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| A comparison of Neutral Atom Detector Unit neutral atom image inversion with a comprehensive ring current model |
| We present energetic neutral atom (ENA) images in the energy range 45 to 50 keV for H and 92 to 138 keV for O measured by the Neutral Atom Detector Unit (NUADU) onboard Double Star TC-2 during a geomagnetic storm on 8 May 2005. We compare the ion fluxes deduced from inversion of the NUADU image with those calculated using the Comprehensive Ring Current Model (CRCM). This comparison shows that the two approaches are consistent when used to derive the configuration of the corresponding global ion distribution and the peak ion fluxes. The deduced peak ion flux is located in the premidnight sector at 1540 UT, while the deduced ion peak flux is located in the midnight sector at 1610 UT. There are strong ion fluxes in the region between L = 2 and L = 4 which form a closed loop configuration. The ion peak flux is about 2.2×106/cm²/sr/keV/s. The deduced ion distribution agrees well with the NUADU measurement. The agreement between the inverted ion distributions and the CRCM results give us confidence in applying our ENA imaging and modeling techniques to the study of the evolution of the inner magnetosphere plasma distribution and the global dynamics of the ring current during magnetic storms. |
| Publication date: 30 May 2008 |
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| High kinetic energy jets in the Earth's magnetosheath: Implications for plasma dynamics and anomalous transport |
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| Publication date: 30 May 2008 |
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| Carrier Module (Thales Alenia Space-Italy) |
| Carrier Module presentation given by Thales Alenia Space-Italy at the ExoMars Industry Day, hosted by Altec in Turin, Italy on 29 May 2008. |
| Publication date: 28 May 2008 |
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| Enhanced ExoMars Mission (ESA) |
| Enhanced ExoMars Mission presentation given by ESA at the ExoMars Industry Day, ExoMars Industry Day, hosted by Altec in Turin, Italy on 29 May 2008. |
| Publication date: 28 May 2008 |
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| Enhanced ExoMars Mission (Thales Alenia Space-Italy) |
| Enhanced ExoMars Mission presentation given by Thales Alenia Space-Italy at the ExoMars Industry Day, hosted by Altec in Turin, Italy on 29 May 2008. |
| Publication date: 28 May 2008 |
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| ExoMars Rover Vehicle (EADS Astrium-UK) |
| ExoMars Rover Vehicle presentation given by EADS Astrium-UK at the ExoMars Industry Day hosted by Altec in Turin, Italy on 29 May 2008. |
| Publication date: 28 May 2008 |
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| Rover Operations Control Centre (Altec) |
| Rover Operations Control Centre presentation given by Altec at the ExoMars Industry Day, hosted by Altec in Turin, Italy on 29 May 2008. |
| Publication date: 28 May 2008 |
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| Magnetosheath Plasma Turbulence and Its Spatiotemporal Evolution as Observed by the Cluster Spacecraft |
| We study the plasma turbulence, at scales larger than the ion inertial length scale, downstream of a quasiparallel bow shock using Cluster multispacecraft measurements. We show that turbulence is intermittent and well described by the extended structure function model, which takes into account the spatial inhomogeneity of the cascade rate. For the first time we use multispacecraft observations to characterize the evolution of magnetosheath turbulence, particularly its intermittency, as a function of the distance from the bow shock. The intermittency significantly changes over the distance of the order of 100 ion inertial lengths, being increasingly stronger and anisotropic away from the bow shock. |
| Publication date: 21 May 2008 |
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| PSR J0737-3039: Interacting Pulsars in X-Rays |
| We present the results of a ~230 ks long X-ray observation of the relativistic double-pulsar system PSR J0737-3039 obtained with the XMM-Newton satellite in 2006 October. We confirm the detection in X-rays of pulsed emission from PSR J0737-3039A (PSR A), mostly ascribed to a soft nonthermal power-law component with a 0.2-3 keV luminosity of ~1.9x1030 erg s-1 (assuming a distance of 500 pc). For the first time, pulsed X-ray emission from PSR J0737-3039B (PSR B) is also detected in part of the orbit. This emission, consistent with thermal radiation with temperature kBT ~ 30 eV and a bolometric luminosity of ~1032erg s-1, is likely powered by heating of PSR B's surface caused by PSR A's wind. A hotter (~130 eV) and fainter (~5x1029erg s-1) thermal component, probably originating from backfalling particles heating polar caps of either PSR A or PSR B, is also required by the data. No signs of X-ray emission from a bow shock between PSR A's wind and the interstellar medium or PSR B's magnetosphere are present. The upper limit on the luminosity of such a shock component (~1029 erg s-1) constrains the wind magnetization parameter of PSR A to values greater than 1. |
| Publication date: 20 May 2008 |
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| First detection of hydroxyl in the atmosphere of Venus |
| We report measurements of night-side airglow emission in the atmosphere of Venus in the OH (2-0), OH (1-0), O2(a-X) (0-1), and O2(a-X) (0-0) bands. This is the first detection of the first three of these airglow emissions on another planet. These observations provide the most direct observational constraints to date on H, OH, and O3, key species in the chemistry of Venus' upper atmosphere.
