分类： 天文学 >> 天文学 提交时间： 2023-02-19
The LIGO Scientific Collaboration
the Virgo Collaboration
the KAGRA Collaboration
R. Abbott
H. Abe
F. Acernese
K. Ackley
S. Adhicary
N. Adhikari
R. X. Adhikari
V. K. Adkins
V. B. Adya
C. Affeldt
D. Agarwal
M. Agathos
O. D. Aguiar
L. Aiello
A. Ain
P. Ajith
T. Akutsu
摘要： We describe a search for gravitational waves from compact binaries with at least one component with mass 0.2 $M_\odot$ -- $1.0 M_\odot$ and mass ratio $q \geq 0.1$ in Advanced LIGO and Advanced Virgo data collected between 1 November 2019, 15:00 UTC and 27 March 2020, 17:00 UTC. No signals were detected. The most significant candidate has a false alarm rate of 0.2 $\mathrm{yr}^{-1}$. We estimate the sensitivity of our search over the entirety of Advanced LIGO's and Advanced Virgo's third observing run, and present the most stringent limits to date on the merger rate of binary black holes with at least one subsolar-mass component. We use the upper limits to constrain two fiducial scenarios that could produce subsolar-mass black holes: primordial black holes (PBH) and a model of dissipative dark matter. The PBH model uses recent prescriptions for the merger rate of PBH binaries that include a rate suppression factor to effectively account for PBH early binary disruptions. If the PBHs are monochromatically distributed, we can exclude a dark matter fraction in PBHs $f_\mathrm{PBH} \gtrsim 0.6$ (at 90% confidence) in the probed subsolar-mass range. However, if we allow for broad PBH mass distributions we are unable to rule out $f_\mathrm{PBH} = 1$. For the dissipative model, where the dark matter has chemistry that allows a small fraction to cool and collapse into black holes, we find an upper bound $f_{\mathrm{DBH}} < 10^{-5}$ on the fraction of atomic dark matter collapsed into black holes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
R. Abbasi
M. Ackermann
J. Adams
N. Aggarwal
J. A. Aguilar
M. Ahlers
M. Ahrens
J. M. Alameddine
A. A. Alves
N. M. Amin
K. Andeen
T. Anderson
G. Anton
C. Argüelles
Y. Ashida
S. Athanasiadou
S. Axani
X. Bai
A. Balagopal V.
M. Baricevic
摘要： IceCube, a cubic-kilometer array of optical sensors built to detect atmospheric and astrophysical neutrinos between 1 GeV and 1 PeV, is deployed 1.45 km to 2.45 km below the surface of the ice sheet at the South Pole. The classification and reconstruction of events from the in-ice detectors play a central role in the analysis of data from IceCube. Reconstructing and classifying events is a challenge due to the irregular detector geometry, inhomogeneous scattering and absorption of light in the ice and, below 100 GeV, the relatively low number of signal photons produced per event. To address this challenge, it is possible to represent IceCube events as point cloud graphs and use a Graph Neural Network (GNN) as the classification and reconstruction method. The GNN is capable of distinguishing neutrino events from cosmic-ray backgrounds, classifying different neutrino event types, and reconstructing the deposited energy, direction and interaction vertex. Based on simulation, we provide a comparison in the 1-100 GeV energy range to the current state-of-the-art maximum likelihood techniques used in current IceCube analyses, including the effects of known systematic uncertainties. For neutrino event classification, the GNN increases the signal efficiency by 18% at a fixed false positive rate (FPR), compared to current IceCube methods. Alternatively, the GNN offers a reduction of the FPR by over a factor 8 (to below half a percent) at a fixed signal efficiency. For the reconstruction of energy, direction, and interaction vertex, the resolution improves by an average of 13%-20% compared to current maximum likelihood techniques in the energy range of 1-30 GeV. The GNN, when run on a GPU, is capable of processing IceCube events at a rate nearly double of the median IceCube trigger rate of 2.7 kHz, which opens the possibility of using low energy neutrinos in online searches for transient events.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
D. L. Zhang
X. L. Sun
Z. H. An
X. Q. Li
X. Y. Wen
K. Gong
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
M. Gao
R. Gao
D. Y. Guo
J. J. He
D. J. Hou
Y. G. Li
C. Y. Li
G. Li
L. Li
摘要： The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy. With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts, the gravitational wave high-energy electromagnetic counterpart all-sky monitor (GECAM) possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
