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Previously derived Faraday rotation constraints on the volume-filling intergalactic magnetic field (IGMF) have used analytic models that made a range of simplifying assumptions about magnetic field evolution in the intergalactic medium and did not consider the effect of baryonic feedback on large-scale structures. In this work we revise existing Faraday rotation constraints on the IGMF using a numerical model of the intergalactic medium from the IllustrisTNG cosmological simulation that includes a sophisticated model of the baryonic feedback. We use the IllustrisTNG model to calculate the rotation measure and compare the resulting mean and median of the absolute value of the rotation measure with data from the NRAO VLA Sky Survey (NVSS). The numerical model of the intergalactic medium includes a full magneto-hydrodynamic model of the compressed primordial magnetic field as well as a model of the regions where the magnetic field is not primordial, but is rather produced by the process of baryonic feedback. Separating these two types of regions, we are able to assess the influence of the primordial magnetic field on the Faraday rotation signal. We find that by correcting for regions of compressed primordial field and accounting for the fact that part of the intergalactic medium is occupied by magnetic fields spread by baryonic feedback processes rather than by the primordial field relaxes the Faraday rotation bound by a factor of $\simeq 3$. This results in $B_0, Replaced with the published version

Expansion of relativistic outflows of gamma-ray bursts (GRB) into medium created by the winds or their progenitor stars is accompanied by interactions of picked-up protons with the medium. These interactions produce neutrinos and γ-rays with energies in the TeV-PeV range. We study if such neutrinos and γ‑rays are detectable with neutrino and γ-ray telescopes. We find that neutrino signal can be detectable with IceCube-Gen2 type telescope(s) if the GRB progenitor has been a low-metallicity star with initial mass (40‒100) $${{M}_{ \odot }}$$ , or if the progenitor system has been a binary with dense circumstellar environment (~1013 cm–3) within the binary system extent. γ-ray emission from pion decays is detectable only in the afterglow phase, because of the pair production opacity of the prompt emission. This emission can contribute to the TeV afterglow flux of GRBs. Detection of the pion decay γ-ray and neutrino emission can serve as a diagnostic of the GRB progenitor evolution during the last years of its life.

Galactic outflows driven by star formation and active galactic nuclei blow bubbles into their local environments, causing galactic magnetic fields to be carried into intergalactic space. We explore the redshift-dependent effect of these magnetized bubbles on the Faraday Rotation Measure (RM) of extragalactic radio sources. Using the IllustrisTNG cosmological simulations, we separate the contribution from magnetic bubbles from that of the volume-filling magnetic component expected to be due to the seed field originating in the Early Universe. We use this separation to extract the redshift dependence of each component and to compare TNG model predictions with observation measurements of the NRAO VLA Sky Survey (NVSS). We find that magnetized bubbles provide a sizeable contribution to the extragalactic RM, with redshift-independent $\langle |{\rm RM}| \rangle \simeq 13$ rad/m$^2$ for sources at redshifts $z\ge 2$. This is close to the mean residual RM of $16$ rad/m$^2$ found from NVSS data in this redshift range. Using the IllustrisTNG simulations, we also evaluate a simple model for the contribution to residual RM from individual host galaxies and show that this contribution is negligible at high-redshift. While the contribution from magnetic bubbles in the IllustrisTNG model is currently compatible with observational measurements of residual RM, the next-generation RM sky surveys, which will be free from the wrapping uncertainty, have larger statistics and better sensitivity should be able to observe predicted flat contribution from magnetic bubbles at large redshifts. This should allow to experimentally probe magnetic bubbles and check models of galaxy feedback in cosmological simulations., 6 pages, 3 figures

We study constraints on the population of neutrino emitting blazars imposed by the absence of doublets in astrophysical muon neutrino signal and z>0.3 redshift of nearest identified neutrino-emitting blazar (an order of magnitude further away than the nearest gamma-ray emitting blazar). We show that in spite of the absence of correlation of neutrino arrival directions with positions of gamma-ray emitting blazars, cumulative blazar flux could explain most of astrophysical neutrino flux measured in muon neutrino channel. This is possible if the population of neutrino emitting blazars has experienced rapid positive evolution at least as (1+z)^5 at z< 1. Such a model avoids previously derived constraint on the low level of blazar contribution to extragalactic neutrino flux because gamma-ray and neutrino fluxes are dominated by different sets of blazars. Rapid evolution of neutrino emitting blazars could be explained by the fact that only high luminosity blazars hosting radiatively efficient accretion flows are efficient neutrino sources., 15 pages, 5 figures

The NANOGrav, Parkes, European, and International Pulsar Timing Array (PTA) Collaborations have reported evidence for a common-spectrum process that can potentially correspond to a stochastic gravitational wave background (SGWB) in the 1--100 nHz frequency range. We consider the scenario in which this signal is produced by magnetohydrodynamic (MHD) turbulence in the early Universe, induced by a nonhelical primordial magnetic field at the energy scale corresponding to the quark confinement phase transition. We perform MHD simulations to study the dynamical evolution of the magnetic field and compute the resulting SGWB. We show that the SGWB output from the simulations can be very well approximated by assuming that the magnetic anisotropic stress is constant in time, over a time interval related to the eddy turnover time. The analytical spectrum that we derive under this assumption features a change of slope at a frequency corresponding to the GW source duration that we confirm with the numerical simulations. We compare the SGWB signal with the PTA data to constrain the temperature scale at which the SGWB is sourced, as well as the amplitude and characteristic scale of the initial magnetic field. We find that the generation temperature is constrained to be in the 1--200 MeV range, the magnetic field amplitude must be $>1$\% of the radiation energy density at that time, and the magnetic field characteristic scale is constrained to be $>10$\% of the horizon scale. We show that the turbulent decay of this magnetic field will lead to a field at recombination that can help to alleviate the Hubble tension and can be tested by measurements in the voids of the Large Scale Structure with gamma-ray telescopes like the Cherenkov Telescope Array., 28 pages, 9 figures, 1 table, accepted for publication in Phys. Rev. D, files and code available in https://github.com/AlbertoRoper/GW_turbulence