(This is an abbreviated abstract from the paper "First detection of hydroxyl in the atmosphere of Venus", by Piccioni et al, published in Astronomy & Astrophysics, A&A 483, L29-L33 (2008)) |
| Publication date: 19 May 2008 |
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| CMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration |
| CMOS-APS imaging detectors open new opportunities for remote sensing in solar physics beyond what classical CCDs can provide, offering far less power consumption, simpler electronics, better radiation hardness, and the possibility of avoiding a mechanical shutter. The SWAP telescope onboard the PROBA2 technology demonstration satellite of the European Space Agency will be the first actual implementation of a CMOS-APS detector for solar physics in orbit. One of the goals of the SWAP project is precisely to acquire experience with the CMOS-APS technology in a real-live space science context. Such a precursor mission is essential in the preparation of missions such as Solar Orbiter where the extra CMOS-APS functionalities will be hard requirements. The current paper concentrates on specific CMOS-APS issues that were identified during the SWAP preflight calibration measurements. We will discuss the different readout possibilities that the CMOS-APS detector of SWAP provides and their associated pros and cons. In particular we describe the image lag effect, which results in a contamination of each image with a remnant of the previous image. We have characterised this effect for the specific SWAP implementation and we conclude with a strategy on how to successfully circumvent the problem and actually take benefit of it for solar monitoring. |
| Publication date: 15 May 2008 |
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| Mars Express/Venus Express |
The European space Agency (ESA) undertook a bold experiment with the Mars Express mission: to develop rapidly a low cost platform for planetary exploration. The myriad scientific achievements of this mission prove the success of the experiment. ESA took a second bold step by adapting the Mars platform for the Venus Express mission, and doing so rapidly and most cost-effectively. While the differences in Venus and Mars necessitated several changes in instrumentation, there are many objectives that remain the same at the two planets. When we issued a call to the MEX and VEX communities for a volume of brief articles covering the latest results from these two missions, the response from those examining the interaction of the solar wind and energetic particles with the planets was most swift. The authors were asked to keep their presentations to four published pages. The guest editor in turn attempted to shepherd these papers through the reviewing process quickly. In those instances where the editor had a conflict of interest, R. J. Strangeway assumed the duties of the editor.
The articles that passed review before the press deadline are included therein. They include discussions of the various plasma boundaries at Venus and Mars, the nature of their plasma environments, the discovery of energetic neutral particles, the configuration of the magnetic field near the planets, space weather and the loss of atmosphere. Papers included contain both modeling and observational work and are written by some of the newest members of the community as well as many of the veteran research scientists. We especially thank the referees of these papers who responded promptly to help speed these early results to the readers of Planetary and Space Science.
