Towards gamma-ray astronomy with timing arrays

M Tluczykont ,A G Bogdanov ,S Kiryuhin ,O Chvalaev ,A Tkachenko ,D Bogorodskii,N Gorbunov ,R Wischnewski ,M Rueger,Л Ткачев ,S Porokhovoy ,Н Лубсандоржиев ,N Karpov ,Р П Кокоулин ,E Popova ,A Dyachok ,D Voronov,О Гришин ,S Epimakhov ,E Konstantinov ,В А Романов ,А Р Гафаров ,Б Лубсандоржиев ,М Куннас ,K O Yurin ,А Загородников ,S.f Beregnev ,V Boreyko ,В С Птускин ,Petr Satunin ,M Popescu ,А В Коробченко ,А А Перевалов ,В А Таболенко ,A Veslopopov,А В Скурихин ,L A Kuzmichev ,N S Barbashina ,А Иванова ,Г Рубцов ,В В Киндин ,C Spiering ,В Самолига ,M I Panasyuk ,V Savinov ,Martin Brückner ,R Nachtigall ,Yu Semeney ,I I Yashin ,В В Просин ,L Pankov ,Y Kazarina ,А Силаев ,O Gress ,D Horns ,R Mirzoyan ,А Порелли ,И И Астапов ,N Kirichkov,Е Е Коростелева ,E Veslopopova,A Saunkin,A Grinyuk ,Б А Шайбонов ,А Чиавасса ,Timofei V Eremin ,Vladimir Lenok ,V N Zirakashvili ,В А Платонов ,V Grebenyuk ,А А Петрухин ,Т Гресс ,В А Кожин ,M Slunečka ,Н Н Калмыков ,А Пахоруков ,Л Свешникова ,Р Р Миргазов ,К Г Компаниец ,V Poleschuk ,Н М Буднев ,E Rybov ,Р Монхоев ,В Л Зурбанов

doi:10.1088/1742-6596/632/1/012042

Abstract

The gamma-ray energy regime beyond 10 TeV is crucial for the search for the most energetic Galactic accelerators. The energy spectra of most known gamma-ray emitters only reach up to few 10s of TeV, with 80 TeV from the Crab Nebula being the highest energy so far observed significantly. Uncovering their spectral shape up to few 100 TeV could answer the question whether some of these objects are cosmic ray Pevatrons, i.e. Galactic PeV accelerators.Sensitive observations in this energy range and beyond require very large effective detector areas of several 10s to 100 square-km. While imaging air Cherenkov telescopes have proven to be the instruments of choice in the GeV to TeV energy range, very large area telescope arrays are limited by the number of required readout channels per instrumented square-km (due to the large number of channels per telescope). Alternatively, the shower-front sampling technique allows to instrument large effective areas and also naturally provides large viewing angles of the instrument. Solely measuring the shower front light density and timing (hence timing- arrays), the primary particle properties are reconstructed on the basis of the measured lateral density function and the shower front arrival times. This presentation gives an overview of the technique, its goals, and future perspective.

Highlights

At its beginning, the main astrophysical motivation for gamma-ray astronomy was the search for Galactic cosmic ray accelerators
A measurement of the continuation of these energy spectra towards higher energies not covered by current generation instruments will help understanding the underlying acceleration mechanism of the sources
Each single telescope taken alone will not be able to reliably measure the core impact for the majority of events. This is where the timing array comes into play: arranged in an array around the IACTs, the HiSCORE timing-array stations will provide their measure of the core impact position RHiSCORE and direction θHiSCORE to each telescope, allowing the determination of a hybrid scaled width, hscw, as given in Equation 2 without recurring to the stereoscopic technique hscw wIACT (RHiSCORE, θHiSCORE, AIACT)

Summary

Introduction

The main astrophysical motivation for gamma-ray astronomy was the search for Galactic cosmic ray accelerators. The current generation of major air Cherenkov telescopes reach down to an integral flux detection sensitivity for point sources of about 10−12erg cm−2 s−1 in the TeV energy regime after 50 h of observaton time. This lead to the discovery of many new sources of different object types in the past decade. A detection of hard gamma-ray spectra up to few 100 TeV and with an exponential cutoff that can be approximated by the form exp(− Eγ/300 T eV ) would represent a smoking-gun signature of the acceleration of cosmic rays up to the knee-feature in the all-particle cosmic ray spectrum (Ep ≈ 3 · 1015 eV).

TeV 100 GeV 5 GeV 10 TeV 1017 eV 1017 eV

The HiSCORE concept

Findings

Combining imaging and timing