Aims. To understand planet formation it is necessary to study the birth environment of planetary systems. Resolved imaging of young planet forming disks allows us to study this environment in great ...detail and find signs of planet-disk interaction and disk evolution. In the present study we aim to investigate the circumstellar environment of the spectroscopic binary T Tauri star CS Cha. From unresolved mid-to far-infrared photometry it is predicted that CS Cha hosts a disk with a large cavity. In addition, spectral energy distribution modeling suggests significant dust settling, pointing toward an evolved disk that may show signs of ongoing or completed planet formation. Methods. We observed CS Cha with the high contrast imager SPHERE at the ESO Very Large Telescope (VLT) in polarimetric differential imaging mode to resolve the circumbinary disk in near-infrared scattered light. These observations were followed up by VLT/NACO L-band observations and complemented by archival VLT/NACO K-band and Hubble Space Telescope WFPC2 I-band data. Results. We resolve the compact circumbinary disk around CS Cha for the first time in scattered light. We find a smooth, low inclination disk with an outer radius of ~55 au (at 165 pc). We do not detect the inner cavity but find an upper limit for the cavity size of ~15 au. Furthermore, we find a faint comoving companion with a projected separation of 210 au from the central binary outside of the circumbinary disk. The companion is detected in polarized light and shows an extreme degree of polarization (13.7 ± 0.4% in the J band). The J- and H-band magnitudes of the companion are compatible with masses of a few MJup. However, K-, L-, and I-band data draw this conclusion into question. We explore with radiative transfer modeling whether an unresolved circum-companion disk can be responsible for the high polarization and complex photometry. We find that the set of observations is best explained by a heavily extincted low-mass (~20 MJup) brown dwarf or high-mass planet with an unresolved disk and dust envelope.
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Background and objectives
The last version of the EFNS dementia guidelines is from 2007. In 2010, the revised guidelines for Alzheimer's disease (AD) were published. The current guidelines involve ...the revision of the dementia syndromes outside of AD, notably vascular cognitive impairment, frontotemporal lobar degeneration, dementia with Lewy bodies, corticobasal syndrome, progressive supranuclear palsy, Parkinson's disease dementia, Huntington's disease, prion diseases, normal‐pressure hydrocephalus, limbic encephalitis and other toxic and metabolic disorders. The aim is to present a peer‐reviewed evidence‐based statement for the guidance of practice for clinical neurologists, geriatricians, psychiatrists and other specialist physicians responsible for the care of patients with dementing disorders. It represents a statement of minimum desirable standards for practice guidance.
Methods
The task force working group reviewed evidence from original research articles, meta‐analyses and systematic reviews, published by June 2011. The evidence was classified (I, II, III, IV) and consensus recommendations graded (A, B, or C) according to the EFNS guidance. Where there was a lack of evidence, but clear consensus, good practice points were provided.
Results and conclusions
New recommendations and good practice points are made for clinical diagnosis, blood tests, neuropsychology, neuroimaging, electroencephalography, cerebrospinal fluid (CSF) analysis, genetic testing, disclosure of diagnosis, treatment of behavioural and psychological symptoms in dementia, legal issues, counselling and support for caregivers. All recommendations were revised compared with the previous EFNS guidelines. The specialist neurologist together with primary care physicians play an important role in the assessment, interpretation and treatment of symptoms, disability and needs of dementia patients.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios, we ...search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose, we utilized VLT/NACO to take several well-calibrated high-resolution images of six target systems and analyse them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical least-squares Monte Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yields best-fitting orbits for this system, which are eccentric (e between 0.21 and 0.69), but cannot rule out circular orbits at high inclinations. Given our astrometry, we discuss formation scenarios of the GQ Lup system. In addition, we detected an even fainter new companion candidate to GQ Lup, which is most likely a background object. We also updated the orbit constraints of the PZ Tel system, confirming that the companion is on a highly eccentric orbit with e > 0.62. Finally, we show with a high significance, that there is no orbital motion observed in the cases of the DH Tau, HD 203030 and 1RXS J160929.1−210524 systems, and give the most precise relative astrometric measurement of the UScoCTIO 108 system to date.
Context.
Accreting planetary-mass objects have been detected at H
α
, but targeted searches have mainly resulted in non-detections. Accretion tracers in the planetary-mass regime could originate from ...the shock itself, making them particularly susceptible to extinction by the accreting material. High-resolution (
R
> 50 000) spectrographs operating at H
α
should soon enable one to study how the incoming material shapes the line profile.
Aims.
We calculate how much the gas and dust accreting onto a planet reduce the H
α
flux from the shock at the planetary surface and how they affect the line shape. We also study the absorption-modified relationship between the H
α
luminosity and accretion rate.
Methods.
We computed the high-resolution radiative transfer of the H
α
line using a one-dimensional velocity–density–temperature structure for the inflowing matter in three representative accretion geometries: spherical symmetry, polar inflow, and magnetospheric accretion. For each, we explored the wide relevant ranges of the accretion rate and planet mass. We used detailed gas opacities and carefully estimated possible dust opacities.
Results.
At accretion rates of
Ṁ
≲ 3 × 10
−6
M
J
yr
−1
, gas extinction is negligible for spherical or polar inflow and at most
A
H
α
≲ 0.5 mag for magnetospheric accretion. Up to
Ṁ
≈ 3 × 10
−4
M
J
yr
−1
, the gas contributes
A
H
α
≲ 4 mag. This contribution decreases with mass. We estimate realistic dust opacities at H
α
to be
κ
~ 0.01–10 cm
2
g
−1
, which is 10–10
4
times lower than in the interstellar medium. Extinction flattens the
L
H
α
–
Ṁ
relationship, which becomes non-monotonic with a maximum luminosity
L
H
α
~ 10
−4
L
⊙
towards
Ṁ
≈ 10
−4
M
J
yr
−1
for a planet mass ~10
M
J
. In magnetospheric accretion, the gas can introduce features in the line profile, while the velocity gradient smears them out in other geometries.
