1,412 research outputs found
Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane
Context. In 2015, Barman et al. (ApJ, 804, 61) presented detections of
absorption from water, carbon monoxide, and methane in the atmosphere of the
directly imaged exoplanet HR8799b using integral field spectroscopy (IFS) with
OSIRIS on the Keck II telescope. We recently devised a new method to analyse
IFU data, called molecule mapping, searching for high-frequency signatures of
particular molecules in an IFU data cube.
Aims. The aim of this paper is to use the molecule mapping technique to
search for the previously detected spectral signatures in HR8799b using the
same data, allowing a comparison of molecule mapping with previous methods.
Methods. The medium-resolution H- and K-band pipeline-reduced archival data
were retrieved from the Keck archive facility. Telluric and stellar lines were
removed from each spectrum in the data cube, after which the residuals were
cross-correlated with model spectra of carbon monoxide, water, and methane.
Results. Both carbon monoxide and water are clearly detected at high
signal-to-noise, however, methane is not retrieved.
Conclusions. Molecule mapping works very well on the OSIRIS data of exoplanet
HR8799b. However, it is not evident why methane is detected in the original
analysis, but not with the molecule mapping technique. Possible causes could be
the presence of telluric residuals, different spectral filtering techniques, or
the use of different methane models. We do note that in the original analysis
methane was only detected in the K-band, while the H-band methane signal could
be expected to be comparably strong. More sensitive observations with the JWST
will be capable of confirming or disproving the presence of methane in this
planet at high confidence.Comment: 5 pages, 5 figures and 2 tables, accepted by A&
Hunt for Starspots in HARPS Spectra of G and K Stars
We present a method for detecting starspots on cool stars using the
cross-correlation function (CCF) of high resolution molecular spectral
templates applied to archival high-resolution spectra of G and K stars observed
with HARPS/HARPS-N. We report non-detections of starspots on the Sun even when
the Sun was spotted, the solar twin 18 Scorpii, and the very spotted Sun-like
star HAT-P-11, suggesting that Sun-like starspot distributions will be
invisible to the CCF technique, and should not produce molecular absorption
signals which might be confused for signatures of exoplanet atmospheres. We
detect strong TiO absorption in the T Tauri K-dwarfs LkCa 4 and AA Tau,
consistent with significant coverage by cool regions. We show that despite the
non-detections, the technique is sensitive to relatively small spot coverages
on M dwarfs and large starspot areas on Sun-like stars.Comment: 12 pages, 8 figures, accepted to A
Small fibre neuropathy : expanding the clinical pain universe
Small fibre neuropathy (SFN) is a disorder of thinly myelinated A\u3b4 and unmyelinated C fibres. SFN is clinically dominated by neuropathic pain and autonomic complaints, leading to a significant reduction in quality of life. According to international criteria, the diagnosis is established by the assessment of intra-epidermal nerve fibre density and/or quantitative sensory testing. SFN is mainly associated with autoimmune diseases, sodium channel gene variants, diabetes mellitus, and vitamin B12 deficiencies, although in more than one-half of patients no etiology can be identified. Recently, gain-of-function variants in the genes encoding for the Nav 1.7, Nav 1.8 and Nav 1.9 sodium channel subunits have been discovered in SFN patients, enlarging the spectrum of underlying conditions. Sodium channel gene variants associated with SFN can lead to a diversity of phenotypes, including different pain distributions and presence or absence of autonomic symptoms. This suggests that SFN is part of a clinical continuum. New assessments might contribute to a better understanding of the cellular and molecular substrates of SFN and might provide improved diagnostic methods and trial designs in the future. Identification of the underlying mechanisms may inform the development of drugs that more effectively address neuropathic pain and autonomic symptoms of SFN
Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e
[Abridged] The aim of this work is to search for an absorption signal from
exospheric sodium (Na) and singly ionized calcium (Ca) in the optical
transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the
current best-fitting models to the planet mass and radius require a possible
atmospheric component, uncertainties in the radius exist, making it possible
that 55 Cancri e could be a hot rocky planet without an atmosphere. High
resolution (R110000) time-series spectra of five transits of 55 Cancri e,
obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6m &
HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and
K lines, the potential planet exospheric signal was filtered out from the much
stronger stellar and telluric signals, making use of the change of the radial
component of the orbital velocity of the planet over the transit from -57 to
+57 km/sec. Combining all five transit data sets, we detect a signal
potentially associated with sodium in the planet exosphere at a statistical
significance level of 3. Combining the four HARPS transits that cover
the calcium H and K lines, we also find a potential signal from ionized calcium
(4.1 ). Interestingly, this latter signal originates from just one of
the transit measurements - with a 4.9 detection at this epoch.
