120 research outputs found
The Luminosity Function of the Hot and Cold Kuiper belt Populations
Abridged. We have performed an ecliptic survey of the Kuiper belt, with an
areal coverage of 8.9 square degrees to a 50% limiting magnitude of r'=24.7,
and have detected 88 Kuiper belt objects, roughly half of which received
follow-up one to two months after detection. Using this survey data alone, we
have measured the luminosity function of the Kuiper belt, thus avoiding any
biases that might come from the inclusion of other observations. We have found
that the Cold population defined as having inclinations less than 5 degrees has
a luminosity function slope alpha=0.82+-0.23, and is different from the Hot
population, which has inclinations greater than 5 degrees and a luminosity
function slope alpha=0.35+-0.21. As well, we have found that those objects
closer than 38 AU have virtually the same luminosity function slope as the Hot
population. This result, along with similar findings of past surveys
demonstrates that the dynamically cold Kuiper belt objects likely have a steep
size distribution, and are unique from all of the excited populations which
have much shallower distributions. This suggests that the dynamically excited
population underwent a different accretion history and achieved a more evolved
state of accretion than the cold population. As well, we discuss the
similarities of the Cold and Hot populations with the size distributions of
other planetesimal populations. We find that while the Jupiter family comets
and the scattered disk exhibit similar size distributions, a power-law
extrapolation to small sizes for the scattered disk cannot account for the
observed influx of comets. As well, we have found that the Jupiter Trojan and
Hot populations cannot have originated from the same parent popuation, a result
that is difficult to reconcile with scattering models similar to the NICE
model.Comment: Accepted for publication in Icarus. 27 pages, 10 figures, 4 table
The La Silla - QUEST Kuiper Belt Survey
We describe the instrumentation and detection software and characterize the
detection efficiency of an automated, all-sky, southern-hemisphere search for
Kuiper Belt objects brighter than R mag 21.4. The search relies on Yale
University's 160-Megapixel QUEST camera, previously used for successful surveys
at Palomar that detected most of the distant dwarf planets, and now installed
on the ESO 1.0-m Schmidt telescope at La Silla, Chile. Extensive upgrades were
made to the telescope control system to support automation, and significant
improvements were made to the camera. To date, 63 new KBOs have been
discovered, including a new member of the Haumea collision family (2009 YE7)
and a new distant object with inclination exceeding 70 deg (2010 WG9). In a
survey covering ~7500 deg2, we have thus far detected 77 KBOs and Centaurs,
more than any other full-hemisphere search to date. Using a pattern of dithered
pointings, we demonstrate a search efficiency exceeding 80%. We are currently
on track to complete the southern-sky survey and detect any bright KBOs that
have eluded detection from the north.Comment: 20 pages, 2 tables, 7 figure
The Small Numbers of Large Kuiper Belt Objects
We explore the brightness distribution of the largest and brightest (m(R) 5°) from the very brightest to m(R) = 23. We find for m(R) ≾ 23, a single slope appears to describe the luminosity function. We estimate that ~12 KBOs brighter than m(R) ~ 19.5 are present in the Kuiper Belt today. With nine bodies already discovered this suggests that the inventory of bright KBOs is nearly complete
Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System
We report the discovery and confirmation of a transiting circumbinary planet (PH1b) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ~137 days, with seven transits identified in Quarters 1-11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities and the Kepler light curve of KIC 4862625. The 6.18 ± 0.17 R_⊕ planet orbits outside the 20 day orbit of an eclipsing binary consisting of an F dwarf (1.734 ± 0.044 R_☉, 1.528 ± 0.087 M_☉) and M dwarf (0.378 ± 0.023 R_☉, 0.408 ± 0.024 M_☉). For the planet, we find an upper mass limit of 169 M_⊕ (0.531 Jupiter masses) at the 99.7% confidence level. With a radius and mass less than that of Jupiter, PH1b is well within the planetary regime. Outside the planet's orbit, at ~1000 AU, a previously unknown visual binary has been identified that is likely bound to the planetary system, making this the first known case of a quadruple star system with a transiting planet
Interpreting the densities of the Kuiper belt's dwarf planets
Kuiper Belt objects with absolute magnitude less than 3 (radius 500
km), the dwarf planets, have a range of different ice/rock ratios, and are more
rock-rich than their smaller counterparts. Many of these objects have moons,
which suggests that collisions may have played a role in modifying their
compositions. We show that the dwarf planets fall into two categories when
analysed by their mean densities and satellite-to-primary size ratio. Systems
with large moons, such as Pluto/Charon and Orcus/Vanth, can form in
low-velocity grazing collisions in which both bodies retain their compositions.
