683 research outputs found
The Survival Rate of Ejected Terrestrial Planets with Moons
During planet formation, a gas giant will interact with smaller protoplanets
that stray within its sphere of gravitational influence. We investigate the
outcome of interactions between gas giants and terrestrial-sized protoplanets
with lunar-sized companions. An interaction between a giant planet and a
protoplanet binary may have one of several consequences, including the delivery
of volatiles to the inner system, the capture of retrograde moons by the giant
planet, and the ejection of one or both of the protoplanets. We show that an
interesting fraction of terrestrial-sized planets with lunar sized companions
will likely be ejected into interstellar space with the companion bound to the
planet. The companion provides an additional source of heating for the planet
from tidal dissipation of orbital and spin angular momentum. This heat flux
typically is larger than the current radiogenic heating of the Earth for up to
the first few hundred million years of evolution. In combination with an
atmosphere of sufficient thickness and composition, the heating can provide the
conditions necesary for liquid water to persist on the surface of the
terrestrial mass planet, making it a potential site for life. We also determine
the possibility for directly detecting such systems through all-sky infrared
surveys or microlensing surveys. Microlensing surveys in particular will
directly measure the frequency of this phenomenon.Comment: 4 pages, 2 figures, Accepted to ApJ
Color Gradients Detected in the HD 15115 Circumstellar Disk
We report HST/NICMOS coronagraphic images of the HD 15115 circumstellar disk
at 1.1\micron. We find a similar morphology to that seen in the visible and at
H band--an edge-on disk that is asymmetric in surface brightness. Several
aspects of the 1.1\micron data are different, highlighting the need for
multi-wavelength images of each circumstellar disk. We find a flattening to the
western surface brightness profile at 1.1\micron interior to 2\arcsec (90 AU)
and a warp in the western half of the disk. We measure the surface brightness
profiles of the two disk lobes and create a measure of the dust scattering
efficiency between 0.55-1.65\micron at 1\arcsec, 2\arcsec, and 3\arcsec. At
2\arcsec the western lobe has a neutral spectrum up to 1.1\micron and a strong
absorption or blue spectrum 1.1\micron, while a blue trend is seen in the
eastern lobe. At 1\arcsec the disk has a red F110W-H color in both lobes.Comment: 4 pages, 4 figures, emulateapj; accepted to ApJ
The WISE InfraRed Excesses around Degenerates (WIRED) Survey
The Wide-field Infrared Survey Explorer (WISE) is a NASA medium class Explorer
mission that performed an all sky survey in four infrared bands. We present an overview of the WISE
InfraRed Excesses around Degenerates (WIRED) Survey, which has the goals of characterizing
white dwarf stars in the WISE bands, confirming objects known to have infrared excess from past
observations, and revealing new examples of white dwarfs with infrared excess that can be attributed
to unresolved companions or debris disks. We obtained preliminary WISE detections (S/N > 2) in
at least one band of 405 white dwarfs from the 9316 unique possible targets in the Sloan Digital
Sky Survey Data Release 4 Catalog of Spectroscopically Identified White Dwarfs (not all potential
targets were available in the sky coverage used here). A companion paper in this volume discusses
specific results from our target detections
The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog
We have compiled photometric data from the Wide-field Infrared Survey
Explorer All Sky Survey and other archival sources for the more than 2200
objects in the original McCook & Sion Catalog of Spectroscopically Identified
White Dwarfs. We applied color-selection criteria to identify 28 targets whose
infrared spectral energy distributions depart from the expectation for the
white dwarf photosphere alone. Seven of these are previously known white dwarfs
with circumstellar dust disks, five are known central stars of planetary
nebulae, and six were excluded for being known binaries or having possible
contamination of their infrared photometry. We fit white dwarf models to the
spectral energy distributions of the remaining ten targets, and find seven new
candidates with infrared excess suggesting the presence of a circumstellar dust
disk. We compare the model dust disk properties for these new candidates with a
comprehensive compilation of previously published parameters for known white
dwarfs with dust disks. It is possible that the current census of white dwarfs
with dust disks that produce an excess detectable at K-band and shorter
wavelengths is close to complete for the entire sample of known WDs to the
detection limits of existing near-IR all-sky surveys. The white dwarf dust disk
candidates now being found using longer wavelength infrared data are drawn from
a previously underrepresented region of parameter space, in which the dust
disks are overall cooler, narrower in radial extent, and/or contain fewer
emitting grains.Comment: accepted for publication in The Astrophysical Journal; 34 pages, 5
figures, 5 tables; added missing reference in Section 2 (p. 7
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