Abstract
The IceCube Neutrino Observatory sends realtime neutrino alerts with a high probability of being astrophysical in origin. We present a new method to correlate these events and possible ...candidate sources using 2089 blazars from the Fermi-LAT 4LAC-DR2 catalog and with 3413 active galactic nuclei (AGNs) from the Radio Fundamental Catalog. No statistically significant neutrino emission was found in any of the catalog searches. The result suggests that a small fraction, <1%, of the studied AGNs emit neutrinos that pass the alert criteria, and is compatible with prior evidence for neutrino emission presented by IceCube and other authors from sources such as TXS 0506 + 056 and PKS 1502 + 106. We also present cross-checks to other analyses that claim a significant correlation using similar data samples.
Abstract
In multi-messenger astronomy, rapid investigation of interesting transients is imperative. As an observatory with a 4
π
steradian field of view, and ∼99% uptime, the IceCube Neutrino ...Observatory is a unique facility to follow up transients, as well as to provide valuable insights for other observatories and inform their observational decisions. Since 2016, IceCube has been using low-latency data to rapidly respond to interesting astrophysical events reported by the multi-messenger observational community. Here, we describe the pipeline used to perform these followup analyses, and provide a summary of the 58 analyses performed as of July 2020. We find no significant signal in the first 58 analyses performed. The pipeline has helped inform various electromagnetic observation strategies, and has constrained neutrino emission from potential hadronic cosmic accelerators.
Pulsar wind nebulae (PWNe) are the main gamma-ray emitters in the Galactic plane. They are diffuse nebulae that emit nonthermal radiation. Pulsar winds, relativistic magnetized outflows from the ...central star, shocked in the ambient medium produce a multiwavelength emission from the radio through gamma-rays. Although the leptonic scenario is able to explain most PWNe emission, a hadronic contribution cannot be excluded. A possible hadronic contribution to the high-energy gamma-ray emission inevitably leads to the production of neutrinos. Using 9.5 yr of all-sky IceCube data, we report results from a stacking analysis to search for neutrino emission from 35 PWNe that are high-energy gamma-ray emitters. In the absence of any significant correlation, we set upper limits on the total neutrino emission from those PWNe and constraints on hadronic spectral components.
Using the IceCube Neutrino Observatory, we search for high-energy neutrino emission coincident with compact binary mergers observed by the LIGO and Virgo gravitational-wave (GW) detectors during ...their first and second observing runs. We present results from two searches targeting emission coincident with the sky localization of each GW event within a 1000 s time window centered around the reported merger time. One search uses a model-independent unbinned maximum-likelihood analysis, which uses neutrino data from IceCube to search for pointlike neutrino sources consistent with the sky localization of GW events. The other uses the Low-Latency Algorithm for Multi-messenger Astrophysics, which incorporates astrophysical priors through a Bayesian framework and includes LIGO-Virgo detector characteristics to determine the association between the GW source and the neutrinos. No significant neutrino coincidence is seen by either search during the first two observing runs of the LIGO-Virgo detectors. We set upper limits on the time-integrated neutrino emission within the 1000 s window for each of the 11 GW events. These limits range from 0.02 to 0.7 . We also set limits on the total isotropic equivalent energy, Eiso, emitted in high-energy neutrinos by each GW event. These limits range from 1.7 × 1051 to 1.8 × 1055 erg. We conclude with an outlook for LIGO-Virgo observing run O3, during which both analyses are running in real time.
We present an all-sky 90% confidence level upper limit on the cosmic flux of relativistic magnetic monopoles using 2886 days of IceCube data. The analysis was optimized for monopole speeds between ...0.750c and 0.995c, without any explicit restriction on the monopole mass. We constrain the flux of relativistic cosmic magnetic monopoles to a level below 2.0×10^{-19} cm^{-2} s^{-1} sr^{-1} over the majority of the targeted speed range. This result constitutes the most strict upper limit to date for magnetic monopoles with β≳0.8 and up to β∼0.995 and fills the gap between existing limits on the cosmic flux of nonrelativistic and ultrarelativistic magnetic monopoles.
The strictly respiratory, diazotrophic bacterium Azoarcus sp. strain BH72 fixes nitrogen under microaerobic conditions. In empirically optimized batch cultures at nanomolar O2 concentrations in the ...presence of proline, cells can shift into a state of higher activity and respiratory efficiency of N2 fixation in which intracytoplasmic membrane stacks (diazosomes) related to N2 fixation are formed. Induction of intracytoplasmic membranes is most pronounced in coculture of Azoarcus sp. strain BH72 with an ascomycete originating from the same host plant, Kallar grass. To initiate studies on function of diazosomes and regulation of their formation, diazosome-containing bacteria were compared with respect to composition of total cellular and membrane proteins with diazosome-free cells fixing nitrogen under standard conditions. In two-dimensional protein gels, we detected striking differences in protein patterns upon diazosome formation: (i) 7.3% of major proteins disappeared, and only 73% of the total proteins of control cells were detectable, indicating that diazosome-containing cells have a more specialized metabolism; (ii) nine new proteins appeared and five proteins increased in concentration, designated DP1 to DP 15; and (iii) five new major membrane proteins (MP1 to MP6) were detected, indicating that membranes might have specialized functions. N-terminal amino acid sequence analysis of DP1 to DP4 allowed us to preliminarily identify DP4 as the glnB gene product PII, an intracellular signal transmitter known to be involved in the regulation of nitrogen metabolism. According to its electrophoretic mobility, it might be uridylylated in diazosome-free cells but not in diazosome-containing cells, or it may represent a second, not identical PII protein. Oligonucleotides deduced from N-terminal sequences of DP1 and DP4 specifically hybridized to chromosomal DNA of Azoarcus sp. strain BH72 in Southern hybridizations
Abstract
Beginning in 2016, the IceCube Neutrino Observatory has sent out alerts in real time containing the information of high-energy (
E
≳ 100 TeV) neutrino candidate events with moderate to high ...(≳30%) probability of astrophysical origin. In this work, we use a recent catalog of such alert events, which, in addition to events announced in real time, includes events that were identified retroactively and covers the time period of 2011–2020. We also search for additional, lower-energy neutrinos from the arrival directions of these IceCube alerts. We show how performing such an analysis can constrain the contribution of rare populations of cosmic neutrino sources to the diffuse astrophysical neutrino flux. After searching for neutrino emission coincident with these alert events on various timescales, we find no significant evidence of either minute-scale or day-scale transient neutrino emission or of steady neutrino emission in the direction of these alert events. This study also shows how numerous a population of neutrino sources has to be to account for the complete astrophysical neutrino flux. Assuming that sources have the same luminosity, an
E
−2.5
neutrino spectrum, and number densities that follow star formation rates, the population of sources has to be more numerous than 7 × 10
−9
Mpc
−3
. This number changes to 3 × 10
−7
Mpc
−3
if number densities instead have no cosmic evolution.
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