A large fraction of the detections to be made by the Gamma-Ray Large Area Space Telescope (GLAST) will initially be unidentified. We argue that traditional methodological approaches to identifying ...individuals and/or populations of g-ray sources will encounter procedural limitations. These limitations will hamper our ability to classify source populations lying in the anticipated data set with the required degree of confidence, particularly those for which no member has yet been convincingly detected in the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO). Here we suggest a new paradigm for achieving the classification of g-ray source populations based on the implementation of an a priori protocol to search for theoretically motivated candidate sources. In order to protect the discovery potential of the sample, it is essential that such a paradigm be defined before the data are revealed. Key to the new procedure is a statistical assessment by which the discovery of a new population can be claimed. Although we explicitly refer here to the case of GLAST, the scheme we present may be adapted to other experiments that are confronted with a similar problematic.
A 13-year-old girl with a painful left neck mass was referred to our institution due to suspicions of malignancy. The patient reported pain that accompanied her frequent neck spasms. Computed ...tomography revealed a large, soft-tissue mass in the left neck, deep to the sternocleidomastoid. The lesion anteriorly displaced the internal carotid artery and both displaced and crushed the internal left jugular vein. Uniquely, a three-dimensional virtual reality model combining magnetic resonance imaging and computed tomography data was used to determine the lesion's resectability and visualize which structures would be encountered or require protection while ensuring total resection. During operation, we confirmed that the mass also laterally displaced the brachial plexus, cranial nerves X and XI, and spinal nerves C3-C5 (including the phrenic) of the cervical plexus. Postsurgical pathological analysis confirmed a diagnosis of desmoid tumor, also known as aggressive fibromatosis, whereas DNA sequencing revealed a
mutation, a somatic genetic marker found in approximately 90% of desmoid tumor cases. When possible, the most widely used method for the treatment of desmoid tumors has been gross resection. Chemotherapy, radiotherapy, and local excision are also used in the treatment of fibromatoses when complete resection is judged infeasible. In this case, a complete surgical resection with tumor-free surgical margins was performed. A standard cervical approach with a modified posterolateral incision site was implemented to avoid a conspicuous anterior neck scar. No flap, nerve repair, or reconstruction was warranted. At 1 year of postsurgical follow-up, the patient showed minimal scarring and no signs of recurrence.
The magnetar SGR J1745-2900 discovered at parsecs distance from the Milky Way central black hole, Sagittarius A*, represents the closest pulsar to a supermassive black hole ever detected. ...Furthermore, its intriguing radio emission has been used to study the environment of the black hole, as well as to derive a precise position and proper motion for this object. The discovery of SGR J1745-2900 has opened interesting debates about the number, age and nature of pulsars expected in the Galactic center region. In this work, we present extensive X-ray monitoring of the outburst of SGR J1745-2900 using the Chandra X-ray Observatory, the only instrument with the spatial resolution to distinguish the magnetar from the supermassive black hole (2.4" angular distance). It was monitored from its outburst onset in April 2013 until August 2019, collecting more than fifty Chandra observations for a total of more than 2.3 Ms of data. Soon after the outburst onset, the magnetar emission settled onto a purely thermal emission state that cooled from a temperature of about 0.9 to 0.6 keV over 6 years. The pulsar timing properties showed at least two changes in the period derivative, increasing by a factor of about 4 during the outburst decay. We find that the long-term properties of this outburst challenge current models for the magnetar outbursts.
ABSTRACT LS I +61°303 is one of the few high-mass X-ray binaries that has been recently observed at TeV and GeV energies. Here we investigate the hard X-ray spectral and timing properties of this ...source using the IBIS/ISGRI instrument on-board theINTEGRALsatellite. We carry out a systematic analysis based on all availableINTEGRALdata since 2002 December 28 up to 2008 April 30. The total exposure time analysed amounts to 2.1Ms, hence more than double the previous reported sample. The source is best detected in the 18-60keV band, with a significance level of 12.0σ. The hard X-ray data are best fitted with a simple power law with a photon index of 1.7 ± 0.2. We detect a periodical signal at 27 ± 4d, matching the orbital period of 26.496d previously reported at other wavelengths. The hard X-ray orbital light curve is obtained and compared with those derived at other frequencies. PUBLICATION ABSTRACT
The acceleration of particles up to GeV or higher energies in microquasars has been the subject of considerable theoretical and observational efforts in the past few years. Sco X-1 is a microquasar ...from which evidence of highly energetic particles in the jet has been found when it is in the so-called Horizontal Branch (HB), a state when the radio and hard X-ray fluxes are higher and a powerful relativistic jet is present. Here we present the first very high energy gamma-ray observations of Sco X-1, obtained with the MAGIC telescopes. An analysis of the whole data set does not yield a significant signal, with 95% CL flux upper limits above 300 GeV at the level of 2.4 X 10--12 cm--2 s--1. Simultaneous RXTE observations were conducted to provide the X-ray state of the source. A selection of the gamma-ray data obtained during the HB based on the X-ray colors did not yield a signal either, with an upper limit of 3.4 X 10--12 cm--2 s--1. These upper limits place a constraint on the maximum TeV luminosity to non-thermal X-ray luminosity of L VHE/L ntX 0.02 that can be related to a maximum TeV luminosity to jet power ratio of L VHE/L j 10--3. Our upper limits indicate that the underlying high-energy emission physics in Sco X-1 must be inherently different from that of the hitherto detected gamma-ray binaries.
We report on a 95 ks Chandra observation of the TeV emitting high-mass X-ray binary LS I +61 degree 303, using the ACIS-S camera in continuous clocking mode to search for a possible X-ray pulsar in ...this system. The observation was performed while the compact object was passing from phase 0.94 to 0.98 in its orbit around the Be companion star (hence close to the apastron passage). We did not find any periodic or quasi-periodic signal (at this orbital phase) in a frequency range of 0.005-175 Hz. We derived an average pulsed fraction (PF) 3 sigma upper limit for the presence of a periodic signal of lsim10 per cent (although this limit is strongly dependent on the frequency and the energy band), the deepest limit ever reached for this object. Furthermore, the source appears highly variable in flux and spectrum even in this very small orbital phase range, in particular we detect two flares, lasting thousands of seconds, with a very hard X-ray spectrum with respect to the average source spectral distribution. The X-ray PF limits we derived are lower than the PF of any isolated rotational-powered pulsar, in particular having a TeV counterpart. In this scenario, most of the X-ray emission of LS I +61 degree 303 should necessarily come from the interwind or innerpulsar wind zone shock rather than from the magnetosphere of the putative pulsar. On the other hand, very low X-ray PFs are not unseen in accreting neutron star systems, although we cannot at all exclude the black hole nature of the hosted compact object, a pulsar with a beam pointing away from our line of sight or spinning faster than similar to 5.6 ms, nor that pulsations might have a transient appearance in only a small fraction of the orbit. Furthermore, we did not find evidence for the previously suggested extended X-ray emission.
In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars ...proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal resolution up to the hard X-ray/soft gamma-ray band and a large field of view imager with good angular resolution to spot hard X-ray transients. In this article, we review the main contributions by INTEGRAL to our understanding of the pulsating hard X-ray sky, such as the discovery and characterization of several accreting and transitional millisecond pulsars, the generation of the first catalog of hard X-ray/soft gamma-ray rotation-powered pulsars, the detection of polarization in the hard X-ray emission from the Crab pulsar, and the discovery of persistent hard X-ray emission from several magnetars.
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