Search Publications
Solar Cycle 23: An Anomalous Cycle?
de Toma, Giuliana; White, Oran R.; Chapman, Gary A. +3 more
The latest SOHO VIRGO total solar irradiance (TSI) time series is analyzed using new solar variability measures obtained from full-disk solar images made at the San Fernando Observatory and the Mg II 280 nm index. We discuss the importance of solar cycle 23 as a magnetically simpler cycle and a variant from recent cycles. Our results show the cont…
The Mid-Infrared Luminosity Function of Galaxies in the European Large Area Infrared Space Observatory Survey Southern Fields
Pozzi, F.; Franceschini, A.; Serjeant, S. +7 more
We present the first determination of the 15 µm luminosity function of galaxies from the European Large Area ISO Survey (ELAIS) southern fields. We have adopted a new criterion to separate the quiescent, nonevolving and the starburst, evolving populations based on the ratio of mid-infrared to optical luminosity. Strong evolution is suggested…
Ion loss on Mars caused by the Kelvin Helmholtz instability
Kallio, E.; Barabash, S.; Gunell, H. +8 more
Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence …
Mid-infrared spectral evidence for a luminous dust enshrouded source in Arp 220
Lutz, D.; Siebenmorgen, R.; Tielens, A. G. G. M. +3 more
We have re-analyzed the 6-12 µm ISO spectrum of the ultra-luminous infrared galaxy Arp 220 with the conclusion that it is not consistent with that of a scaled up version of a typical starburst. Instead, both template fitting with spectra of the galaxies NGC 4418 and M 83 and with dust models suggest that it is best represented by combination…
The Variable Quiescence of Centaurus X-4
Campana, S.; Mereghetti, S.; Stella, L. +2 more
Centaurus X-4 is one of the best-studied low-mass neutron star transients in quiescence. Thanks to XMM-Newton's large throughput, Centaurus X-4 was observed at the highest signal-to-noise ratio ever. This allowed us to discern rapid (>100 s), large (45%+/-7% rms in the 10-4 to 1 Hz range) intensity variability, especially at low ener…
XMM-Newton survey of the Local Group galaxy M 33
Pietsch, W.; Haberl, F.; Hatzidimitriou, D. +3 more
In an XMM-Newton raster observation of the bright Local Group spiral galaxy
Predictions of the arrival time of Coronal Mass Ejections at 1AU: an analysis of the causes of errors
Cargill, P.; Owens, M.
. Three existing models of Interplanetary Coronal Mass Ejection (ICME) transit between the Sun and the Earth are compared to coronagraph and in situ observations: all three models are found to perform with a similar level of accuracy (i.e. an average error between observed and predicted 1AU transit times of approximately 11h). To improve long-term…
Compact sources as the origin of the soft γ-ray emission of the Milky Way
Strong, A. W.; Walter, R.; Ubertini, P. +16 more
The Milky Way is known to be an abundant source of γ-ray photons, now determined to be mainly diffuse in nature and resulting from interstellar processes. In the soft γ-ray domain, point sources are expected to dominate, but the lack of sensitive high-resolution observations did not allow for a clear estimate of the contribution from such sources.…
A purely geometric distance to the binary star Atlas, a member of the Pleiades
Eyer, L.; North, P.; Groenewegen, M. A. T. +4 more
We present radial velocity and new interferometric measurements of the double star Atlas, which permit, with the addition of published interferometric data, to precisely derive the orbital parameters of the binary system and the masses of the components. The derived semi-major axis, compared with its measured angular size, allows to determine a di…
Wind clumping and the wind-wind collision zone in the Wolf-Rayet binary γ2 Velorum observations at high and low state. XMM-Newton observations at high and low state
Schmutz, W.; Raassen, A. J. J.; Mewe, R. +7 more
We present XMM-Newton observations of γ2 Velorum (WR 11, WC8+O7.5III, P = 78.53 d), a nearby Wolf-Rayet binary system, at its X-ray high and low states. At high state, emission from a hot collisional plasma dominates from about 1 to 8 keV. At low state, photons between 1 and 4 keV are absorbed. The hot plasma is identified with the shoc…