We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an ...extended post-Pluto mission. This Neptune Trojan, 2011 HM{sub 102}, has the highest inclination (29. Degree-Sign 4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at H{sub V} {approx} 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ{sub 103} and 2007 VL{sub 305}), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM{sub 102}, and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM{sub 102} from the New Horizons spacecraft during its close approach in mid- to late-2013.
We present the results of narrowband photometry of 85 comets observed over a period of 17 years. The data have been reduced homogeneously to molecular production rates and a proxy for the dust ...production rate. We confirm previous investigations, both our own and those of others, showing that there is no differentiation with depth in the cometary nucleus, that most comets are very similar to each other in chemical composition, and that the dust-to-gas ratio does not vary with the dynamical age of the comet. There is little variation of relative abundances with heliocentric distance, implying that for the species we observe the role of density-dependent processes in the coma is small. There is also little variation from one apparition to the next for most short-period comets.
We show, however, that there are significant compositional groupings of comets, apparently related to place of formation. Specifically, the majority of comets originating in the Kuiper belt appear to be significantly depleted in the carbon-chain molecules that lead to the observed C2 and C3. Kuiper belt comets also exhibit smaller active areas, steeper slopes, and greater asymmetries about perihelion than do other comets, implying smaller active fractions. We argue that at least the compositional effect is primordial rather than evolutionary.
We also show a significant but unexplained correlation of some properties, notably the dust-to-gas ratio, with perihelion distance. We provide strong evidence that most CN, some C2, and virtually no NH are produced from grains in the coma rather than from nuclear ices. Evidence suggests that the mixing between water and other ices occurs at the level of grains rather than at the molecular level. We also show that there must be a large population of comets having very low activity. The data appear to require mixing of cometesimals with different compositions into individual nuclei, with some nuclei containing nearly the full range of compositions seen in the ensemble while others contain a much smaller range of compositions.
We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an ...extended post-Pluto mission. This Neptune Trojan, 2011 HM sub(102), has the highest inclination (29degrees.4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at H sub(V) ~ 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ sub(103) and 2007 VL sub(305)), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM sub(102), and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM sub(102) from the New Horizons spacecraft during its close approach in mid- to late-2013.
Abstract
We report on a chemo-dynamical analysis of SPLUS J142445.34−254247.1 (SPLUS J1424−2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process (
...r
-process). This star was first selected as a metal-poor candidate from its narrowband S-PLUS photometry and followed up spectroscopically in medium resolution with Gemini-South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini-South, allowing for the determination of the chemical abundances for 36 elements, from carbon to thorium. At Fe/H = −3.39, SPLUS J1424−2542 is one of the lowest-metallicity stars with measured Th and has the highest
log
ϵ
(
Th
/
Eu
)
observed to date, making it part of the “actinide-boost” category of
r
-process–enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424−2542 formed must have been enriched by at least two progenitor populations. The light-element (
Z
≤ 30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3–13.4
M
⊙
, and the heavy-element (
Z
≥ 38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66
M
⊙
and 1.27
M
⊙
) event. A kinematical analysis also reveals that SPLUS J1424−2542 is a low-mass, old halo star with a likely in situ origin, not associated with any known early merger events in the Milky Way.
We present the photometric analysis of 4 transits of the exoplanet WASP-4b, obtained with the Baade 6.5m telescope, one of the two Magellan telescopes at Las Campanas. The light curves have a ...photometric precision of 0.5 mmag and a time sampling of 30s. This high precision has allowed us to detect several “spot anomalies”: temporary brightenings due to the occultation of a starspot on the transit chord. By analyzing these anomalies we find the sky-projected stellar obliquity to be λ = 1°+12°−14°. The small value suggests that the planet migration mechanism preserved the initially low obliquity, or that tidal evolution has realigned the system.
Following the Pluto fly-by of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in-situ. The possibility existed to fly-by a Kuiper Belt object (KBO) ...as well as to observe additional objects at distances closer than are feasible from earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft. In this paper we present the results of 10 years of observations and three uniquely dedicated efforts -- two ground-based using the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with the Hubble Space Telescope -- to find such KBOs for study. In this paper we overview the search criteria and strategies employed in our work and detail the analysis efforts to locate and track faint objects in the galactic plane. We also present a summary of all of the KBOs that were discovered as part of our efforts and how spacecraft targetability was assessed, including a detailed description of our astrometric analysis which included development of an extensive secondary calibration network. Overall, these efforts resulted in the discovery of 89 KBOs including 11 which became objects for distant observation by New Horizons and (486958) Arrokoth which became the first post-Pluto fly-by destination.
We present photometry of two transits of the giant planet WASP-4b with a photometric precision of 400-800 parts per million and a time sampling of 25-40 s. The two midtransit times are determined to ...within 6 s. Together with previously published times, the data are consistent with a constant orbital period, giving no compelling evidence for period variations that would be produced by a satellite or additional planets. Analysis of the new photometry, in combination with stellar-evolutionary modeling, gives a planetary mass and radius of 1.237 {+-} 0.064 M {sub Jup} and 1.365 {+-} 0.021 R {sub Jup}, respectively. The planet is 15% larger than expected based on previously published models of solar-composition giant planets. With data of the quality presented here, the detection of transits of a 'super-Earth' of radius 1.75 R {sub +} would have been possible.
Abstract
The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely ...experienced minimal dynamical disruptions, the spin–orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin–orbit orientations of near-resonant systems. We present a Rossiter–McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin–orbit angle
λ
=
26
−
15
+
12
°
and a 3D spin–orbit angle
ψ
=
31
−
11
+
13
°
, finding that TOI-2202 b—the most massive near-resonant exoplanet with a 3D spin–orbit constraint to date—likely deviates from exact alignment with the host star’s equator. Incorporating the full census of spin–orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios
P
2
/
P
1
≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin–orbit excitation. Our result constitutes the first population-wide analysis of spin–orbit geometries for near-resonant planetary systems.
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