Search Publications
The Merger in Abell 576: A Line-of-Sight Bullet Cluster?
Bregman, Joel N.; Dupke, Renato A.; Mirabal, Nestor +1 more
Using a combination of Chandra and XMM-Newton observations, we confirmed the presence of a significant velocity gradient along the northeast-southwest direction in the intracluster gas of the cluster Abell 576. The results are consistent with a previous ASCA SIS analysis of this cluster. The error-weighted average over the ACIS-S3 and EPIC MOS1 an…
Initial Observations of Sunspot Oscillations Excited by Solar Flare
Kosovichev, A. G.; Sekii, T.
Observations of a large solar flare on 2006 December 13 using Solar Optical Telescope (SOT) on board the Hinode spacecraft revealed high-frequency oscillations excited by the flare in the sunspot chromosphere. These oscillations are observed in the region of strong magnetic field of the sunspot umbra and may provide a new diagnostic tool for probi…
The First Direct Detection of a Gravitational µ-Lens toward the Galactic Bulge
Kozłowski, S.; Mao, S.; Woźniak, P. R. +1 more
We present a direct detection of the gravitational lens that caused the microlensing event MACHO-95-BLG-37. This is the first fully resolved microlensing system involving a source in the Galactic bulge, and the second such system in general. The lens and source are clearly resolved in images taken with the High Resolution Channel of the Advanced C…
Very High Energy Observations of Gamma-Ray Burst Locations with the Whipple Telescope
Fegan, S. J.; Fortin, P.; Horan, D. +56 more
Gamma-ray burst (GRB) observations at very high energies (VHE; E>100 GeV) can impose tight constraints on some GRB emission models. Many GRB afterglow models predict a VHE component similar to that seen in blazars and plerions, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. VHE emission co…
Hard X-Ray Intensity Distribution along Hα Ribbons
Liu, Chang; Jing, Ju; Wang, Haimin +2 more
Unusual ribbon-like hard X-ray sources were found with the RHESSI observation of a 2B/M8.0 flare on 2005 May 13. We use this unique observation to investigate the spatial distribution of the hard X-ray intensity along the ribbons and compare it with the local magnetic reconnection rate and energy release rate predicted by the standard magnetic rec…
Spectral Modeling of the High-Energy Emission of the Magnetar 4U 0142+614
Stella, L.; Rea, N.; Tramacere, A. +4 more
We present an empirical spectral modeling of the high-energy emission of the anomalous X-ray pulsar 4U 0142+614 based on simultaneous Swift and INTEGRAL observations from X- to γ-ray energies. We adopted models contained in the XSPEC analysis package, as well as models based on recent theoretical studies, and restricted ourselves to those combinat…
Transient and Highly Polarized Double-Peaked Hα Emission in the Seyfert 2 Nucleus of NGC 2110
Moran, Edward C.; Eracleous, Michael; Barth, Aaron J. +1 more
We have discovered an extremely broad, double-peaked Hα emission line in the polarized flux spectrum of NGC 2110, establishing that this well-studied Seyfert 2 galaxy contains a disk-like hidden broad-line region (BLR). Several properties of NGC 2110 suggest that it is an obscured twin of Arp 102B, the prototypical double-peaked emission-line acti…
Strength of Coronal Mass Ejection-driven Shocks near the Sun and Their Importance in Predicting Solar Energetic Particle Events
Wang, Yuming; Shen, Chenglong; Wang, S. +3 more
Coronal shocks are important structures, but there are no direct observations of them in solar and space physics. The strength of shocks plays a key role in shock-related phenomena, such as radio bursts and solar energetic particle (SEP) generation. This paper presents an improved method of calculating Alfvén speed and shock strength near the Sun.…
A Possible Magnetar Nature for IGR J16358-4726
Kouveliotou, C.; Walter, R.; Ubertini, P. +10 more
We present detailed spectral and timing analysis of the hard X-ray transient IGR J16358-4726 using multisatellite archival observations. A study of the source flux time history over 6 yr suggests that lower luminosity transient outbursts can be occurring in intervals of at most 1 yr. Joint spectral fits of the higher luminosity outburst using simu…
IGR J22517+2218=MG3 J225155+2217: A New Gamma-Ray Lighthouse in the Distant Universe
Gehrels, N.; Giommi, P.; Bird, A. J. +7 more
We report on the identification of a new soft gamma-ray source, namely, IGR J22517+2218, detected with INTEGRAL IBIS. The source, which has an observed 20-100 keV flux of ~4×10-11 ergs cm-2 s-1, is spatially coincident with MG3 J225155+2217, a quasar at z=3.668. The Swift XRT 0.5-10 keV continuum is flat (Γ=1.5) wi…