117 research outputs found
Disk Radii and Grain Sizes in Herschel-Resolved Debris Disks
(Abridged) The radii of debris disks and the sizes of their dust grains are
tracers of the formation mechanisms and physical processes operating in these
systems. We use a sample of 34 debris disks spatially resolved in various
Herschel programs to constrain them. While we modeled disks with both warm and
cold components, we focus our analysis only on the cold outer disks, i.e.
Kuiper-belt analogs. The disk radii derived from the resolved images reveal a
large dispersion, but no significant trend with the stellar luminosity, which
argues against ice lines as a dominant player in setting the debris disk sizes.
Fixing the disk radii to those inferred from the resolved images, we model the
spectral energy distributions to determine the dust temperatures and the grain
size distributions. While the dust temperature systematically increases towards
earlier spectral types, its ratio to the blackbody temperature at the disk
radius decreases with the stellar luminosity. This is explained by an increase
of typical grain sizes towards more luminous stars. The sizes are compared to
the radiation pressure blowout limit that is proportional to
the stellar luminosity-to-mass ratio and thus also increases towards earlier
spectral classes. The grain sizes in the disks of G- to A-stars are inferred to
be several times at all stellar luminosities, in agreement with
collisional models of debris disks. The sizes, measured in the units of
, appear to decrease with the luminosity, which may be
suggestive of the disk's stirring level increasing towards earlier-type stars.Comment: accepted for publication in ApJ, 22 pages, 7 figure
Quasi-doubly periodic solutions to a generalized Lame equation
We consider the algebraic form of a generalized Lame equation with five free
parameters. By introducing a generalization of Jacobi's elliptic functions we
transform this equation to a 1-dim time-independent Schroedinger equation with
(quasi-doubly) periodic potential. We show that only for a finite set of
integral values for the five parameters quasi-doubly periodic eigenfunctions
expressible in terms of generalized Jacobi functions exist. For this purpose we
also establish a relation to the generalized Ince equation.Comment: 15 pages,1 table, accepted for publication in Journal of Physics
Quantum mass correction for the twisted kink
We present an analytic result for the 1-loop quantum mass correction in
semiclassical quantization for the twisted \phi^4 kink on S^1 without explicit
knowledge of the fluctuation spectrum. For this purpose we use the contour
integral representation of the spectral zeta function. By solving the Bethe
ansatz equations for the n=2 Lame equation we obtain an analytic expression for
the corresponding spectral discriminant. We discuss the renormalization issues
of this model. An energetically preferred size for the compact space is finally
obtained.Comment: 18 pages, 2 figures;v2:references and discussion added, typos
correcte
The Big Sibling of AU Mic: A Cold Dust-rich Debris Disk around CP-72 2713 in the β Pic Moving Group
Analyzing Spitzer and Herschel archival measurements we identified a hitherto
unknown debris disk around the young K7/M0 star CP-72 2713. The system belongs
to the 24Myr old Pic moving group. Our new 1.33mm continuum
observation, obtained with the ALMA 7-m array, revealed an extended dust disk
with a peak radius of 140au, probably tracing the location of the planetesimal
belt in the system. The disk is outstandingly large compared to known spatially
resolved debris disks and also to protoplanetary disks around stars of
comparable masses. The dynamical excitation of the belt at this radius is found
to be reconcilable with planetary stirring, while self-stirring by large
planetesimals embedded in the belt can work only if these bodies form very
rapidly, e.g. via pebble concentration. By analyzing the spectral energy
distribution we derived a characteristic dust temperature of 43K and a
fractional luminosity of 1.110. The latter value is prominently
high, we know only four other similarly dust-rich Kuiper-belt analogs within
40pc of the Sun
Stirring in massive, young debris discs from spatially resolved Herschel images
A significant fraction of main-sequence stars are encircled by dusty debris
discs, where the short-lived dust particles are replenished through collisions
between planetesimals. Most destructive collisions occur when the orbits of
smaller bodies are dynamically stirred up, either by the gravitational effect
of locally formed Pluto-sized planetesimals (self-stirring scenario), or via
secular perturbation caused by an inner giant planet (planetary stirring). The
relative importance of these scenarios in debris systems is unknown. Here we
present new Herschel Space Observatory imagery of 11 discs selected from the
