ABSTRACT We report on the search for gamma-ray emission from 20 magnetars using six years of Fermi Large Area Telescope observations. No significant evidence for gamma-ray emission from any of the ...currently known magnetars is found. We derived the most stringent upper limits to date on the 0.1-10 GeV emission of Galactic magnetars, which are estimated between ∼10−12 and 10−11 erg s−1 cm−2. We searched gamma-ray pulsations for the four magnetars having reliable ephemerides over the observing period, but detected none. We also report updated morphologies and spectral properties of seven spatially extended gamma-ray sources, which are most likely attributed to supernova remnants associated with or adjacent to the magnetars.
ABSTRACT
Star-forming regions have been proposed as potential Galactic cosmic ray accelerators for decades. Cosmic ray acceleration can be probed through observations of gamma-rays produced in ...inelastic proton–proton collisions at GeV and TeV energies. In this paper, we analyse more than 11 yr of Fermi–LAT data from the direction of Westerlund 2, one of the most massive and best-studied star-forming regions in our Galaxy. In particular, we investigate the characteristics of the bright pulsar PSR J1023–5746 that dominates the gamma-ray emission below a few GeV at the position of Westerlund 2 and the underlying extended source FGES J1023.3–5747. The analysis results in a clear identification of FGES J1023.3–5747 as the GeV counterpart of the TeV source HESS J1023-575, through its morphological and spectral properties. This identification provides new clues about the origin of the HESS J1023-575 gamma-ray emission, favouring a hadronic origin of the emission, powered by Westerlund 2, rather than a leptonic origin related to either the pulsar wind nebula associated with PSR J1023–5746 or the cluster itself. This result indirectly supports the hypothesis that star-forming regions can contribute to the cosmic ray sea observed in our Galaxy.
Background
Idiopathic achalasia is an uncommon esophageal motor disorder. The disease involves interaction between inflammatory and autoimmune responses. However, the antigens related to the disease ...are still unknown.
Aim
To identify the possible antigen targets in muscle biopsies from lower esophageal sphincter (LES) of achalasia patients.
Methods
Esophageal biopsies of patients with type I and type II achalasia and esophagogastric junction outflow obstruction (EGJOO) were analyzed. Lower esophageal sphincter muscle biopsy from a Healthy organ Donor (HD) was included as control for two‐dimensional gel electrophoresis. Immunoblotting of muscle from LES lysate with sera of type I, type II achalasia, or type III achalasia, sera of EGJOO and sera of healthy subjects (HS) was performed. The target proteins of the serum were identified by mass spectrometry Matrix‐assited laser desorption/ionization time‐of‐flight (MALDI‐TOF).
Key Results
The proteomic map of muscle from LES tissue lysates of type I, and type II achalasia, EGJOO, and HD were analyzed and divided into three important regions. We found a difference in the concentration of certain spots. Further, we observed the serum reactivity of type I achalasia and type II achalasia against 45 and 25 kDa bands of type I achalasia tissue. Serum of type III achalasia and EGJOO mainly recognized 25 kDa band. Bands correspond to triosephosphate isomerase (TPI) (25 kDa), carbonic anhydrase (CA) (25 kDa) and creatinine kinase‐brain (CKB) isoform (45 kDa).
Conclusions and Inferences
We identify three antigen targets, TPI, CA, and CKB isoform, which are recognized by sera from patients with achalasia.
Immunoblotting of esophageal tissue lysate against the 25kDa and 45kDa proteins in patients achalasia.
