2,086 research outputs found
Detection of Additional Members of the 2003 EL61 Family via Infrared Spectroscopy
We have acquired near-infrared spectra of Kuiper belt objects 2003 UZ117,
2005 CB79 and 2004 SB60 with NIRC on the Keck I Telescope. These objects are
dynamically close to the core of the 2003 EL61 collisional family and were
suggested to be potential fragments of this collision by Ragozzine and Brown
(2007). We find that the spectra of 2003 UZ117 and 2005 CB79 both show the
characteristic strong water ice absorption features seen exclusively on 2003
EL61, its largest satellite, and the six other known collisional fragments. In
contrast, we find that the near infrared spectrum of 2004 SB60 is essentially
featureless with a fraction of water ice of less than 5%. We discuss the
implications of the discovery of these additional family members for
understanding the formation and evolution of this collisional family in the
outer solar system.Comment: 9 Pages, 2 figure
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&
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: 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&
The effect of orbital evolution on the Haumea (2003 EL61) collisional family
The Haumea family is currently the only identified collisional family in the
Kuiper belt. We numerically simulate the long-term dynamical evolution of the
family to estimate a lower limit of the family's age and to assess how the
population of the family and its dynamical clustering are preserved over Gyr
timescales. We find that the family is not younger than 100 Myr, and its age is
at least 1 Gyr with 95% confidence. We find that for initial velocity
dispersions of 50-400 m/s, approximately 20-45% of the family members are lost
to close encounters with Neptune after 3.5 Gyr of orbital evolution. We apply
these loss rates to two proposed models for the formation of the Haumea family,
a graze-and-merge type collision between two similarly sized, differentiated
KBOs or the collisional disruption of a satellite orbiting Haumea. For the
graze-and-merge collision model, we calculate that >85% of the expected mass in
surviving family members within 150 m/s of the collision has been identified,
but that one to two times the mass of the known family members remains to be
identified at larger velocities. For the satellite-break-up model, we estimate
that the currently identified family members account for ~50% of the expected
mass of the family. Taking observational incompleteness into account, the
observed number of Haumea family members is consistent with either formation
scenario at the 1 sigma level, however both models predict more objects at
larger relative velocities (>150 m/s) than have been identified.Comment: 25 pages, accepted to Icaru
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