LOFAR 144-MHz follow-up observations of GW170817

ABSTRACT We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO–Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13${_{.}^{\circ}}$7 when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130–138 and 371–374 d after the merger event, we obtain 3σ upper limits for the afterglow component of 6.6 and 19.5 mJy beam−1, respectively. Using our best upper limit and previously published, contemporaneous higher frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha ^{610}_{144} \gtrsim$ −2.5. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.</jats:p

The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.Comision Nacional de Energia Atomica, ArgentinaFundacion AntorchasGobierno De La Provincia de Mendoza, Municipalidad de Malargue, ArgentinaNDM HoldingsValle Las Lenas, ArgentinaAustralian Research Council (ARC)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Financiadora de Estudos e Projetos (FINEP)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Ministério da Ciência, Tecnologia e Inovação do Brasil (MCTI)Academy of Sciences of the Czech Republic (AVCR) [AV0Z10100502] [AV0Z10100522] [GAAV KJB300100801] [KJB100100904] [MSMT-CR LA08016] [LC527] [1M06002] [MSM0021620859]Centre National de la Recherche Scientifique (CNRS), Centre de Calcul IN2P3/CNRSConseil Regional Ile-de-France, Departement Physique Nucleaire et Corpusculaire [PNC-IN2P3/CNRS]Departement Sciences de l`Univers (SDU-INSU/CNRS), FranceBundesministerium fur Bildung und Forschung (BMBF)Deutsche Forschungsgemeinschaft (DFG)Finanzministerium Baden-WurttembergHelmholtz-Gemeinschaft Deutscher Forschungszentren (HGF)Ministerium fur Wissenschaft und Forschung, Nordrhein-Westfalen, GermanyMinisterium fur Wissenschaft, Forschung und Kunst, Baden-Wurttemberg, GermanyIstituto Nazionale di Fisica Nucleare (INFN)Istituto Nazionale di Astrofisica (INAF)Ministero dell Istruzione, dell Universita e della Ricerca (MIUR), ItalyConsejo Nacional de Ciencia y Tecnologia (CONACYT), MexicoMinisterie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)Stichting voor Fundamenteel Onderzoek der Materie (FOM), NetherlandsMinistry of Science and Higher Education, Poland [1 P03 D 014 30] [N N202 207238]Fundacao para a Ciencia e a Tecnologia (FCT), PortugalMinistry for Higher Education, Science, and Technology, Slovenian Research Agency, SloveniaComunidad de Madrid, SpainConsejeria de Educacion de la Comunidad de Castilla La ManchaFondo Europeo de Desarrollo Regional (FEDER)Ministerio de Ciencia e Innovacion, Consolider-Ingenio, SpainGeneralitat ValencianaJunta de AndaluciaXunta de Galicia, SpainScience and Technology Facilities Council, United KingdomU.S. Department of Energy (DOE) [DE-AC02-07CH11359] [DE-FR02-04ER41300]National Science Foundation (NSF) [0450696]Grainger Foundation USAALFA-EC / HELENEuropean Union [MEIF-CT-2005-025057] [PIEF-GA-2008-220240]United Nations Educational, Scientific and Cultural Organization (UNESCO

Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array

This paper presents the results of different searches for correlations between very high-energy neutrino candidates detected by IceCube and the highest-energy cosmic rays measured by the Pierre Auger Observatory and the Telescope Array. We first consider samples of cascade neutrino events and of high-energy neutrino-induced muon tracks, which provided evidence for a neutrino flux of astrophysical origin, and study their cross-correlation with the ultrahigh-energy cosmic ray (UHECR) samples as a function of angular separation. We also study their possible directional correlations using a likelihood method stacking the neutrino arrival directions and adopting different assumptions on the size of the UHECR magnetic deflections. Finally, we perform another likelihood analysis stacking the UHECR directions and using a sample of through-going muon tracks optimized for neutrino point-source searches with sub-degree angular resolution. No indications of correlations at discovery level are obtained for any of the searches performed. The smallest of the p-values comes from the search for correlation between UHECRs with IceCube high-energy cascades, a result that should continue to be monitored.ope