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| Publication date: 15 May 2008 |
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| Discovery of a Very Bright Strongly Lensed Galaxy Candidate at z ~ 7.6 |
| Using Hubble Space Telescope (HST) and Spitzer IRAC imaging, we report the discovery of a very bright strongly lensed Lyman break galaxy (LBG) candidate at z ~ 7.6 in the field of the massive galaxy cluster Abell 1689 (z=0.18). The galaxy candidate, which we refer to as A1689-zD1, shows a strong z850-J110 break of at least 2.2 mag and is completely undetected (<1 sigma) in HST Advanced Camera for Surveys (ACS) g475, r625, i775, and z850 data. These properties, combined with the very blue J110-H160 and H160-4.5 micron colors, are exactly the properties of an z ~ 7.6 LBG, and can only be reasonably fit by a star-forming galaxy at z=7.6±0.4 (Chimu-square=1.1). Attempts to reproduce these properties with a model galaxy at z < 4 yield particularly poor fits (Chimu-square=25). A1689-zD1 has an observed (lensed) magnitude of 24.7 AB (8 sigma) in the NICMOS H160 band and is 1.3 mag brighter than the brightest known z850-dropout galaxy. When corrected for the cluster magnification of ~9.3 at z~7.6, the candidate has an intrinsic magnitude of H160=27.1 AB, or about an L* galaxy at z~7.6. The source-plane deprojection shows that the star formation is occurring in compact knots of size <~300 pc. The best-fit stellar population synthesis models yield a median redshift of 7.6, stellar masses (1.6-3.9)×109 Msolar, stellar ages 45-320 Myr, star formation rates <~7.6 Msolar yr-1, and low reddening with AV<=0.3. These properties are generally similar to those of LBGs found at z~5-6. The inferred stellar ages suggest a formation redshift of z~8-10 (t<~0.63Gyr). A1689-zD1 is the brightest observed, highly reliable z>7.0 galaxy candidate found to date. |
| Publication date: 10 May 2008 |
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| ESA's report to the 37th COSPAR meeting - Euclid section |
| ESA's report to the 37th COSPAR meeting (13-20 July 2008) covers the missions of the Science Programme of ESA. This section contains the report on the Cosmic Vision candidate, Euclid. |
| Publication date: 10 May 2008 |
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| Multispacecraft observation of electron beam in reconnection region |
| On the 18th of August 2002, during a crossing of the near-Earth plasma sheet Cluster observed an ion flow burst, caused by a near-Earth reconnection event. Cluster observed a tailward bulk flow which reverse to earthward flow, indicating a close passage of the diffusion region. We show that reversals in BZ and BY are consistent with reconnection. During the event, a short duration burst of electrons in the range of a few keV up to more than 100 keV are observed streaming away from the reconnection region. The accelerated electrons were aligned with the magnetic field, streaming tailward, and were observed simultaneously by all four spacecraft located on both the northern and southern side of the current sheet. The four Cluster spacecraft, separated by ~3700 km, observe the electrons for a time period of ~60 s, indicating the burst to be a temporal rather than localized feature. A second burst of tailward accelerated electrons observed for ~40 s was observed by Cluster 1 and 2 upon entering the earthward outflow region. The second beam thus appear to be directed toward the X-line. The flux levels of the energetic electron bursts exceed those of the ambient plasma sheet by a factor 2-4. In general, the highest energetic electron fluxes during this event were observed in the earthward outflow region. Observations indicate that reconnection operates on closed plasma sheet field lines in this event and does not reach lobe field lines. |
| Publication date: 10 May 2008 |
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| A New Red Giant–based Distance Modulus of 13.3 Mpc to the Antennae Galaxies and Its Consequences |
| The Antennae galaxies are the closest example of an ongoing major galaxy merger and, as such, represent a unique laboratory for furthering the understanding of the formation of exotic objects (e.g., tidal dwarf galaxies, ultraluminous X-ray sources, super stellar clusters). In a previous paper HST WFPC2 observations were used to demonstrate that the Antennae system might be at a distance considerably less than that conventionally assumed in the literature. Here we report new, much deeper HST ACS imaging that resolves the composite stellar populations and, most importantly, reveals a well-defined red giant branch. The tip of this red giant branch (TRGB) is unambiguously detected at I0TRGB=26.65+-0.09 mag. Adopting the most recent calibration of the luminosity of the TRGB then yields a distance modulus for the Antennae of (m-M)0 = 30.62+-0.17 corresponding to a distance of 13.3+-1.0 Mpc. This is consistent with our earlier result, once the different calibrations for the standard candle are considered. We briefly discuss the implications of this now well-determined shorter distance. |
| Publication date: 09 May 2008 |
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| Reconnection at the dayside magnetopause: Comparisons of global MHD simulation results with Cluster and Double Star observations |