IceCube Collaboration
R. Abbasi
M. Ackermann
J. Adams
J. A. Aguilar
M. Ahlers
M. Ahrens
J. M. Alameddine
C. Alispach
A. A. Alves
N. M. Amin
K. Andeen
T. Anderson
G. Anton
C. Argüelles
Y. Ashida
S. Axani
X. Bai
A. Balagopal V.
A. Barbano
摘要： We report three searches for high energy neutrino emission from astrophysical objects using data recorded with IceCube between 2011 and 2020. Improvements over previous work include new neutrino reconstruction and data calibration methods. In one search, the positions of 110 a priori selected gamma-ray sources were analyzed individually for a possible surplus of neutrinos over atmospheric and cosmic background expectations. We found an excess of $79_{-20}^{+22}$ neutrinos associated with the nearby active galaxy NGC 1068 at a significance of 4.2$\,\sigma$. The excess, which is spatially consistent with the direction of the strongest clustering of neutrinos in the Northern Sky, is interpreted as direct evidence of TeV neutrino emission from a nearby active galaxy. The inferred flux exceeds the potential TeV gamma-ray flux by at least one order of magnitude.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. J. He
Z. H. An
W. X. Peng
X. Q. Li
S. L. Xiong
D. L. Zhang
R. Qiao
D. Y. Guo
C. Cai
Z. Chang
C. Chen
G. Chen
Y. Y. Du
M. Gao
R. Gao
K. Gong
D. J. Hou
C. Y. Li
G. Li
L. Li
摘要： As the main detector of the GECAM satellite, the calibration of the energy response and detection efficiency of the GRD detector is the main content of the ground-based calibration. The calibration goal requires the calibrated energy points to sample the full energy range (8 keV-2 MeV) as much as possible. The low energy band (8-160 keV) is calibrated with the X-ray beam, while the high energy band (>160 keV) with radioactive sources. This article mainly focuses on the calibration of the energy response and detection efficiency in the 8-160 keV with a refined measurement around the absorption edges of the lanthanum bromide crystal. The GRD performances for different crystal types, data acquisition modes, working modes, and incident positions are also analyzed in detail. We show that the calibration campaign is comprehensive, and the calibration results are generally consistent with simulations as expected.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Y. Q. Liu
K. Gong
X. Q. Li
X. Y. Wen
Z. H. An
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
M. Gao
R. Gao
D. Y. Guo
J. J. He
D. J. Hou
Y. G. Li
C. Y. Li
G. Li
L. Li
X. F. Li
摘要： The Gravitational Wave Burst High-energy Electromagnetic Counterpart All-sky Monitor (GECAM), consists of 2 small satellites that each contain 25 LaBr3 (lanthanum bromide doped with cerium chloride) detectors and 8 plastic scintillator detectors. The detector signals are read out using a silicon photomultiplier (SiPM) array. In this study, an acquisition algorithm for in-orbit real-time SiPM array data is designed and implemented, and the output event packet is defined. Finally, the algorithm's efficacy for event acquisition is verified.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
R. Abbasi
M. Ackermann
J. Adams
N. Aggarwal
J. A. Aguilar
M. Ahlers
J. M. Alameddine
A. A. Alves
N. M. Amin
K. Andeen
T. Anderson
G. Anton
C. Argüelles
Y. Ashida
S. Athanasiadou
S. N. Axani
X. Bai
A. Balagopal V.
M. Baricevic
S. W. Barwick
摘要： The D-Egg, an acronym for ``Dual optical sensors in an Ellipsoid Glass for Gen2,'' is one of the optical modules designed for future extensions of the IceCube experiment at the South Pole. The D-Egg has an elongated-sphere shape to maximize the photon-sensitive effective area while maintaining a narrow diameter to reduce the cost and the time needed for drilling of the deployment holes in the glacial ice for the optical modules at depths up to 2700 meters. The D-Egg design is utilized for the IceCube Upgrade, the next stage of the IceCube project also known as IceCube-Gen2 Phase 1, where nearly half of the optical sensors to be deployed are D-Eggs. With two 8-inch high-quantum efficiency photomultiplier tubes (PMTs) per module, D-Eggs offer an increased effective area while retaining the successful design of the IceCube digital optical module (DOM). The convolution of the wavelength-dependent effective area and the Cherenkov emission spectrum provides an effective photodetection sensitivity that is 2.8 times larger than that of IceCube DOMs. The signal of each of the two PMTs is digitized using ultra-low-power 14-bit analog-to-digital converters with a sampling frequency of 240 MSPS, enabling a flexible event triggering, as well as seamless and lossless event recording of single-photon signals to multi-photons exceeding 200 photoelectrons within 10 nanoseconds. Mass production of D-Eggs has been completed, with 277 out of the 310 D-Eggs produced to be used in the IceCube Upgrade. In this paper, we report the des\ ign of the D-Eggs, as well as the sensitivity and the single to multi-photon detection performance of mass-produced D-Eggs measured in a laboratory using the built-in data acquisition system in each D-Egg optical sensor module.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Z. H. An
X. L. Sun
D. L. Zhang
S. Yang
X. Q. Li
X. Y. Wen
K. Gong
X. H. Liang
X. J. Liu
Y. Q. Liu
Y. G. Li
S. L. Xiong
Y. B. Xu
Fan Zhang
X. Y. Zhao
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
摘要： Background: Each GECAM satellite payload contains 25 gamma-ray detectors (GRDs), which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts (GRBs). GRD was designed using lanthanum bromide (LaBr3) crystal as the sensitive material with the rear end coupled with silicon photomultiplier (SiPM) array for readout. Purpose: In aerospace engineering design of GRD, there are many key points to be studied. In this paper, we present the specific design scheme of GRD, the assembly and the performance test results of detectors. Methods: Based on Monte Carlo simulation and experimental test results, the specific schematic design and assembling process ofGRDwere optimized. After being fully assembled, theGRDswere conducted performance tests by using radioactive source and also conducted random vibration tests. Result and conclusion: The test results show that all satellite-borne GRDs have energy resolution <16% at 59.5 keV, meeting requirements of satellite in scientific performance. The random vibration test shows that GRD can maintain in a stable performance, which meets the requirement of spatial application.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Electrons in atoms and molecules can not react immediately to the action of intense laser field. A time lag (about 100 attoseconds) between instants of the field maximum and the ionization-rate maximum emerges. This lag characterizes the response time of the electronic wave function to the strong-field ionization event and has important effects on subsequent ultrafast dynamics of the ionized electron. The absolute time lag is not accessible in experiments. Here, a calibrated attoclock procedure, which is related to a simple Coulomb-induced temporal correction to electron trajectories, is proposed to measure the relative lag of two different ionization events. Using this procedure,the difference (i.e., the relative lag) between the ionization time lags of polar molecules in two consecutive half laser cycles can be probed with a high accuracy.
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