Abstracts of Interest
Selected by:
Ryan Burley
Abstract: 1903.03092
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Title:Revisiting Kunitomo's Sunspot Drawings during 1835-1836 in Japan
(Submitted on 7 Mar 2019)
Abstract: We revisit the sunspot drawings made by the Japanese astronomer Kunitomo Toubei during 1835-1836 and recount the sunspot group number for each image. There are two series of drawings, preliminary (P, containing 17 days with observations) and summary (S, covering 156 days with observations), all made using brush and ink. S is a compilation of drawings for the period from February 1835, to March 1836. Presently, the P drawings are available only for one month, September 1835; those of other periods have presumably been lost. Another drawing (I) lets us recover the raw group count (RGC) for 25 September 1836, on which the RGC has not been registered in the existing catalogs. We also revise the RGCs from P and S using the Zurich classification and determine that Kunitomo's results tend to yield smaller RGCs than those of other contemporary observers. In addition, we find that Kunitomo's RGCs and spot areas have a correlation (0.71) that is not very different from the contemporary observer Schwabe (0.82). Although Kunitomo's spot areas are much larger than those determined by Schwabe due to skill and instrument limitations, Kunitomo at least captured the growing trend of the spot activity in the early phase of the Solar Cycle 8. We also determine the solar rotation axis to estimate the accurate position (latitude and longitude) of the sunspot groups in Kunitomo's drawings.
Abstract: 1903.03045
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Full Text: [ PostScript, PDF]
Title:Evidence for recent GeV brightening of the SN 1987A region
(Submitted on 7 Mar 2019)
Abstract: We report on a recent (2016-2018) enhancement of the GeV emission from the SN 1987A region as observed with Fermi/LAT. The observed signal is characterised by a power-law spectrum with a slope of 2.1 +/- 0.2 and is detected only at energies >1 GeV. The Fermi/LAT data constrain the position of the signal to within 0.15 degree around SN 1987A. Although a recent increase in the gamma-ray emission from SN 1987A seems to be a natural explanation for the detected emission, given the youth of the source and its rapid evolution, the Fermi/LAT location also overlaps with several other potential gamma-ray sources: 30 Dor C, Honeycomb nebula, RX J0536.9-6913, and a hypothetical, previously unknown transient source. We argue that multiwavelength observations of the region performed during the next few years can clarify the nature of the signal and encourage such observations. We also present upper limits on the time-averaged flux of SN 1987A based on 10 years of Fermi/LAT exposure, which can be used to better constrain the particle acceleration models of this source.
Abstract: 1903.02994
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Full Text: [ PostScript, PDF]
Title:Effect of nonlinearity between density and curvature perturbations on the primordial black hole formation
(Submitted on 7 Mar 2019)
Abstract: We study the effect of the nonlinear relation between density and curvature perturbations on the formation of PBHs. By calculating the variance and skewness of the density perturbation we derive the non-Gaussian property. As a criterion for PBH formation, the compaction function is used and it is found that larger curvature perturbations are required due to the nonlinear effect. We estimate the PBH abundance based on the Press-Schechter formalism with non-Gaussian probability density function during Radiation dominated era. It is found that the nonlinear effect slightly suppresses the PBH formation and the suppression is comparable to that expected if the primordial curvature perturbation would have the local form of non-Gaussianity with nonlinear parameter $f_\text{NL} \sim -1$.
Abstract: 1903.02905
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Full Text: [ PostScript, PDF]
Title:A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope
(Submitted on 7 Mar 2019)
Abstract: The Fermi Large Area Telescope (LAT) has amassed a large data set of primary cosmic-ray protons throughout its mission. The LAT's wide field of view and full-sky survey capabilities make it an excellent instrument for studying cosmic-ray anisotropy. As a space-based survey instrument, the LAT is sensitive to anisotropy in both right ascension and declination, while ground-based observations only measure the anisotropy in right ascension. We present the results of the first ever proton anisotropy search using Fermi LAT. The data set uses eight years of data and consists of approximately 179 million protons above 78 GeV, enabling it to probe dipole anisotropy below an amplitude of $10^{-3}$, resulting in the most stringent limits on the declination dependence of the dipole to date. We measure a dipole amplitude $\delta = 3.9\pm1.5 \times 10^{-4}$ with a p-value of 0.01 (pre-trials) for protons with a minimum energy of 78 GeV. We discuss various systematic effects that could give rise to a dipole excess and calculate upper limits on the dipole amplitude as a function of minimum energy. The 95% CL upper limit on the dipole amplitude is $\delta_{UL}=1.3\times 10^{-3}$ for protons with a minimum energy of 78 GeV and $\delta_{UL}=1.2 \times 10^{-3}$ for protons with a minimum energy of 251 GeV.
