The rapidly varying non-thermal X-ray emission observed from Sgr A⋆ points to particle acceleration taking place close to the supermassive black hole. The TeV γ-ray source HESS J1745−290 is coincident with Sgr A⋆ and may be closely related to the X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these two objects. Here we report on joint ...

Innate immune cells can sense hepatitis C virus (HCV)-infected cells and respond with anti-viral actions including secretion of interferons (IFNs). In previous studies, the response of individual innate immune cells against HCV was analyzed in detail. We hypothesized that interaction of multiple innate immune cells increases the magnitude of the immune response and eventually leads to clearance...

Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A∗, utilizing the High Energy Transmission Grating Spectrometer (HETGS) instrument on the Chandra X-Ray Observatory. These observations will allow us to measure the quiescent X-ray spectra of Sgr A∗ for the first time at both high spatial and spectral resolut...

There are now four low mass X-ray binaries with black holes which show twin resonant-like HFQPOs. Similar QPOs might have been found in Sgr A∗. I review the power spectral density distributions of the three X-ray flares and the six NIR flares published for Sgr A∗ so far, in order to look for more similarities than just the frequencies between the microquasar black holes and Sgr A∗. The three X-...

We present results from observations of NH3(1,1), (2,2), (3,3), and (6,6) with the Very Large Array. The data sample the inner 10 pc (4′) of the Galaxy and have a velocity coverage of –140 to +130 km s−1. The velocity integrated NH3(3,3) image shows that the Sgr A East supernova remnant is impacting the 50 km s−1 GMC in the northeast, the northern ridge in the north, and the western streamer in...

Menten et al. (1997) accurately determined the position of Sgr A* on an infrared image, by aligning the infrared image with positions measured for SiO masers, associated with infrared-bright evolved stars, at radio wavelengths. We now report greatly improved radio positions and, for the first time, proper motions of many stellar SiO masers at the Galactic Center. These positions and motions, co...

The fluorescent X-ray emission from neutral iron in the molecular clouds (Sgr B) indicates that the clouds are being irradiated by an external X-ray source. The source is probably associated with the Galactic central black hole (Sgr A*), which triggered a bright outburst one hundred years ago. We suggest that such an outburst could be due to a partial capture of a star by Sgr A*, during which a...

We present preliminary iron abundances and α element (Ca, Mg) abundance ratios for a sample of 22 Red Giant Branch (RGB) Stars in the Sagittarius galaxy (Sgr), selected near the RGB-Tip. The sample is representative of the Sgr dominant population. The mean iron abundance is [Fe/H]=-0.49. The α element abundance ratios are slightly subsolar, in agreement with the results recently prensented by [...

I review some recent developments in our understanding of the environments of soft gamma-ray repeaters. I pay particular attention to the apparent association betwwen SGR 1900+14 and SGR 1806-20 and embedded clusters of stars.

We show that the recently-discovered orbits of massive stars with closest approach of ∼ 10 Schwarzschild radii from Sgr A* , allow winds from these stars to provide the required mass deposition rate near the black hole horizon. The observed luminosity of Sgr A* does not require viscous transport of angular momentum, as long as the total wind mass loss rate reaches ∼ 10M⊙ yr −1 from the close-in...