193 research outputs found
Long-term infrared variability of the UX Ori-type star SV Cep
We investigate the long-term optical-infrared variability of SV Cep, and
explain it in the context of an existing UX Ori (UXOR) model. A 25-month
monitoring programme was completed with the Infrared Space Observatory in the
3.3-100 um wavelength range. Following a careful data reduction, the infrared
light curves were correlated with the variations of SV Cep in the V-band. A
remarkable correlation was found between the optical and the far-infrared light
curves. In the mid-infrared regime the amplitude of variations is lower, with a
hint for a weak anti-correlation with the optical changes. In order to
interpret the observations, we modelled the spectral energy distribution of SV
Cep assuming a self-shadowed disc with a puffed-up inner rim, using a
2-dimensional radiative transfer code. We found that modifying the height of
the inner rim, the wavelength-dependence of the long-term optical-infrared
variations is well reproduced, except the mid-infrared domain. The origin of
variation of the rim height might be fluctuation in the accretion rate in the
outer disc. In order to model the mid-infrared behaviour we tested to add an
optically thin envelope to the system, but this model failed to explain the
far-infrared variability. Infrared variability is a powerful tool to
discriminate between models of the circumstellar environment. The proposed
mechanism of variable rim height may not be restricted to UXOR stars, but might
be a general characteristic of intermediate-mass young stars.Comment: 11 pages, 9 figures, accepted for publiction in Monthly Notices of
the Royal Astronomical Societ
Revealing signatures of planets migrating in protoplanetary discs with ALMA multi-wavelength observations
Recent observations show that rings and gaps are ubiquitous in protoplanetary
discs. These features are often interpreted as being due to the presence of
planets; however, the effect of planetary migration on the observed morphology
has not been investigated hitherto. In this work we investigate whether
multiwavelength mm/submm observations can detect signatures of planet
migration, using 2D dusty hydrodynamic simulations to model the structures
generated by migrating planets and synthesising ALMA continuum observations at
0.85 and 3 mm. We identify three possible morphologies for a migrating planet:
a slowly migrating planet is associated with a single ring outside the planet's
orbit, a rapidly migrating planet is associated with a single ring inside the
planet's orbit while a planet migrating at intermediate speed generates one
ring on each side of the planet's orbit. We argue that multiwavelength data can
distinguish multiple rings produced by a migrating planet from other scenarios
for creating multiple rings, such as multiple planets or discs with low
viscosity. The signature of migration is that the outer ring has a lower
spectral index, due to larger dust grains being trapped there. Of the recent
ALMA observations revealing protoplanetary discs with multiple rings and gaps,
we suggest that Elias 24 is the best candidate for a planet migrating in the
intermediate speed regime.Comment: Accepted for publication in MNRA
The twofold debris disk around HD 113766 A - Warm and cold dust as seen with VLTI/Midi and Herschel/Pacs
Warm debris disks are a sub-sample of the large population of debris disks,
and display excess emission in the mid-IR. Around solar-type stars, very few
objects show emission features in mid-IR spectroscopic observations, that are
attributed to small, warm silicate dust grains. The origin of this warm dust
can possibly be explained either by a collision between several bodies or by
transport from an outer belt. We present and analyse new far-IR Herschel/Pacs
observations, supplemented by ground-based data in the mid-IR (VLTI/Midi and
VLT/Visir), for one of these rare systems: the 10-16 Myr old debris disk around
HD 113766 A. We improve an existing model to account for these new
observations, and better constrain the spatial distribution of the dust and its
composition. We underline the limitations of SED modelling and the need for
spatially resolved observations. We find that the system is best described by
an inner disk located within the first AU, well constrained by the Midi data,
and an outer disk located between 9-13 AU. In the inner dust belt, our previous
finding of Fe-rich crystalline olivine grains still holds. We do not observe
time variability of the emission features over at least a 8 years time span, in
a environment subjected to strong radiation pressure. The time stability of the
emission features indicates that {\mu}m-sized dust grains are constantly
replenished from the same reservoir, with a possible depletion of
sub-{\mu}m-sized grains. We suggest that the emission features may arise from
multi-composition aggregates. We discuss possible scenarios concerning the
origin of the warm dust. The compactness of the innermost regions as probed by
Midi, as well as the dust composition, suggest that we are witnessing the
outcomes of (at least) one collision between partially differentiated bodies,
in an environment possibly rendered unstable by terrestrial planetary
formation
The minimum mass of detectable planets in protoplanetary discs and the derivation of planetary masses from high-resolution observations.