The Tibet ASγ collaboration has recently reported the detection of γ-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We note that the analysis of γ-ray flux by the Tibet-ASγ experiment also implies an upper bound on the diffuse γ-ray flux from high Galactic latitudes (|b|> 20°) in the energy range between 100 TeV and 1 PeV. This bound is up to an order of magnitude stronger than previously derived bounds from GRAPES3, KASCADE, and CASA-MIA experiments. We discuss the new Tibet-ASγ limit on the high Galactic latitude γ-ray flux in the context of possible mechanisms of multi-messenger (γ-ray and neutrino) emission from nearby cosmic ray sources, dark matter decays, and the large-scale cosmic ray halo of the Milky Way.

New field of multi-messenger astronomy has experienced rapid expansion over the last several years. The range of astronomical “messenger” channels now includes, along with electromagnetic radiation, also neutrinos and gravitational waves. Signals detected in these channels span over 43 decades in energy / frequency. This talk provides an overview of the most recent developments in the field, across different types of messengers and energy / frequency ranges.

International audience; We study the sensitivity reach of the gamma-ray method for measurement of relatively strong cosmological magnetic field with strength in the 1-10 pG range using deep exposure of the nearest hard spectrum blazar Mrk 501 with CTA telescopes. We show that the gamma-ray measurement technique can sense the primordial magnetic field with a strength of up to 10^{−11} G. Combination of the cosmic microwave background and gamma-ray constraints can thus sense the full range of possible cosmological magnetic fields to confirm or rule out their relevance to the problem of the origin of cosmic magnetic fields, as well as their influence on recombination and reionization epochs.

International audience; Context. During more than 17 years of operation in space, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) telescope has accumulated a large data set that contains records of hard X-ray and soft γ-ray astronomical sources. These data can be reused in the context of multi-wavelength or multi-messenger studies of astronomical sources and have to be preserved on long timescales.Aims. We present a scientific validation of an interactive online INTEGRAL data analysis system for multi-wavelength studies of hard X-ray and soft γ-ray sources.Methods. The online data analysis system generates publication-quality high-level data products: sky images, spectra, and light curves in response to user queries that define analysis parameters such as source position, time and energy interval, and binning. The data products can be requested via a web browser interface or via an application programming interface that is available as a Python package. The products for the Imager on Board the INTEGRAL Satellite/INTEGRAL Soft Gamma-Ray Imager instrument of INTEGRAL are generated using the offline science analysis (OSA) software, which is provided by the instrument teams and is conventionally used to analyse INTEGRAL data. The analysis workflow is organised to preserve and reuse various intermediate analysis products, ensuring that frequently requested results are available without delay. The platform is implemented in a Docker cluster that allows operation of the software in a controlled virtual environment and can be deployed in any compatible infrastructure. The scientific results produced by the open data analysis (ODA) are identical to those produced by OSA because ODA simply provides a platform to retrieve the OSA results online while leveraging a provenance-indexed database of precomputed (cached) results to optimise and reuse the result.Results. We report the functionalities and performance of the online data analysis system by reproducing the benchmark INTEGRAL results on different types of sources, including bright steady and transient Galactic sources, and bright and weak variable extra-galactic sources. We compare the results obtained with the online data analysis system with previously published results on these sources. We also discuss limitations of the online analysis system.Conclusions. We consider the INTEGRAL online data analysis as a demonstration of a more general web-based ‘data analysis as a service’ approach that provides a promising solution for the preservation and maintenance of data analysis tools of astronomical telescopes on (multi)decade long timescales and facilitates combining data in multi-wavelength and multi-messenger studies of astronomical sources.Key words: methods: data analysis / X-rays: general / methods: observational

A primordial magnetic field with the strength in the 1-10 pG range can resolve the tension between different measurements of the Hubble constant and provide an explanation for the excess opacity in the 21 cm line at redshift $15, Comment: 9 pages, 7 figures, accepted to ApJ

International audience; The Tibet-ASγ Collaboration has recently reported a measurement of diffuse γ-ray flux from the outer Galactic disk in the energy range reaching PeV. We complement this measurement with the Fermi/LAT measurement of the diffuse flux from the same sky region and study the pion decay model of the combined Fermi/LAT+Tibet-ASγ spectrum. We find that within such a model the average cosmic-ray spectrum in the outer Galactic disk has the same characteristic features as the local cosmic-ray spectrum. In particular, it experiences a hardening at several hundred GV rigidity and a knee feature in the PV rigidity range. The slope of the average cosmic-ray spectrum above the break is close to the locally observed slope of the helium spectrum γ≃2.5, but is harder than the slope of the local proton spectrum in the same rigidity range. Although the combination of Fermi/LAT and Tibet-ASγ data points to the presence of the knee in the average cosmic-ray spectrum, the quality of the data is not yet sufficient for the study of knee shape and cosmic-ray composition.

