Context. Several extended sources of very-high-energy (VHE; E > 100 GeV) gamma rays have been found that lack counterparts belonging to an established class of VHE gamma-ray emitters. Aims. The ...nature of the first unidentified VHE gamma-ray source with significant angular offset from the Galactic plane of 3.5°, HESS J1507–622, is explored. Methods.Fermi-LAT data in the high-energy (HE, 100 MeV < E < 100 GeV) gamma-ray range collected over 34 month are used to describe the spectral energy distribution (SED) of the source. Additionally, implications of the off-plane location of the source for a leptonic and hadronic gamma-ray emission model are investigated. Results. HESS J1507–622 is detected in the Fermi energy range and its spectrum is best described by a power law in energy with Γ = 1.7 ± 0.1stat ± 0.2sys and integral flux between (0.3−300) GeV of F = (2.0 ± 0.5stat ± 1.0sys) × 10-9 cm-2 s-1. The SED constructed from the Fermi and H.E.S.S. data for this source does not support a smooth power-law continuation from the VHE to the HE gamma-ray range. With the available data it is not possible to discriminate between a hadronic and a leptonic scenario for HESS J1507–622. The location and compactness of the source indicate a considerable physical offset from the Galactic plane for this object. In case of a multiple-kpc distance, this challenges a pulsar wind nebula (PWN) origin for HESS J1507–622 since the time of travel for a pulsar born in the Galactic disk to reach such a location would exceed the inverse Compton (IC) cooling time of electrons that are energetic enough to produce VHE gamma-rays. However, an origin of this gamma-ray source connected to a pulsar that was born off the Galactic plane in the explosion of a hypervelocity star cannot be excluded. Conclusions. The nature of HESS J1507–622 is still unknown to date, and a PWN scenario cannot be ruled out in general. On the contrary HESS J1507–622 could be the first discovered representative of a population of spatially extended VHE gamma-ray emitters with HE gamma-ray counterpart that are located at considerable offsets from the Galactic plane. Future surveys in the VHE gamma-ray range are necessary to probe the presence or absence of such a source population.
Oxidation of thermocouple elements can degrade the accuracy of thermocouple-based temperature measurements. As a particular example of such effects, oxidation of the Pd element of a ...platinum/palladium thermocouple is known to increase the thermoelectric emf by an amount equivalent to a temperature change of the order of 100 mK to 200 mK at 420 °C (G. W. Burns, D. C. Ripple, Proceedings of TEMPMEKO ‘96, 6th International Symposium on Temperature and Thermal Measurements in Industry and Science. Levrotto and Bella, Torino, 1997, 171–176). A possible physical mechanism to explain how oxidation affects the thermoelectric output of a Pt/Pd thermocouple is proposed. The analysis hinges on the hypothesis that the oxide-induced strain within the Pd thermoelement leads to a change in the Seebeck coefficient, and therefore to the thermoelectric emf. A theoretical model relating deformation of the palladium lattice to the change in the Seebeck coefficient is presented. The level of agreement between the calculation and the experimental observations suggests that oxide-induced strain in the Pd thermoelement is a likely explanation for the change in thermoelectric output of a Pt/Pd thermocouple within the temperature range where oxidation is active.
In the Embla oil field on the northern flank of the Mid North Sea High, the central North Sea, multiple quartz porphyric volcanic beds at ca. 4600 m depth form part of a volcano-sedimentary interval ...above the Caledonian basement as interpreted from seismic data. Zircon U–Pb laser ablation ICPMS date one bed to 374 ± 3 Ma, indicating that the volcanic rocks and interbedded sediments are early Famennian and correlate to the Buchan Formation. The volcanic rocks have been extensively clay and carbonate altered in a near-surface environment, but high field strength element data show that the protoliths were alkali rhyolites, yielding intra-plate signatures in tectonic discrimination diagrams. Famennian quartz porphyric volcanic rocks have also been reported from well A17-1 on the southern flank of the Mid North Sea High. The Famennian volcanism on the northern and southern flanks testify to an active magmatic environment in the central North Sea in the early Famennian, supporting the existence of a late Devonian proto-Central Graben rift extending northwards into the central North Sea. The rift is likely an early example of strain localisation to a zone of reduced crustal strength along the Caledonian suture between Avalonia and Baltica.
► Altered alkali rhyolites on the Mid North Sea High are dated to 374 ± 3 Ma. ► The protoliths of the altered rocks are only identifiable using HFSE elements. ► The volcanism is interpreted to reflect a late Devonian proto-Central Graben rift. ► The rift indicates strain localisation to the weak Avalonia – Baltica suture zone.
