69 research outputs found
Magnetic field structures in star-forming regions : mid-infrared imaging polarimetry of K3-50
We report new imaging polarimetry observations of the Galactic compact H ii region K3-50 using CanariCam at the Gran Telescopio Canarias. We use a standard polarimetric analysis technique, first outlined by Aitken, to decompose the observed polarization images centred at 8.7, 10.3, and 12.5 μm into the emissive and absorptive components from silicate grains that are aligned with the local magnetic field. These components reveal the spatially resolved magnetic field structures across the mid-infrared emission area of K3-50. We examine these structures and show that they are consistent with previously observed features and physical models of K3-50, such as the molecular torus and the ionized outflow. We propose a 3D geometry for all the structures seen at different wavelengths. We also compute relevant physical quantities in order to estimate the associated magnetic field strengths that would be implied under various physical assumptions. We compare these results with magnetohydrodynamic simulations of protostar formation that predict the magnetic field strength and configuration. We find that the magnetic field may be dynamically important in the innermost 0.2 pc of the molecular torus, but that the torus is more likely to be rotationally supported against gravity outside this radius. Similarly, magnetic fields are unlikely to dominate the global physics of the ionized outflow, but they may be important in helping confine the flow near the cavity wall in some locations. Ours is the first application of the Aitken technique to spatially resolved magnetic field structures in multiple layers along the line of sight, effectively a method of ‘polarization tomography’Peer reviewe
First atom lifetime and scattering length measurements
The results of a search for hydrogen-like atoms consisting of
mesons are presented. Evidence for atom production
by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen
in terms of characteristic pairs from their breakup in the same target
() and from Coulomb final state interaction (). Using
these results the analysis yields a first value for the atom lifetime
of fs and a first model-independent measurement of
the S-wave isospin-odd scattering length
( for isospin ).Comment: 14 pages, 8 figure
The influence of radiative core growth on coronal X-ray emission from pre-main sequence stars
SGG acknowledges support from the Science & Technology Facilities Council (STFC) via an Ernest Rutherford Fellowship [ST/J003255/1]. CLD acknowledges support from STFC via a PhD studentship and additional funding via the STFC Studentship Enhancement Programme [ST/J500744/1], and support from the ERC Starting Grant "Image-PlanetFormDiscs" (Grant Agreement No. 639889).Pre-main sequence (PMS) stars of mass ≳ 0.35 M⊙ transition from hosting fully convective interiors to configurations with a radiative core and outer convective envelope during their gravitational contraction. This stellar structure change influences the external magnetic field topology and, as we demonstrate herein, affects the coronal X-ray emission as a stellar analog of the solar tachocline develops. We have combined archival X-ray, spectroscopic, and photometric data for ∼1000 PMS stars from five of the best studied star forming regions; the ONC, NGC 2264, IC 348, NGC 2362, and NGC 6530. Using a modern, PMS calibrated, spectral type-to-effective temperature and intrinsic colour scale, we deredden the photometry using colours appropriate for each spectral type, and determine the stellar mass, age, and internal structure consistently for the entire sample. We find that PMS stars on Henyey tracks have, on average, lower fractional X-ray luminosities (LX/L★) than those on Hayashi tracks, where this effect is driven by changes in LX. X-ray emission decays faster with age for higher mass PMS stars. There is a strong correlation between L★ and LX for Hayashi track stars but no correlation for Henyey track stars. There is no correlation between LX and radiative core mass or radius. However, the longer stars have spent with radiative cores, the less X-ray luminous they become. The decay of coronal X-ray emission from young early K to late G-type PMS stars, the progenitors of main sequence A-type stars, is consistent with the dearth of X-ray detections of the latter.PostprintPeer reviewe
Experience With Bexarotene to Treat Cutaneous T-Cell Lymphomas: A Study of the Spanish Working Group of Cutaneous Lymphomas
Background and objectives: Bexarotene has been approved to treat advanced stage cutaneous T -cell lymphomas (CTCL) since 1999. However, very few data have been published on its long-term safety and efficacy profile. The aim of this study is to determine the tolerability to bexarotene and outcomes by collecting the 2nd largest case series to date on its long-term use vs CTCL. Material and method: This was a multicenter retrospective review of 216 patients with mycosis fungoides (174), or S & eacute;zary syndrome (42) on a 10 -year course of bexarotene alone or in combination with other therapies at 19 tertiary referral teaching hospitals. Results: A total of 133 men (62%) and 83 women (38%) were included, with a mean age of 63.5 year (27 - 95). A total of 45% were on bexarotene monotherapy for the entire study period, 22% started on bexarotene but eventually received an additional therapy, 13% were on another treatment but eventually received bexarotene while the remaining 20% received a combination therapy since the beginning. The median course of treatment was 20.78 months (1 - 114); and the overall response rate, 70.3%. Complete and partial response rates were achieved in 26% and 45% of the patients, respectively. Treatment was well tolerated, being the most common toxicities hypertriglyceridemia (79%), hypercholesterolemia (71%), and hypothyroidism (52%). No treatment -related grade 5 adverse events were reported. Conclusions: Our study confirms bexarotene is a safe and effective therapy for the long-term treatment of CTCL. (c) 2024 AEDV. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
