Search Publications
The Double-Peak Spectral Energy Density of Gamma-Ray Bursts and the True Identity of GRB 031203
Dar, Arnon; Dado, Shlomo
A double-peak spectral energy density of prompt γ-rays, similar to that observed in blazars, is expected in the cannonball (CB) model of gamma-ray bursts (GRBs) produced in supernova (SN) explosions. The first sub-MeV ordinary peak is formed by inverse Compton scattering (ICS) of the ambient SN light by the CBs' electrons, while the second peak at…
XMM-Newton observations of β Centauri (B1 III): The temperature structure in the hot plasma and the photosphere-wind connection
Raassen, A. J. J.; Mewe, R.; Cassinelli, J. P. +2 more
We present XMM-Newton observations of the B giant β Centauri (B1 III). The spectra are rich of spectral lines from a wide range of ionization stages which indicate temperatures in the range ~0.1-0.6 keV. Simultaneous fits to the rgs, epic-mos, and epic-pn spectra yield three plasma temperatures (0.1, 0.2, and 0.6 keV), emission measures, and eleme…
Internal colour gradients for E/S0 galaxies in Abell 2218
Driver, Simon P.; De Propris, Roberto; Colless, Matthew +2 more
We determine colour gradients of -0.15 +/- 0.08 mag per decade in radius in F450W-F606W and -0.07 +/- 0.06 mag per decade in radius in F606W-F814W for a sample of 22 E/S0 galaxies in Abell 2218. These gradients are consistent with the existence of a mild (~-0.3 dex per decade in radius) gradient in metal abundance (cf. previous work at lower and h…
Relating White-Light Coronal Images to Magnetic Fields and Plasma Flow
Woo, Richard
The solar magnetic field is key to a detailed understanding of the Sun's atmosphere and its transition to the solar wind. However, the lack of detailed magnetic field measurements everywhere except at the photosphere has made it challenging to determine its topology and to understand how it produces the observed plasma properties of the corona and…
Clusters in the Luminous Giant H II Regions in M101
Johnson, Kelsey E.; Chu, You-Hua; Chen, C. -H. Rosie
We have obtained HST WFPC2 observations of three very luminous but morphologically different giant H II regions (GHRs) in M101, NGC 5461, NGC 5462, and NGC 5471, in order to study cluster formation in GHRs. Images obtained in the F547M and F675W bands are used to identify cluster candidates and for photometric measurements, and images in the F656N…
The Hubble Space Telescope ACS Grism Parallel Survey. II. First Results and a Catalog of Faint Emission-Line Galaxies at z<=1.6
Chen, Hsiao-Wen; Spinrad, Hyron; Stern, Daniel +4 more
We present the first results from the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. We report on 11 high Galactic latitude fields here, each with grism integration times of more than 12 ks. We identify 601 c…
Chemically Decoupled Nuclei in Five Lenticular Galaxies from SAURON Data
Sil'Chenko, O. K.
We analyze data from the SAURON integral-field spectrograph of the William Herschel 4-m telescope for five lenticular galaxies in which we previously found chemically decoupled nuclei from observations with the Multipupil Fiber Spectrograph of the 6-m Special Astrophysical Observatory telescope. In a larger field of view, we confirmed the presence…
Cataclysmic and Close Binaries in Star Clusters. V. Erupting Dwarf Novae, Faint Blue Stars, X-Ray Sources, and the Classical Nova in the Core of M80
Zurek, David R.; Hinkley, Sasha; Shara, Michael M.
Large populations of cataclysmic variables (CVs) in globular clusters have long been predicted, but the number of absolutely certain cluster CVs known in globular clusters is still less than 10. HST and Chandra observers have recently found dozens of CV candidates in several populous globular clusters. Confirmation and characterization of these ca…
Classical novae in outburst: evolution of the ultraviolet emission lines in CO novae
Altamore, A.; González-Riestra, R.; Cassatella, A.
A comparative study is made of the temporal changes of the ionization level in seven CO novae well monitored with the IUE satellite at low resolution. The investigation is based on the evolution of the fluxes in eight strong ultraviolet emission lines covering a wide range of ionization potentials, from Mg II (7.6 eV) to N V (77.5 eV). We find tha…
Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24
Sokoloski, J. L.; Tiengo, A.; Miller, J. M. +4 more
We present the spectral analysis of an XMM-Newton observation of the X-ray binary 4U 1700+24, performed during an outburst in August 2002. The EPIC-PN spectrum above 1 keV can be modeled by a blackbody plus Comptonization model, as in previous observations. At lower energies, however, we detect a prominent soft excess, which we model with a broad …