| This study uses two conjunctions between Cluster and Double Star TC-1 spacecraft together with global magnetohydrodynamic (MHD) simulations to investigate the large-scale configuration of magnetic reconnection at the dayside magnetopause. Both events involve southward interplanetary magnetic fields with significant By components. The first event occurred on 8 May 2004, while both spacecraft were exploring the dawn flank of the magnetosphere; TC-1 was skimming the magnetopause whereas Cluster was exploring higher latitudes. Results from a global MHD simulation show the formation of an equatorial merging line in the morning sector and suggest that the three-dimensional geometry of the merging region is mostly a radial juxtaposition of planes displaying X-type reconnection geometries. The second conjunction was on 6 April 2004. During this event, Cluster was located at high latitudes and close to the noon-midnight meridian, while TC-1 was exploring the dawnside at low latitudes. Analysis of the simulation reveals that both antiparallel and component merging occurred simultaneously. Three-dimensional rendering of the parallel electric field indicates that component merging initiated in the subsolar magnetopause. Simulation runs carried out using different parameters in the model suggest that the spread of the merging region depends on the local resistivity. The subsolar-merging region grows with increasing resistivity values and becomes patchy when a resistivity threshold is used. However, the region of component merging appears to remain spatially constrained to the subsolar region where stronger parallel electric fields occur and no clear connection with the antiparallel-merging regions is found for the range of parameters surveyed. |
| Publication date: 08 May 2008 |
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| Semi-annual oscillations in Saturn's low-latitude stratospheric temperatures |
| Observations of oscillations of temperature and wind in planetary atmospheres provide a means of generalizing models for atmospheric dynamics in a diverse set of planets in the Solar System and elsewhere. An equatorial oscillation similar to one in the Earth's atmosphere has been discovered in Jupiter. Here we report the existence of similar oscillations in Saturn's atmosphere, from an analysis of over two decades of spatially resolved observations of its 7.8-micron methane and 12.2-micron ethane stratospheric emissions, where we compare zonal-mean stratospheric brightness temperatures at planetographic latitudes of 3.6° and 15.5° in both the northern and the southern hemispheres. These results support the interpretation of vertical and meridional variability of temperatures in Saturn's stratosphere as a manifestation of a wave phenomenon similar to that on the Earth and in Jupiter. The period of this oscillation is 14.8 +- 1.2 terrestrial years, roughly half of Saturn's year, suggesting the influence of seasonal forcing, as is the case with the Earth's semi-annual oscillation. |
| Publication date: 08 May 2008 |
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| Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223 |
Context: About half of the baryons in the local Universe are invisible and - according to simulations - their dominant fraction resides in filaments connecting clusters of galaxies in the form of low density gas with temperatures in the range of 105 < T < 107 K. This warm-hot intergalactic medium has never been detected indisputably using X-ray observations.
Aims: We aim to probe the low gas densities expected in the large-scale structure filaments by observing a filament connecting the massive clusters of galaxies A 222 and A 223 (z = 0.21), which has a favorable orientation approximately along our line-of-sight. This filament has been previously detected using weak lensing data and as an over-density of colour-selected galaxies.
Methods: We analyse X-ray images and spectra obtained from a deep observation (144 ks) of A 222/223 with XMM-Newton.
Results: We present observational evidence of X-ray emission from the filament connecting the two clusters. We detect the filament in the wavelet-decomposed soft-band (0.5-2.0 keV) X-ray image with a 5-sigma significance. Following the emission down to the 3-sigma significance level, the observed filament is ~1.2 Mpc wide. The temperature of the gas associated with the filament, determined from the spectra, is kT = 0.91±0.25 keV, and its emission measure corresponds to a baryon density of (3.4±1.3)×10-5(l/15 Mpc)-1/2 cm-3, where l is the length of the filament along the line-of-sight. This density corresponds to a baryon over-density of rho/<rhoC> ~150. The properties of the gas in the filament are consistent with results of simulations of the densest and hottest parts of the warm-hot intergalactic medium. |
| Publication date: 05 May 2008 |
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| XMM-Newton slew survey discovery of the nova XMMSL1 J070542.7-381442 (V598 Puppis) |
Aims. In an attempt to catch new X-ray transients while they are still bright, the data taken by XMM-Newton as it slews between targets are being processed and cross-correlated with other X-ray observations as soon as the slew data appear in the XMM-Newton archive.
Methods. A bright source, XMMSL1 J070542.7-381442, was detected on 9 Oct. 2007 at a position where no previous X-ray source had been seen. The XMM slew data and optical data acquired with the Magellan Clay 6.5 m telescope were used to classify the new object.
Results. No XMM slew X-ray counts are detected above 1 keV and the source is seen to be 750 times brighter than the ROSAT All-Sky Survey upper limit at that position. The normally mV ~ 16 star, USNO-A2.0 0450-03360039, which lies 3.5" from the X-ray position, was seen in our Magellan data to be very much enhanced in brightness. Our optical spectrum showed emission lines that identified the source as a nova in the auroral phase; hence, this optical source is undoubtedly the progenitor of the X-ray source - a new nova (now also known as V598 Pup). The X-ray spectrum indicates that the nova was in a super-soft state (with kTeff ~ 35 eV). We estimate the distance to the nova to be ~ 3 kpc. Analysis of archival robotic optical survey data shows a rapid-decline light curve consistent with what is expected for a very fast nova.
Conclusions. The XMM-Newton slew data present a powerful opportunity to find new X-ray transient objects while they are still bright. Here we present the first such source discovered by the analysis of near real-time slew data. |
| Publication date: 05 May 2008 |
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