Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux.
We report on the long-term X-ray monitoring with Swift, RXTE, Suzaku, Chandra, and
The center of our Galaxy hosts a supermassive black hole, Sagittarius (Sgr) A *. Young, massive stars within 0.5 pc of Sgr A * are evidence of an episode of intense star formation near the black hole a few million years ago, which might have left behind a young neutron star traveling deep into Sgr A * 's gravitational potential. On 2013 April 25, a short X-ray burst was observed from the direction of the Galactic center. With a series of observations with the Chandra and the Swift satellites, we pinpoint the associated magnetar at an angular distance of 2.4 ± 0.3 arcsec from Sgr A * , and refine the source spin period and its derivative (P = 3.7635537(2) s andṖ = 6.61(4) × 10 −12 s s −1), confirmed by quasi simultaneous radio observations performed with the Green Bank Telescope and Parkes Radio Telescope, which also constrain a dispersion measure of DM = 1750 ± 50 pc cm −3 , the highest ever observed for a radio pulsar. We have found that this X-ray source is a young magnetar at ≈0.07-2 pc from Sgr A *. Simulations of its possible motion around Sgr A * show that it is likely (∼90% probability) in a bound orbit around the black hole. The radiation front produced by the past activity from the magnetar passing through the molecular clouds surrounding the Galactic center region might be responsible for a large fraction of the light echoes observed in the Fe fluorescence features.
The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma-ray telescopes. Although small-scale variations in the nebula are well known, since the start of science operations of
During the summer of 2006, the accreting X-ray pulsar EXO 2030+375 underwent its first giant outburst since its discovery in 1985. Our observations include the first ever of the rise of a giant outburst of EXO 2030+375. EXO 2030+375 was monitored daily with the Rossi X-Ray Timing Explorer (RXTE ) from 2006 June to 2007 May. During the giant outburst we discovered evidence for a cyclotron feature at $11 keV. This feature was confidently detected for about 90 days, during the brighter portion of the outburst. Daily observations of the next five EXO 2030+375 orbits detected pulsations at all orbital phases and normal outbursts shifted to a later orbital phase than before the giant outburst. An accretion disk appears to be present in both the normal and giant outbursts, suggesting that the long-term behavior is a product of the state of the Be star disk and the accretion disk. Here we will present flux and frequency histories from our detailed RXTE observations of the giant outburst and the normal outbursts that surrounded it. A new orbital analysis is presented that includes observations from
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