AbstractStellar flares have been extensively studied in soft X-rays (SXRs) by basically every X-ray mission. Hard X-ray (HXR) emission from stellar superflares, however, have only been detected from ...a handful of objects over the past years. One very extreme event was the superflare from the young M-dwarf DG CVn binary star system, which triggered Swift/BAT as if it was a γ-ray burst. In this work, we estimate the expected γ-ray emission from DG CVn and the most extreme stellar flares by extrapolating from solar flares based on measured solar energetic particles (SEPs), as well as thermal and non-thermal emission properties. We find that ions are plausibly accelerated in stellar superflares to 100 GeV energies, and possibly up to TeV energies in the associated coronal mass ejections. The corresponding π0 -decay γ-ray emission could be detectable from stellar superflares with ground-based γ-ray telescopes. On the other hand, the detection of γ-ray emission implies particle densities high enough that ions suffer significant losses due to inelastic proton-proton scattering. The next-generation Cherenkov Telescope Array (CTA) should be able to probe superflares from M dwarfs in the solar neighbourhood and constrain the energy in interacting cosmic rays and/or their maximum energy. The detection of γ-ray emission from stellar flares would open a new window for the study of stellar physics, the underlying physical processes in flares and their impact on habitability of planetary systems.
Nano-precision gap measurement in the sub-micron range presents its own unique engineering challenge. The popular capacitive sensor platform, for example, is susceptible to the erroneous effect of ...electrode tilting and high noise floor, both of which are exacerbated by the small form factor required of a nano-precision gap sensor. In this paper, a capacitive gap sensor with a hemispherical electrode, used in combination with a SAW filter is presented. The proposed system outperforms the existing ones on two fronts. First, the system is virtually immune to the effect of electrode tilting due to the improved capacitor geometry. Second, it benefits from the outstanding signal conditioning capability of the SAW filter. Construction and characterization of a SAW-based capacitive gap sensor having resolution as fine as 10
nm are described.
In recent years, Imaging Atmospheric Cherenkov Telescopes (IACTs) have discovered a rich diversity of very high energy (VHE, >100
GeV)
γ
-ray emitters in the sky. These instruments image Cherenkov ...light emitted by
γ
-ray induced particle cascades in the atmosphere. Background from the much more numerous cosmic-ray cascades is efficiently reduced by considering the shape of the shower images, and the capability to reduce this background is one of the key aspects that determine the sensitivity of a IACT. In this work we apply a tree classification method to data from the High Energy Stereoscopic System (H.E.S.S.). We show the stability of the method and its capabilities to yield an improved background reduction compared to the H.E.S.S. Standard Analysis.
Non-thermal hard X-ray and high-energy (HE; 1 MeV < E < 100 GeV) γ-ray emission in the direction of η Carinae has been recently detected using the INTEGRAL, AGILE and Fermi satellites. This emission ...has been interpreted either in the framework of particle acceleration in the colliding wind region between the two massive stars or in the very fast moving blast wave which originates in the historical 1843 “great eruption”. Archival Chandra data has been reanalysed to search for signatures of particle acceleration in η Carinae’s blast wave. No shell-like structure could be detected in hard X-rays and a limit has been placed on the non-thermal X-ray emission from the shell. The time dependence of the target radiation field of the Homunculus is used to develop a single zone model for the blast wave. Attempting to reconcile the X-ray limit with the HE γ-ray emission using this model leads to a very hard electron injection spectrum dN/dE ∝ E − Γ with Γ < 1.8, harder than the canonical value expected from diffusive shock acceleration.
Flash memory has become the most important storage media in the mobile multimedia products such as MP3 players, mobile phones, and digital cameras. Most mobile multimedia devices, however, use one of ...the conventional FAT file systems slightly modified for flash memory environments. Our analysis shows that theses file systems have some restriction in recording a live multimedia stream stably because they have irregular write response times. In this paper, we have considered the problems of the existing FAT file system and propose two new techniques to solve the problems. The first technique called sector reservation method reduces internal overhead effectively. And the other method called ACPA avoids the periodic cluster allocation of the conventional FAT file system and removes the frequent modifications on the file allocation table in the FAT file system. To evaluate our new techniques, we implemented a prototype real-time FAT file system on ARM9 board with our two novel techniques. The experimental results show that our system achieves our goal successfully in that its write response times are very deterministic and more uniform.
Several extended sources of very-high-energy (VHE) gamma rays have been found that lack counterparts belonging to an established class of VHE gamma-ray emitters. The nature of the first unidentified ...VHE gamma-ray source with significant angular offset from the Galactic plane of 3.5 degree , HESS J1507-622, is explored. Fermi-LAT data in the high-energy (HE) gamma-ray range collected over 34 month are used to describe the spectral energy distribution (SED) of the source. HESS J1507-622 is detected in the Fermi energy range and its spectrum is best described by a power law in energy with ... and integral flux between 0.3-300 GeV of ... . The SED constructed from the Fermi and H.E.S.S. data for this source does not support a smooth power-law continuation from the VHE to the HE gamma-ray range. With the available data it is not possible to discriminate between a hadronic and a leptonic scenario for HESS J1507-622. (ProQuest: ... denotes formulae/symbols omitted.)
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![On the expected [gamma]-ray...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0035-8711/small "On the expected [gamma]-ray emission from nearby flaring stars")