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. POEMMA will observe the extensive air showers (EASs) from UHECRs and UHE neutrinos above 20 EeV via air fluorescence. Additionally, POEMMA will observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45$^\circ$) Schmidt telescope with over 6 m$^2$ of collecting area. The hybrid focal surface of each telescope includes a fast (1~$\mu$s) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10~ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these otherwise inaccessible energies., Comment: 66 pages, 53 figures; JCAP accepted version

International audience; The NANOGrav Collaboration has recently reported evidence for the existence of a stochastic gravitational wave background in the 1–100 nHz frequency range. We argue that such a background could have been produced by magnetohydrodynamic (MHD) turbulence at the QCD scale. From the NANOGrav measurement, one can infer the magnetic field parameters: a comoving field strength close to microGauss and a correlation length close to 10% of the Hubble radius at the QCD phase transition epoch. We point out that the turbulent decay of a nonhelical magnetic field with such parameters leads to a magnetic field at the recombination epoch, which would be sufficiently strong to provide a solution to the Hubble tension problem, as recently proposed. We also show that the MHD turbulence interpretation of the NANOGrav signal can be tested via measurements of the relic magnetic field in the voids of the large scale structure, with gamma-ray telescopes like CTA.

The eHWC J1825-134 gamma-ray source is located in the southern sky and has been recently detected by the HAWC observatory. Amongst the HAWC sources, it is the most luminous in the multi-TeV domain. We show the prospects to detect this source at the forthcoming KM3NeT detector and comment on the possibilities of detection with other neutrino telescopes.

Measurement of diffuse gamma-ray emission from the Milky Way with Imaging Atmospheric Cherenkov Telescopes (IACT) is difficult because of high level of charged cosmic ray background and small field-of-view. We show that such a measurement is nevertheless possible in the energy band 10-100 TeV. The minimal charged particle background for IACTs is achieved in event selections used for the analyses of the cosmic ray electrons. Tight cuts on the event quality in these event selections allow to achieve the background level sufficiently low to allow the measurements of the diffuse Galactic gamma-ray flux above 10 TeV. We calculate the sensitivities of different types of IACT arrays for the Galactic diffuse emission measurements and compare them with the diffuse gamma-ray flux from different parts of the sky measured by the Fermi Large Area Telescope below 3 TeV and with the astrophysical neutrino signal measured by IceCube telescope. We show that deep exposure of existing IACT systems is sufficient for detection of the diffuse flux from all the Galactic Plane up to Galactic latitude |b|~ degrees. Medium Size Telescope array of CTA will be able to detect the diffuse flux up 30 degree Galactic latitude. Its sensitivity will be sufficient for detection of the gamma-ray counterpart of the Galactic component of the IceCube astrophysical neutrino signal above 10 TeV. We also propose that a dedicated IACT system composed of small but wide field-of-view telescopes could be used for mapping the 10-100 TeV the diffuse gamma-ray emission from across all the sky., Comment: 7 pages, 5 figures, version accepted to A&A

www.astro.unige.ch/cdci/astrooda_?src_name=Crab&RA=83.633080&DEC=22.014500&E1_keV=20&E2_keV=40&T1=2007-03-15T00:00:00.0&T2=2008-03-15T00:00:00.0&T_format=isot&catalog_selected_objects=1,2,3,4&detection_threshold=7.5&instrument=isgri&osa_version=OSA10.2&product_type=isgri_spectrum&query_status=ready&query_type=Real&radius=15&use_scws=no&selected_catalog=%7B%22cat_column_descr%22:%5B%5B%22meta_ID%22,%22%3Ci8%22%5D,%5B%22src_names%22,%22%7CS18%22%5D,%5B%22significance%22,%22%3Ef4%22%5D,%5B%22ra%22,%22%3Ef4%22%5D,%5B%22dec%22,%22%3Ef4%22%5D,%5B%22NEW_SOURCE%22,%22%3Ei2%22%5D,%5B%22ISGRI_FLAG%22,%22%3Ci8%22%5D,%5B%22FLAG%22,%22%3Ci8%22%5D,%5B%22ERR_RAD%22,%22%3Cf8%22%5D%5D,%22cat_column_list%22:%5B%5B1,2,3,4%5D,%5B%221A+0535%2B262%22,%224U+0517%2B17%22,%22Crab%22,%22H+0614%2B091%22%5D,%5B116.7,7.9,1232.6,8.1%5D,%5B84.726,77.667,83.631,94.254%5D,%5B26.314,16.487,22.015,9.165%5D,%5B-32768,-32768,-32768,-32768%5D,%5B2,2,2,2%5D,%5B0,0,0,0%5D,%5B0.0002,0.0002,0.0002,0.0002%5D%5D,%22cat_column_names%22:%5B%22meta_ID%22,%22src_names%22,%22significance%22,%22ra%22,%22dec%22,%22NEW_SOURCE%22,%22ISGRI_FLAG%22,%22FLAG%22,%22ERR_RAD%22%5D,%22cat_coord_units%22:%22deg%22,%22cat_frame%22:%22fk5%22,%22cat_lat_name%22:%22dec%22,%22cat_lon_name%22:%22ra%22%7D

We estimate the sensitivity of LHAASO telescope for the large angular scale diffuse $\ensuremath{\gamma}$-ray flux in multi-TeV---multi-PeV energy range. We discuss possible sources of the signal in this energy range including the guaranteed flux from cosmic ray interactions in the interstellar medium and possible flux from decaying dark matter. We show that LHAASO will be able to detect the diffuse cosmic ray induced $\ensuremath{\gamma}$-ray flux up to high Galactic latitude regions thus providing firm identification of the Galactic cosmic ray component of the astrophysical neutrino signal detected by IceCube and clarification of the nature of the knee feature of the cosmic ray spectrum. Comparing the diffuse flux sensitivity with the diffuse $\ensuremath{\gamma}$-ray flux expected from the dark matter decays, we show LHAASO will be able to detect the $\ensuremath{\gamma}$-ray signal from dark matter particles of PeV--EeV mass decaying on the time scale up to $3\ifmmode\times\else\texttimes\fi{}{10}^{29}\text{ }\text{ }\mathrm{s}$.