Abstract: 1903.02792
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Full Text: [ PostScript, PDF]
Title:Radio detection of cosmic rays below 10 MHz: the EXTASIS experiment
(Submitted on 7 Mar 2019)
Abstract: Since 2003, significant efforts have been devoted to the understanding of the radio emission of extensive air showers above 20 MHz. Despite some studies led until the early nineties, the band available above 20 MHz has remained unused for 20 years. However, it has been claimed by some pioneering experiments that extensive air showers emit a strong electric field in this band and that there is evidence of a large increase of the radio pulse amplitude with decreasing frequencies. The EXTASIS experiment, located within the Nançay Radioastronomy Observatory and supported by the CODALEMA experiment, aims to reinvestigate the [1-10] MHz band, and especially to study the so-called "sudden death" contribution, the expected electric field radiated by the shower front when hitting ground level. In this work, we present the instrumental setup, the objectives of the EXTASIS experiment and our first results.
Abstract: 1903.02756
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Full Text: [ PostScript, PDF]
Title:Origin of Cosmic Ray Electrons and Positrons
(Submitted on 7 Mar 2019)
Abstract: With experimental results of AMS on the spectra of cosmic ray (CR) $e^{-}$, $e^{+}$, $e^{-}+e^{+}$ and positron fraction, as well as new measurements of CR $e^{-}+e^{+}$ flux by HESS, one can better understand the CR lepton ($e^{-}$ and $e^{+}$) spectra and the puzzling electron-positron excess above $\sim$10 GeV. In this article, spectra of CR $e^{-}$ and $e^{+}$ are fitted with a physically motivated simple model, and their injection spectra are obtained with a one-dimensional propagation model including the diffusion and energy loss processes. Our results show that the electron-positron excess can be attributed to uniformly distributed sources that continuously inject into the galactic disk electron-positron with a power-law spectrum cutting off near 1 TeV and a triple power-law model is needed to fit the primary CR electron spectrum. The lower energy spectral break can be attributed to propagation effects giving rise to a broken power-law injection spectrum of primary CR electrons with a spectral hardening above $\sim$40 GeV.
Abstract: 1903.03302
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Full Text: [ PostScript, PDF]
Title:Constraining dark matter-neutrino interactions with IceCube-170922A
(Submitted on 8 Mar 2019)
Abstract: Astrophysical neutrinos travel long distances from their sources to the Earth traversing dark matter halos of clusters of galaxies and that of our own Milky Way. The interaction of neutrinos with dark matter may affect the flux of neutrinos. The recent multi-messenger observation of a high energy neutrino, IceCube-170922A, can give a robust upper bound $\sigma /M_{dm} \lesssim 5.1\times 10^{-23} {\rm cm}^2 /$GeV on the interaction between neutrino and dark matter at a neutrino energy of 290 TeV allowing 90\% suppression. Combining the constraints from CMB and LSS at different neutrino energies, we can constrain models of dark matter-neutrino interactions.
