153 research outputs found
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
The Orbit, Mass, and Albedo of Transneptunian Binary 1999 RZ253
We have observed 1999 RZ253 with the Hubble Space Telescope at seven separate
epochs and have fit an orbit to the observed relative positions of this binary.
Two orbital solutions have been identified that differ primarily in the
inclination of the orbit plane. The best fit corresponds to an orbital period,
P=46.263 +0.006/-0.074 days, semimajor axis a=4,660 +/-170 km and orbital
eccentricity e=0.460 +/-0.013 corresponding to a system mass m=3.7 +/-0.4
x10^18 kg. For a density of rho = 1000 kg m^-3 the albedo at 477 nm is p = 0.12
+/-0.01, significantly higher than has been commonly assumed for objects in the
Kuiper Belt. Multicolor, multiepoch photometry shows this pair to have colors
typical for the Kuiper belt with a spectral gradient of 0.35 per 100 nm in the
range between 475 and 775 nm. Photometric variations at the four epochs we
observed were as large as 12 +/-3% but the sampling is insufficient to confirm
the existence of a lightcurve
Neptune Trojans and Plutinos: colors, sizes, dynamics, and their possible collisions
Neptune Trojans and Plutinos are two subpopulations of trans-Neptunian
objects located in the 1:1 and the 3:2 mean motion resonances with Neptune,
respectively, and therefore protected from close encounters with the planet.
However, the orbits of these two kinds of objects may cross very often,
allowing a higher collisional rate between them than with other kinds of
trans-Neptunian objects, and a consequent size distribution modification of the
two subpopulations.
Observational colors and absolute magnitudes of Neptune Trojans and Plutinos
show that i) there are no intrinsically bright (large) Plutinos at small
inclinations, ii) there is an apparent excess of blue and intrinsically faint
(small) Plutinos, and iii) Neptune Trojans possess the same blue colors as
Plutinos within the same (estimated) size range do.
For the present subpopulations we analyzed the most favorable conditions for
close encounters/collisions and address any link there could be between those
encounters and the sizes and/or colors of Plutinos and Neptune Trojans. We also
performed a simultaneous numerical simulation of the outer Solar System over 1
Gyr for all these bodies in order to estimate their collisional rate.
We conclude that orbital overlap between Neptune Trojans and Plutinos is
favored for Plutinos with large libration amplitudes, high eccentricities, and
small inclinations. Additionally, with the assumption that the collisions can
be disruptive creating smaller objects not necessarily with similar colors, the
present high concentration of small Plutinos with small inclinations can thus
be a consequence of a collisional interaction with Neptune Trojans and such
hypothesis should be further analyzed.Comment: 15 pages, 9 figures, 6 tables, accepted for publication in A&
Characterisation of candidate members of (136108) Haumea's family
Ragozzine & Brown [2007] presented a list of candidate members of the first
collisional family to be found among the trans-Neptunian Objects (TNOs), the
one associated with (136108) Haumea (2003 EL61). We aim to identify which of
the candidate members of the Haumea collisional family are true members, by
searching for water ice on their surfaces. We also attempt to test the theory
that the family members are made of almost pure water ice by using optical
light-curves to constrain their densities. We use optical and near-infrared
photometry to identify water ice, in particular using the (J - H_S) colour as a
sensitive measure of the absorption feature at 1.6 micron. We use the CH_4
filter of the new Hawk-I instrument at the VLT as a short H-band (H_S) for this
as it is more sensitive to the water ice feature than the usual H filter. We
report colours for 22 candidate family members, including NIR colours for 15.
