A Persistent High-Energy Flux from the Heart of the Milky Way : Integral's view of the Galactic Center

Abstract

The Ibis/Isgri imager on Integral detected for the first time a hard X-ray source, IGR J17456-2901, located within 1' of Sgr A* over the energy range 20-100 keV. Here we present the results of a detailed analysis of ~7 Ms of Integral observations of the GC. With an effective exposure of 4.7 Ms we have obtained more stringent positional constraints on this HE source and constructed its spectrum in the range 20-400 keV. Furthermore, by combining the Isgri spectrum with the total X-ray spectrum corresponding to the same physical region around SgrA* from XMM data, and collected during part of the Integral observations, we constructed and present the first accurate wide band HE spectrum for the central arcmins of the Galaxy. Our complete analysis of the emission properties of IGR shows that it is faint but persistent with no variability above 3 sigma contrary to what was alluded to in our first paper. This result, in conjunction with the spectral characteristics of the X-ray emission from this region, suggests that the source is most likely not point-like but, rather, that it is a compact, yet diffuse, non-thermal emission region. The centroid of IGR is estimated to be R.A.=17h45m42.5, decl.=-28deg59'28'', offset by 1' from the radio position of Sgr A* and with a positional uncertainty of 1'. Its 20-400 keV luminosity at 8 kpc is L=5.4x10^35 erg/sec. Very recently, Hess detected of a source of ~TeV g-rays also located within 1' of Sgr A*. We present arguments in favor of an interpretation according to which the photons detected by Integral and Hess arise from the same compact region of diffuse emission near the central BH and that the supernova remnant Sgr A East could play an important role as a contributor of very HE g-rays to the overall spectrum from this region.

14 pages, 11 figures, Accepted for publication in ApJ

References in corpus (52)

• ISGRI: the INTEGRAL Soft Gamma-Ray Imager
• Stellar Orbits Around the Galactic Center Black Hole
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre
• SINFONI in the Galactic Center: young stars and IR flares in the central light month
• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• The Supermassive Black Hole at the Galactic Center
• Very high energy gamma rays from the direction of Sagittarius A*
• Stellar dynamics in the central arcsecond of our galaxy
• The INTEGRAL Science Data Centre (ISDC)
• The all-sky distribution of 511 keV electron-positron annihilation emission
• A new population of very high energy gamma-ray sources in the Milky Way
• Variable Infrared Emission from the Supermassive Black Hole at the Center of the Milky Way
• A Jet-ADAF model for Sgr A*
• The INTEGRAL/IBIS Scientific Data Analysis
• The Nature of the 10 Kilosecond X-ray Flare in Sgr A*
• Diffuse X-ray Emission in a Deep Chandra Image of the Galactic Center
• XMM-Newton observation of the brightest X-ray flare detected so far from SgrA*
• A Chandra Study of Sgr A East: A Supernova Remnant Regulating The Activity Of Our Galactic Center?
• First Simultaneous NIR/X-ray Detection of a Flare from SgrA*
• An Overabundance of Transient X-ray Binaries within 1 pc of the Galactic Center
• A $\lambda$20cm Survey of the Galactic Center Region I: Detection of Numerous Linear Filaments
• Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
• ASCA X-ray source catalogue in the Galactic Center region
• Very high energy gamma rays from the composite SNR G0.9+0.1
• High energy gamma rays from the massive black hole in the Galactic Center
• A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton Photon Imaging Cameras
• The Spectra and Variability of X-ray Sources in a Deep Chandra Observation of the Galactic Center
• An Accretion-Induced X-ray Flare in Sgr A*
• The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location Accuracy
• Electron Acceleration around the Supermassive Black Hole at the Galactic Center
• A Remarkable Low-Mass X-ray Binary within 0.1 pc of the Galactic Center
• The AGASA/SUGAR Anisotropies and TeV Gamma Rays from the Galactic Center: A Possible Signature of Extremely High-energy Neutrons
• The Origin of X-ray Emission from a Galactic Center Molecular Cloud: Low Energy Cosmic Ray Electrons
• The Zoo of X-ray sources in the Galactic Center Region: Observations with BeppoSAX
• TeV Emission from the Galactic Center Black-Hole Plerion
• Accretion of cool stellar winds on Sgr A*: another puzzle of the Galactic Centre?
• Repeated X-ray Flaring Activity in Sagittarius A*
• Characteristics of Diffuse X-Ray Line Emission within 20 pc of the Galactic Center
• XMM-Newton spectral analysis of the Pulsar Wind Nebula within the composite SNR G0.9+0.1
• Chandra observations of the pulsar wind nebula in SNR G0.9+0.1
• XMM-Newton observations of Sagittarius A East
• The Galactic Center: An Interacting System of Unusual Sources
• Detection of hard X-ray emission from the Galactic nuclear region with INTEGRAL
• A Kinship between the EGRET SNR's and Sgr A East
• X-ray Line Emission from Supernova Ejecta Fragments
• On the Nature of the EGRET Source at the Galactic Center
• In flight calibration of the ISGRI camera
• Discovery of a bright X-ray transient in the Galactic Center with XMM-Newton
• X-ray Scattering Halos from the Galactic Center: Implications for Diffuse Emission Around SgrA*
• A Model of the EGRET Source at the Galactic Center: Inverse Compton Scattering Within Sgr A East and its Halo