We explore possible physical origin of correlation between radio wave and very-high-energy neutrino emission in active galactic nuclei (AGN), suggested by recently reported evidence for correlation between neutrino arrival directions and positions of brightest radio-loud AGN. We show that such correlation is expected if both synchrotron emitting electrons and neutrinos originate from decays of charged pions produced in proton-proton interactions in parsec-scale relativistic jet propagating through circum-nuclear medium of the AGN., Comment: 6 pages, 1 figure, accepted to JETP Lett

Measuring the diffuse Galactic gamma-ray flux in the TeV range is difficult for ground-based gamma-ray telescopes because of the residual cosmic-ray background, which is higher than the gamma-ray flux by several orders of magnitude. Its detection is also challenging for space-based telescopes because of low signal statistics. We characterize the diffuse TeV flux from the Galaxy using decade-long exposures of the Fermi Large Area Telescope. Considering that the level of diffuse Galactic emission in the TeV band approaches the level of residual cosmic-ray background, we estimated the level of residual cosmic-ray background in the SOURCEVETO event selection and verified that the TeV diffuse Galactic emission flux is well above the residual cosmic-ray background up to high Galactic latitude regions. We study spectral and imaging properties of the diffuse TeV signal from the Galactic plane. We find much stronger emission from the inner Galactic plane than in previous HESS telescope estimates (lower bound). We also find a significant difference in the measurement of the Galactic longitude and latitude profiles of the signal measured by Fermi and HESS. These discrepancies are presumably explained by the fact that regions of background estimate in HESS have non-negligible gamma-ray flux. Comparing Fermi measurements with those of ARGO-YBJ, we find better agreement, with the notable exception of the Cygnus region, where we find much higher flux (by a factor 1.5). We also measure the TeV diffuse emission spectrum up to high Galactic latitude and show that the spectra of different regions of the sky have spectral slopes consistent with Gamma=2.34+/- 0.04. We discuss the possible origin of the hard slope of the TeV diffuse emission. Fermi/LAT provides reliable measurements of the diffuse Galactic emission spectrum in the TeV range., Comment: 10 pages, 7 figures, accepted to A&A

arXiv:2012.01346v1, et al., In the last 25 years a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal resolution up to the hard X-ray/soft, γ-ray band and a large field of view imager with good angular resolution to spot hard X-ray transients. In this article we review the main contributions by INTEGRAL to our understanding of the pulsating hard X-ray sky, such as the discovery and characterization of several accreting and transitional millisecond pulsars, the generation of the first catalog of hard X-ray/soft γ-ray rotation-powered pulsars, the detection of polarization in the hard X-ray emission from the Crab pulsar, and the discovery of persistent hard X-ray emission from several magnetars., Al. P., D. d. M. and T. D. S. acknowledge financial support from ASI/INAF I/037/12/0, ASI/INAF 2017-14-H.0 (PI: De Rosa, PI: Belloni) and from INAF “Sostegno alla ricerca scientifica main streams dell’INAF”, Presidential Decree 43/2018 and from “SKA/CTA projects”, Presidential Decree N. 70/2016. J.P. was supported by the Ministry of Science and Higher Education of the Russian Federation grant 14.W03.31.0021. The INTEGRAL French teams acknowledge partial funding from the French Space Agency (CNES). Z.L. thanks the International Space Science Institute in Bern for the hospitality. Z.L was supported by National Natural Science Foundation of China (Grant nos. U1938107, 11703021, U1938107, 11873041). Ad. P. and S. M. acknowledge continuous support from the Italian Space Agency ASI through the ASI/INAF agreement n.2019-35-HH. D. F. T and the group at the Institute of Space Sciences acknowledges support via grants PGC2018-095512-B-I00, SGR2017-1383, and AYA2017-92402-EXP. F .C. Z. is supported by a Juan de la Cierva fellowship. V. D. F. acknowledges Silesian University in Opava and Gruppo Nazionale di Fisica Matematica of Istituto Nazionale di Alta Matematica for support. This research was supported by the Polish National Science Centre grant number 2017/25/B/ST9/02805. J.L. acknowledges the support from the Alexander von Humboldt Foundation.

