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Do Fermi-LAT observations really imply very large Lorentz factors in GRB outflows ?
gamma-ray burst: general gamma-ray burst: individual: GRB 080916C radiative transfer radiation mechanisms: non-thermal
2011/10/20
Recent detections of GeV photons in a few GRBs by Fermi-LAT imply huge bulk Lorentz factors to avoid a large gamma gamma optical depth at high energy. Estimates can be as high as Gamma ~ 1000 in the m...
Blazars as Ultra-High-Energy Cosmic-Ray Sources: Implications for TeV Gamma-Ray Observations
Ultra-High-Energy Cosmic-Ray Sources Implications TeV Gamma-Ray Observations
2011/10/20
Spectral fitting of correlated multiwavelength data of BL Lac objects and Fanaroff-Riley I radio galaxies gives the mean comoving magnetic field strength B', the bulk outflow Doppler factor Gamma, and...
X-ray Observations of Radio Transients without Optical Hosts
X-ray Observations Radio Transients without Optical Hosts
2011/10/19
We present a 50 ks Chandra ACIS-I X-ray observation of the Bower et al. VLA archival field. The observations reach a limiting sensitivity of ~1E-4 counts/s, corresponding to a flux of a few times 1E-1...
RXTE Observations of the Low-Mass X-Ray Binary 4U 1608-522 in Upper-Banana State
RXTE Observations Low-Mass X-Ray Binary 4U 1608-522 Upper-Banana State
2011/10/11
To investigate the physics of mass accretion onto weakly-magnetized neutron stars, 95 archival RXTE datasets of an atoll source 4U 1608-522, acquired over 1996-2004 in so-called upper-banana state, we...
Unveiling the nature of IGR J17177-3656 with X-ray, NIR and Radio observations
accretion accretion disks – X-rays binaries – binaries
2011/8/24
We report on the first broad-band (1-200 keV) simultaneous Chandra-INTEGRAL observations of the recently discovered hard X-ray transient IGR J17177-3656 that took place on 2011, March 22, about two we...
The metallicity of gamma-ray burst environments from high energy observations
Gamma-ray burst general – Gamma-ray burst individual GRB050904 – early Universe – dark ages
2010/11/10
Context. Gamma-ray bursts (GRBs) and their early afterglows ionise their circumburst material. Only high-energy spectroscopy therefore, allows examination of the matter close to the burst itself. Soft...
Evidence for Low Black Hole Spin and Physically Motivated Accretion Models from Millimeter VLBI Observations of Sagittarius A*
black hole physics—Galaxy center—techniques interferometric—submillimeter—accretion accretion
2010/11/15
Millimeter very-long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr ...
The Wide-Field X-ray Telescope (WFXT) is a proposed NASA mission dedicated to performing surveys of the sky in the soft X-ray band (0.3 − 6 keV).The key characteristics of this missions are a co...
Contribution of amateur observations to Saturn storm studies
Contribution of amateur observations Saturn storm studies
2010/11/11
Since 2004, Saturn Electrostatic Discharges (SEDs),which are the radio signatures of lightning in Saturn’s atmosphere, have been observed by the Cassini Radio and Plasma Wave Science instrument (RPWS)...
INTEGRAL observations of the GeV blazar PKS1502+106 and of the hard X-ray bright Seyfert Galaxy Mkn841
galaxies active – quasars individual PKS 1502+106 – Galaxies Seyfert – galaxies individual Mkn 841 – radiation
2010/11/16
Context. Extragalactic nuclear activity is best explored with observations at high energies, where the most extreme flux and spectral variations are expected to occur, witnessing changes in the accret...
Radio Halos and the importance of future observations at low frequency
Radio Halos future observations low frequency
2010/11/11
Radio observations discovered large scale non thermal sources in the central Mpc regions of
dynamically disturbed galaxy clusters (radio halos). The morphological and spectral properties of these sou...
Precise Gamma-Ray Timing and Radio Observations of 17 Fermi Gamma-Ray Pulsars
Gamma rays stars pulsars general Radio continuum stars X-rays: stars
2010/11/15
We present precise phase-connected pulse timing solutions for 16 gamma-ray-selected pulsars
recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one ve...
Cosmic Ray e^+/(e^- + e^+) and pbar/p Ratios Explained by an Injection Model Based on Gamma-ray Observations
High Energy Astrophysical Phenomena (astro-ph.HE)
2011/1/6
We present a model of cosmic ray injection into the Galactic space based on recent gamma-ray observations of supernova remnants (SNRs) and pulsar wind nebulae (PWNe) by the Fermi Large Area Telescope ...
Investigating the Cosmic-Ray Ionization Rate Near the Supernova Remnant IC 443 Through H3+ Observations
High Energy Astrophysical Phenomena (astro-ph.HE)
2011/1/6
Observational and theoretical evidence suggests that high-energy Galactic cosmic rays are primarily accelerated by supernova remnants. If also true for low-energy cosmic rays, the ionization rate near...
Status and Strategies of Current LUNASKA Lunar Cherenkov Observations with the Parkes Radio Telescope
High Energy Astrophysical Phenomena (astro-ph.HE) Instrumentation and Methods for Astrophysics (astro-ph.IM)
2010/12/28
LUNASKA (Lunar UHE Neutrino Astrophysics with the Square Kilometre Array) is an ongoing project conducting lunar Cherenkov observations in order to develop techniques for detecting neutrinos with the ...