kuiper belt covering ~ 1/3 a square degree of the sky using Suprime-cam on the Subaru telescope, to a limiting magnitude of m(R)~ 26.8 (50% threshold) and have found 36 new KBOs. We have confirmed that the luminosity
function of the Kuiper belt must break as previously observed (Bernstein et al. 2004; Fuentes & Holman 2008). From the luminosity function, we have inferred the underlying size distribution and find that it is consistent with a large object power-law slope q1~4.8 that breaks to a slope q2~1.9 at object diameter Db~60 km assuming 6% albedos. We have found no conclusive evidence that the size distribution of KBOs with inclinations i<5 is different than that of those with i>5. We discuss implications of this measurement for early accretion in the outer solar system and Neptune migration scenarios.
We have derived a model of the Kuiper belt luminosity function exhibited by a broken power-law size distribution. This model allows direct comparison of the observed luminosity function to the underlying size distribution. We discuss the importance o
f the radial distribution model in determining the break diameter. We determine a best-fit break-diameter of the Kuiper belt size-distribution of 30<Db<90 km via a maximum-likelihood fit of our model to the observed luminosity function. We also confirm that the observed luminosity function for m(R) ~ 21-28 is consistent with a broken power-law size distribution, and exhibits a break at m(R)=26.0+0.7-1.8.
