Cygnus X-3, among the X-ray binaries, is one of the brightest in the radio band, repeatedly exhibiting huge radio flares. The X-ray spectra shows two definite states, low (correspondingly hard) and high (correspondingly soft). During the hard state the X-ray spectra shows a pivoting behaviour correlated to the radio emission. In the high state the X-ray spectra shows a gamut of behaviour which ...

The nearby galaxy M33 hosts the most luminous steady X-ray source in the Local Group. The high spatial resolution of Chandra allows us to confirm that this ultra-luminous X-ray source is within the nucleus and rule out at the 4.6σ level a previously proposed possible counterpart located 1 away. The X-ray spectrum is well fitted by a disc blackbody with kTin=1.18±0.02 keV and Rin(cos θ)=57±3 km,...

Bright Ar quasimonochromatic K-shell x ray with very little background has been generated using an Ar clustering gas jet target irradiated with a 30 fs ultrahigh-contrast laser, with a measured flux of 2.2×10(11)   photons/J into 4π. This intense x-ray source critically depends on the laser contrast and intensity. The optimization of source output with interaction length is addressed. Simulatio...

In the error box of 3EG J1835+5918, the brightest as-yet unidentified EGRET source at intermediate Galactic latitude, we find a weak, ultrasoft X-ray source at energies E < 0.3 keV in the ROSAT All-Sky Survey. Deep optical imaging at the location of this source, as pinpointed by an observation with the ROSAT HRI, reveals a blank field to a limit of V > 25.2. The corresponding lower limit on fX/...

We present a multiwavelength study of the field containing the unidentified X-ray source AX J1639.0−4642, discovered with the ASCA observatory and recently detected with the IBIS telescope, onboard the INTEGRAL satellite. The huge hydrogen column density towards the source, the hard spectral index in the 0.7–10 keV band and its flux variability suggest that the source is a High Mass X-ray Binar...

Sub-arcsecond resolution Chandra observations of η Car reveal a 40 × 70 ring or partial shell of X-ray emission surrounding an unresolved, bright, central source. The spectrum of the central source is strongly absorbed and can be fit with a high-temperature thermal continuum and emission lines. The surrounding shell is well outside the optical/IR bipolar nebula and is coincident with the Outer ...

We have obtained snapshot images of an X-ray nova in M31 from Chandra ACIS-I and the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The Chandra position of the X-ray nova was R.A.=00:44:06.68 ±1.74, Dec.=+41:12:20.0 ±2.31. A follow-up HST observation 24 days later revealed a source at R.A.=00:44:06.81, Dec.=+41:12:24.0 that was B = 25.75± 0.05. This optical source faded to B = ...

We have demonstrated the first optically driven X-ray source based on carbon nanotube (CNT) photocathodes. It is a compact dual X-ray source and the two sources are accurately and independently controlled with two laser diodes illuminating the photocathodes. Thanks to the emission stability, high quality images have been obtained. This dual source provides two images from two different viewing ...

The observations of a newly discovered X-ray transient source XTE J1748−288 were made in the energy band 2 − 18 keV with the Indian X-ray Astronomy Experiment(IXAE) on the IRS−P3 satellite during 1998, June 14−25. The source count rate declined gradually with an exponential decay time of 19 ± 1.6 days. The X-ray light curves showed no significant intensity variations on short time scales (≤ 10s...