Search Publications
Missions
Journals
Publication Years
Kinetic equilibrium of iron in the atmospheres of cool stars. III. The ionization equilibrium of selected reference stars
Korn, A. J.; Gehren, T.; Shi, J.
Non-LTE line formation calculations of Fe I are performed for a small number of reference stars to investigate and quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravit…
Flaring X-Ray Emission from HST-1, a Knot in the M87 Jet
Sparks, W. B.; Wilson, A. S.; Harris, D. E. +3 more
We present Chandra X-ray monitoring of the M87 jet in 2002, which shows that the intensity of HST-1, an optical knot 0.8" from the core, increased by a factor of 2 in 116 days and a factor of 4 in 2 yr. There was also a significant flux decrease over 2 months, with suggestive evidence for a softening of the spectrum. From this variability behavior…
Study of Ribbon Separation of a Flare Associated with a Quiescent Filament Eruption
Zhang, Hongqi; Qiu, Jiong; Jing, Ju +1 more
In this paper, we present a detailed study of a two-ribbon flare in the plage region observed by Kanzelhohe Solar Observatory (KSO), which is one of the stations in our global Hα network. We select this event due to its very clear filament eruption, two-ribbon separation, and association with a fast coronal mass ejection (CME). We study the separa…
Simultaneous Cluster and IMAGE observations of cusp reconnection and auroral proton spot for northward IMF
Lundin, R.; Sauvaud, J. -A.; Balogh, A. +22 more
On March 18, 2002, under northward interplanetary magnetic field (IMF) and high (~15 nPa) solar wind dynamic pressure conditions, Cluster observed reconnection signatures and the passage of an X-line at the large (~175°) magnetic-shear high-latitude magnetopause (MP). The observations are consistent with the occurrence of a reconnection site tailw…
A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton Photon Imaging Cameras
Goldoni, P.; Decourchelle, A.; Warwick, R. S. +5 more
Sgr A*, the compact radio source believed to be the counterpart of the massive black hole at the Galactic nucleus, was observed to undergo rapid and intense flaring activity in X-rays with Chandra in 2000 October. We report here the detection with XMM-Newton European Photon Imaging Cameras of the early phase of a similar X-ray flare from this sour…
Thermal X-Ray Emission from Shocked Ejecta in Type Ia Supernova Remnants: Prospects for Explosion Mechanism Identification
Badenes, Carles; Borkowski, Kazimierz J.; Bravo, Eduardo +1 more
The explosion mechanism behind Type Ia supernovae is a matter of continuing debate. The diverse attempts to identify or at least constrain the physical processes involved in the explosion have been only partially successful so far. In this paper we propose to use the thermal X-ray emission from young supernova remnants (SNRs) originating in Type I…
Tracing the Warm-Hot Intergalactic Medium at Low Redshift: X-Ray Forest Observations toward H1821+643
Mathur, Smita; Weinberg, David H.; Chen, Xuelei
We present a high-resolution (λ/Δλ~500) X-ray spectrum of the bright quasar H1821+643 (z=0.297), obtained in a 470 ks observation with the Chandra X-Ray Observatory. We search for X-ray absorption by highly ionized metal species, O VII and O VIII in particular, at the redshifts of the six intervening O VI absorption systems known from UV studies. …
Iron Emission in z~6 QSOS
Korista, Kirk T.; Corbin, Michael R.; Freudling, Wolfram
We have obtained low-resolution near-infrared spectra of three QSOs at 5.7<z<6.3 using the Near-Infrared Camera and Multi-Object Spectrometer on the Hubble Space Telescope. The spectra cover the rest-frame ultraviolet emission of the objects between λrest~1600 and 2800 Å. The Fe II emission-line complex at 2500 Å is clearly detect…
An Estimate of the Sun's ROSAT-PSPC X-Ray Luminosities Using SNOE-SXP Measurements
Ayres, Thomas R.; Judge, Philip G.; Solomon, Stanley C.
Using solar soft X-ray irradiance measurements from the SXP instrument on the SNOE satellite, we relate the solar surface flux densities and their variability to those of stars as measured with the PSPC instrument on ROSAT. We translate SNOE-SXP measurements into equivalent ROSAT-PSPC counts using model spectra calculated from the CHIANTI package.…
Discovery of a Little Homunculus within the Homunculus Nebula of η Carinae
Kaiser, Mary Elizabeth; Smith, Nathan; Gull, Theodore R. +17 more
We report long-slit spectroscopic mapping of the η Carinae nebula obtained using the Space Telescope Imaging Spectrograph. The observations reveal the presence of a previously unknown bipolar emission nebula (roughly +/-2" along its major axis) embedded within the well-known and larger Homunculus Nebula. A preliminary analysis suggests that this e…