We propose that these systems retain a primordial composition, with a density
of about 1.8 g/cm. Triton, thought to be a captured KBO, could have lost
enough ice during its early orbital evolution to explain its rock-enrichment
relative to the primordial material. Systems with small moons, Eris, Haumea,
and Quaoar, formed from a different type of collision in which icy material,
perhaps a few tens of percent of the total colliding mass, is lost. The
fragments would not remain in physical or dynamical proximity to the parent
body. The ice loss process has not yet been demonstrated numerically, which
could be due to the paucity of KBO origin simulations, or missing physical
processes in the impact models. If our hypothesis is correct, we predict that
large KBOs with small moons should be denser than the primordial material, and
that the mean density of Orcus should be close to the primordial value.Comment: 8 pages, 2 figures. Accepted for publication in MNRA
The Peculiar Photometric Properties of 2010 WG9: A Slowly-Rotating Trans-Neptunian Object from the Oort Cloud
We present long-term BVRI observations of 2010 WG9, an ~100-km diameter
trans-Neptunian object (TNO) with an extremely high inclination of 70 deg
discovered by the La Silla - QUEST southern sky survey. Most of the
observations were obtained with ANDICAM on the SMARTS 1.3m at Cerro Tololo,
Chile from Dec 2010 to Nov 2012. Additional observations were made with EFOSC2
on the 3.5-m NTT telescope of the European Southern Observatory at La Silla,
Chile in Feb 2011. The observations reveal a sinusoidal light curve with
amplitude 0.14 mag and period 5.4955 +/- 0.0025d, which is likely half the true
rotation period. Such long rotation periods have previously been observed only
for tidally-evolved binary TNOs, suggesting that 2010 WG9 may be such a system.
We predict a nominal separation of at least 790 km, resolvable with HST and
ground-based systems. We measure B-R = 1.318 +/- 0.029 and V-R = 0.520 +/-
0.018, consistent with the colors of modestly red Centaurs and Damocloids. At
I-band wavelengths, we observe an unusually large variation of color with
rotational phase, with R-I ranging from 0.394 +/- 0.025 to 0.571 +/- 0.044. We
also measure an absolute R-band absolute magnitude of 7.93 +/- 0.05 and solar
phase coefficient 0.049 +/- 0.019 mag/deg.Comment: 17 pages, 5 figure
TRIPPy: Trailed Image Photometry in Python
Photometry of moving sources typically suffers from reduced signal-to-noise
(SNR) or flux measurements biased to incorrect low values through the use of
circular apertures. To address this issue we present the software package,
TRIPPy: TRailed Image Photometry in Python. TRIPPy introduces the pill
aperture, which is the natural extension of the circular aperture appropriate
for linearly trailed sources. The pill shape is a rectangle with two
semicircular end-caps, and is described by three parameters, the trail length
and angle, and the radius. The TRIPPy software package also includes a new
technique to generate accurate model point-spread functions (PSF) and trailed
point-spread functions (TSF) from stationary background sources in sidereally
tracked images. The TSF is merely the convolution of the model PSF, which
consists of a moffat profile, and super sampled lookup table. From the TSF,
accurate pill aperture corrections can be estimated as a function of pill
radius with a accuracy of 10 millimags for highly trailed sources. Analogous to
the use of small circular apertures and associated aperture corrections, small
radius pill apertures can be used to preserve signal-to-noise of low flux
sources, with appropriate aperture correction applied to provide an accurate,
unbiased flux measurement at all SNR.Comment: 8 Figures, 11 Pages, Accepted to the Astronomical Journa
Properties of the Distant Kuiper Belt: Results from the Palomar Distant Solar System Survey
We present the results of a wide-field survey using the 1.2-m Samuel Oschin
Telescope at Palomar Observatory. This survey was designed to find the most
distant members of the Kuiper belt and beyond. We searched ~12,000 deg2 down to
a mean limiting magnitude of 21.3 in R. A total number of 52 KBOs and Centaurs
have been detected, 25 of which were discovered in this survey. Except for the
re-detection of Sedna, no additional Sedna-like bodies with perihelia greater
than 45 AU were detected despite sensitivity out to distances of 1000 AU. We
discuss the implications for a distant Sedna- like population beyond the Kuiper
belt, focusing on the constraints we can place on the embedded stellar cluster
environment the early Sun may be have been born in, where the location and
distribution of Sedna-like orbits sculpted by multiple stellar encounters is
indicative of the birth cluster size. We also report our observed latitude
distribution and implications for the size of the plutino population.Comment: 40 pages, 12 figures, 3 tables Accepted by Ap
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