Search Publications
A new paradigm for the X-ray emission of O stars from XMM-Newton observations of the O9.7 supergiant ζ Orionis
Pollock, A. M. T.
XMM-Newton observations of the O supergiant ζ Orionis (O9.7 Ib) extend knowledge of its high-resolution spectrum beyond the C VI line at 33.7 Å and suggest a new framework for the interpretation of the X-ray spectra of single hot stars. All the lines are broad and asymmetric with similar velocity profiles. X-rays probably originate in the wind's t…
Source of whistler emissions at the dayside magnetopause
André, M.; Stenberg, G.; Vaivads, A. +4 more
Observations of whistler emissions are common in the magnetosphere near the dayside magnetopause. We show that one of the major source regions for these emissions is magnetic field minima that form along magnetic flux tubes at high latitudes. Using multispacecraft Cluster observations we experimentally confirm for the first time the existence of t…
Olympus Mons, Mars: Inferred changes in late Amazonian aged effusive activity from lava flow mapping of Mars Express High Resolution Stereo Camera data
Greeley, Ronald; Williams, David A.; Bleacher, Jacob E. +3 more
Lava flow mapping was conducted on a north-south transect of Olympus Mons using the European Space Agency's Mars Express High Resolution Stereo Camera (HRSC) image H0037. The HRSC image was coregistered to Mars Orbiter Laser Altimeter, Thermal Emission Imaging System, and Mars Orbiter Camera data, enabling lava flow structures to be differentiated…
Electrostatic structure around spacecraft in tenuous plasmas
Eriksson, A. I.; Cully, C. M.; Ergun, R. E.
Most satellite-based in situ plasma experiments are affected in some manner by the electrostatic structure surrounding the spacecraft. In order to better understand this structure, we have developed a fully three-dimensional self-consistent model that can accept realistic spacecraft geometry, including both thin (∼10-4 m) wires and long…
Optical Studies of the Ultraluminous X-Ray Source NGC 1313 X-2
Kaaret, Philip; Miller, Jon; Liu, Ji-Feng +1 more
NGC 1313 X-2 was among the first ultraluminous X-ray sources discovered, and has been a frequent target of X-ray and optical observations. Using the HST ACS multiband observations, this source is identified with a unique counterpart within an error circle of 0.2". The counterpart is a blue star on the edge of a young cluster of <=107…
A Young Stellar Cluster Surrounding the Peculiar Eruptive Variable V838 Monocerotis
Bond, Howard E.; Afşar, Melike
V838 Monocerotis is an unusual variable star that underwent a sudden outburst in 2002. Unlike a classical nova, which quickly evolves to high temperatures, V838 Mon remained an extremely cool, luminous supergiant throughout its eruption. It continues to illuminate a spectacular series of light echoes, as the outburst light is scattered from nearby…
Evidence for wave harmonics in cool loops
Srivastava, A. K.; Doyle, J. G.; Banerjee, D. +1 more
Aims:Using temporal series image data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in intensity (radiance) measurements from the transition region O v 629 line with the aim of finding evidence of wave harmonics in cool loops.
Methods: Using standard Fourier techniques, together with a pre-whitening method…
Space weather at Venus and its potential consequences for atmosphere evolution
Luhmann, J. G.; Russell, C. T.; Kasprzak, W. T.
Space weather storms at the Earth are dominated by the magnetosphere's response to coronal mass ejections, or CMEs, whose disturbances propagate through the solar wind to 1 AU, and to a lesser extent by the pressure ridges associated with the interactions of solar wind streams with different properties. The interplanetary signatures of these event…
INTEGRAL observation of the accreting pulsar GX 1+4
Santangelo, A.; Wilms, J.; Segreto, A. +4 more
Aims:We present the results of the INTEGRAL monitoring campaign on the accreting low mass X-ray binary pulsar GX 1+4 performed during the Galactic plane scan of the INTEGRAL Core Programme.
Methods: The source was observed in different luminosity states ranging from L20-40 keV= 1.7 × 10-10 erg cm-2 s^{-1}, to L…
Solar Arcades as Possible Minimum Dissipative Relaxed States
Zank, G. P.; Dasgupta, B.; Janaki, M. S. +1 more
In this work, arcade structures are modeled to be in minimum dissipative relaxed states using a two-fluid description of the plasma. The obtained relaxed state is non-force-free in nature and appropriate to an open system with external drives. The Euler - Lagrange equations are solved in Cartesian coordinates subject to the appropriate photospheri…