The Experts below are selected from a list of 2424 Experts worldwide ranked by ideXlab platform
P Meszaros - One of the best experts on this subject based on the ideXlab platform.
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high energy neutrinos from the gravitational wave event gw150914 possibly associated with a short gamma ray burst
Physical Review D, 2016Co-Authors: Reetanjali Moharana, S Razzaque, Nayantara Gupta, P MeszarosAbstract:High-energy neutrinos (HEN) and gravitational waves (GW) can probe astrophysical sources in addition to electromagnetic observations. Multimessenger studies can reveal the nature of the sources, which may not be discerned from one type of signal alone. We discuss HEN emission in connection with the Advanced Laser Interferometer Gravitational-Wave Observatory event GW150914, which could be associated with a short gamma-ray burst detected by the Fermi Gamma-Ray Burst Monitor 0.4 s after the GW event and within localization uncertainty of the GW event. We calculate HEN flux from this short gamma-ray burst, GW150914-GBM, and show that Nondetection of a high-energy starting event by the IceCube Neutrino Observatory can constrain the total isotropic-equivalent jet energy of this short burst to be less than $3\ifmmode\times\else\texttimes\fi{}{10}^{52}\text{ }\text{ }\mathrm{erg}$.
Serylak M. - One of the best experts on this subject based on the ideXlab platform.
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Follow-up of 27 radio-quiet gamma-ray pulsars at 110-190 MHz using the international LOFAR station FR606
'EDP Sciences', 2021Co-Authors: Grießmeier Jean-mathias, Smith D.a., Theureau Gilles, Johnson T.j., Kerr M., Bondonneau L., Cognard Ismaël, Serylak M.Abstract:International audienceThe Fermi Large Area Telescope has detected over 260 gamma-ray pulsars. About one quarter of these are labeled as radio-quiet. In the population of nonrecycled gamma-ray pulsars, the fraction of radio-quiet pulsars is higher, about one half. Most radio observations of gamma-ray pulsars have been performed at frequencies between 300 MHz and 2 GHz. However, pulsar radio fluxes increase rapidly with decreasing frequency, and their radio beams often broaden at low frequencies. As a consequence, some of these pulsars might be detectable at low radio frequencies even when no radio flux is detected above 300 MHz. Our aim is to test this hypothesis with low-frequency radio observations. We have observed 27 Fermi-discovered gamma-ray pulsars with the international LOw Frequency ARray (LOFAR) station FR606 in single-station mode. We used the LOFAR high band antenna (HBA) band (110-190 MHz). On average, we use 9 h of observation per target after the removal of affected datasets, resulting in a sensitivity for pulse-averaged flux on the order of 1-10 mJy. We do not detect radio pulsations from any of the 27 sources, and we establish stringent upper limits on their low-frequency radio fluxes. These Nondetections are compatible with the upper limits derived from radio observations at other frequencies. We also determine the pulsars' geometry from the gamma-ray profiles to see for which pulsars the low-frequency radio beam is expected to cross Earth. This set of observations provides the most constraining upper limits on the flux density at 150 MHz for 27 radio-quiet gamma-ray pulsars. In spite of the beam-widening expected at low radio frequencies, most of our Nondetections can be explained by an unfavorable viewing geometry; for the remaining observations, especially those of pulsars detected at higher frequencies, the Nondetection is compatible with insufficient sensitivity
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Follow-up of 27 radio-quiet gamma-ray pulsars at 110-190 MHz using the international LOFAR station FR606
