Search for GRB related prompt optical emission and other fast varying objects with “Pi of the Sky” detector

Experiment “Pi of the Sky” is designed to search for prompt optical emission from GRB sources. 32 CCD cameras covering 2 steradians will monitor the sky continuously. The data will be analysed on-line in search for optical flashes. The prototype with 2 cameras operated at Las Campanas (Chile) since 2004 has recognised several outbursts of flaring stars and has given limits for a few GRB.     

Seasonal redistribution of water in the surficial Martian regolith: Results from the <Emphasis Type="Italic">Mars Odyssey</Emphasis> high-energy neutron detector (HEND)

The seasonal variation of neutron emissions from Mars in different spectral intervals measured by the HEND neutron detector for the entire Martian year are analyzed. Based on these data, the spatial variations of the neutron emissions from the planet are globally mapped as a function of season, and the dynamics of seasonal variation of neutron fluxes with different energies is analyzed in detail. No differences were found between seasonal regimes of neutron fluxes in different energy ranges in the southern hemisphere of Mars, while the regime of fast neutrons (with higher energies) during the northern winter strongly differs from that during the southern winter. In winter (L _s = 270°–330°), the fast neutron fluxes are noticeably reduced in the northern hemisphere (along with the consecutive thickening of the seasonal cap of solid carbon dioxide). This provides evidence of a temporary increase in the water content in the effective layer of neutron generation. According to the obtained estimates, the observed reduction of the flux of fast neutrons in the effective layer corresponds to an increase in the water abundance of up to 5% in the seasonal polar cap (70°–90°N), about 3% at mid-latitudes, and from 1.5 to 2% at low latitudes. The freezing out of atmospheric water at the planetary surface (at middle and high latitudes) and the hydration of salt minerals composing the Martian soil are considered as the main processes responsible for the temporary increase in the water content in the soil and upper layer of the seasonal polar cap. The meridional atmospheric transport of water vapor from the summer southern to the winter northern hemisphere within the Hadley circulation cell is a basic process that delivers water to the subsurface soil layer and ensures the observed scale of the seasonal increase in water abundance. In the summer northern hemisphere, the similar Hadley circulation cell transports mainly dry air masses to the winter southern hemisphere. The point is that the water vapor becomes saturated at lower heights during aphelion, and the bulk of the atmospheric water mass is captured in the near-equatorial cloudy belt and, thus, is only weakly transferred to the southern hemisphere. This phenomenon, known as the Clancy effect, was suggested by Clancy et al. (1996) as a basic mechanism for the explanation of the interhemispheric asymmetry of water storage in permanent polar caps. The asymmetry of seasonal meridional circulation of the Martian atmosphere seems to be another factor determining the asymmetry of the seasonal water redistribution in the “atmosphere-regolith-seasonal polar caps” system, found in the peculiarities of the seasonal regime of the neutron emission of Mars.     

Whipple telescope observations of LS I +61 303: 2004–2006

In this paper we present the results of the past two years observations on the galactic microquasar LS I +61 303 with the Whipple 10 m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005–2006 season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are placed on emission during the orbital phases of 0→0.1 and 0.8→1, phases which are not included in the MAGIC data set.      

Large Proton Anisotropies in the 18 August 2010 Solar Particle Event

The solar particle event observed at STEREO Ahead on 18?August 2010 displayed a rich variety of behavior in the particle anisotropies. Sectored rates measured by the Low Energy Telescope (LET) on STEREO showed very large bidirectional anisotropies in 4??C?6?MeV protons for the first ???17?hours of the event while inside a magnetic cloud, with intensities along the field direction several hundred to nearly 1000 times greater than those perpendicular to the field. At the trailing end of the cloud, the protons became isotropic and their spectrum hardened slightly, while the He/H abundance ratio plunged by a factor of approximately four for about four hours. Associated with the arrival of a shock on 20?August was a series of brief (<?10?minute duration) intensity increases (commonly called ??shock spikes??) with relatively narrow angular distributions (???45^° FWHM), followed by an abrupt decrease in particle intensities at the shock itself and a reversal of the proton flow to a direction toward the Sun and away from the receding shock. We discuss the STEREO/LET observations of this interesting event in the context of other observations reported in the literature.     

