arXiv subjects

J. L. Skilton

Publications and source records attributed to J. L. Skilton.

4 recordsLinked to original sources

arXiv2012

Constraints on the non-thermal emission from Eta Carinae's blast wave of 1843

Non-thermal hard X-ray and high-energy (HE; 1 MeV < E < 100 GeV) gamma-ray emission in the direction of Eta Carinae has been recently detected using the INTEGRAL, AGILE and Fermi satellites. This emission has been interpreted either in the framework of particle acceleration in the colliding wind region between the two massive stars or in the very fast moving blast wave which originates in the historical 1843 "Great Eruption". Archival Chandra data has been reanalysed to search for signatures of particle acceleration in Eta Carinae's blast wave. No shell-like structure could be detected in hard X-rays and a limit has been placed on the non-thermal X-ray emission from the shell. The time dependence of the target radiation field of the Homunculus is used to develop a single zone model for the blast wave. Attempting to reconcile the X-ray limit with the HE -ray emission using this model leads to a very hard electron injection spectrum dN/dE ~ E^-Gamma with Gamma < 1.8, harder than the canonical value expected from diffusive shock acceleration.

astro-ph.HE↗

arXiv2011

Detection of the Pulsar Wind Nebula HESS J1825-137 with the Fermi Large Area Telescope

We announce the discovery of 1 - 100 GeV gamma-ray emission from the archetypal TeV pulsar wind nebula HESS J1825-137 using 20 months of survey data from the Fermi Large Area Telescope (LAT). The gamma-ray emission detected by the LAT is significantly spatially extended, with a best-fit rms extension of sigma = 0.56° $\pm$ 0.07° for an assumed Gaussian model. The 1 - 100 GeV LAT spectrum of this source is well described by a power-law with a spectral index of 1.38 $\pm$ 0.12 $\pm$ 0.16 and an integral flux above 1 GeV of (6.50 $\pm$ 0.21 $\pm$ 3.90) x 10^{-9} cm^{-2} s^{-1}. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. Detailed morphological and spectral analyses bring new constraints on the energetics and magnetic field of the pulsar wind nebula system. The spatial extent and hard spectrum of the GeV emission are consistent with the picture of an inverse Compton origin of the GeV-TeV emission in a cooling-limited nebula powered by the pulsar PSR J1826-1334.

astro-ph.HE↗

arXiv2009

The radio counterpart of the likely TeV binary HESS J0632+057

The few known gamma-ray binary systems are all associated with variable radio and X-ray emission. The TeV source HESS J0632+057, apparently associated with the Be star MWC148, is plausibly a new member of this class. Following the identification of a variable X-ray counterpart to the TeV source we conducted GMRT and VLA observations in June-September 2008 to search for the radio counterpart of this object. A point-like radio source at the position of the star is detected in both 1280 MHz GMRT and 5 GHz VLA observations, with an average spectral index, alpha, of ~0.6. In the VLA data there is significant flux variability on ~month timescales around the mean flux density of ~0.3 mJy. These radio properties (and the overall spectral energy distribution) are consistent with an interpretation of HESS J0632+057 as a lower power analogue of the established gamma-ray binary systems.

astro-ph.HE↗

arXiv2008

HESS J0632+057 : A new gamma-ray binary?

The High Energy Stereoscopic System (HESS) survey of the Galactic plane has established the existence of a substantial number (~40) of Galactic TeV gamma-ray sources, a large fraction of which remain unidentified. HESS J0632+057 is one of a small fraction of these objects which is point-like in nature(<2' rms), and is one of only two point-like sources that remain unidentified. Follow-up observations of this object with XMM-Newton have revealed an X-ray source coincident with the TeV source and with the massive star MWC 148, of the spectral type B0pe. This source exhibits a hard spectrum, consistent with an absorbed power law with Gamma = 1.26 +/- 0.04, and shows significant variability on hour timescales. We discuss this spatial coincidence and the implied spectral energy distribution of this object and argue that it is likely a new gamma-ray binary system with a close resemblance to the three known members of this class, and in particular to LS I +61 303. Further X-ray, radio and optical observations of this system are needed to firmly establish HESS J0632+057 as a new member of this rare class of Galactic objects.

astro-ph↗