'EDP Sciences', 2021Co-Authors: Grießmeier Jean-mathias, Smith D.a., Theureau Gilles, Johnson T.j., Kerr M., Bondonneau L., Cognard Ismaël, Serylak M.Abstract:The Fermi Large Area Telescope has detected over 260 gamma-ray pulsars. About one quarter of these are labeled as radio-quiet. In the population of nonrecycled gamma-ray pulsars, the fraction of radio-quiet pulsars is higher, about one half. Most radio observations of gamma-ray pulsars have been performed at frequencies between 300 MHz and 2 GHz. However, pulsar radio fluxes increase rapidly with decreasing frequency, and their radio beams often broaden at low frequencies. As a consequence, some of these pulsars might be detectable at low radio frequencies even when no radio flux is detected above 300 MHz. Our aim is to test this hypothesis with low-frequency radio observations. We have observed 27 Fermi-discovered gamma-ray pulsars with the international LOw Frequency ARray (LOFAR) station FR606 in single-station mode. We used the LOFAR high band antenna (HBA) band (110-190 MHz). On average, we use 9 h of observation per target after the removal of affected datasets, resulting in a sensitivity for pulse-averaged flux on the order of 1-10 mJy. We do not detect radio pulsations from any of the 27 sources, and we establish stringent upper limits on their low-frequency radio fluxes. These Nondetections are compatible with the upper limits derived from radio observations at other frequencies. We also determine the pulsars' geometry from the gamma-ray profiles to see for which pulsars the low-frequency radio beam is expected to cross Earth. This set of observations provides the most constraining upper limits on the flux density at 150 MHz for 27 radio-quiet gamma-ray pulsars. In spite of the beam-widening expected at low radio frequencies, most of our Nondetections can be explained by an unfavorable viewing geometry; for the remaining observations, especially those of pulsars detected at higher frequencies, the Nondetection is compatible with insufficient sensitivity
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Follow-up of 27 radio-quiet gamma-ray pulsars at 110-190 MHz using the international LOFAR station FR606
'EDP Sciences', 2021Co-Authors: Grießmeier J. -m., Kerr M., Bondonneau L., Smith D. A., Theureau G., Johnson T. J., Serylak M.Abstract:The Fermi Large Area Telescope has detected over 260 gamma-ray pulsars. About one quarter of these are labeled as radio-quiet. In the population of nonrecycled gamma-ray pulsars, the fraction of radio-quiet pulsars is higher, about one half. Most radio observations of gamma-ray pulsars have been performed at frequencies between 300 MHz and 2 GHz. However, pulsar radio fluxes increase rapidly with decreasing frequency, and their radio beams often broaden at low frequencies. As a consequence, some of these pulsars might be detectable at low radio frequencies even when no radio flux is detected above 300 MHz. Our aim is to test this hypothesis with low-frequency radio observations. We have observed 27 Fermi-discovered gamma-ray pulsars with the international LOw Frequency ARray (LOFAR) station FR606 in single-station mode. We used the LOFAR high band antenna (HBA) band (110-190 MHz). On average, we use 9 h of observation per target after the removal of affected datasets, resulting in a sensitivity for pulse-averaged flux on the order of 1-10 mJy. We do not detect radio pulsations from any of the 27 sources, and we establish stringent upper limits on their low-frequency radio fluxes. These Nondetections are compatible with the upper limits derived from radio observations at other frequencies. We also determine the pulsars' geometry from the gamma-ray profiles to see for which pulsars the low-frequency radio beam is expected to cross Earth. This set of observations provides the most constraining upper limits on the flux density at 150 MHz for 27 radio-quiet gamma-ray pulsars. In spite of the beam-widening expected at low radio frequencies, most of our Nondetections can be explained by an unfavorable viewing geometry; for the remaining observations, especially those of pulsars detected at higher frequencies, the Nondetection is compatible with insufficient sensitivity.Comment: 17 pages, 3 figures, 1 appendix. Accepted by A&
D Hofma - One of the best experts on this subject based on the ideXlab platform.
