The radio source Sgr A at the center of our Galaxy is believed to be a 2.6× 10M⊙ black hole which accretes gas from the winds of nearby stars. We show that limits on the X-ray and infrared emission from the Galactic Center provide an upper limit of ∼ 8 × 10M⊙ yr −1 on the mass accretion rate in Sgr A. The advection-dominated accretion flow (ADAF) model favors a rate <∼ 10 M⊙ yr . In comparison,...

Using the Chandra X-Ray Observatory, we have detected the black hole transients V4641 Sgr and XTE J1859 226 in their low-luminosity quiescent states. The 0.3–8 keV luminosities are (d/7 kpc) ergs s 1 and 3.3 31 (4.0 ) # 10 2.4 (d/11 kpc) ergs s 1 for V4641 Sgr and XTE J1859 226, respectively. With the addition of 4.8 31 (4.2 ) # 10 2.2 these two systems, 14 out of the 15 transients with confirm...

The Sgr B2 giant molecular cloud is claimed to be an ”X–ray reflection nebula” – the reprocessing site of a powerful flare of the Sgr A* source, occurred few hundred years ago. The shape of the X–ray spectrum and the strength of the iron fluorescent line support this hypothesis. We argue that the most clean test of the origin of X–rays from Sgr B2 would be a detection of polarized emission from...

We report the results of X–ray (2–10 keV) observations of the giant molecular clouds Sgr B, Sgr C and Sgr D in the Galactic Center region, together with the discovery of the point-like source SAX J1748.2–2808. The data have been obtained with the MECS instrument on the BeppoSAX satellite. The core of Sgr B2 has an X–ray luminosity of ∼6×10 erg s and its spectrum is characterized by a strong Fe ...

Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and persistent emission during episodes of intense burst activity. SGR 1900+14 has undergone large flux increases following recent burst activity. Both SGR 1900+14 and SGR 1806−20 have shown significant changes in their pulse profile and spindown rates during the last several years. The pulse profile changes are linked with t...

We present K -band (2.12 μm) imaging observations of the SGR 1806–20 field taken during its very active phase in mid 2004, which reveal brightening of sources within the Chandra X-ray error circle when compared with earlier images obtained in 2002. One source brightened by more than a factor of 2, and so we consider this to be the probable infrared counterpart for SGR 1806–20. The other two sou...

We report the detection of ∼1 500 RR Lyrae of Bailey type ab located in the Sagittarius dwarf galaxy (Sgr). These variables have been detected on two ESO Schmidt fields centred on (l,b)=(3.1,-7.1) and (6.6,10.8), covering an area of ∼50 deg. We present a surface density map of Sgr based on the spatial distribution of these RRab, allowing us to trace its structure in a region that was still almo...

Hepatitis C virus (HCV) genotype (GT) 3 is the second most prevalent of the seven HCV genotypes and exhibits the greatest resistance to the highly potent, direct-acting antivirals (DAAs) that are currently in use. Previously a stable cell line harbouring the S52 GT3 sub-genomic replicon (SGR) was established, but this SGR was unable to robustly replicate transiently. As transient SGRs are a cri...

This paper reports on the early Chandra view of the Galactic center (GC) activities. The massive black hole Sgr A is extremely faint, while more bright diffuse X-ray emission is prevailing in the circumnuclear disk. Another high temperature plasma is found in the Sgr A East shell. This may indicate that Sgr A East is a supernova remnant, although no clear X-ray shell is found. A hint of non-the...

A time-variability study of the neutral iron line flux at 6.40 keV in the Sgr B2 region from data of Suzaku and Chandra is presented. The highly ionized iron line at 6.68 keV is due to Galactic Center Diffuse X-rays (GCDX), and is thus time invariable. By comparing the 6.68 keV and 6.40 keV line fluxes, we found that the 6.40 keV flux from the Sgr B2 complex region is time variable; particularl...