Search Publications
Effect of the H I Lyα Chromospheric Flux Anisotropy on the Total Intensity of the Resonantly Scattered Coronal Radiation
Auchère, F.
In modeling of the resonantly scattered solar coronal Lyα line of H I, the intensity of the chromospheric source is often assumed to be uniform. We investigate the validity of this assumption. After establishing a correlation between the H I 121.6 nm and He II 30.4 nm line intensities, we build Carrington maps of the Lyα chromosphere from SOHO EUV…
Deconstructing NGC 7130
Heckman, T. M.; Levenson, N. A.; Weaver, K. A. +2 more
Observations of the Seyfert 2 and starburst galaxy NGC 7130 with the Chandra X-Ray Observatory illustrate that both of these phenomena contribute significantly to the galaxy's detectable X-ray emission. The active galactic nucleus (AGN) is strongly obscured, buried beneath column density NH>1024cm-2, and it is m…
Far Ultraviolet Spectroscopic Explorer Measurements of Interstellar Fluorine
Federman, S. R.; Lambert, David L.; Smith, V. V. +1 more
The source of fluorine is not well understood, although core-collapse supernovae, Wolf-Rayet stars, and asymptotic giant branch stars have been suggested. A search for evidence of the ν-process during Type II supernovae is presented. Absorption from interstellar F I is seen in spectra of HD 208440 and HD 209339A acquired with the Far Ultraviolet S…
On the Afterglow and Host Galaxy of GRB 021004: A Comprehensive Study with the Hubble Space Telescope
Pian, E.; Kouveliotou, C.; Tanvir, N. +24 more
We report on Hubble Space Telescope (HST) observations of the late-time afterglow and host galaxy of GRB 021004 (z=2.33). Although this gamma-ray burst (GRB) is one of the best observed so far in terms of sampling in the time domain, multiwavelength coverage, and polarimetric observations, there is substantial disagreement between different interp…
Possible AGN Shock Heating in the Cool-Core Galaxy Cluster Abell 478
Finoguenov, Alexis; Mohr, Joseph J.; Sanderson, Alastair J. R.
We present a detailed X-ray study of the intracluster medium (ICM) of the nearby cool-core galaxy cluster Abell 478 (z=0.088), based on Chandra and XMM-Newton observations. Using a wavelet-smoothing hardness analysis, we derive detailed temperature maps of A478, revealing a surprising amount of temperature structure for an apparently well-relaxed …
An Unusual Spectral State of an Ultraluminous Very Soft X-Ray Source during Outburst
Kong, A. K. H.; Di Stefano, R.
We report the results of Chandra and XMM-Newton observations of a new outburst of an ultraluminous X-ray source in M101. During a Chandra monitoring observation of M101, M101 ULX-1 was found to be in outburst in 2004 December, the second outburst in 2004. The peak bolometric luminosity is about 3×1040 ergs s-1 (7×1039
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…
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
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…