Dark Matter Model Selection and the ATIC/PPB-BETS anomaly

We argue that we may be able to sort out dark matter models in which electrons are generated through the annihilation and/or decay of dark matter, by using a fact that the initial energy spectrum is reflected in the cosmic-ray electron flux observed at the Earth even after propagation through the galactic magnetic field. To illustrate our idea we focus on three representative initial spectra: (i)monochromatic (ii)flat and (iii)double-peak ones. We find that those three cases result in significantly different energy spectra, which may be probed by the Fermi satellite in operation or an up-coming cosmic-ray detector such as CALET.Comment: 19 pages, 8 figure

Multi-messenger Observations of a Binary Neutron Star Merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Energy Spectrum of Cosmic-Ray Electron and Positron from 10 GeV to 3 TeV Observed with the Calorimetric Electron Telescope on the International Space Station

First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 X0 and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of -3.152±0.016 (stat+syst). Possible structure observed above 100 GeV requires further investigation with increased statistics and refined data analysis

An overview of CALET observations after three years on the international space station

The CALorimetric Electron Telescope CALET is a space-based instrument designed to carry out precision measurements of high energy cosmic-rays on the JEM-EF external platform of the ISS where it has been collecting science data continuously since mid October 2015. Equipped with a thick (30 X0 and ∼1.3 λI) calorimeter with an imaging pre-shower and with two independent subsystems to identify the charge of the incident particle, CALET has the depth, tracking capability, electron/proton discrimination and energy resolution to study hadrons, electrons and gamma rays in the cosmic radiation. An overview of CALET observations is presented, based on the data taken during the first three years. It includes a direct measurement of the electron+positron energy spectrum from 11 GeV to 4.8 TeV in good agreement with AMS-02 data in the region below ∼ 1 TeV and suggesting a flux suppression above 1 TeV. In the energy region below ∼ 300 GeV, CALET's spectral index is consistent with AMS-02, Fermi-LAT and DAMPE, while from ∼ 300 GeV to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The proton spectrum has been measured from 50 GeV to 10 TeV covering, for the first time with a single space-borne instrument, the whole energy interval previously investigated in separate sub-ranges by magnetic spectrometers and calorimetric instruments. The observed spectrum is consistent with AMS-02 but it extends by nearly one order of magnitude higher in energy, showing a smooth transition of the power-law spectral index from -2.81 ± 0.03 (50-500 GeV) to -2.56 ± 0.04 (1-10 TeV), thereby providing evidence of a deviation from a single power law by more than 3 sigma. In addition to its primary goal of identifying nearby sources of high-energy electrons and possible signatures of dark matter in the electron spectrum, CALET is carrying out extensive measurements of the energy spectra, relative abundances and secondary-to-primary ratios of elements from proton to iron and above (up to Z=40) studying the details of galactic particle propagation and acceleration. Preliminary spectra of cosmic-ray nuclei are presented, together with gamma-ray observations and searches of an e.m. counterpart of LIGO/Virgo GW events. © Owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)

High-Energy Gamma-ray Observations Using the CALorimetric Electron Telescope

35th International Cosmic Ray Conference -ICRC2017; Bexco, Busan, Korea; 10-20 July 2017We present the analysis methodology and preliminary results of the gamma-ray event analysis using the CALorimetric Electron Telescope (CALET). CALET, a 30 radiation length deep calorimeter, was deployed aboard the International Space Station (ISS) in August 2015. In this work we demonstrate the sensitivity of CALET to gamma-rays, the efficiency of separation between gamma-ray and charged particle events, and CALET’s exposure on the sky after the first 17 months of observation. Consistency of the flux of the bright sources Geminga and the Crab with established Fermi-LAT results is discussed and initial results of a search for high-energy counterparts to CALET Gamma-ray Burst Monitor gamma-ray bursts are presented.This work was supported in Japan by JAXA, in Italy by ASI, and in the U.S. by NASA. The author appreciates support provided by the Louisiana Board of Regents. The CERN ROOT4 framework (R. Brun and F. Rademakers, NIM. in Phys. Res. A, 389 (1997)) and the HEALPix package (K.M. Gorski et al., ApJ, 622 (2005)) were used in deriving some results in this work.https://pos.sissa.it/301/720

The CALorimetric Electron Telescope (CALET): High Energy Astroparticle Physics Observatory on the International Space Station