Abstract: 1903.03193
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Full Text: [ PostScript, PDF]
Title:Non-linear diffusion of cosmic rays escaping from supernova remnants - II. Hot ionized media
(Submitted on 7 Mar 2019)
Abstract: We study the problem of the escape and transport of Cosmic-Rays (CR) from a source embedded in a fully ionised, hot phase of the interstellar medium (HIM). In particular, we model the CR escape and their propagation in the source vicinity taking into account excitation of Alfvénic turbulence by CR streaming and mechanisms damping the self-excited turbulence itself. Our estimates of escape radii and times result in large values (100 pc, $2\times10^5$ yr) for particle energies $\lesssim20$ GeV and smaller values for particles with increasing energies (35 pc and 14 kyr at 1 TeV). These escape times and radii, when used as initial conditions for the CR propagation outside the source, result in relevant suppression of the diffusion coefficient (by a factor 5-10) on time-scales comparable with their (energy dependent) escape time-scale. The damping mechanisms are fast enough that even on shorter time scales the Alfvénic turbulence is efficiently damped, and the ratio between random and ordered component of the magnetic field is $\delta B/B_0\ll 1$, justifying the use of quasi-linear theory. In spite of the suppressed diffusion coefficient, and then the increased residence time in the vicinity (<200 pc) of their source, the grammage accumulated by CRs after their escape is found to be negligible (at all energies) as compared to the one accumulated while diffusing in the whole Galaxy, due to the low density of the HIM.
Abstract: 1903.03155
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Full Text: [ PostScript, PDF]
Title:Astrophysical Tests of Dark Matter with Maunakea Spectroscopic Explorer
(Submitted on 7 Mar 2019)
Abstract: We discuss how astrophysical observations with the Maunakea Spectroscopic Explorer (MSE), a high-multiplexity (about 4300 fibers), wide field-of-view (1.5 square degree), large telescope aperture (11.25 m) facility, can probe the particle nature of dark matter. MSE will conduct a suite of surveys that will provide critical input for determinations of the mass function, phase-space distribution, and internal density profiles of dark matter halos across all mass scales. N-body and hydrodynamical simulations of cold, warm, fuzzy and self-interacting dark matter suggest that non-trivial dynamics in the dark sector could have left an imprint on structure formation. Analysed within these frameworks, the extensive and unprecedented datasets produced by MSE will be used to search for deviations away from cold and collisionless dark matter model. MSE will provide an improved estimate of the local density of dark matter, critical for direct detection experiments, and will improve estimates of the J-factor for indirect searches through self-annihilation or decay into Standard Model particles. MSE will determine the impact of low mass substructures on the dynamics of Milky Way stellar streams in velocity space, and will allow for estimates of the density profiles of the dark matter halos of Milky Way dwarf galaxies using more than an order of magnitude more tracers. In the low redshift Universe, MSE will provide critical redshifts to pin down the luminosity functions of vast numbers of satellite systems, and MSE will be an essential component of future strong lensing measurements to constrain the halo mass function. Across nearly all mass scales, the improvements offered by MSE, in comparison to other facilities, are such that the relevant analyses are limited by systematics rather than statistics.
Abstract: 1903.03126
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Full Text: [ PostScript, PDF]
Title:A GeV-TeV Measurement of the Extragalactic Background Light
(Submitted on 7 Mar 2019)
Abstract: The Extragalactic Background Light (EBL) can be probed via the absorption imprint it leaves in the spectra of gamma-ray sources ($\gamma\gamma \rightarrow e^-e^+$). We recently developed a dedicated technique to reconstruct the EBL, and its evolution with redshift, from $\gamma$ ray optical depth data using a large sample of blazars detected by the {\it Fermi} Large Area Telescope. Here, we extend this dataset to the TeV regime using ground-based Cherenkov observations of 38 blazars and report the first homogeneous measurement of the EBL spectral intensity covering the ultraviolet to infrared wavelengths ($\sim$0.1-100$\mathrm{\mu m}$). A minimal EBL throughout the wavelength range with respect to integrated galaxy light is found, allowing little additional unresolved emission from faint or truly diffuse populations setting an upper limit of $\lesssim 4~{\rm nW\cdot m^{-2}sr^{-1}}$ at 1.4\,${\rm \mu m}$. In particular, the cosmic optical background (COB) at $z=0$ is found to be $27.8_{-2.0}^{+2.1}~{\rm nW\cdot m^{-2}sr^{-1}}$. This work lays the foundation for accurate gamma-ray measurements of the EBL across its whole spectral range using a combination of GeV and TeV data.