Petrologic and textural diversity among the PCA 02 howardite group,one of the largest pieces of the Vestan surface

Abstract— Nine howardites and two diogenites were recovered from the Pecora Escarpment Icefield (PCA) in 2002. Cosmogenic radionuclide abundances indicate that the samples are paired and that they constituted an approximately 1 m (diameter) meteoroid prior to atmospheric entry. At about 1 m in diameter, the PCA 02 HED group represents one of the largest single pre‐atmospheric pieces of the Vestan surface yet described. Mineral and textural variations were measured in six of the PCA 02 howardites to investigate meter‐scale diversity of the Vestan surface. Mineral compositions span the range of known eucrite and diogenite compositions. Additional non‐diogenitic groups of Mg‐ and Fe‐rich olivine are observed, and are interpreted to have been formed by exogenic contamination and impact melting, respectively. These howardites contain olivine‐rich impact melts that likely formed from dunite‐ and harzburgite‐rich target rocks. Containing the first recognized olivine‐rich HED impact melts, these samples provide meteoritic evidence that olivine‐rich lithologies have been exposed on the surface of Vesta. Finally, we present a new method for mapping distributions of lithologies in howardites using 8 elemental X‐ray maps. Proportions of diogenite and eucrite vary considerably among the PCA 02 howardites, suggesting they originated from a heterogeneous portion of the Vestan surface. While whole sample modes are dominated by diogenite, the finer grain size fractions are consistently more eucritic. This discrepancy has implications for near‐infrared spectral observations of portions of Vesta’s surface that are similar to the PCA 02 howardites, as the finer grained eucritic material will disproportionately dominate the spectra.     

Distribution and characteristics of Adirondack-class basalt as observed by Mini-TES in Gusev crater,Mars and its possible volcanic source

We identified 104 unique rock targets belonging to the olivine-rich Adirondack class using Mini-TES data. Rare rocks on the West Spur of the Columbia Hills and on the plains east of the Hills also belong to this class. We present evidence that Adirondack-class basaltic lavas may have had their origin at Apollinaris Tholus. Linear modeling of Adirondack-class rock spectra shows only minor variations in mineralogy and the primary phases identified are consistent with olivine basalt having an average olivine composition of ～Fo₄₅. We used factor analysis and target transformation to identify variability within a single class of rocks for the first time, and we find that olivine abundance varies independently of a basaltic matrix. A spectral component previously attributed to downwelling radiance is proposed here to be attributable to optically thin dust on rocks, which has a greater effect on Mini-TES spectra than previously recognized, but can explain the sloping continuum observed in Adirondack-class rock spectra as well as the apparent distortion of an olivine absorption. Spectral mixing is not completely linear, leading to the overestimation of sulfate and olivine fractions and the underestimation of plagioclase feldspar, although linear mixing appears to successfully replicate the majority of the observed signal. Published TES spectra of low albedo, low dust cover, olivine-bearing materials do not exhibit the spectral telltales of non-linear behavior, probably because orbital spectra represent mostly mobile regolith that has not accumulated a sufficient dust cover over ～3 × 6 km areas.     

The Heliospheric Plasma Sheet Observed in situ by Three Spacecraft over Four Solar Rotations

Solar Physics - In this paper we present in&nbsp;situ observations of the heliospheric plasma sheet (HPS) from STEREO-A, Wind, and STEREO-B over four solar rotations in the declining phase of...     

The GREGOR polarimetric calibration unit

The new Solar telescope GREGOR is designed to observe small‐scale dynamic magnetic structures below a size of 70 km on the Sun with high spectral resolution and polarimetric accuracy. For this purpose, the polarimetric concept of GREGOR is based on a combination of post‐focus polarimeters with pre‐focus equipment for high precision calibration. The Leibniz‐Institute for Astrophysics Potsdam developed the GREGOR calibration unit which is an integral part of the telescope. We give an overview of the function and design of the calibration unit and present the results of extensive testing series done in the Solar Observatory “Einsteinturm” and at GREGOR (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Improving efficiency in radio surveys for gravitational lenses

Many lens surveys have hitherto used observations of large samples of background sources to select the small minority which are multiply imaged by lensing galaxies along the line of sight. Recently surveys such as SLACS and OLS have improved the efficiency of surveys by pre-selecting double-redshift systems from SDSS. We explore other ways to improve survey efficiency by optimum use of astrometric and morphological information in existing large-scale optical and radio surveys. The method exploits the small position differences between FIRST radio positions of lensed images and the SDSS lens galaxy positions, together with the marginal resolution of some larger gravitational lens systems by the FIRST beam. We present results of a small pilot study with the VLA and MERLIN, and discuss the desirable criteria for future surveys.