Unfortunately, due to the low significance of the measured sodium signal and
the potentially variable Ca signal, we estimate the p-values of these
signals to be too high (corresponding to <4) to claim unambiguous
exospheric detections. By comparing the observed signals with artificial
signals injected early in the analysis, the absorption by Na and Ca are
estimated to be at a level of approximately 2.3 and 7.0 respectively, relative to the stellar spectrum.Comment: 15 pages, 8 figures, submission updated after English language
editing, submission updated to correct a mistaken cross-reference noticed in
A&A proo
Subclinical myasthenia gravis in thymomas
Background: A proportion of thymoma-patients without a history of myasthenia gravis (MG) before thymectomy, appears to have positive anti-AChR-antibodies in the serum. These subclinical MG-patients could be under diagnosed because analyzation of anti-AChR-antibodies in thymomas is not always performed in patients who did not experience neurological symptoms. The prevalence and long-term outcomes of subclinical MG are never described in literature yet.Methods: We retrospectively analyzed 398 consecutive patients who underwent a robotic-assisted thoracoscopic surgery at the Maastricht University Medical Center+ (MUMC+) between April 2004 and December 2018. In the MUMC+, a robotic approach is the standard surgical approach in patients with thymic diseases. Inclusion criteria were thymomas, thymectomy performed in the MUMC + with a follow-up of at least one year and age above 18 years old. Exclusion criteria were patients with thymic carcinomas, refused participation, or those who were lost to follow-up.Results: Of the 102 included thymoma-patients, 87 patients (85 %) were tested for anti-AChR-antibodies before thymectomy, of which 57 patients were diagnosed with clinical MG and seven subclinical MG-patients were found. Of the 15 patients who were not tested for anti-AChR-antibodies, four more subclinical MG-patients were discovered in the years after thymectomy. The median follow-up time was 62 months. In total, 11 subclinical MG-patients were found, with a mean age of 54 years and predominantly females (64 %). Ten subclinical MG patients (91 %) developed clinical-MG, within six years after thymectomy. Immunosuppressive drugs were prescribed in five patients. Four patients were diagnosed with a recurrence of the thymoma. No surgical mortality was reported. Two patients died due to a myasthenic crisis.Conclusions: The prevalence of subclinical MG in thymomas was found to be 10.8 %. One in four patients who experienced no neurological symptoms before thymectomy, appeared to have anti-AChR-antibodies and 91 % of these patients developed clinical MG within six years after the thymectomy. Analyzing anti-AChR-antibodies in the serum is recommended in all suspected thymomas before a thymectomy is performed
Numerical Simulation of Flow Control by Synthetic Jet Actuation
Numerical simulations of active flow control have been carried out for the flow around the NACA0018 profile for Mach = 0.15, Re = 2× 106, a = 15o using the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. Two types of flow control, zero-net-mass jets (synthetic jets) and continuously blowing jets, have been considered to delay the onset of separation. The synthetic jets have been applied to the 2D situation, i.e. infinitely long slits in the spanwise, for which the angle between the jet and surface normal has been varied to study the effect on the separation. For the continuously blowing jets the effect of 3D mixing is taken into account and an optimization of several jet parameters has been carried out to obtain the best result possible
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