We confirm that 2003 SQ317 and 2005 CB79 are family members, bringing the total
number of confirmed family members to 10. We reject 8 candidates as having no
water ice absorption based on our Hawk-I measurements, and 5 more based on
their optical colours. The combination of the large proportion of rejected
candidates and time lost to weather prevent us from putting strong constraints
on the density of the family members based on the light-curves obtained so far;
we can still say that none of the family members (except Haumea) require a
large density to explain their light-curve.Comment: 9 pages, 5 figures, accepted for publication in A&
"TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations
The classical Kuiper belt contains objects both from a low-inclination,
presumably primordial, distribution and from a high-inclination dynamically
excited population. Based on a sample of classical TNOs with observations at
thermal wavelengths we determine radiometric sizes, geometric albedos and
thermal beaming factors as well as study sample properties of dynamically hot
and cold classicals. Observations near the thermal peak of TNOs using infra-red
space telescopes are combined with optical magnitudes using the radiometric
technique with near-Earth asteroid thermal model (NEATM). We have determined
three-band flux densities from Herschel/PACS observations at 70.0, 100.0 and
160.0 m and Spitzer/MIPS at 23.68 and 71.42 m when available. We have
analysed 18 classical TNOs with previously unpublished data and re-analysed
previously published targets with updated data reduction to determine their
sizes and geometric albedos as well as beaming factors when data quality
allows. We have combined these samples with classical TNOs with radiometric
results in the literature for the analysis of sample properties of a total of
44 objects. We find a median geometric albedo for cold classical TNOs of 0.14
and for dynamically hot classical TNOs, excluding the Haumea family and dwarf
planets, 0.085. We have determined the bulk densities of Borasisi-Pabu (2.1
g/cm^3), Varda-Ilmare (1.25 g/cm^3) and 2001 QC298 (1.14 g/cm^3) as well as
updated previous density estimates of four targets. We have determined the
slope parameter of the debiased cumulative size distribution of dynamically hot
classical TNOs as q=2.3 +- 0.1 in the diameter range 100<D<500 km. For
dynamically cold classical TNOs we determine q=5.1 +- 1.1 in the diameter range
160<D<280 km as the cold classical TNOs have a smaller maximum size.Comment: 22 pages, 7 figures Accepted to be published in Astronomy and
Astrophysic
Col-OSSOS: The Colours of the Outer Solar System Origins Survey
The Colours of the Outer Solar System Origins Survey (Col-OSSOS) is acquiring
near-simultaneous , , and photometry of unprecedented precision with
the Gemini North Telescope, targeting nearly a hundred trans-Neptunian objects
(TNOs) brighter than mag discovered in the Outer Solar System
Origins Survey. Combining the optical and near-infrared photometry with the
well-characterized detection efficiency of the Col-OSSOS target sample will
provide the first flux-limited compositional dynamical map of the outer Solar
System. In this paper, we describe our observing strategy and detail the data
reduction processes we employ, including techniques to mitigate the impact of
rotational variability. We present optical and near-infrared colors for 35
TNOs. We find two taxonomic groups for the dynamically excited TNOs, the
neutral and red classes, which divide at . Based on simple
albedo and orbital distribution assumptions, we find that the neutral class
outnumbers the red class, with a ratio of 4:1 and potentially as high as 11:1.
Including in our analysis constraints from the cold classical objects, which
are known to exhibit unique albedos and colors, we find that within our
measurement uncertainty, our observations are consistent with the primordial
Solar System protoplanetesimal disk being neutral-class-dominated, with two
major compositional divisions in color space.Comment: Accepted to ApJS; on-line supplemental files will be available with
the AJS published version of the pape
"TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects
Trans-Neptunian objects (TNO) represent the leftovers of the formation of the
Solar System. Their physical properties provide constraints to the models of
formation and evolution of the various dynamical classes of objects in the
outer Solar System. Based on a sample of 19 classical TNOs we determine
radiometric sizes, geometric albedos and beaming parameters. Our sample is
composed of both dynamically hot and cold classicals. We study the correlations
of diameter and albedo of these two subsamples with each other and with orbital
parameters, spectral slopes and colors. We have done three-band photometric
observations with Herschel/PACS and we use a consistent method for data
reduction and aperture photometry of this sample to obtain monochromatic flux
densities at 70.0, 100.0 and 160.0 \mu m. Additionally, we use Spitzer/MIPS
flux densities at 23.68 and 71.42 \mu m when available, and we present new
Spitzer flux densities of eight targets. We derive diameters and albedos with
the near-Earth asteroid thermal model (NEATM). As auxiliary data we use
reexamined absolute visual magnitudes from the literature and data bases, part
of which have been obtained by ground based programs in support of our Herschel
key program. We have determined for the first time radiometric sizes and
albedos of eight classical TNOs, and refined previous size and albedo estimates
or limits of 11 other classicals. The new size estimates of 2002 MS4 and 120347
Salacia indicate that they are among the 10 largest TNOs known. Our new results
confirm the recent findings that there are very diverse albedos among the