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high energy neutrino follow up search of gravitational wave event gw150914 with antares and icecube
Physical Review D, 2016Co-Authors: S Adrianmartinez, M G Aartse, P Abbo, T Pradie, G Cagnoli, J Degallai, V Dolique, R Flaminio, M Granata, D HofmaAbstract:We present the high-energy-neutrino follow-up observations of the first gravitational wave transient GW150914 observed by the Advanced LIGO detectors on September 14, 2015. We search for coincident neutrino candidates within the data recorded by the IceCube and Antares neutrino detectors. A possible joint detection could be used in targeted electromagnetic follow-up observations, given the significantly better angular resolution of neutrino events compared to gravitational waves. We find no neutrino candidates in both temporal and spatial coincidence with the gravitational wave event. Within ±500 s of the gravitational wave event, the number of neutrino candidates detected by IceCube and Antares were three and zero, respectively. This is consistent with the expected atmospheric background, and none of the neutrino candidates were directionally coincident with GW150914. We use this Nondetection to constrain neutrino emission from the gravitational-wave event.
H H Zeineldin - One of the best experts on this subject based on the ideXlab platform.
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scheduled perturbation to reduce Nondetection zone for low gain sandia frequency shift method
IEEE Transactions on Smart Grid, 2015Co-Authors: Mohamed Al Hosani, H H ZeineldinAbstract:It is known that the choice of gain ( ${K}$ ) in the Sandia frequency shift (SFS) scheme has direct impacts on the stability of a system with grid-connected distributed generations (DGs). In this paper, a scheduled perturbation technique is proposed to reduce the stability impact of ${K}$ . In the proposed technique, chopping fraction ( cf ) is used to compensate for reduction in the value of ${K}$ , where higher cf values are used to achieve zero Nondetection zone (NDZ) under low gain SFS. It is shown by analysis that theoretical reduction of NDZ can be always achieved for a nonzero value of cf . Simulations for single- and multi-DGs systems are performed to verify the analytical analysis. It is shown that an appropriate design of scheduled signal duty cycle ( ${d}$ ) is of critical importance to realize the proposed reduction in NDZ. While close synchronization of perturbation signals for multi-DG system is required, a delay of 0.33 s is shown to be tolerated for a two-DG system. Synchronization can be achieved either through locally synchronized timers or by limited communication among DGs. The proposed technique provides an attractive option for systems with high DG penetration by reducing the negative impact of ${K}$ on stability.
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impact of load frequency dependence on the ndz and performance of the sfs islanding detection method
IEEE Transactions on Industrial Electronics, 2011Co-Authors: H H Zeineldin, M M A SalamaAbstract:Sandia frequency shift (SFS) falls under the active islanding detection methods that rely on frequency drift to detect an islanding condition for inverter-based distributed generation. Active islanding detection methods are commonly tested on constant RLC loads where the load's active power is directly proportional to the square of voltage and is independent on the system frequency. Since the SFS method relies primarily on frequency to detect islanding, the load's active power frequency dependence could have an impact on its performance and the Nondetection zone (NDZ). In this paper, the impact of the load's active power frequency dependence on the performance of the SFS method, during an islanding condition, is analyzed. A NDZ model that takes into account the load's frequency dependence parameter is derived mathematically and validated through digital simulation. The results show that the load's frequency dependence has a significant impact on the NDZ of the SFS method and thus is an important factor to consider when designing and testing this method.
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a simple technique for islanding detection with negligible Nondetection zone
IEEE Transactions on Power Delivery, 2009Co-Authors: H H Zeineldin, J L KirtleyAbstract:Although active islanding detection techniques have smaller Nondetection zones than passive techniques, active methods could degrade the system power quality and are not as simple and easy to implement as passive methods. The islanding detection strategy, proposed in this paper, combines the advantages of both active and passive islanding detection methods. The distributed-generation (DG) interface was designed so that the DG maintains stable operation while being grid connected and loses its stability once islanded. Thus, the over/undervoltage and over/underfrequency protection method would be sufficient to detect islanding. The main advantage of the proposed technique is that it relies on a simple approach for islanding detection and has negligible Nondetection zone. The system was simulated on PSCAD/EMTDC and simulation results are presented to highlight the effectiveness of the proposed technique.