ALMA Reveals the Anatomy of the mm-sized Dust and Molecular Gas in the HD 97048 Disk
Transitional disks show a lack of excess emission at infrared wavelengths due to a large dust cavity, that is often corroborated by spatially resolved observations at ∼mm wavelengths. We present the first spatially resolved ∼ mm-wavelength images of the disk around the Herbig Ae/Be star, HD 97048. Scattered light images show that the disk extends to ≈640 au. ALMA data reveal a circular-symmetric dusty disk extending to ≈350 au, and a molecular disk traced in CO J = 3-2 emission, extending to ≈750 au. The CO emission arises from a flared layer with an opening angle ≈30°–40°. HD 97048 is another source for which the large (∼ mm-sized) dust grains are more centrally concentrated than the small (∼μm-sized) grains and molecular gas, likely due to radial drift. The images and visibility data modeling suggest a decrement in continuum emission within ≈50 au, consistent with the cavity size determined from mid-infrared imaging (34 ± 4 au). The extracted continuum intensity profiles show ring-like structures with peaks at ≈50, 150, and 300 au, with associated gaps at ≈100 and 250 au. This structure should be confirmed in higher-resolution images (FWHM ≈ 10–20 au). These data confirm the classification of HD 97048 as a transitional disk that also possesses multiple ring-like structures in the dust continuum emission. Additional data are required at multiple and well-separated frequencies to fully characterize the disk structure, and thereby constrain the mechanism(s) responsible for sculpting the HD 97048 disk
Forward tracking at the next e+ e- collider part I: the physics case
In a series of notes we explore the detector requirements of the forward
tracking region for a future collider with a center-of-mass energy
in the range from 500 GeV to 3 TeV. In this first part we investigate the
relevance of the forward region for a range of physics processes that are
likely to be relevant in such a machine. We find that many examples can be
found where excellent performance of the forward detector system may lead to a
considerable increase of the physics output of the experiment. A particularly
clear physics case can be made for the reconstruction of electrons at small
polar angle.Comment: category: instrumentation
Investigation of pairs in the effective mass region near
The DIRAC experiment at CERN investigated in the reaction
the particle pairs and with relative momentum in the pair system less than 100 MeV/c.
Because of background influence studies, DIRAC explored three subsamples of
pairs, obtained by subtracting -- using time-of-flight (TOF) technique
-- background from initial distributions with sample fractions
more than 70\%, 50\% and 30\%. The corresponding pair distributions in and
in its longitudinal projection were analyzed first in a Coulomb model,
which takes into account only Coulomb final state interaction (FSI) and
assuming point-like pair production. This Coulomb model analysis leads to a
yield increase of about four at MeV/c compared to 100 MeV/c.
In order to study contributions from strong interaction, a second more
sophisticated model was applied, considering besides Coulomb FSI also strong
FSI via the resonances and and a variable distance
between the produced mesons. This analysis was based on three different
parameter sets for the pair production. For the 70\% subsample and with best
parameters, pairs was found to be compared to extracted by means of the Coulomb model. Knowing the efficiency
of the TOF cut for background suppression, the total number of detected
pairs was evaluated to be around , which agrees with
the result from the 30\% subsample. The pair number in the 50\%
subsample differs from the two other values by about three standard deviations,
confirming -- as discussed in the paper -- that experimental data in this
subsample is less reliable
Evidence for -atoms with DIRAC
We present evidence for the first observation of electromagnetically bound
-pairs (-atoms) with the DIRAC experiment at the CERN-PS.
The -atoms are produced by the 24 GeV/c proton beam in a thin Pt-target
and the and -mesons from the atom dissociation are analyzed in
a two-arm magnetic spectrometer. The observed enhancement at low relative
momentum corresponds to the production of 173 54 -atoms. The mean
life of -atoms is related to the s-wave -scattering lengths, the
measurement of which is the goal of the experiment. From these first data we
derive a lower limit for the mean life of 0.8 fs at 90% confidence level.Comment: 15 pages, 9 figure
Belle II Vertex Detector Performance
The Belle II experiment at the SuperKEKB accelerator (KEK, Tsukuba, Japan) collected its first e+e− collision data in the spring 2019. The aim of accumulating a 50 times larger data sample than Belle at KEKB, a first generation B-Factory, presents substantial challenges to both the collider and the detector, requiring not only state-of-the-art hardware, but also modern software algorithms for tracking and alignment.
The broad physics program requires excellent performance of the vertex detector, which is composed of two layers of DEPFET pixels and four layers of double sided-strip sensors. In this contribution, an overview of the vertex detector of Belle II and our methods to ensure its optimal performance, are described, and the first results and experiences from the first physics run are presented
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