[Context] Markarian 501 (Mrk 501) is a very high-energy (VHE) gamma-ray blazar located at z = 0:034, which is regularly monitored by a wide range of multi-wavelength instruments, from radio to VHE gamma rays. During a period of almost two weeks in July 2014, the highest X-ray activity of Mrk 501 was observed in -14 years of operation of the Neil Gehrels Swift Gamma-ray Burst Observatory., [Aims] We characterize the broadband variability of Mrk 501 from radio to VHE gamma rays during the most extreme X-ray activity measured in the last 14 years, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars., [Methods] The emission of Mrk 501 was measured at radio with Metsähovi, at optical–UV with KVA and Swift/UVOT, at X-ray with Swift/XRT and Swift/BAT, at gamma ray with Fermi-LAT, and at VHE gamma rays with the FACT and MAGIC telescopes. The multi-band variability and correlations were quantified, and the broadband spectral energy distributions (SEDs) were compared with predictions from theoretical models., [Results] The VHE emission of Mrk 501 was found to be elevated during the X-ray outburst, with a gamma-ray flux above 0.15 TeV varying from ∼0.5 to ∼2 times the Crab nebula flux. The X-ray and VHE emission both varied on timescales of 1 day and were found to be correlated. We measured a general increase in the fractional variability with energy, with the VHE variability being twice as large as the X-ray variability. The temporal evolution of the most prominent and variable segments of the SED, characterized on a day-by-day basis from 2014 July 16 to 2014 July 31, is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. These results suggest that the main flux variations during this extreme X-ray outburst are produced by the acceleration and the cooling of the high-energy electrons. A narrow feature at ∼3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (>0.3 keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3σ. A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4σ, and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3σ. Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: (a) a pileup in the EED due to stochastic acceleration; (b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and (c) an emission from an IC pair cascade induced by electrons accelerated in a magnetospheric vacuum gap, in addition to the SSC emission from a more conventional region along the jet of Mrk 501., The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, FPA2017-90566-REDC), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Instituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. The important contributions from ETH Zurich grants ETH-10.08-2 and ETH-27.12-1 as well as the funding by the Swiss SNF and the German BMBF (Ver-bundforschung Astro-und Astroteilchenphysik) and HAP (Helmoltz Alliance for Astroparticle Physics) are gratefully acknowledged. Part of this work is supported by Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Center SFB 876, project C3. We thank the Instituto de Astrofisica de Canarias for allowing us to operate the telescope at the Observatorio del Roque de los Muchachos in La Palma, the Max-Planck-Institut fur Physik for providing us with the mount of the former HEGRA CT3 telescope, and the MAGIC Collaboration for their support. JBG acknowledges the support of the Viera y Clavijo program funded by ACIISI and ULL. C. W. is grateful for the support by the project “Promotion inklusive” of the Universität zu Köln and the German Bundesmin-isterium für Arbeit und Soziales. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University, Finland.

New astronomy reviews 86, 101546 (2019). doi:10.1016/j.newar.2020.101546, High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies.In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system.We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields.We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations., Published by Elsevier Science, Amsterdam [u.a.]

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures to map the faint Cherenkov light emitted in extensive air showers onto their image sensors. Segmented reflectors fulfill these needs using mass produced and light weight mirror facets. However, as the overall image is the sum of the individual mirror facet images, alignment is important. Here we present a method to determine the mirror facet positions on a segmented reflector in a very direct way. Our method reconstructs the mirror facet positions from photographs and a laser distance meter measurement which goes from the center of the image sensor plane to the center of each mirror facet. We use our method to both align the mirror facet positions and to feed the measured positions into our IACT simulation. We demonstrate our implementation on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT)., 11 figures, small ray tracing performance simulation, and implementation demonstration

The eHWC J1825-134 source is located in the southern sky and has been recently detected by the HAWC observatory. It presents an hard spectral index and its gamma-ray flux extends up to energies close to 100 TeV without significant suppression. Amongst the HAWC sources, it is the most luminous in the multi-TeV domain and therefore is one of the first that should be searched for with a neutrino telescope in the northern hemisphere. Using an updated effective area for the forthcoming KM3NeT detector, we study the possibility to detect this source within ten years of its running time. We conclude that about a 4 to 5 sigma detection has to be expected after ten years of observations, depending on the details of the considered scenario., Comment: 10 pages, 4 figures, 2 tables. Typos corrected, updated references, acknowledgments and plots, conclusions unchanged

Markarian 421 and Markarian 501 are Active Galactic Nuclei and two of the most prominent sources of very high energetic gamma rays. In contrast to the predominantly stable Crab Nebula, the two blazars have extremely variable gamma-ray fluxes. Those could be caused by erratic accretion flow instabilities, but also by processes leading to quasi periodic oscillations (QPOs). Recently, hints of such a QPO of Mrk 501 with a period of about 322 days have been observed with the Large Area Telescope on-board of the Fermi satellite at GeV energies featuring global and local significances of the signal above 99%. The First G-APD Cherenkov Telescope (FACT) has monitored a small sample of known TeV gamma-ray sources including Mrk 421 and Mrk 501 over the last seven years. Therefore, it is ideally suited for periodicity studies of Active Galactic Nuclei, as they require unbiased and continuous long-term observations. Based on measurements of the well-known gamma-ray flux originating from the Crab Nebula, corrections to the measured light curves are applied. In total, 2500~hours of data for each of the two blazars have been analysed using the Lomb-Scargle algorithm. The resulting periodogram of Mrk 501 shows a hint of QPO with a similar period as the one observed by Fermi/LAT., PoS: Proceedings of Science, 358, ISSN:1824-8039, Proceedings of 36th International Cosmic Ray Conference (ICRC 2019)

International audience; Tau neutrinos with energies in the PeV-EeV range produce up-going extensive air showers (UEAS) if they interact underground close enough to the surface of the Earth. This work studies detectability of the UEAS with a system of fluorescence telescopes overlooking dark, low reflectivity, area on the ground up to the distances 20–50 km from mountain top(s). Such system could provide sensitivity sufficient for accumulation of the astrophysical neutrino signal statistics at the rate ten(s) events per year in the energy range beyond 10 PeV, thus allowing to extend the energy frontier of neutrino astronomy into 10–100 PeV range. Comparison of sensitivities of the top-of-the-mountain telescope and IceCube Generation II shows that the two approaches for neutrino detection are complementary, providing comparable performance in adjacent energy bands below and above 10 PeV. Sensitivity of the top-of-the-mountain fluorescence telescope system is also sufficient for the discovery of theoretically predicted cosmogenic neutrino signal.

Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample., Galaxies, 7 (2)

A γ-ray excess at high Galactic latitudes starting at energies 300 GeV was recently discovered in the data of the Fermi telescope. The multi-TeV γ-ray emission found has spectral characteristics at both low and high Galactic latitudes compatible with those of the IceCube neutrinos in the same sky regions. This suggests that these γ-rays are the counterpart of the IceCube neutrino signal, implying that a sizeable part of the IceCube neutrino flux originates from the Milky Way. The diffuse neutrino and γ-ray signal at high Galactic latitudes may originate either from a nearby cosmic ray "PeVatron" cosmic ray source, an extended Galactic cosmic ray halo or from decays of heavy dark matter particles. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

In this paper we describe the different software and hardware elements of a mini-telescope for the detection of cosmic rays and gamma-rays using the Cherenkov light emitted by their induced particle showers in the atmosphere. We estimate the physics reach of the standalone mini-telescope and present some results of the measurements done at the Sauverny Observatory of the University of Geneva and at the Saint-Luc Observatory, which demonstrate the ability of the telescope to observe cosmic rays with energy above about 100 TeV. Such a mini-telescope can constitute a cost-effective out-trigger array that can surround other gamma-ray telescopes or extended air showers detector arrays. Its development was born out of the desire to illustrate to students and amateurs the cosmic ray and gamma-ray detection from ground, as an example of what is done in experiments using larger telescopes. As a matter of fact, a mini-telescope can be used in outreach night events. While outreach is becoming more and more important in the scientific community to raise interest in the general public, the realisation of the mini-telescope is also a powerful way to train students on instrumentation such as photosensors, their associated electronics, acquisition software and data taking. In particular, this mini-telescope uses silicon photomultipliers (SiPM) and the dedicated ASIC, CITIROC., Comment: submitted to JINST

We show that the Galactic latitude distribution of IceCube astrophysical neutrino events with energies above 100~TeV is inconsistent with the isotropic model of the astrophysical neutrino flux. Namely, the Galactic latitude distribution of the events shows an excess at low latitudes |b| 50 degrees. We use Monte-Carlo simulations to show that the inconsistency of the isotropic signal model with the data is at > 3 sigma level, after the account of trial factors related to the choice of the low-energy threshold and Galactic latitude binning in our analysis., 4 pages, 2 figures, accepted to Astroparticle Physics

Cumulative optical and infrared emission from galaxies accumulated over cosmological time scales, the extragalactic background light (EBL), could be probed by complementary techniques of direct observations and source counting in the visible and infrared as well as via its imprint on the signal of distant active galactic nuclei in gamma rays. We compare the visible and infrared measurements with the gamma-ray constraints and study if the discrepancies of the measurements with different methods could be due to the presence of features in the EBL spectrum that are localised in the micron wavelength range. We combined data on time-averaged spectra of selected blazars that were obtained by Fermi and ground-based gamma-ray telescopes. We also modelled the effect of absorption on EBL while allowing for the existence of a previously unaccounted spectral feature. We show that a previously reported 'excess' in EBL flux in the $\sim 1$~micron wavelength range is consistent with gamma-ray measurements, that is, if the excess has the form of a narrow feature of the width $\delta \lambda < \lambda$ and an overall flux of up to 15 nW/(m$^2$ sr) above the 'minimal' EBL, which is estimated from the visible and infrared source counts. Such 'bump-like' spectral features could originate, for example, from decaying dark-matter particles, or either axions or peculiar astrophysical processes in the course of star-formation history. We discuss the possibilities for the search of spectral features in the EBL with the Cherenkov Telescope Array (CTA)., Comment: V2: 7 pages, 4 figures. Considerable changes in the blazar sample, results unchanged; discussions extended - version accepted by A&A

The new field of multi-messenger astronomy aims at the study of astronomical sources using different types of "messenger" particles: photons, neutrinos, cosmic rays and gravitational waves. These lectures provide an introductory overview of the observational techniques used for each type of astronomical messenger, of different types of astronomical sources observed through different messenger channels and of the main physical processes involved in production of the messenger particles and their propagation through the Universe., Comment: Lectures at ISAPP-Baikal Summer school 2018, "Exploring the Universe through multiple messengers"

We present the first individual and stacking systematic search for $\gamma$-ray emission in the GeV band with the {\it Fermi} Large Area Telescope (LAT), in the directions of 45 super-luminous supernovae (SLSNe). No excess of \gam rays from the SLSN positions was found. We report $\gamma$-ray luminosity upper limits and discuss the implication of these results on the origin of SLSNe in particular on the scenario of central compact object-aided SNe. From the stacking search, we derive an upper limit at 95\% confidence level (CL) to the $\gamma$-ray luminosity (above 600 MeV) $L_{\gamma}, Comment: 12 pages, 6 figures, 7 tables, accepted by A&A

