Search Publications
A Refined Ephemeris and Phase-resolved X-Ray Spectroscopy of the Geminga Pulsar
Jackson, M. S.; Halpern, J. P.
We present a refined, phase-connected, postglitch ephemeris for the Geminga pulsar that is a good fit to all the postglitch data from EGRET, ASCA, and XMM-Newton. We also present the results of phase-resolved spectroscopy of two XMM-Newton X-ray observations of the Geminga pulsar obtained in 2002 and 2004. An investigation is made into a previousl…
The massive binary CPD - 41° 7742. II. Optical light curve and X-ray observations
Gosset, E.; Rauw, G.; Vreux, J. -M. +4 more
In the first paper of this series, we presented a detailed high-resolution spectroscopic study of
Discovery of X-Ray Emission from Supernova 1970G with Chandra: Filling the Void between Supernovae and Supernova Remnants
Kuntz, K. D.; Immler, Stefan
We report the discovery of X-ray emission from SN 1970G in M101, 35 yr after its outburst, using deep X-ray imaging with the Chandra X-Ray Observatory. The Chandra ACIS spectrum shows that the emission is soft (<~2 keV) and characteristic of the reverse-shock region. The X-ray luminosity, L0.3-2=(1.1+/-0.2)×1037 ergs s
The Multitude of Molecular Hydrogen Knots in the Helix Nebula
McCullough, Peter; Meixner, Margaret; Speck, Angela +2 more
We present Hubble Space Telescope NICMOS imaging of the H2 2.12 µm emission in five fields in the Helix Nebula ranging in radial distance from 250" to 450" from the central star. The images reveal arcuate structures with their apexes pointing toward the central star. These molecular hydrogen knots are most highly structured in the…
GRBs and the 511 keV emission of the Galactic bulge
Paul, J.; Cassé, M.; Parizot, E. +1 more
We consider the phenomenology of the 511 keV emission in the Galactic bulge, as recently observed by INTEGRAL, and propose a model in which the positrons are produced by gamma-ray bursts (GRB) associated with mini-starbursts in the central molecular zone (CMZ). We show that the positrons can easily diffuse across the bulge on timescales of ∼ 10
Links between magnetic fields and plasma flows in a coronal hole
Marsch, E.; Xia, L. D.; Wiegelmann, T.
We compare the small-scale features visible in the Ne viii Doppler-shift map of an equatorial coronal hole (CH) as observed by SUMER with the small-scale structures of the magnetic field as constructed from a simultaneous photospheric magnetogram by a potential magnetic-field extrapolation. The combined data set is analysed with respect to the sma…
Observations of the Transient X-ray Pulsar KS 1947+300 by the INTEGRAL and RXTE Observatories
Tsygankov, S. S.; Lutovinov, A. A.
We analyze the observations of the X-ray pulsar KS 1947+300 performed by the INTEGRAL and RXTE observatories over a wide (3 100 keV) X-ray energy range. The shape of the pulse profile was found to depend on the luminosity of the source. Based on the model of a magnetized neutron star, we study the characteristics of the pulsar using the change in …
Magnetic Free Energies of Breakout Coronal Mass Ejections
Antiochos, Spiro K.; DeVore, C. Richard
A critical issue in understanding and eventually predicting coronal mass ejections (CMEs) is determining the magnetic free energy that can drive the explosive eruption. We present calculations of this free energy for the breakout CME model, which postulates that the preeruption magnetic topology is a multipolar field with a null point in the coron…
The Ages of Globular Clusters in NGC 4365 Revisited with Deep HST Observations
Vesperini, Enrico; Kundu, Arunav; Zepf, Stephen E. +6 more
We present new Hubble Space Telescope (HST) NIC3, near-infrared H-band photometry of globular clusters (GCs) around NGC 4365 and NGC 1399 in combination with archival HST WFPC2 and ACS optical data. We find that NGC 4365 has a number of globular clusters with bluer optical colors than expected for their red optical-to-near-infrared colors and an o…
The Absorption Spectrum of High-Density Stellar Ejecta in the Line of Sight to η Carinae
Gull, T. R.; Nielsen, K. E.; Bruhweiler, F. +3 more
Using the high-dispersion near-UV (NUV) mode of the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) to observe η Carinae, we have resolved and identified over 500 sharp circumstellar absorption lines of iron-group singly ionized and neutral elements with ~20 velocity components ranging from -146 to -585 km s