most massive and extended known debris systems. All discs were found to be
extended at far-infrared wavelengths, five of them being resolved for the first
time. We evaluated the feasibility of the self-stirring scenario by comparing
the measured disc sizes with the predictions of the model calculated for the
ages of our targets. We concluded that the self-stirring explanation works for
seven discs. However, in four cases, the predicted pace of outward propagation
of the stirring front, assuming reasonable initial disc masses, was far too low
to explain the radial extent of the cold dust. Therefore, for HD 9672, HD
16743, HD 21997, and HD 95086, another explanation is needed. We performed a
similar analysis for {\ss} Pic and HR 8799, reaching the same conclusion. We
argue that planetary stirring is a promising possibility to explain the disk
properties in these systems. In HR 8799 and HD 95086 we may already know the
potential perturber, since their known outer giant planets could be responsible
for the stirring process. Our study demonstrates that among the largest and
most massive debris discs self-stirring may not be the only active scenario,
and potentially planetary stirring is responsible for destructive collisions
and debris dust production in a number of systems.Comment: Accepted for publication in MNRAS, 22 pages, 7 figures, 6 tables
(abstract abridged due to arXiv requirements
YETI observations of the young transiting planet candidate CVSO 30 b
CVSO 30 is a unique young low-mass system, because, for the first time, a
close-in transiting and a wide directly imaged planet candidates are found
around a common host star. The inner companion, CVSO 30 b, is the first
possible young transiting planet orbiting a previously known weak-lined T-Tauri
star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI)
located in Asia, Europe and South America we monitored CVSO 30 over three years
in a total of 144 nights and detected 33 fading events. In two more seasons we
carried out follow-up observations with three telescopes. We can confirm that
there is a change in the shape of the fading event between different
observations and that the fading event even disappears and reappears. A total
of 38 fading event light curves were simultaneously modelled. We derived the
planetary, stellar, and geometrical properties of the system and found them
slightly smaller but in agreement with the values from the discovery paper. The
period of the fading event was found to be 1.36 s shorter and 100 times more
precise than the previous published value. If CVSO 30 b would be a giant planet
on a precessing orbit, which we cannot confirm, yet, the precession period may
be shorter than previously thought. But if confirmed as a planet it would be
the youngest transiting planet ever detected and will provide important
constraints on planet formation and migration time-scales.Comment: 14 pages (20 with appendix), 7 figures (16 with appendix), 6 tables
(7 with appendix
Abundant sub-micron grains revealed in newly discovered extreme debris discs
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record DATA AVAILABILITY:
The VISIR data used in this paper are publicly available at ESO
Archive (http://archive.eso.org/eso/eso_archive_main.
html).Extreme debris discs (EDDs) are bright and warm circumstellar dusty structures around main sequence stars. They may represent the outcome of giant collisions occuring in the terrestrial region between large planetesimals or planetary bodies, and thus provide a rare opportunity to peer into the aftermaths of these events. Here, we report on results of a mini-survey we conducted with the aim to increase the number of known EDDs, investigate the presence of solid-state features around 10 μm in eight EDDs, and classify them into the silica or silicate dominated groups. We identify four new EDDs and derive their fundamental properties. For these, and for four other previously known discs, we study the spectral energy distribution around 10 μm by means of VLT/VISIR photometryin three narrow-band filters and conclude that all eight objects likely exhibit solid-state emission features from sub-micron grains. We find that four discs probably belong to the silicate dominated subgroup. Considering the age distribution of the entire EDD sample, we find that their incidence begins to decrease only after 300 Myr, suggesting that the earlier common picture that these objects are related to the formation of rocky planets may not be exclusive, and that other processes may be involved for older objects (≳100 Myr). Because most of the older EDD systems have wide, eccentric companions, we suggest that binarity may play a role in triggering late giant collisions.Hungarian National Research, Development and Innovation OfficeHungarian National Research, Development and Innovation OfficeBolyai+Royal SocietyNASANASAHungarian Academy of Science
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