A signal of high-energy extraterrestrial neutrinos from unknown source(s) was recently discovered by the IceCube experiment. Neutrinos are always produced together with $\ensuremath{\gamma}$-rays, but the $\ensuremath{\gamma}$-ray flux from extragalactic sources is suppressed due to attenuation in the intergalactic medium. We report the discovery of a $\ensuremath{\gamma}$-ray excess at high galactic latitudes starting at energies 300 GeV in the data of the Fermi telescope. We show that the multi-TeV $\ensuremath{\gamma}$-ray diffuse emission has spectral characteristics at both low and high galactic latitudes compatible with those of the IceCube high neutrino signal in the same sky regions. This suggests that these $\ensuremath{\gamma}$-rays are the counterpart of the IceCube neutrino signal, implying that a sizable part of the IceCube neutrino flux originates from the Milky Way. We argue that the diffuse neutrino and $\ensuremath{\gamma}$-ray signal at high galactic latitudes originates either from previously unknown nearby cosmic ray ``PeVatron'' source(s), an extended galactic cosmic ray halo or from decays of heavy dark matter particles.

The supernova explosion which deposited $^{60}$Fe isotopes on Earth 2-3 million years ago should have also produced cosmic rays which contribute to the locally observed cosmic ray flux. We show that the contribution of this "local source" explains the "anomalies" observed in the positron and antiproton fluxes and explains why their spectral shape agrees with that of the proton flux. At the same time, this local source component accounts for the difference in the slopes of the spectra of cosmic ray nuclei as the result of the slightly varying relative importance of the "local" and the average component for distinct CR nuclei. Such a "local supernova" model for the spectra of nuclei can be tested via a combined measurement of the energy dependence of the boron-to-carbon (primary-to-secondary cosmic rays) ratio and of the antiproton spectrum: While the antiproton spectrum is predicted to extend approximately as a power law into the TeV range without any softening break, the B/C ratio is expected to show a "plateau" at a level fixed by the observed positron excess in the 30-300 GeV range. We discuss the observability of such a plateau with dedicated experiments for the measurement of the cosmic ray composition in 10 TeV energy range (NUCLEON, ISS-CREAM)., v2: added section on electrons, references and extended discussion; to appear in PRD; 10 pages, 7 pdf figures

Imaging Atmospheric Cherenkov Telescopes (IACT) are designed to detect γ -ray photons in the very-high energy (VHE) band from 50 GeV to more than 10 TeV. The few degree-scale field of view and the good angular resolution γ -ray photons of IACTs using Crab Nebula data collected with the MAGIC stereoscopic system. Through a careful description of the background and response of the instrument we can build the γ -ray PSF corrected for the angular acceptance. We find a good analytical model describing the γ -ray PSF for IACTs and assess its stability.

Imaging Atmospheric Cherenkov Telescopes provide large gamma-ray collection areas > 10^4 m^2 and successfully probe the high energetic gamma-ray sky by observing extensive air showers during the night. The First G-APD Cherenkov Telescope (FACT) explores silicon based photoelectric converters (called G-APDs or SiPMs) which provide more observation time with strong moonlight, a more stable photon gain over years of observations, and mechanically simpler imaging cameras. So far, the signal extraction methods used for FACT originate from sensors with no intrinsic quantized responses like photomultiplier tubes. This standard signal extraction is successfully used for the long time monitoring of the gamma-ray flux of bright blazars. However, we now challenge our classic signal extraction and explore single photon extraction methods to take advantage of the highly stable and quantized single photon responses of FACT's SiPM sensors. Instead of having one main pulse with one arrival time and one photon equivalent extracted for each pixel, we extract the arrival times of all individual photons in a pixel’s time line which opens up a new dimension in time for representing extensive air showers with an IACT. In this contribution, we will introduce our novel IACT event representation which is a list of single photon arrival times for each pixel (Photon-Stream). We will discuss our single photon extractor, its performance and its limitations. We will present example events where we identify individual, single air shower Cherenkov photons in the pool of individual, single night sky background photons., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

Solid state photosensors, usually called SiPM or G-APD, seem ideal devices to be used in Imaging Atmospheric Cherenkov Telescopes (IACT). Nevertheless, their temperature dependence poses questions about their suitability in the harsh environment intrinsic to the operation of IACTs. While detailed measurements in the laboratory are possible with some sample sensors, limited data about the performance and uniformity of large samples exist. The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of SiPMs for IACTs. Its camera consists of 1440 SiPMs and it is operated since October 2011 each night when observation conditions permit. Using no temperature stabilization system for the sensors, their temperature is closely coupled to the outside temperature that can change by more than 20 ∘C. While the strong temperature dependence of the gain of the sensors was shown to be easily compensated by adapting the applied voltage, there could also be higher order temperature dependencies of parameters like optical cross-talk, after-pulsing and wavelength dependent photon-detection efficiency. While external calibration devices could be used, one would have to proof that these devices do not have their own temperature dependencies. Instead, we use the constant flux of high energetic cosmic ray particles as calibration device. Their measured flux can depend on variable absorption and scattering of Cherenkov light e.g. due to dust and clouds, as well as on seasonal variations of the atmosphere. Nevertheless, using data sets where the temperature drastically changed within short time periods, we show that temperature dependencies of FACT, including the SiPMs, are well under control., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of silicon photo mul- tipliers (SiPMs also known as G-APDs) for the imaging atmospheric Cherenkov technique. It is located at the Observatorio Roque de los Muchachos on the Canary island of La Palma. Since first light in October 2011, it is monitoring bright TeV blazars in the northern sky. By now, FACT is the only imaging atmospheric Cherenkov telescope operating with S I PMs on a nightly basis. Over the course of the last five years, FACT has been demonstrating their reliability and excel- lent performance. Moreover, their robustness allowed for an increase of the duty cycle including nights with strong moon light without the need for UV-filters. In this contribution, we will present the performance of the first Cherenkov telescope using solid state photo sensors, which was determined in analysis of data from Crab Nebula, the so called standard candle in gamma-ray astronomy. The presented analysis chain utilizes modern data mining methods and unfolding techniques to obtain the energy spectrum of this source. The characteristical results of such an analysis will be reported providing, e. g., the angular and energy resolution of FACT, as well as, the energy spectrum of the Crab Nebula. Furthermore, these results are discussed in the context of the performance of coexisting Cherenkov telescopes., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

