Refine
Has Fulltext
- no (23)
Language
- English (23)
Is part of the Bibliography
- yes (23)
Keywords
- gamma rays: general (9)
- ISM: supernova remnants (6)
- cosmic rays (5)
- radiation mechanisms: non-thermal (4)
- X-rays: binaries (3)
- acceleration of particles (3)
- astroparticle physics (3)
- galaxies: active (2)
- galaxies: jets (2)
- gamma rays: ISM (2)
- gamma rays: galaxies (2)
- gamma rays: stars (2)
- Acceleration of particles (1)
- Air showers (1)
- BL Lacertae objects: general (1)
- BL Lacertae objects: individual: PKS 2155-304 (1)
- Cherenkov Telescopes (1)
- Design concepts (1)
- Galaxy: center (1)
- Gamma rays: General (1)
- Ground based gamma ray astronomy (1)
- ISM: Supernova remnants (1)
- ISM: clouds (1)
- ISM: jets and outflows (1)
- Next generation Cherenkov telescopes (1)
- Radiation mechanisms: Non-termal (1)
- TeV gamma-ray astronomy (1)
- X-rays: individuals: Circinus X-1 (1)
- X-rays: individuals: GRS 1915+105 (1)
- X-rays: individuals: V4641 Sgr (1)
- astroparticle physic (1)
- catalogs (1)
- cosmic background radiation (1)
- galaxies: individual: PKS 0625-354 (1)
- galaxies: nuclei (1)
- gamma-rays: galaxies (1)
- infrared: diffuse background (1)
- pulsars: general (1)
- stars: black holes (1)
- stars: early-type (1)
- stars: individual: 1FGL J1018.6-5856 (1)
- stars: magnetars (1)
- stars: massive (1)
- surveys (1)
Institute
The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using gamma-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant gamma-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section <sigma nu >. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach <sigma nu > values of 6 x 10(-26) cm(3) s(-1) in the W+W- channel for a DM particle mass of 1.5 TeV, and 2 x 10(-26) cm(3) s(-1) in the tau(+)tau(-) channel for a 1 TeV mass. For the first time, ground-based gamma-ray observations have reached sufficient sensitivity to probe <sigma nu > values expected from the thermal relic density for TeV DM particles.
Supernova remnants (SNRs) are among the most important targets for gamma-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRS). To firmly establish the SNR paradigm for the origin of cosmic rays, it should be confirmed that protons are indeed accelerated in, and released from, SNRs with the appropriate flux and spectrum. This can be done by detailed theoretical models which account for microphysics of acceleration and various radiation processes of hadrons and leptons. The current generation of Cherenkov telescopes has insufficient sensitivity to constrain theoretical models. A new facility, the Cherenkov Telescope Array (CTA), will have superior capabilities and may finally resolve this long standing issue of high-energy astrophysics. We want to assess the capabilities of CTA to reveal the physics of various types of SNRs in the initial 2000 years of their evolution. During this time, the efficiency to accelerate cosmic rays is highest. We perform time-dependent simulations of the hydrodynamics, the magnetic fields, the cosmic-ray acceleration, and the non-thermal emission for type Ia, Ic and IIP SNRs. We calculate the CTA response to the y-ray emission from these SNRs for various ages and distances, and we perform a realistic analysis of the simulated data. We derive distance limits for the detectability and resolvability of these SNR types at several ages. We test the ability of CTA to reconstruct their morphological and spectral parameters as a function of their distance. Finally, we estimate how well CTA data will constrain the theoretical models. (C) 2014 Elsevier B.V. All rights reserved.
The 11 July 1889 Chilik earthquake (M-w 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, similar to 100 km southeast of Almaty, Kazakhstan (similar to 2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the similar to 30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of similar to 175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.