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As one of the best-characterized stellar-mass black holes, with good measurements of its mass, distance and inclination, V404 Cyg is the ideal candidate to study Eddington-limited accretion episodes. After a long quiescent period, V404 Cyg underwent a new outburst in June 2015. We obtained two Chandra HETG exposures of 20 ksec and 25 ksec. Many strong emission lines are observed; the ratio of Si He-like triplet lines gives an estimate for the formation region distance of $4times10^{11}$ cm, while the higher ionization Fe XXV He-like triplet gives an estimate of $7times10^9$ cm. A narrow Fe K$alpha$ line is detected with an equivalent width greater than 1 keV in many epochs, signaling that we do not directly observe the central engine. Obscuration of the central engine and strong narrow emission lines signal that the outer disk may be illuminated, and its structure may help to drive the strong variability observed in V404 Cyg. In the highest flux phases, strong P-Cygni profiles consistent with a strong disk wind are observed. The kinetic power of this wind may be extremely high.
We report our measurements of the bulk radial velocity from a sample of small, metal-rich ejecta knots in Keplers Supernova Remnant (SNR). We measure the Doppler shift of the He-like Si K$alpha$ line center energy in the spectra of these knots based
The black-hole binary, V404 Cygni, went into outburst in June 2015, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present optical/UV observations taken with the Swift Ultra-violet Optical Tel
The microquasar V404 Cygni underwent a series of outbursts in 2015, June 15-31, during which its flux in hard X-rays (20-40 keV) reached about 40 times the Crab Nebula flux. Because of the exceptional interest of the flaring activity from this source
The HETG can be used to obtain spatially resolved spectra of moderately extended sources. We present preliminary results for two well studied, oxygen rich supernova remnants in the Magellanic clouds, E0102-72 and N132D. The dispersed spectrum of E010
We report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in June-July 2015. Detailed analyses reveal a possible excess of $gamma$-ray emission on 26 June 2015, with a very s