The Galactic microquasar GRS 1915+105 exhibits several episodes of steady X-ray emission characterized by a hard power-law spectrum and intense Quasi Periodic Oscillations. It is known that there are two types of such low-hard states, one with steady radio emission and the other without any significant radio emission. We present the results of a detailed X-ray spectroscopic study of GRS 1915+10...

We report the discovery of a transient radio source 2.7 arcsec (0.1 pc projected distance) South of the Galactic Center massive black hole, Sagittarius A*. The source flared with a peak of at least 80 mJy in March 2004. The source was resolved by the Very Large Array into two components with a separation of ∼ 0.7 arcsec and characteristic sizes of ∼ 0.2 arcsec. The two components of the source ...

We present new XM M − N ewton X-ray observations of the z = 1.246 narrow-line radioquasar RX J1011.2+5545 serendipitously discovered by ROSAT. The flat X-ray spectrum previously measured by ROSAT and ASCA is shown to be the result of a steep Γ ∼ 1.8 power law spectrum seen through a moderate intrinsic absorbing column (N H ∼ 4 × 10 21 cm −2). The position of the X-ray source is entirely coincid...

Aims. In order to discover new X-ray transients, the data taken by XMM-Newton as it slews between targets are being processed and crosscorrelated with other X-ray observations. Methods. A bright source, XMMSL1 J060636.2-694933, was detected on 18 July 2006 at a position where no previous X-ray source had been seen. The XMM-Newton slew data, plus follow-up dedicated XMM-Newton and Swift observat...

Aims. We investigate the X-ray spectral and timing properties of the high mass X-ray binary EXO 2030+375 observed during its June–September 2006 giant (type II) outburst. Methods. The data analyzed in this work are from partly simultaneous observations with INTEGRAL and Swift. The pulse period P and its temporal derivative Ṗ are measured. X-ray pulse profiles in different energy ranges and time...