γ-ray radiation from pulsars is usually thought to be mostly produced by the synchro-curvature (SC) losses of accelerated particles. Here, we present a systematic study of all currently reported, ...good-quality Fermi-LAT pulsar spectral data. We do so by applying a model which follows the particle dynamics and consistently computes the emission of SC radiation. By fitting observational data on a case by case basis, we are able to obtain constraints about the parallel electric field, the typical length-scale over which particles emit the bulk of the detected radiation, and the number of involved particles. The model copes well with data of several dozens of millisecond and young pulsars. By correlating the inferred model parameters with the observed timing properties, some trends are discovered. First, a non-negligible part of the radiation comes from the loss of perpendicular momentum soon after pair creation. Second, the electric field strongly correlates with both the inverse of the emission length-scale and the magnetic field at light cylinder, thus ruling out models with high-energy photon production close to the surface. These correlations unify young and millisecond pulsars under the same physical scenario, and predict that magnetars are intrinsically γ-ray quiet via synchro-curvature processes, since magnetospheric particles are not accelerated enough to emit a detectable γ-ray flux.
Abstract
We report on the analysis of a deep Chandra observation of the high-magnetic-field pulsar (PSR) J1119–6127 and its compact pulsar wind nebula (PWN) taken in 2019 October, three years after ...the source went into outburst. The 0.5–7 keV postoutburst (2019) spectrum of the pulsar is best described by a two-component blackbody plus power-law model with a temperature of 0.2 ± 0.1 keV, photon index Γ = 1.8 ± 0.4, and X-ray luminosity of
1.9
−
0.3
+
0.3
×
10
33
erg s
−1
, consistent with its preburst quiescent phase. We find that the pulsar has gone back to quiescence. The compact nebula shows a jet-like morphology elongated in the north–south direction, similar to the preburst phase. The postoutburst PWN spectrum is best fit by an absorbed power law with a photon index Γ = 2.3 ± 0.5 and a flux of
3.2
−
0.2
+
0.3
×10
−14
erg cm
−2
s
−1
(0.5–7 keV). The PWN spectrum shows evidence of spectral softening in the postoutburst phase, with the preburst photon index Γ = 1.2 ± 0.4 changing to Γ = 2.3 ± 0.5 and the preburst luminosity of
1.5
−
0.2
+
0.3
× 10
32
erg s
−1
changing to
2.7
−
0.2
+
0.3
× 10
32
erg s
−1
in the 0.5–7 keV band, suggesting magnetar outbursts can impact PWNe. The observed timescale for returning to quiescence, of just a few years, implies a rather fast cooling process and favors a scenario where J1119 is temporarily powered by magnetic energy following the magnetar outburst, in addition to its spin-down energy.
Considering about seven years of Fermi-Large Area Telescope (LAT) data, we present a systematic search for variability that is possibly related to transitions between states in redbacks and black ...widow systems. The transitions are characterized by sudden and significant changes in the gamma-ray flux that persist on a timescale that is much larger than the orbital period. This phenomenology was already detected in the case of two redback systems, PSR J1023+0038 and PSR J1227−4853, which we present here. We show the existence of only one transition for each of these systems over the past seven years. We determine their spectra, establishing high-energy cutoffs at a few GeV for the high gamma-ray state of PSR J1023+0038, and for both states of PSR J1227−4853. The surveying capability of the Fermi-LAT allows further study of whether similar phenomenology has occurred in other sources. Although we have not found any evidence of a state transition for most of the studied pulsars, we note two black-widow systems, PSR J2234+0944 and PSR J1446−4701, whose apparent variabilities are reminiscent of the transitions in PSR J1023+0038 and PSR J1227−4853. For the other systems, we set limits on potential transitions in their measured gamma-ray light curves.
γ-ray spectra of pulsars have been mostly studied in a phenomenological way, by fitting them to a cut-off power-law function. Here, we analyse a model where pulsed emission comes from ...synchro-curvature processes in a gap. We calculate the variation of kinetic energy of magnetospheric particles along the gap and the associated radiated spectra, considering an effective particle distribution. We fit the phase-averaged and phase-resolved Fermi-LAT (Large Area Telescope) spectra of the three brightest γ-ray pulsars: Geminga, Crab, and Vela, and constrain the three free parameters we leave free in the model. Our best-fitting models well reproduce the observed data, apart from residuals above a few GeV in some cases, range for which the inverse Compton scattering likely becomes the dominant mechanism. In any case, the flat slope at low energy (≲ GeV) seen by Fermi-LAT both in the phase-averaged and phase-resolved spectra of most pulsars, including the ones we studied, requires that most of the detected radiation below ∼GeV is produced during the beginning of the particle trajectories, when radiation mostly come from the loss of perpendicular momentum.