A foreground galaxy cluster is magnifying a more distant blazar by gravitationally bending the emitted radiation. Using such a lens, it is possible to resolve a jet close to the central supermassive black hole as being the source of the gamma rays. Gamma-ray emission from blazars is known to originate from jets emitted by supermassive black holes1. However, the exact location and size of the γ-ray emitting part of the jets is uncertain2,3,4,5,6. The main difficulty is the very small angular size of these sources, beyond the angular resolution of γ-ray telescopes. Here, we report a measurement of the projected size of the γ-ray jet, revealed by the detection of microlensing in the gravitationally lensed blazar PKS 1830-211. This measurement is consistent with a constraint from the intrinsic variability timescale of the blazar. Our measurement shows that the γ-ray emission originates from the vicinity of the central supermassive black hole. Combining the X-ray and γ-ray data, we use the microlensing effect to constrain the size of the X-ray source. We show that the effect of pair production of γ-rays on X-ray photons does not make the source opaque, owing to the large size of the X-ray emission region.

FACT, the First G-APD Cherenkov Telescope, is an Imaging Air Cherenkov Telescope (IACT) operating since 2011 at the Observatorio del Roque de los Muchachos on the Canary Island of La Palma. As typical for IACTs, its reflector is comprised of smaller mirror facets and not protected by a dome. In the case of FACT, 30 hexagonal facets form a total mirror area of 9.5 m 2 . Hence, it is crucial to monitor the optical properties of this system and realign the facets if necessary. Up to now, measuring the Point Spread Function of FACT required human interaction to mount a screen and an optical camera. In this contribution, a new method to measure the optical Point Spread Function using directly the Cherenkov camera of the telescope is presented. Inspired by the method radio telescopes use to determine their resolution, the telescope is pointed towards a fixed position on the trajectory of a star. During the star’s passage through the field of view, the camera is read out using a fixed rate. In each event, the pedestal variance is determined for each pixel. This value is directly correlated with the amount of night sky background light a pixel received. Translating the time of the measurement to the position of the star in the camera enables to determine the optical point spread function from this measurement. As the measurement is done for each pixel along the trajectory of the star, the Point Spread Function can be determined not only for the camera center but for the entire field of view. In this contribution, the new method will also be compared with the existing methods of determining the optical Point Spread Function: direct measurement with an optical camera and the width of Muon ring events, PoS: Proceedings of Science, 301, ISSN:1824-8039

The SST-1M is a 4-m Davies-Cotton atmospheric Cherenkov telescope optimized to provide gamma-ray sensitivity above a few TeV. The SST-1M is proposed as part of the Small-Size Telescope array for the Cherenkov Telescope Array (CTA), the first prototype has already been deployed. The SST-1M control software of all subsystems (active mirror control, drive system, safety system, photo-detection plane, DigiCam, CCD cameras) and the whole telescope itself (master controller) uses the standard software design proposed for all CTA telescopes based on the ALMA Common Software (ACS) developed to control the Atacama Large Millimeter Array (ALMA). Each subsystem is represented by a separate ACS component, which handles the communication to and the operation of the subsystem. Interfacing with the actual hardware is performed via the OPC UA communication protocol, supported either natively by dedicated industrial standard servers (PLCs) or separate service applications developed to wrap lower level protocols (e.g. CAN bus, camera slow control) into OPC UA. Early operations of the telescope without the camera were already carried out. The camera is fully assembled and is capable to perform data acquisition using artificial light source.

Blazars are highly variable objects and their spectral energy distribution (SED) features two peaks. The emission at low energies is understood, however, the origin of the emission at TeV energies is strongly debated. While snapshots of SEDs usually can be explained with simple models, the evolution of SEDs challenges many models and allows for conclusions on the emission mechanisms. Leptonic models expect a correlation between the two peaks, while hadronic models can accommodate more complex correlations. To study time-resolved SEDs, we set up a target-of-opportunity program triggering high-resolution X-ray observations based on the monitoring at TeV energies by the First G-APD Cherenkov Telescope (FACT). To search for time lags and identify orphan flares, this is accompanied by X-ray monitoring with the Swift satellite. These observations provide an excellent multi-wavelength (MWL) data sample showing the temporal behaviour of the blazar emission along the electromagnetic spectrum. To constrain the origin of the TeV emission, we extract the temporal evolution of the low energy peak from Swift data and calculate the expected flux at TeV energies using a theoretical model. Comparing this to the flux measured by FACT, we want to conclude on the underlying physics. Results from more than five years of monitoring will be discussed., PoS: Proceedings of Science, 301, ISSN:1824-8039