107 research outputs found
Spectral and spatial variations of the diffuse gamma-ray background in the vicinity of the Galactic plane and possible nature of the feature at 130 GeV
We study the properties of the diffuse gamma-ray background around the
Galactic plane at energies 20 -- 200 GeV. We find that the spectrum of this
emission possesses significant spacial variations with respect to the average
smooth component. The positions and shapes of these spectral features change
with the direction on the sky. We therefore argue, that the spectral feature
around 130 GeV, found in several regions around the Galactic Center and in the
Galactic plane in [1203.1312, 1204.2797, 1205.1045, 1206.1616], can not be
interpreted with confidence as a gamma-ray line, but may be a component of the
diffuse background and can be of instrumental or astrophysical origin.
Therefore, the dark matter origin of this spectral feature becomes dubious.Comment: Extended analysis that further confirms the existence of several "hot
spots" around the Galactic plane and discussion of their possible origi
Analysis Methods for Gamma-ray Astronomy
The launch of the Fermi satellite in 2008, with its Large Area Telescope
(LAT) on board, has opened a new era for the study of gamma-ray sources at GeV
( eV) energies. Similarly, the commissioning of the third generation of
imaging atmospheric Cherenkov telescopes (IACTs) - H.E.S.S., MAGIC, and VERITAS
- in the mid-2000's has firmly established the field of TeV ( eV)
gamma-ray astronomy. Together, these instruments have revolutionised our
understanding of the high-energy gamma-ray sky, and they continue to provide
access to it over more than six decades in energy. In recent years, the
ground-level particle detector arrays HAWC, Tibet, and LHAASO have opened a new
window to gamma rays of the highest energies, beyond 100 TeV. Soon,
next-generation facilities such as CTA and SWGO will provide even better
sensitivity, thus promising a bright future for the field. In this chapter, we
provide a brief overview of methods commonly employed for the analysis of
gamma-ray data, focusing on those used for Fermi-LAT and IACT observations. We
describe the standard data formats, explain event reconstruction and selection
algorithms, and cover in detail high-level analysis approaches for imaging and
extraction of spectra, including aperture photometry as well as advanced
likelihood techniques.Comment: 56 pages, 12 figures. Invited chapter for "Handbook of X-ray and
Gamma-ray Astrophysics" (Eds. C. Bambi and A. Santangelo, Springer Singapore,
expected in 2023
Technical comment on the paper of Dessert et al. "The dark matter interpretation of the 3.5 keV line is inconsistent with blank-sky observations"
An unidentified line at energy around 3.5 keV was detected in the spectra of
dark matter-dominated objects. Recent work of Dessert et al. [1812.06976] used
30 Msec of XMM-Newton blank-sky observations to constrain the admissible line
flux, challenging its dark matter decay origin. We demonstrate that these
bounds are overestimated by more than an order of magnitude due to improper
background modeling. Therefore the dark matter interpretation of the 3.5 keV
signal remains viable.Comment: Technical comment on the paper by Dessert et al.
10.1126/science.aaw377
Search for primordial black hole dark matter with X-ray spectroscopic and imaging satellite experiments and prospects for future satellite missions
Ultra-light primordial black holes (PBHs) in the mass range of 10 -
10 g are allowed by current observations to constitute a significant
fraction, if not all, of the dark matter in the Universe. In this work, we
present limits on ultra-light, non-rotating PBHs which arise from the
non-detection of the Hawking radiation signals from such objects in the keV-MeV
energy band. Namely, we consider observations from the current-generation
missions XMM-Newton and INTEGRAL/SPI and discuss the observational perspectives
of the future missions Athena, eXTP, and THESEUS for PBH searches. Based on 3.4
Msec total exposure time XMM-Newton observations of Draco dwarf spheroidal
galaxy, we conclude that PBH with masses g can not make all
dark matter at 95% confidence level. Our ON-OFF-type analysis of Msec of
INTEGRAL/SPI data on the Milky Way halo puts significantly stronger
constraints. Only % dark matter can be presented by PBHs with
masses g while the majority of dark matter can not be
represented by PBHs lighter than g at 95% confidence level. We
discuss the strong impact of systematic uncertainty related to the variations
of instrumental and astrophysical INTEGRAL/SPI background on the derived
results and estimate its level. We also show that future large-field-of-view
missions such as THESEUS/X-GIS will be able to improve the constraints by a
factor of 10-100 depending on the level of control under the systematics of
these instruments.Comment: To match accepted for publication in Phys. Rev. D. versio
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