Abstract: 1903.02889
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Full Text: [ PostScript, PDF]
Title:Radio detection of atmospheric air showers of particles
(Submitted on 7 Mar 2019)
Abstract: Since 2002, the CODALEMA experiment located within the Nançay Radio Observatory studies the ultra-high energy cosmic rays (above 10^{17} eV) arriving in the Earth atmosphere. These cosmic rays interact with the component of the atmosphere, inducing an extensive air shower (EAS) composed mainly of charged particles (electrons and positrons). During the development of the shower in the atmosphere, these charged particles in movement generate a fast electric field transient (a few nanoseconds to a few tens of ns), detected at ground by CODALEMA with dedicated radio antennas over a wide frequency band (between 20 MHz and 200 MHz). The study of this electric field emitted during the shower development aims to determine the characteristics of the primary cosmic ray which has induced the particle shower: its nature, its arrival direction and its energy. After some theoretical considerations and a short description of the SELFAS simulation code, we will present the CODALEMA experiment, its performances and main results. At last, we will show how the EAS radio-detection technique could be used to observe very high energy gamma rays sources, with the NenuFAR radio telescope.
Abstract: 1903.02496
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Full Text: [ PostScript, PDF]
Title:Gamma Rays from colliding winds in massive binaries. Status and prospects
(Submitted on 6 Mar 2019)
Abstract: Binary systems formed by early-type stars with strong winds are known to display variable non-thermal radio emission, thermal X-rays, and, at least in one case (Eta Carina), $\gamma$ rays. Some of these systems are quite eccentric and the conditions for efficient particle acceleration and $\gamma$-ray production might manifest only occasionally. In this paper I briefly review the physics of colliding wind binaries with emphasis on the observational signatures of non-thermal particle acceleration. I discuss, in particular, the case of the system HD 93129A which is made up by an O2 If* star (the primary) and an O3.5 V star (the secondary). The primary is among the earliest, hottest, most massive, luminous, and windy O stars in the Galaxy. The periastron passage during 2018 will offer an outstanding observational window that will be exploited by an international multi-wavelength campaign.
Abstract: 1903.02420
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Full Text: [ PostScript, PDF]
Title:Detection of Ultra-High Energy neutrinos skimming the Earth due to decay of superheavy dark matter at JEM-EUSO
(Submitted on 5 Mar 2019)
Abstract: The possibility of detecting Ultra-high energy (UHE from now on) neutrinos due to superheavy dark matter are considered by the neutrinos interaction with the nuclei in the air in the present paper. To reject other standard model particles, UHE neutrinos, from superheavy dark matter and astrophysical sources, skimming the Earth are detected at JEM-EUSO. Then the numbers of UHE neutrinos detected by JEM-EUSO are evaluated at different energies (1 EeV < E < 1 ZeV) in 5 years. If the energy thresholds are taken to be 100 EeV, the astrophysical neutrino contamination could be negligible in this detection. It is possible that UHE neutrinos from the decay of superheavy dark matter are detected at JEM-EUSO when $O(10^{27})s < \tau_{\phi}< O(10^{31})s$. For example, O($10^4$) UHE neutrino events could be detected by JEM-EUSO at 30 EeV in 5 years when $\tau_{\phi}=O(10^{27})$s. If so, it may be confirmed that there may exist superheavy dark matter in the Universe.
Abstract: 1903.02373
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Full Text: [ PostScript, PDF]
Title:Is Supernova Remnant Cassiopeia A a PeVatron?
(Submitted on 6 Mar 2019)
Abstract: Cassiopeia A, a well-observed young core-collapse supernova remnant (SNR), is considered as one of the best candidates for studying very high-energy particle acceleration up to PeV via the diffusive shock mechanism. Recently, MAGIC observations revealed a $\gamma$-ray spectral cutoff at $\sim3.5$ TeV, suggesting that if the TeV $\gamma$-rays have a hadronic origin, SNR Cas A can only accelerate particles to tens of TeV. Here, we propose a two-zone emission model for regions associated with the forward (zone 1) and inward/reverse shocks (zone 2). Given the low density in zone 1, it dominates the high-frequency radio emission, soft X-ray rim via the synchrotron process and TeV $\gamma$-ray via the inverse Comptonization. With a relatively softer particle distribution and a higher cut-off energy for electrons, emissions from zone 2 dominate the low-frequency radio, hard X-ray via the synchrotron process and GeV $\gamma$-ray via hadronic processes. There is no evidence for high-energy cutoffs in the proton distributions implying that Cas A can still be a PeVatron. Hadronic processes from zone 1 dominate very high-energy gamma-ray emission. Future observations in hundreds of TeV range can test this model.