Conclusions.
For a wide part of parameter space, extinction by the accreting matter should be negligible, simplifying the interpretation of observations, especially for planets in gaps. At high
Ṁ
, strong absorption reduces the H
α
flux, and some measurements can be interpreted as two
Ṁ
values. Highly resolved line profiles (
R
~ 10
5
) can provide (complex) constraints on the thermal and dynamical structure of the accretion flow.
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The directly detected planetary mass companion candidate close to the young, nearby star Fomalhaut is a subject of intense discussion. While the detection of common proper motion led to the ...interpretation as Jovian-mass companion, later non-detections in the infrared raised doubts. Recent astrometric measurements indicate a belt crossing or highly eccentric orbit for the object, if a companion, making the planetary interpretation potentially even more problematic. In this study we discuss the possibility of Fomalhaut b being a background object with a high proper motion. By analysing the available photometric and astrometric data of the object, we show that they are fully consistent with a neutron star: neutron stars are faint, hot (blue), and fast moving. Neutron stars with an effective temperature of the whole surface area being 112 000–126 500 K (with small to negligible extinction) at a distance of roughly 11 pc (best fit) would be consistent with all observables, namely with the photometric detections in the optical, with the upper limits in the infrared and X-rays, as well as with the astrometry (consistent with a distances of 11 pc or more and high proper motion as typical for neutron stars) and non-detection of pulsation (not beamed). We consider the probability of finding an unrelated object or even a neutron star nearby and mostly co-aligned in proper motion with Fomalhaut A and come to the conclusion that this is definitely well possible.
Homogeneous observations and careful analysis of transit light curves can lead to the identification of transit timing variations (TTVs). TrES-2 is one of few exoplanets, which offer the matchless ...possibility to combine long-term ground-based observations with continuous satellite data. Our research aimed at the search for TTVs that would be indicative of perturbations from additional bodies in the system. We also wanted to refine the system parameters and the orbital elements. We obtained 44 ground-based light curves of 31 individual transit events of TrES-2. Eight 0.2–2.2-m telescopes located at six observatories in Germany, Poland and Spain were used. In addition, we analysed 18 quarters (Q0–Q17) of observational data from NASA's space telescope Kepler including 435 individual transit events and 11 publicly available ground-based light curves. Assuming different limb darkening (LD) laws we performed an analysis for all light curves and redetermined the parameters of the system. We also carried out a joint analysis of the ground- and space-based data. The long observation period of seven years (2007–2013) allowed a very precise redetermination of the transit ephemeris. For a total of 490 transit light curves of TrES-2, the time of transit mid-point was determined. The transit times support neither variations on long time-scale nor on short time-scales. The nearly continuous observations of Kepler show no statistically significant increase or decrease in the orbital inclination i and the transit duration D. Only the transit depth shows a slight increase which could be an indication of an increasing stellar activity. In general, system parameters obtained by us were found to be in agreement with previous studies but are the most precise values to date.
We present long-term photometric observations of the young open cluster IC 348 with a baseline time-scale of 2.4 yr. Our study was conducted with several telescopes from the Young Exoplanet Transit ...Initiative (YETI) network in the Bessel R band to find periodic variability of young stars. We identified 87 stars in IC 348 to be periodically variable; 33 of them were unreported before. Additionally, we detected 61 periodic non-members of which 41 are new discoveries. Our wide field of view was the key to those numerous newly found variable stars. The distribution of rotation periods in IC 348 has always been of special interest. We investigate it further with our newly detected periods but we cannot find a statistically significant bimodality. We also report the detection of a close eclipsing binary in IC 348 composed of a low-mass stellar component (M ≳ 0.09 M⊙) and a K0 pre-main-sequence star (M ≈ 2.7 M⊙). Furthermore, we discovered three detached binaries among the background stars in our field of view and confirmed the period of a fourth one.
Context.
To understand the formation of planetary systems, it is important to understand the initial conditions of planet formation, that is, the young gas-rich planet forming disks. Spatially ...resolved, high-contrast observations are of particular interest since substructures in disks that are linked to planet formation can be detected. In addition, we have the opportunity to reveal close companions or even planets in formation that are embedded in the disk.
Aims.
In this study, we present the first results of the Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS), an ESO/SPHERE large program that is aimed at studying disk evolution in scattered light, mainly focusing on a sample of low-mass stars (< 1
M
⊙
) in nearby (∼200 pc) star-forming regions. In this particular study, we present observations of the ET Cha (RECX 15) system, a nearby “old” classical T Tauri star (5−8 Myr, ∼100 pc), which is still strongly accreting.
Methods.
We used SPHERE/IRDIS in the
H
-band polarimetric imaging mode to obtain high spatial resolution and high-contrast images of the ET Cha system to search for scattered light from the circumstellar disk as well as thermal emission from close companions. We additionally employed VLT/NACO total intensity archival data of the system taken in 2003.
Results.
Here, we report the discovery, using SPHERE/IRDIS, of a low-mass (sub)stellar companion to the
η
Cha cluster member ET Cha. We estimate the mass of this new companion based on photometry. Depending on the system age, it is either a 5 Myr, 50
M
Jup
brown dwarf or an 8 Myr, 0.10
M
⊙
M-type, pre-main-sequence star. We explore possible orbital solutions and discuss the recent dynamic history of the system.
Conclusions.
Independent of the precise companion mass, we find that the presence of the companion likely explains the small size of the disk around ET Cha. The small separation of the binary pair indicates that the disk around the primary component is likely clearing from the outside in, which explains the high accretion rate of the system.
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