Search Publications
Searching for Dark Matter with X-Ray Observations of Local Dwarf Galaxies
Profumo, S.; Jeltema, T. E.
A generic feature of weakly interacting massive particle (WIMP) dark matter models is the emission of photons over a broad energy band resulting from the stable yields of dark matter pair annihilation. Inverse Compton scattering off cosmic microwave background photons of energetic electrons and positrons produced in dark matter annihilation is exp…
Spectral variability of GX339-4 in a hard-to-soft state transition
Belloni, T.; Ubertini, P.; Malzac, J. +2 more
We report on INTEGRAL observations of the bright black hole transient GX339-4 performed during the period 2004 August-September, including the fast transition (10h) observed simultaneously with INTEGRAL and RXTE on August 15 and previously reported. Our data cover three different spectral states, namely hard/intermediate state (HIMS), soft/interme…
Intermediate long X-ray bursts from the ultra-compact binary candidate SLX 1737-282
Kuulkers, E.; Falanga, M.; Chenevez, J. +3 more
Aims: The low persistent flux X-ray burster source SLX 1737-282 is classified as an ultra-compact binary candidate. We compare the data on SLX 1737-282 with the other similar objects and attempt to derive constraints on the physical processes responsible for the formation of intermediate long bursts.
Methods: Up to now only four bursts, all wi…
Chandra Localizations and Spectra of INTEGRAL Sources in the Galactic Plane
Kaaret, Philip; Walter, Roland; Tomsick, John A. +2 more
We report on the results of observations of hard X-ray sources in the Galactic plane with the Chandra X-Ray Observatory. The hard X-ray "IGR" sources were discovered by the INTEGRAL satellite, and the goals of the Chandra observations are to provide subarcsecond localizations to obtain optical and infrared counterparts and to provide constraints o…
Luminosity Indicators in the Ultraviolet Spectra of Type Ia Supernovae
Filippenko, Alexei V.; Foley, Ryan J.; Jha, Saurabh W.
We present a complete sample of International Ultraviolet Explorer and Hubble Space Telescope ultraviolet (UV) spectra of Type Ia supernovae (SNe Ia) through 2004. We measure the equivalent width (EW) and blueshifted velocity of the minimum of the one strong UV feature, Fe II λ3250. We also quantify the slope of the near-UV spectra using a new par…
The evolution of planetary nebulae. V. The diffuse X-ray emission
Steffen, M.; Schönberner, D.; Warmuth, A.
Context: Observations with space-borne X-ray telescopes revealed the existence of soft, diffuse X-ray emission from the inner regions of planetary nebulae. Although the existing images support the idea that this emission arises from the hot shocked central-star wind which fills the inner cavity of a planetary nebula, existing models have difficult…
X-ray spectra from magnetar candidates - II. Resonant cross-sections for electron-photon scattering in the relativistic regime
Zane, S.; Nobili, L.; Turolla, R.
Recent models of spectral formation in magnetars called renewed attention on electron-photon scattering in the presence of ultrastrong magnetic fields. Investigations presented so far mainly focused on mildly relativistic particles and magnetic scattering was treated in the non-relativistic (Thomson) limit. This allows for consistent spectral calc…
Models of solar irradiance variations: Current status
Solanki, Sami K.; Krivova, Natalie A.
Regular monitoring of solar irradiance has been carried out since 1978 to show that solar total and spectral irradiance varies at different time scales. Whereas variations on time scales of minutes to hours are due to solar oscillations and granulation, variations on longer time scales are driven by the evolution of the solar surface magnetic fiel…
Stellar Exotica in 47 Tucanae
Zurek, David R.; Shara, Michael M.; Long, Knox S. +3 more
We present far-ultraviolet (FUV) spectroscopy obtained with HST for 48 blue objects in the core of 47 Tuc. Based on their position in a FUV-optical color-magnitude diagram, these were expected to include cataclysmic variables (CVs), blue stragglers (BSs), white dwarfs (WDs), and other exotic objects. For a subset of these sources, we also construc…
Mobile lid convection beneath Enceladus' south polar terrain
Barr, Amy C.
Enceladus' south polar region has a large heat flux, 55-110 mW m-2, that is spatially associated with cryovolcanic and tectonic activity. Tidal dissipation and vigorous convection in the underlying ice shell are possible sources of heat, however, prior predictions of the heat flux carried by stagnant lid convection range from F con…