Abstract
The Ground Wide Angle Camera Network (GWAC-N) is a network of robotic multi-aperture, multiple field-of-view (FoV) optical telescopes. The main contingent of GWAC-N instruments are provided ...by the Ground Wide Angle Cameras Array (GWAC-A), and additional, narrower FoV telescopes are utilized to provide fast multi-band follow-up capabilities. The primary scientific goal of the GWAC-N is to search for optical counterparts of gamma-ray bursts that will be detected by the Space Variable Object Monitor (SVOM) satellite. The GWAC-N performs many additional observing tasks including follow-up of Target of Opportunities (ToO) targets and the detection (and monitoring) of variable objects and optical transients. To handle these use cases (and to allow for extensibility), we have designed ten observation modes and 175 observation strategies, including a joint strategy with multiple GWAC-N telescopes for the follow-up of gravitational wave (GW) events. To perform these observations, we develop an Automatic Observation Management (AOM) system capable of performing object management, dynamic scheduling, automatic broadcasting across the network, and image handling. The AOM system combines the individual telescopes which comprise the GWAC-N into a network and smoothly organizes all associated operations, completely meeting the requirements dictated by GWAC-N. With its modular design, the AOM is scientifically and technically viable for other general-purpose telescope networks. As the GWAC-N extends and evolves, the AOM will greatly enhance its discovery potential. In this first paper of a series, we present the scientific goals of the GWAC-N and detail the hardware, software, and workflow developed to achieve these goals. The structure, technical design, implementation, and performance of the AOM system are also described in detail. We conclude with a summary of the current status of the GWAC-N and our near-future development plan.
The concentration of the natural ultra-trace radionuclides ^36Cl and ^236U in the uranium depended on the neutron flux. In this article, a method for measuring ^36Cl and ^236U in the same uranium ...mineral with accelerator mass spectrometry was developed in China Institute of Atomic Energy, providing a protocol of the potential application of ^236U in uranium mining, environmental, and geological research. The two samples were from Guangxi and Shanxi province, China, and their ratios ^36Cl/Cl and ^236U/^238U were measured. More experimental data conduced to understand the natural nuclides in the uranium mineral. We plan to conduct more efforts on the research.
Plutonium isotopes in the coral were determined with chemical separation method using AG 1-X8 and AG-MP-1M anion exchange resins and sector field inductively coupled plasma mass spectrometry ...(SF-ICP-MS) in order to elucidate the activity concentration and source of Pu around Weizhou land in Beibu Gulf, China. Furthermore, the activity concentrations of other radionuclides (238U, 226Ra, 232Th, 137Cs, 40K and 210Pb) were measured by a HPGe spectrometer. The activity concentration of 240+239Pu in the coral is determined to be in the range of 8.95–27.84 mBq/kg. The 240Pu/239Pu atom ratios in the samples range from 0.173 to 0.225, indicating that the main source of plutonium in this area is global fallout while the contribution of PPG is about 30%. Further, the activity concentrations of 238U, 232Th, 40K and 226Ra are determined to be in the range of 18.72–64.63, 1.37–20.8, 29.78–72.52 and 3.48–61.97 Bq/kg, respectively.
•240Pu/239Pu atom ratio, 239+240Pu, 238U, 232Th, 226Ra activity concentration in coral around Weizhou Island are analyzed.•Different coral species have different 239+240Pu activity concentrations.•The primary source of plutonium in coral is global fallout.
The jet compositions, central engines, and progenitors of gamma-ray bursts (GRBs) remain open questions in GRB physics. Applying broadband observations, including GRB prompt emission and afterglow ...properties derived from Fermi and Swift data, as well as from Keck host-galaxy observations, we address these questions for the peculiar, bright GRB 110731A. By using the pair-opacity method, we derive Γ0 > 190 during the prompt emission phase. Alternatively, we derive Γ0 580 and Γ0 154 by invoking the early-afterglow phase within the homogeneous density and wind cases, respectively. On the other hand, nondetection of a thermal component in the spectra suggests that the prompt emission is likely powered by dissipation of a Poynting-flux-dominated jet leading to synchrotron radiation in an optically thin region. The nondetection of a jet break in the X-ray and optical bands allows us to place a lower limit on the jet opening angle θj > 5 5. Within a millisecond magnetar central engine scenario, we derive the period P0 and polar magnetic field strength Bp, which have extreme (but still allowed) values. The moderately short observed duration (7.3 s) and relatively large redshift (z = 2.83) place the burst as a "rest-frame short" GRB, so the progenitor of the burst is subject to debate. Its relatively large parameter (ratio of the 1 s peak flux of a pseudo-GRB and the background flux) and a large physical offset from a potential host galaxy suggest that the progenitor of GRB 110731A may be a compact-star merger.