classical TNOs and that cold classicals possess a high average albedo (0.17 +/-
0.04). Diameters of classical TNOs strongly correlate with orbital inclination
in our sample. We also determine the bulk densities of six binary TNOs.Comment: 21 pages, 9 figures, accepted for publication in Astronomy and
Astrophysic
Characterisation of candidate members of (136108) Haumea's family: II. Follow-up observations
From a dynamical analysis of the orbital elements of transneptunian objects
(TNOs), Ragozzine & Brown reported a list of candidate members of the first
collisional family found among this population, associated with (136108) Haumea
(a.k.a. 2003 EL61). We aim to distinguish the true members of the Haumea
collisional family from interlopers. We search for water ice on their surfaces,
which is a common characteristic of the known family members. The properties of
the confirmed family are used to constrain the formation mechanism of Haumea,
its satellites, and its family. Optical and near-infrared photometry is used to
identify water ice. We use in particular the CH4 filter of the Hawk-I
instrument at the European Southern Observatory Very Large Telescope as a short
H-band (Hs), the (J-Hs) colour being a sensitive measure of the water ice
absorption band at 1.6 {\mu}m. Continuing our previous study headed by
Snodgrass, we report colours for 8 candidate family members, including
near-infrared colours for 5. We confirm one object as a genuine member of the
collisional family (2003 UZ117), and reject 5 others. The lack of infrared data
for the two remaining objects prevent any conclusion from being drawn. The
total number of rejected members is therefore 17. The 11 confirmed members
represent only a third of the 36 candidates. The origin of Haumea's family is
likely to be related to an impact event. However, a scenario explaining all the
peculiarities of Haumea itself and its family remains elusive.Comment: 8 pages, 4 figures, accepted for publication in A&
Stellar spectral-type (mass) dependence of the dearth of close-in planets around fast-rotating stars. Architecture of Kepler confirmed single-exoplanet systems compared to star-planet evolution models
In 2013 a dearth of close-in planets around fast-rotating host stars was
found using statistical tests on Kepler data. The addition of more Kepler and
Transiting Exoplanet Survey Satellite (TESS) systems in 2022 filled this region
of the diagram of stellar rotation period (Prot) versus the planet orbital
period (Porb). We revisited the Prot extraction of Kepler planet-host stars, we
classify the stars by their spectral type, and we studied their Prot-Porb
relations. We only used confirmed exoplanet systems to minimize biases. In
order to learn about the physical processes at work, we used the star-planet
evolution code ESPEM (French acronym for Evolution of Planetary Systems and
Magnetism) to compute a realistic population synthesis of exoplanet systems and
compared them with observations. Because ESPEM works with a single planet
orbiting around a single main-sequence star, we limit our study to this
population of Kepler observed systems filtering out binaries, evolved stars,
and multi-planets. We find in both, observations and simulations, the existence
of a dearth in close-in planets orbiting around fast-rotating stars, with a
dependence on the stellar spectral type (F, G, and K), which is a proxy of the
mass in our sample of stars. There is a change in the edge of the dearth as a
function of the spectral type (and mass). It moves towards shorter Prot as
temperature (and mass) increases, making the dearth look smaller. Realistic
formation hypotheses included in the model and the proper treatment of tidal
and magnetic migration are enough to qualitatively explain the dearth of hot
planets around fast-rotating stars and the uncovered trend with spectral type.Comment: Accepted in A&A. 13 pages, 8 figure
Visible spectroscopy of the new ESO Large Program on trans-Neptunian objects and Centaurs: final results
A second large programme (LP) for the physical studies of TNOs and Centaurs,
started at ESO Cerro Paranal on October 2006 to obtain high-quality data, has
recently been concluded. In this paper we present the spectra of these pristine
bodies obtained in the visible range during the last two semesters of the LP.
We investigate the spectral behaviour of the TNOs and Centaurs observed, and we
analyse the spectral slopes distribution of the full data set coming from this
LP and from the literature. We computed the spectral slope for each observed
object, and searched for possible weak absorption features. A statistical
analysis was performed on a total sample of 73 TNOs and Centaurs to look for
possible correlations between dynamical classes, orbital parameters, and
spectral gradient. We obtained new spectra for 28 bodies, 15 of which were
observed for the first time. All the new presented spectra are featureless,
including 2003 AZ84, for which a faint and broad absorption band possibly
attributed to hydrated silicates on its surface has been reported. The data
confirm a wide variety of spectral behaviours, with neutral--grey to very red
gradients. An analysis of the spectral slopes available from this LP and in the
literature for a total sample of 73 Centaurs and TNOs shows that there is a
lack of very red objects in the classical population. We present the results of
the statistical analysis of the spectral slope distribution versus orbital
parameters. In particular, we confirm a strong anticorrelation between spectral
slope and orbital inclination for the classical population. A strong
correlation is also found between the spectral slope and orbital eccentricity
for resonant TNOs, with objects having higher spectral slope values with
increasing eccentricity.Comment: 11 pages, 9 figure
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