We investigate the minimum planet mass that produces observable signatures in infrared scattered light and submillimetre (submm) continuum images and demonstrate how these images can be used to measure planet masses to within a factor of about 2. To this end, we perform multi-fluid gas and dust simulations of discs containing low-mass planets, generating simulated observations at 1.65, 10 and 850 μm. We show that the minimum planet mass that produces a detectable signature is ∼15 M⊕: this value is strongly dependent on disc temperature and changes slightly with wavelength (favouring the submm). We also confirm previous results that there is a minimum planet mass of ∼20 M⊕ that produces a pressure maximum in the disc: only planets above this threshold mass generate a dust trap that can eventually create a hole in the submm dust. Below this mass, planets produce annular enhancements in dust outwards of the planet and a reduction in the vicinity of the planet. These features are in steady state and can be understood in terms of variations in the dust radial velocity, imposed by the perturbed gas pressure radial profile, analogous to a traffic jam. We also show how planet masses can be derived from structure in scattered light and submm images. We emphasize that simulations with dust need to be run over thousands of planetary orbits so as to allow the gas profile to achieve a steady state and caution against the estimation of planet masses using gas-only simulations.We thank an anonymous referee for a careful reading of our manuscript and many useful comments. We thank Leonardo Testi for a stimulating discussion that started this work, Sijme-Jan Paardekooper and Richard Alexander for their constructive criticism, Judith Ngoumou and the Munich Star Formation Coffee for a very lively discussion. This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. This work used the DIRAC Shared Memory Processing system at the University of Cambridge, operated by the COSMOS Project at the Department of Applied Mathematics and Theoretical Physics on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk). This equipment was funded by BIS National E-infrastructure capital grant ST/J005673/1, STFC capital grant ST/H008586/1, and STFC DiRAC Operations grant ST/K00333X/1. DiRAC is part of the National E-Infrastructure.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw69
Adaptable Radiative Transfer Innovations for Submillimeter Telescopes (ARTIST)
Submillimeter observations are a key for answering many of the big questions
in modern-day astrophysics, such as how stars and planets form, how galaxies
evolve, and how material cycles through stars and the interstellar medium. With
the upcoming large submillimeter facilities ALMA and Herschel a new window will
open to study these questions. ARTIST is a project funded in context of the
European ASTRONET program with the aim of developing a next generation model
suite for comprehensive multi-dimensional radiative transfer calculations of
the dust and line emission, as well as their polarization, to help interpret
observations with these groundbreaking facilities.Comment: 4 pages, 1 figure; to appear in "IAU Symposium 270: Computational
Star formation", Eds. J. Alves, B. Elmegreen, J. Girart, V. Trimbl
The Rapid Outbursting Star GM Cep: An EX-or in Tr 37?
We present optical, IR and millimeter observations of the solar-type star
13-277, also known as GM Cep, in the 4 Myr-old cluster Tr 37. GM Cep
experiences rapid magnitude variations of more than 2 mag at optical
wavelengths. We explore the causes of the variability, which seem to be
dominated by strong increases in the accretion, being similar to EX-or
episodes. The star shows high, variable accretion rates (up to ~10
Msun/yr), signs of powerful winds, and it is a very fast rotator (Vsini~43
km/s). Its strong mid-IR excesses reveal a very flared disk and/or a remnant
envelope, most likely out of hydrostatic equilibrium. The 1.3 millimeter fluxes
suggest a relatively massive disk (Mdisk~0.1 Msun). Nevertheless, the
millimeter mass is not enough to sustain increased accretion episodes over
large timescales, unless the mass is underestimated due to significant grain
growth. We finally explore the possibility of GM Cep having a binary companion,
which could trigger disk instabilities producing the enhanced accretion
episodes.Comment: 43 pages, including 10 figures, ApJ in pres
Decreased Openness to Experience Is Associated with Migraine-Type Headaches in Subjects with Lifetime Depression
IntroductionMigraine and depression frequently occur as comorbid conditions, and it has been hypothesized that migraine with and without depression may have a different genetic background. A distinct personality trait constellation has been described in migraineurs. Less attention, however, was paid to personality differences in migraineurs with and without depression which may also shed light on differences in the neurobiological, background. The aim of our study was to investigate big five personality traits, headaches, and lifetime depression (DEP) in a large European general population sample.MethodsRelationship between DEP, Big Five Inventory personality traits, and headaches identified by the ID-Migraine Questionnaire were investigated in 3,026 individuals from Budapest and Manchester with multivariate and logistic regression analyses.ResultsBoth DEP and migraine(ID) showed differences in personality traits. Neuroticism was an independent risk factor for both conditions while a significant interaction effect appeared between the two in the case of openness. Namely, subjects with migraine(ID) and without DEP scored higher on openness compared to those who had depression.ConclusionWhile we confirmed previous results that high neuroticism is a risk factor for both depression and migraine, openness to experience was significantly lower in the co-occurrence of migraine and depression. Our results suggest that increased openness, possibly manifested in optimal or advantageous cognitive processing of pain experience in migraine may decrease the risk of co-occurrence of depression and migraine and thus may provide valuable insight for newer prevention and intervention approaches in the treatment of these conditions
Genome-wide association analysis reveals KCTD12 and miR-383-binding genes in the background of rumination
Ruminative response style is a passive and repetitive way of responding to stress, associated with several disorders.
Although twin and candidate gene studies have proven the genetic underpinnings of rumination, no genome-wide
association study (GWAS) has been conducted yet. We performed a GWAS on ruminative response style and its two
subtypes, brooding and reflection, among 1758 European adults recruited in the general population of Budapest,
Hungary, and Manchester, United Kingdom. We evaluated single-nucleotide polymorphism (SNP)-based, gene-based
and gene set-based tests, together with inferences on genes regulated by our most significant SNPs. While no
genome-wide significant hit emerged at the SNP level, the association of rumination survived correction for multiple
testing with KCTD12 at the gene level, and with the set of genes binding miR-383 at the gene set level. SNP-level
results were concordant between the Budapest and Manchester subsamples for all three rumination phenotypes. SNPlevel
results and their links to brain expression levels based on external databases supported the role of KCTD12,
SRGAP3, and SETD5 in rumination, CDH12 in brooding, and DPYSL5, MAPRE3, KCNK3, ATXN7L3B, and TPH2 in reflection,
among others. The relatively low sample size is a limitation of our study. Results of the first GWAS on rumination identified genes previously implicated in psychiatric disorders underscoring the transdiagnostic nature of rumination, and pointed to the possible role of the dorsolateral prefrontal cortex, hippocampus, and cerebellum in this cognitive
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