We report first results from a multiwavelength campaign to measure the simultaneous spectrum of Sgr A* from cm to mm wavelengths. The observations confirm that the previously detected submm-excess is not due to variability; the presence of an ultracompact component with a size of a few Schwarzschild radii is inferred. In a VLA survey of LINER galaxies, we found Sgr A*-like nuclei in one quarter...

We present results of our Chandra observation with ACIS-I centered on the position of Sagittarius A (Sgr A), the compact nonthermal radio source associated with the massive black hole (MBH) at the dynamical center of the Milky Way Galaxy. We have obtained the first high spatial resolution (≈ 1), hard X-ray (0.5–7 keV) image of the central 40 pc (17) of the Galaxy. We have discovered an X-ray so...

Variable emission from Sgr A*, the luminous counterpart to the super-massive black hole at the center of our Galaxy, arises from the innermost portions of the accretion flow. Better characterization of the variability is important for constraining models of the low-luminosity accretion mode powering Sgr A*, and could further our ability to use variable emission as a probe of the strong gravitat...

We present Infrared Space Observatory (ISO) observations of OH and OH toward Sgr B2 with a spectral resolution of ∼35 km s. The OH J=5/2→3/2 and J=3/2→1/2 rotational lines of the 2Π1/2 ladder are seen in emission while the cross-ladder transitions (from the 2Π3/2 J=3/2 to the J=1/2, 3/2 and 5/2 levels of the 2Π1/2 ladder), and the 2Π3/2 J=5/2←3/2 and J=7/2←5/2 lines are detected in absorption. ...

We present statistics of SGR 1806220 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 events detected with the Burst and Transient Source Experiment, and 134 events detected with the International Cometary Explorer. We find that the fluence distribution of bursts observed with each instrument are well described by power laws with indices...

Sgr A is currently being fed by winds from a cluster of gravitationally bound young mass-loosing stars. Using observational constraints on the orbits, mass loss rates and wind velocities of these stars, we numerically model the distribution of gas in the ∼ 0.1–10 region around Sgr A. We find that radiative cooling of recently discovered slow winds leads to the formation of many cool filaments a...

We present an analysis of a recent XMM-Newton observation of Sgr A East, a supernova remnant located close to the Galactic Centre. Very high quality X-ray spectra reveal many emission lines from highly ionized atoms consistent with a multitemperature thin thermal plasma in ionization equilibrium. We use a two-temperature model to fit the spectra and derive temperatures of 1 keV and 4 keV. There...

We present observations of CO, CO and of H2O in the middle and far-infrared taken with the ISO-SWS and ISO-LWS spectrometers toward two positions in the Galactic Center region (Sgr A and GCS-3). Both ice and gas phase molecules are detected. The ISO data have been complemented with observations of the J=3-2 and J=7-6 lines of CO carried out at the Caltech Submillimeter Observatory. The ISO and ...

SGR 0526–66 was the first soft gamma-ray repeater (SGR) from which a giant flare was detected in March 1979, suggesting the existence of magnetars, i.e. neutron stars powered by the decay of their extremely strong magnetic field. Since then, very little information has been obtained on this object, mainly because it has been burst-inactive since 1983 and the study of its persistent X–ray emissi...

Since the discovery of the largest positive superhump period in TV Col (6.4 h), we have started a program to search for superhumps in cataclysmic variables (CVs) with large orbital periods. In this work, we summarize preliminary results of our observations of TX Col and V4742 Sgr. TX Col is an intermediate polar with a 5.7-h orbital period. V4742 Sgr is a recent (2002) nova with no known period...