X-ray betatron radiation is produced by oscillations of electrons in the intense focusing field of a laser-plasma accelerator. These hard x-rays show promise for use in femtosecond-scale time-resolved radiography of ultrafast processes. However, the spectral characteristics of betatron radiation have only been inferred from filter pack measurements. In order to achieve higher resolution spectra...

We report on the analysis of an XMM observation of the X-ray source IGR J16320–4751 = AX J1631.9– 4752. Our analysis allowed us to obtain the most accurate X-ray position to date (Rodriguez et al. 2003), and to identify a likely infrared counterpart (Tomsick et al. 2003). We present the detailed analysis of the IGR J16320–4751 XMM spectra. The PN spectrum can be well represented by a single pow...

We present Hubble Space Telescope images of the Heiii region surrounding the bright X-ray source in the dwarf irregular galaxy Holmberg II. Using Chandra, we find a position for the X-ray source of α = 08h 19m 28.98s, δ = +70 • 42 ′ 19. ′′ 3 (J2000) with an uncertainty of 0.6 ′′. We identify a bright, point-like optical counterpart centered in the nebula with the X-ray source. The optical magni...

The spectra of disc accreting neutron stars generally show complex curvature, and individual components from the disc, boundary layer and neutron star surface cannot be uniquely identified. Here we show that much of the confusion over the spectral form derives from inadequate approximations for comptonization and for the iron line. There is an intrinsic low energy cutoff in comptonised spectra ...

Archival XMM-Newton data on the nearby Seyfert galaxy NGC 4051, taken in relatively high and low flux states, offer a unique opportunity to explore the complexity of its X-ray spectrum. We find the hard X-ray band to be significantly affected by reflection from cold matter, which can also explain a non-varying, narrow Fe K fluorescent line. We interpret major differences between the high and lo...

X iv :0 90 7. 18 51 v1 [ as tr oph .C O ] 1 0 Ju l 2 00 9 GRB 011211: An alternative interpretation of the optical and X-ray spectra in terms of blueshifts D. Basu Abstract The redshift of the gamma ray burst (GRB) GRB 011211 has been determined as 2.14 from several absorption lines seen in the spectrum of its optical afterglow. The spectrum of its X-ray afterglow exhibited several emission lin...

Recently, convincing evidence was found for extremely large X-ray absorption by column densities > 1023 cm−2 in broad absorption line quasars. One consequence of this is that any soft X-ray emission from these QSOs would be the scattered light or leaked light from partially covering absorbing material. A detection of the unabsorbed soft X-ray and absorbed hard X-ray component will allow to dete...

We study the binary corrected X-ray light curve of Cygnus X-3 using the RXTE-ASM (All Sky Monitor) data and RXTE-PCA data. We find that the X-ray template derived from the EXOSAT observations adequately explains the binary variations. Using the recently determined quadratic binary ephemeris we correct the RXTE-PCA lightcurve and obtain the power spectrum which shows distinct features of shiftin...