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• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Radiative Models of Sgr A* from GRMHD Simulations
• The 3rd IBIS/ISGRI soft gamma-ray survey catalog
• INTEGRAL/IBIS all-sky survey in hard X-rays
• Observational signatures of particle acceleration in supernova remnants
• A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft $\gamma$-ray and Sub-millimeter Emission
• Disrupted Globular Clusters Can Explain the Galactic Center Gamma Ray Excess
• Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2
• Spectrum and variability of the Galactic Center VHE gamma-ray source HESS J1745-290
• The Origin of Diffuse X-ray and $\gamma$-ray Emission from the Galactic Center Region: Cosmic Ray Particles
• The XMM-Newton view of the central degrees of the Milky Way
• Hard X-ray emission from the Galactic ridge
• INTEGRAL/IBIS nine-year Galactic Hard X-Ray Survey
• G359.95-0.04: Pulsar Candidate Near Sgr A*
• The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
• INTEGRAL/IBIS 7-year All-Sky Hard X-Ray Survey. Part II: Catalog of Sources
• Surviving the hole I: Spatially resolved chemistry around Sgr A*
• Inverse Compton Scenarios for the TeV Gamma-Ray Emission of the Galactic Centre
• State Transitions in Bright Galactic X-ray Binaries: Luminosities Span by Two Orders of Magnitude
• NuSTAR Hard X-ray Survey of the Galactic Center Region II: X-ray Point Sources
• Far-Infrared Spectroscopy of the Galactic Center. Hot Molecular Gas: Shocks versus Radiation near SgrA*
• Low-mass X-ray binaries in the bulge of the Milky Way
• INTEGRAL/IBIS 17-yr hard X-ray all-sky survey
• Metrics and Motivations for Earth-Space VLBI: Time-Resolving Sgr A* with the Event Horizon Telescope
• Periodic Modulations in an X-ray Flare from Sagittarius A*
• Self-consistent spectra from radiative GRMHD simulations of accretion onto Sgr A*
• Unveiling the high energy tail of 1E 1740.7-2942 with INTEGRAL
• INTEGRAL: science highlights and future prospects
• Gamma rays from the Galactic Centre region: a review
• The INTEGRAL view on Black Hole X-ray Binaries
• Multiwavelength Astronomy and CTA: X-rays
• The Galactic LMXB Population and the Galactic Centre Region
• Bremsstrahlung in GRMHD models of accreting black holes
• RXTE/ASM and Swift/BAT Observations of Spectral Transitions in Bright X-ray Binaries in 2005-2010
• Soft gamma-ray constraints on a bright flare from the Galactic Center supermassive black hole
• Diffusive Cosmic Ray Acceleration at the Galactic Centre
• Sgr B2 hard X-ray emission with INTEGRAL after 2009: still detectable?
• First broad band study of the mysterious source 1E 1743.1-2843
• Three-dimensional Radiative Properties of Hot Accretion Flows onto the Galactic Centre Black Hole
• The catalog of variable sources detected by INTEGRAL I: Catalog and Techniques
• Chandra X-ray counterpart of KS 1741-293
• G0.57-0.018: A young supernova remnant? INTEGRAL and VLA observations
• Coded Mask Instruments for Gamma-Ray Astronomy
• High Energy Activity of the Super-Massive Black Hole at the Galactic Center
• Observing with a space-borne gamma-ray telescope: selected results from INTEGRAL
• Ten years of INTEGRAL observations of the hard X-ray emission from SGR 1900+14
• Gamma-Ray Telescopes (in "400 Years of Astronomical Telescopes")
• Polarimetric Imaging of Sgr A* in its Flaring State
• High Energy Emission from the Galactic Center