Search Publications
Magnetohydrodynamic Models of the Bipolar Knotty Jet in Henize 2-90
Lee, Chin-Fei; Sahai, Raghvendra
A remarkably linear, bipolar, knotty jet was recently discovered in Hen 2-90, an object classified as a young planetary nebula. Using two-dimensional, magnetohydrodynamic simulations, we investigate periodic variations in jet density and velocity as the mechanism for producing the jet and its knotty structures. From a detailed comparison between t…
Cometary Ions Trapped in a Coronal Mass Ejection
Geiss, J.; Jones, G. H.; McComas, D. J. +5 more
Ion tails of comets are known to extend radially away from the Sun over very large distances. Crossing these tails by spacecraft not specifically targeted to intercept them was believed to be extremely improbable, since that requires precise angular alignment of the spacecraft with a comet. We report here the fortuitous detection of cometary ions …
Accretion and Outflow in the Active Galactic Nucleus and Starburst of NGC 5135
Heckman, T. M.; Levenson, N. A.; Weaver, K. A. +2 more
Observations of the Seyfert 2 and starburst galaxy NGC 5135 with the Chandra X-Ray Observatory demonstrate that both of these phenomena contribute significantly to its X-ray emission. We spatially isolate the active galactic nucleus (AGN) and demonstrate that it is entirely obscured by column density NH>1024 cm-2
XMM-Newton Study of A3562 and Its Immediate Shapley Environs
Finoguenov, A.; Kaastra, J. S.; de Plaa, J. +2 more
Using a mosaic of six XMM-Newton observations, we study the hydrodynamic state of A3562, a cluster in the center of the Shapley supercluster. The X-ray image reveals a sharp surface brightness gradient within the core of A3562, a 200 kpc ridge extending to the southwest. A nearby group, SC 1329-313, imaged within this program also exhibits a tail …
Ni Abundance in the Core of the Perseus Cluster: An Answer to the Significance of Resonant Scattering
Gastaldello, Fabio; Molendi, Silvano
Using an XMM-Newton observation of the Perseus cluster we show that the excess in the flux of the 7-8 keV line complex previously detected by ASCA and BeppoSAX is due to an overabundance of nickel rather than to an anomalously high Fe Heβ/Fe Heα ratio. This observational fact leads to the main result that resonant scattering, which was assumed to …
XMM-Newton Observations of an Intermediate X-Ray Object in NGC 2276
Mushotzky, Richard F.; Davis, David S.
We present the results from a ~53 ks XMM-Newton observation of NGC 2276. This galaxy has an unusual optical morphology with the disk of this spiral appearing to be truncated along the western edge. This XMM-Newton observation shows that the X-ray source at the western edge is a bright intermediate X-ray object (IXO). Its spectrum is well fitted by…
On Star Effective Temperatures and H II Region Ionization Parameter Gradients in the Galaxy
Morisset, C.
Extensive photoionization model grids are computed for single-star H II regions using stellar atmosphere models from the WM-Basic code. Mid-IR emission-line intensities are predicted, and diagnostic diagrams of [Ne III/II] and [S IV/III] excitation ratios are built, taking into account the metallicities of both the star and the H II region. The di…
PSR B1951+32: A Bow Shock-confined X-Ray Nebula, a Synchrotron Knot, and an Optical Counterpart Candidate
Chatterjee, S.; Cordes, J. M.; Gallant, Y. A. +7 more
The radio pulsar PSR B1951+32 and the supernova remnant CTB 80 provide a rich laboratory for the study of neutron stars and supernova remnants. Here, we present ground-based optical and near-infrared observations of them, along with X-ray observations with Chandra and a reanalysis of archival data obtained with the Hubble Space Telescope. The X-ra…
INTEGRAL Field Spectroscopy of the Extended Ionized Gas in Arp 220
Arribas, Santiago; Colina, Luis; Clements, David
Integral field optical spectroscopy with the INTEGRAL system has been used to investigate for the first time the two-dimensional kinematic and ionization properties of the extended, warm, ionized gas in Arp 220 over an area of 75.0"×40.0" (i.e., 28×15 kpc). The structure of the ionized gas is divided into well-identified regions associated with th…
Solar Energetic Particle Acceleration in Refracting Coronal Shock Waves
Vainio, Rami; Khan, Josef I.
Gradual solar energetic particle (SEP) events are known to be correlated with coronal mass ejections (CMEs) and soft X-ray flares. The current paradigm of particle acceleration in these events attributes it to CME-driven shock waves in the solar corona and in interplanetary space. Even in small gradual SEP events related to CMEs with speeds in the…