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sandia frequency shift parameter selection to eliminate Nondetection zones
IEEE Transactions on Power Delivery, 2009Co-Authors: H H Zeineldin, Scott KennedyAbstract:The Sandia frequency-shift (SFS) method is one of the active islanding detection methods that possesses small Nondetection zones (NDZs). The effectiveness of the SFS depends to a great extent on its design parameters ( cfo and k). In this letter, a formula is derived to aid protection engineers to determine the optimal parameter setting for the SFS islanding detection method. It is concluded that the parameter (k) has a significant effect on the NDZ and a modified version of the SFS is proposed that relies only on this parameter.
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impact of dg interface control on islanding detection and Nondetection zones
IEEE Transactions on Power Delivery, 2006Co-Authors: H H Zeineldin, E F Elsaadany, M M A SalamaAbstract:Islanding detection of Distributed Generation (DG) is considered as one of the most important aspects when interconnecting DGs to the distribution system. With the increasing penetration and reliance of the distribution systems on DGs, new interface control strategies are being proposed. Aside from its main task of supplying active power, the DG could provide voltage support, improve the power factor, or mitigate other power quality problems. This paper examines the impact of the interface control strategy of inverter based DGs on islanding detection. The Nondetective Zone (NDZ) for over/under voltage and over/under frequency is derived analytically for each interface control and validated by simulation.
Kohta Murase - One of the best experts on this subject based on the ideXlab platform.
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tev pev neutrinos from low power gamma ray burst jets inside stars
Physical Review Letters, 2013Co-Authors: Kohta Murase, Kunihito IokaAbstract:We study high-energy neutrino production in collimated jets inside progenitors of gamma-ray bursts (GRBs) and supernovae, considering both collimation and internal shocks. We obtain simple, useful constraints, using the often overlooked point that shock acceleration of particles is ineffective at radiation-mediated shocks. Classical GRBs may be too powerful to produce high-energy neutrinos inside stars, which is consistent with IceCube Nondetections. We find that ultralong GRBs avoid such constraints and detecting the TeV signal will support giant progenitors. Predictions for low-power GRB classes including low-luminosity GRBs can be consistent with the astrophysical neutrino background IceCube may detect, with a spectral steepening around PeV. The models can be tested with future GRB monitors.
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icecube Nondetection of gamma ray bursts constraints on the fireball properties
The Astrophysical Journal, 2012Co-Authors: R Liu, Xiangyu Wang, Shigehiro Nagataki, Kohta Murase, Z G DaiAbstract:The increasingly deep limit on the neutrino emission from gamma-ray bursts (GRBs) with IceCube observations has reached a level that could place useful constraints on the fireball properties. We first present a revised analytic calculation of the neutrino flux that predicts a flux of one order of magnitude lower than that obtained by the IceCube Collaboration. For the benchmark model parameters (e.g., the bulk Lorentz factor is Γ = 102.5, the observed variability time for the long GRBs is t ob v = 0.01 s, and the ratio between the energy in the accelerated protons and in the radiation is η p = 10 for every burst) in the standard internal shock scenario, the predicted neutrino flux from 215 bursts during the period of the 40- and 59-string configurations is a factor of ~3 below the IceCube sensitivity. However, if we accept the recently found inherent relation between the bulk Lorentz factor and the burst energy, then the expected neutrino flux significantly increases and the spectral peak shifts to a lower energy. In this case, the Nondetection implies that the baryon-loading ratio should be η p 10 if the variability time of the long GRBs is fixed to t ob v = 0.01 s. Instead, if we relax the standard internal-shock scenario but still assume η p = 10, then the Nondetection constrains the dissipation radius, R 4 × 1012 cm, assuming the same dissipation radius for every burst and benchmark parameters for the fireballs. We also calculate the diffuse neutrino flux from the GRBs for different luminosity functions from the literature. The expected flux exceeds the current IceCube limit for some of the luminosity functions, and, thus, the Nondetection constrains η p 10 when the variability time of the long GRBs is fixed at t ob v = 0.01 s.