Abstract: 1903.02086
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Full Text: [ PostScript, PDF]
Title:Neutrino self-interaction and MSW effects on the supernova neutrino-process
(Submitted on 28 Feb 2019)
Abstract: We investigate nuclear abundances produced from the neutrino ($\nu$)-process in supernova explosions. For the first time, we have calculated the flux propagation including both its modification by $\nu$ self-interaction ($\nu$-SI) near the $\nu$-sphere and the Mikheyev-Smirnov-Wolfenstein (MSW) effect in the outer O-Ne-Mg layer. The abundances of heavier isotopes $^{92}$Nb, $^{98}$Tc and $^{138}$La are largely enhanced by the $\nu$-SI for the inverted mass hierarchy. The ratio of $^7$Li/$^{11}$B is lower in the inverted hierarchy than in the normal hierarchy. Abundance ratios of the heavy to the light neutrino isotopes such as $^{138}$La/$^{11}$B are sensitive to the mass hierarchy by the $\nu$-SI.
Abstract: 1903.02036
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Full Text: [ PostScript, PDF]
Title:Inflation meets neutrinos
(Submitted on 5 Mar 2019)
Abstract: Constraints on inflationary models typically assume only the standard models of cosmology and particle physics. By extending the neutrino sector to include a new interaction with a light scalar mediator ($m_{\phi}\sim$MeV), it is possible to relax these constraints, in particular via opening up regions of the parameter space of the spectral index $n_s$. These new interactions can be probed at IceCube via interactions of astrophysical neutrinos with the Cosmic Neutrino Background for nearly all of the relevant parameter space.
Abstract: 1903.02006
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Full Text: [ PostScript, PDF]
Title:High-Energy Neutrinos from Blazar Flares and Implications of TXS 0506+056
(Submitted on 5 Mar 2019)
Abstract: Motivated by the observation of a $>290$ TeV muon neutrino by IceCube, coincident with a $\sim$6 month-long $\gamma$-ray flare of the blazar TXS 0506+056, and an archival search which revealed $13 \pm 5$ further, lower-energy neutrinos in the direction of the source in 2014-2015, we discuss the likely contribution of blazars to the diffuse high-energy neutrino intensity, the implications for neutrino emission from TXS 0506+056 based on multi-wavelength observations of the source, and a multi-zone model that allows for sufficient neutrino emission so as to reconcile the multi-wavelength cascade constraints with the neutrino emission seen by IceCube in the direction of TXS 0506+056.
Abstract: 1903.01626
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Full Text: [ PostScript, PDF]
Title:Air Shower Observation by a Simple Structured Fresnel lens Telescope with Single Pixel for the Next Generation of Ultra-High Energy Cosmic Ray Observatory
(Submitted on 5 Mar 2019)
Abstract: Improved statistics and mass-composition-sensitive observation are required to clarify the origin of ultra-high energy cosmic rays (UHECRs). Inevitably in the future, the UHECR observatories will have to be expanded due to the small flux; however, the upgrade will be expensive with the detectors currently in use. Hence, we are developing a new fluorescence detector for UHECR observation. The proposed fluorescence detector, called cosmic ray air fluorescence Fresnel-lens telescope (CRAFFT), has an extremely simple structure and can observe the longitudinal development of an air shower. Furthermore, CRAFFT has the potential to significantly reduce costs for the realization of a huge observatory for UHECR research. We deployed four CRAFFT detectors at the Telescope Array site and conducted the test observation. We have successfully observed ten air-shower events using CRAFFT. Thus, CRAFFT can be a solution to realize the next generation of UHECR observatories.
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