91 research outputs found
Thermal Infrared and Optical Photometry of Asteroidal Comet C/2002 CE
C/2002 CE is an object in a retrograde elliptical orbit with Tisserand
parameter indicating a likely origin in the Oort Cloud. It appears to
be a rather inactive comet since no coma and only a very weak tail was detected
during the past perihelion passage. We present multi-color optical photometry,
lightcurve and thermal mid-IR observations of the asteroidal comet.
\textcolor{blue}{ With the photometric analysis in , the surface color is
found to be redder than asteroids, corresponding to cometary nuclei and
TNOs/Centaurs. The time-resolved differential photometry supports a rotation
period of 8.190.05 h. The effective diameter and the geometric albedo are
17.90.9 km and 0.030.01, respectively, indicating a very dark
reflectance of the surface. The dark and redder surface color of C/2002
CE may be attribute to devolatilized material by surface aging suffered
from the irradiation by cosmic rays or from impact by dust particles in the
Oort Cloud. Alternatively, C/2002 CE was formed of very dark refractory
material originally like a rocky planetesimal. In both cases, this object lacks
ices (on the surface at least). The dynamical and known physical
characteristics of C/2002 CE are best compatible with those of the
Damocloids population in the Solar System, that appear to be exhaust cometary
nucleus in Halley-type orbits. The study of physical properties of rocky Oort
cloud objects may give us a key for the formation of the Oort cloud and the
solar system.Comment: 9 pages, 4 figures accepted to Icaru
Significantly high polarization degree of the very low-albedo asteroid (152679) 1998 KU
We present a unique and significant polarimetric result regarding the
near-Earth asteroid (152679) 1998 KU , which has a very low
geometric albedo. From our observations, we find that the linear polarization
degrees of 1998 KU are 44.6 0.5\% in the R band
and 44.0 0.6\% in the V band at a solar phase angle of 81.0\degr. These
values are the highest of any known airless body in the solar system (i.e.,
high-polarization comets, asteroids, and planetary satellites) at similar phase
angles. This polarimetric observation is not only the first for primitive
asteroids at large phase angles, but also for low-albedo (< 0.1) airless
bodies.
Based on spectroscopic similarities and polarimetric measurements of
materials that have been sorted by size in previous studies, we conjecture that
1998 KU has a highly microporous regolith structure comprising
nano-sized carbon grains on the surface.Comment: 9 pages, 5 figures, and 3 tables, accepted for publication in A&
The Millimeter Sky Transparency Imager (MiSTI)
The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave
scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is
installed at Atacama, Chile, and it measures emission from atmospheric water
vapor and its fluctuations to estimate atmospheric absorption in the millimeter
to submillimeter. MiSTI observes the water vapor distribution at a spatial
resolution of 0.5 deg, and it is sensitive enough to detect an excess path
length of <~ 0.05 mm for an integration time of 1 s. By comparing the MiSTI
measurements with those by a 220 GHz tipper, we validate that the 183 GHz
measurements of MiSTI are correct, down to the level of any residual systematic
errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time
(every 1 hr) monitoring of the all-sky opacity distribution and atmospheric
transmission curves in the (sub)millimeter through the internet, allowing to
know the (sub)millimeter sky conditions at Atacama.Comment: 12 pages, 1 table, 10 figures, accepted for publication in PAS
Photometry and Polarimetry of 2010 XC: Observational Confirmation of E-type Near-Earth Asteroid Pair
Asteroid systems such as binaries and pairs are indicative of physical
properties and dynamical histories of the Small Solar System Bodies. Although
numerous observational and theoretical studies have been carried out, the
formation mechanism of asteroid pairs is still unclear, especially for
near-Earth asteroid (NEA) pairs. We conducted a series of optical photometric
and polarimetric observations of a small NEA 2010 XC in 2022 December to
investigate its surface properties. The rotation period of 2010 XC is
possibly a few to several dozen hours and color indices of 2010 XC are
derived as , , and in
the Pan-STARRS system. The linear polarization degrees of 2010 XC are a
few percent at the phase angle range of 58 to 114. We found
that 2010 XC is a rare E-type NEA on the basis of its photometric and
polarimetric properties. Taking the similarity of not only physical properties
but also dynamical integrals and the rarity of E-type NEAs into account, we
suppose that 2010 XC and 1998 WT are of common origin (i.e.,
asteroid pair). These two NEAs are the sixth NEA pair and first E-type NEA pair
ever confirmed, possibly formed by rotational fission. We conjecture that the
parent body of 2010 XC and 1998 WT was transported from the
main-belt through the resonance or Hungaria region.Comment: Resubmitted to AAS Journals. Any comments are welcom
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