91 research outputs found
The Collisional Evolution of Debris Disks
We explore the collisional decay of disk mass and infrared emission in debris
disks. With models, we show that the rate of the decay varies throughout the
evolution of the disks, increasing its rate up to a certain point, which is
followed by a leveling off to a slower value. The total disk mass falls off ~
t^-0.35 at its fastest point (where t is time) for our reference model, while
the dust mass and its proxy -- the infrared excess emission -- fades
significantly faster (~ t^-0.8). These later level off to a decay rate of
M_tot(t) ~ t^-0.08 and M_dust(t) or L_ir(t) ~ t^-0.6. This is slower than the ~
t^-1 decay given for all three system parameters by traditional analytic
models.
We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100
micron observations. Assuming a log-normal distribution of initial disk masses,
we generate model population decay curves for the fraction of debris disk
harboring stars observed at 24 micron and also model the distribution of
measured excesses at the far-IR wavelengths (70-100 micron) at certain age
regimes. We show general agreement at 24 micron between the decay of our
numerical collisional population synthesis model and observations up to a Gyr.
We associate offsets above a Gyr to stochastic events in a few select systems.
We cannot fit the decay in the far infrared convincingly with grain strength
properties appropriate for silicates, but those of water ice give fits more
consistent with the observations.Comment: 32 pages, 16 figures, emulateapj format, Accepted for publication in
Ap
On the mass-coupling relation of multi-scale quantum integrable models
We determine exactly the mass-coupling relation for the simplest multi-scale
quantum integrable model, the homogenous sine-Gordon model with two independent
mass-scales. We first reformulate its perturbed coset CFT description in terms
of the perturbation of a projected product of minimal models. This
representation enables us to identify conserved tensor currents on the UV side.
These UV operators are then mapped via form factor perturbation theory to
operators on the IR side, which are characterized by their form factors. The
relation between the UV and IR operators is given in terms of the sought-for
mass-coupling relation. By generalizing the sum rule Ward identity we
are able to derive differential equations for the mass-coupling relation, which
we solve in terms of hypergeometric functions. We check these results against
the data obtained by numerically solving the thermodynamic Bethe Ansatz
equations, and find a complete agreement.Comment: 55 pages, 9 figures, reference added, minor changes, published
versio
Search for signatures of dust in the Pluto-Charon system using Herschel/PACS observations
In this letter we explore the environment of Pluto and Charon in the far
infrared with the main aim to identify the signs of any possible dust ring,
should it exist in the system. Our study is based on observations performed at
70 um with the PACS instrument onboard the Herschel Space Observatory at 9
epochs between March 14 and 19, 2012. The far-infrared images of the
Pluto-Charon system are compared to those of the point spread function (PSF)
reference quasar 3C454.3. The deviation between the observed Pluto-Charon and
reference PSFs are less then 1 sigma indicating that clear evidence for an
extended dust ring around the system was not found. Our method is capable of
detecting a hypothetical ring with a total flux of ~3.3 mJy at a distance of
~153 000 km (~8.2 Pluto-Charon distances) from the system barycentre. We place
upper limits on the total disk mass and on the column density in a reasonable
disk configuration and analyse the hazard during the flyby of NASAs New
Horizons in July 2015. This realistic model configuration predicts a column
density of 8.7x10^(-10) gcm^(-2) along the path of the probe and an impactor
mass of 8.7x10^(-5) g.Comment: 10 pages, 4 figures, 2 table
Herschel-PACS photometry of faint stars
Our aims are to determine flux densities and their photometric accuracy for a
set of seventeen stars that range in flux from intermediately bright (<2.5 Jy)
to faint (>5 mJy) in the far-infrared (FIR). We also aim to derive
signal-to-noise dependence with flux and time, and compare the results with
predictions from the Herschel exposure-time calculation tool. The PACS faint
star sample has allowed a comprehensive sensitivity assessment of the PACS
photometer. Accurate photometry allows us to establish a set of five FIR
primary standard candidates, namely alpha Ari, epsilon Lep, omega,Cap, HD41047
and 42Dra, which are 2 -- 20 times fainter than the faintest PACS fiducial
standard (gamma Dra) with absolute accuracy of <6%. For three of these primary
standard candidates, essential stellar parameters are known, meaning that a
dedicated flux model code may be run.Comment: 42 pages, 12 figure
Terrestrial Zone Debris Disk Candidates in h and chi Persei
We analyze 8 sources with strong mid-infrared excesses in the 13 Myr-old
double cluster h and chi Persei. New optical spectra and broadband SEDs (0.36-8
mu_m) are consistent with cluster membership. We show that material with T ~
300-400 K and Ld/Lstar ~ 10^-4-10^-3 produces the excesses in these sources.
Optically-thick blackbody disk models - including those with large inner holes
- do not match the observed SEDs. The SEDs of optically-thin debris disks
produced from terrestrial planet formation calculations match the observations
well. Thus, some h and chi Persei stars may have debris from terrestrial zone
planet formation.Comment: 5 pages, 3 figures, Matched to published version, Astrophysical
Journal Letters, in press: 2007, ApJL, 663, 10
A Deep Spitzer Survey of Circumstellar Disks in the Young Double Cluster, h and chi Persei
We analyze very deep IRAC and MIPS photometry of 12,500 members of the
14 Myr old Double Cluster, h and Persei, building upon on our earlier,
shallower Spitzer studies (Currie et al. 2007a, 2008a). Numerous likely members
show infrared (IR) excesses at 8 {\mu}m and 24 m indicative of
circumstellar dust. The frequency of stars with 8 m excess is at least 2%
for our entire sample, slightly lower (higher) for B/A stars (later type,
lower-mass stars). Optical spectroscopy also identifies gas in about 2% of
systems but with no clear trend between the presence of dust and gas. Spectral
energy distribution (SED) modeling of 18 sources with detections at optical
wavelengths through MIPS 24 reveals a diverse set of disk evolutionary
states, including a high fraction of transitional disks, although similar data
for all disk-bearing members would provide better constraints. We combine our
results with those for other young clusters to study the global evolution of
dust/gas disks. For nominal cluster ages, the e-folding times () for
the frequency of warm dust and gas are 2.75 Myr and 1.75 Myr respectively.
Assuming a revised set of ages for some clusters (e.g. Bell et al. 2013), these
timescales increase to 5.75 and 3.75 Myr, respectively, implying a
significantly longer typical protoplanetary disk lifetime. The transitional
disk duration, averaged over multiple evolutionary pathways, is 1 Myr.
Finally, 24 m excess frequencies for 4-6 M stars appear lower
than for 1-2.5 M stars in other 10-30 Myr old clusters.Comment: 35 pages, 6 tables, 21 figures; Accepted for publication in The
Astrophysical Journa
Running coupling and non-perturbative corrections for O free energy and for disk capacitor
We reconsider the complete solution of the linear TBA equation describing the
energy density of finite density states in the nonlinear sigma models by
the Wiener-Hopf method. We keep all perturbative and non-perturbative
contributions and introduce a running coupling in terms of which all asymptotic
series appearing in the problem can be represented as pure power series without
logs. We work out the first non-perturbative contribution in the case
and show that (presumably because of the instanton corrections) resurgence
theory fails in this example. Using the relation of the problem to the
coaxial disks capacitor problem we work out the leading non-perturbative terms
for the latter and show that (at least to this order) resurgence theory, in
particular the median resummation prescription, gives the correct answer. We
demonstrate this by comparing the Wiener-Hopf results to the high precision
numerical solution of the original integral equation.Comment: 56 pages, 4 figures, LaTeX. v3: discussion of resurgence clarified, 1
reference adde
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