The 34th International Cosmic Ray Conference; The Hague, The Netherlands; 30 July- 6 August, 2015The CALorimetric Electron Telescope (CALET) space experiment, which has been developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission to be installed on the International Space Station (ISS). The primary goals of the CALET mission include investigating possible nearby sources of high energy electrons, studying the details of galactic particle propagation and searching for dark matter signatures. During a two-year mission, extendable to five years, the CALET experiment will measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei with Z=1 to 40 up to several 100 TeV. The instrument consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument is currently being prepared for launch on August 16, 2015 to the ISS with HTV-5 (H-II Transfer Vehicle 5) and installed on the Japanese Experiment Module- Exposed Facility (JEM-EF)The CALET mission is conducted by Japanese space agency, JAXA, in collaboration with NASA and ASI. This work is partially supported by JSPS KAKENHI Grant Number 21224006.https://pos.sissa.it/236/581

Development of the Waseda CALET Operations Center (WCOC) for Scientific Operations of CALET

The 34th International Cosmic Ray Conference; The Hague, The Netherlands; 30 July- 6 August, 2015The CALET project aims at a long duration observation of high energy cosmic rays onboard the International Space Station (ISS). The CALET detector features a very thick calorimeter of 30 radiation-lengths which consists of imaging and total absorption calorimeters. It will directly measure the cosmic-ray electron spectrum in the energy range of 1GeV–20TeV with 2 % energy resolution. The data obtained with CALET onboard ISS will be transferred to JAXA using two data relay satellite systems operated by NASA and JAXA, respectively. To operate the CALET onboard ISS, the CALET Ground Support Equipment (CALET-GSE) is being prepared in JAXA. Simultaneously, Waseda CALET Operations Center (WCOC) is being established to perform operations and monitoring related to the scientific mission. The real-time data received by CALET-GSE is immediately transferred to WCOC. Scientific raw data are also transferred to WCOC on an hourly basis after time-order correcting and complementing replay data. Mission operations at WCOC includes the following roles: 1. Real-time monitoring and operations: To monitor the CALET observation and its status in real-time, Quick Look (QL) programs are developed to visualize and summarize both cosmic-ray event data and housekeeping data. Operators at WCOC use QLs to understand the CALET situation and validate the observation on orbit in 24 hour. Upon necessity, appropriate commands will be issued through CALET-GSE. 2. Operation planning: Scheduled command sequences are utilized to control the CALET observation mode on orbit. Calibration data taking such as pedestal and penetrating particle events, low energy electron data taking at high geomagnetic latitude, and other dedicated trigger modes can be scheduled along with the ISS orbit. 3. Scientific data processing: The scientific raw data called CALET Level-0 data are processed to CALET Level-1 data, and Level-1 data are distributed to the collaboration for scientific analysis. Quick analyses based on both Level-0 and Level-1 data are performed and their results are used to feedback for better operation planning and real-time monitoring. In this contribution, we will review the role of WCOC and report WCOC development.This work was supported by JSPS KAKENHI Grant Number 26220708.https://pos.sissa.it/236/603

CALET GBM Observations of Gamma-ray Bursts and Gravitational Wave Sources

35th International Cosmic Ray Conference – ICRC2017; Bexco, Busan, Korea; 10-20 July, 2017The CALET Gamma-ray Burst Monitor (CGBM) is secondary scientific instrument of the Calorimetric Electron Telescope (CALET) mission on the International Space Station (ISS). The primary instrument Calorimeter (CAL) is capable of detecting gamma-ray bursts (GRBs) in the GeV-TeV range, and the CGBM was attached to complement CAL gamma-ray observations in the keV-MeV range. The CGBM consists of 2 Hard X-ray Monitors (HXMs) and one Soft Gamma-ray Monitor (SGM), utilizing different scintillators LaBr3 (Ce) and BGO respectively. The CGBM covers a broadband energy range of 7 keV - 20 MeV with a wide field of view (FOV). Since the launch on August 19, 2015, the CGBM has been sucessfully operated on the ISS for about 1.5 years, and detecting about 50 GRBs (roughly 20% short GRBs among them) per year as expected from pre-launch estimation. The CALET also concluded memolandam of understanding (MOU) with LIGO/Virgo collaboration, and we are searching for hard X-ray and gamma-ray counterparts for gravitational wave (GW) sources. In this paper, we will report on CGBM in-orbit operation, performance and observations of GRBs and GW sources.This work is partly supported by Grant-in-Aid (24684015 KY) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT).https://pos.sissa.it/301/614