ABSTRACT Based on more than seven years of Fermi Large Area Telescope Pass 8 data, we report on a detailed analysis of the bright gamma-ray pulsar (PSR) J0007+7303. We confirm that PSR J0007+7303 is ...significantly detected as a point source also during the off-peak phases with a test statistic value of 262 (∼16 ). In the description of the off-peak spectrum of PSR J0007+7303, a power law with an exponential cutoff at 2.7 1.2 1.3 GeV (the first/second uncertainties correspond to statistical/systematic errors) is preferred over a single power law at a level of 3.5 . The possible existence of a cutoff hints at a magnetospheric origin of the emission. In addition, no extended gamma-ray emission is detected that is compatible with either the supernova remnant (CTA 1) or the very high-energy (>100 GeV) pulsar wind nebula. A flux upper limit of 6.5 × 10−12 erg cm−2 s−1 in the energy range 10-300 GeV is reported, for an extended source assuming the morphology of the VERITAS detection. During on-peak phases, a sub-exponential cutoff is significantly preferred (∼11 ) for representing the spectral energy distribution, in both the phase-averaged and phase-resolved spectra. Three glitches are detected during the observation period and we found no flux variability at the time of the glitches or in the long-term behavior. We also report the discovery of a previously unknown gamma-ray source in the vicinity of PSR J0007+7303, Fermi J0020+7328, which we associate with the z = 1.781 quasar S5 0016+73. A concurrent analysis of this source is needed to correctly characterize the behavior of CTA 1 and it is also presented in the paper.
THE FUNDAMENTAL PLANE FOR RADIO MAGNETARS Rea, Nanda; Pons, Jose A; Torres, Diego F ...
Astrophysical journal. Letters,
03/2012, Letnik:
748, Številka:
1
Journal Article
Recenzirano
High magnetic fields are a distinguishing feature of neutron stars and the existence of sources (the soft gamma repeaters, SGRs, and the anomalous X-ray pulsars) hosting an ultramagnetized neutron ...star (or magnetar) has been recognized in the past few decades. Magnetars are believed to be powered by magnetic energy and not by rotation, as with normal radio pulsars. Until recently, the radio quietness and magnetic fields typically above the quantum critical value (B sub(Q) Asymptotically = to 4.4 x 10 super(13) G) were among the characterizing properties of magnetars. The recent discovery of radio-pulsed emission from a few of them, and of a low dipolar magnetic field SGR, weakened further the idea of a clean separation between normal pulsars and magnetars. In this Letter, we show that radio emission from magnetars might be powered by rotational energy, similarly to what occurs in normal radio pulsars. The peculiar characteristics of magnetars radio emission should be traced in the complex magnetic geometry of these sources. Furthermore, we propose that magnetar radio activity or inactivity can be predicted from the knowledge of the star's rotational period, its time derivative, and the quiescent X-ray luminosity.
The popular outer gap model of magnetospheric emission from pulsars has been widely applied to explain the properties observed in gamma -rays. However, its quantitative predictions rely on a number ...of approximations and assumptions that are usually overlooked. Here we examine them, reviewing the main ingredients entering the model, evaluating their range of uncertainties. Usually, in the quantitative applications of the model, key parameters like the radius of curvature and the energies of the interacting photons are taken to be a fixed, single value. Instead, here we explore their realistic ranges, and the impact of these on the consistency of the model itself. We conclude that the popular evaluation of the transfield size of the gap as a function of period and period derivative, is unreliable and affected by a huge dispersion. Last, the exploration of the possible values for the radius of curvature, the local magnetic field and other quantities deserve more attention for quantitative applications of the outer gap model, like the calculation of gamma -ray spectra, which is the subject of an accompanying paper.
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