The Ground Wide Angle Camera Network (GWAC-N) is a network of robotic multi-aperture, multiple field-of-view (FoV) optical telescopes. The main contingent of GWAC-N instruments are provided by the ...Ground Wide Angle Cameras Array (GWAC-A), and additional, narrower FoV telescopes are utilized to provide fast multi-band follow-up capabilities. The primary scientific goal of the GWAC-N is to search for optical counterparts of gamma-ray bursts that will be detected by the Space Variable Object Monitor (SVOM) satellite. The GWAC-N performs many additional observing tasks including follow-up of Target of Opportunities (ToO) targets and the detection (and monitoring) of variable objects and optical transients. To handle these use cases (and to allow for extensibility), we have designed ten observation modes and 175 observation strategies, including a joint strategy with multiple GWAC-N telescopes for the follow-up of gravitational wave (GW) events. To perform these observations, we develop an Automatic Observation Management (AOM) system capable of performing object management, dynamic scheduling, automatic broadcasting across the network, and image handling. The AOM system combines the individual telescopes which comprise the GWAC-N into a network and smoothly organizes all associated operations, completely meeting the requirements dictated by GWAC-N. With its modular design, the AOM is scientifically and technically viable for other general-purpose telescope networks. As the GWAC-N extends and evolves, the AOM will greatly enhance its discovery potential. In this first paper of a series, we present the scientific goals of the GWAC-N and detail the hardware, software, and workflow developed to achieve these goals. The structure, technical design, implementation, and performance of the AOM system are also described in detail. We conclude with a summary of the current status of the GWAC-N and our near-future development plan.
We continue our systematic statistical study on optical afterglow data of gamma-ray bursts (GRBs). We present the apparent magnitude distributions of early optical afterglows at different epochs (t = ...10 super(2) s, 10 super(3) s, and 1 hr) for the optical light curves of a sample of 93 GRBs (the global sample) and for sub-samples with an afterglow onset bump or a shallow decay segment. For the onset sample and shallow decay sample we also present the brightness distribution at the peak time t sub(p) and break time t sub(b), respectively. All the distributions can be fit with Gaussian functions. We further perform Monte Carlo simulations to infer the luminosity function of GRB optical emission at the rest-frame time 10 super(3) s, t sub(p), and t sub(b). Our results show that a single power-law luminosity function is adequate to model the data with indices -1.40 + or - 0.10, -1.06 + or - 0.16, and -1.54 + or - 0.22. Based on the derived rest-frame 10 super(3) s luminosity function, we generate the intrinsic distribution of the R-band apparent magnitude M sub(R) at the observed time 10 super(3) s post-trigger, which peaks at M sub(R) = 22.5 mag. The fraction of GRBs whose R-band magnitude is fainter than 22 mag and 25 mag and at the observer time 10 super(3) s are ~63% and ~25%, respectively. The detection probabilities of the optical afterglows with ground-based robotic telescopes and the UV-Optical Telescope on board Swift are roughly consistent with that inferred from this intrinsic M sub(R) distribution, indicating that the variations of the dark GRB fraction among the samples with different telescopes may be due to the observational selection effect, although the existence of an intrinsically dark GRB population cannot be ruled out.
The cross-sections of
238U (n, 2n)
237U induced by neutrons with energies around 14
MeV were determined by measuring the emission rate of 208.00
keV γ-rays from
237U decay with an accurately ...calibrated HPGe γ-ray spectrometer at CIAE. In order to correct for the self-attenuation of 208.0
keV γ-ray in U sample, a
177Lu-spiking method was introduced. As a result, a total relative standard uncertainty of 2.5% was achieved for the measured cross-section values.
The cross-sections of super(238)U (n, 2n) super(237)U induced by neutrons with energies around 14 MeV were determined by measuring the emission rate of 208.00 keV g-rays from super(237)U decay with ...an accurately calibrated HPGe g-ray spectrometer at CIAE. In order to correct for the self-attenuation of 208.0 keV g-ray in U sample, a super(177)Lu-spiking method was introduced. As a result, a total relative standard uncertainty of 2.5% was achieved for the measured cross-section values.
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