Comparison of four meteorite penetration funnels in the Campo del Cielo crater field,Argentina

Abstract– More craters may be discovered in the future, but as it is currently known, the Campo del Cielo crater field is 18 km long by 4 km at its widest point. Such a distribution of craters suggests that the parent meteoroid entered and traversed the atmosphere at a very low angle relative to horizontal. The crater field contains at least 20 small craters produced by the larger fragments of the parent meteoroid. Four of these are explosion analog craters and the rest are penetration funnels. During four field seasons, we have constructed topographic and magnetic maps of four of the penetration funnels as found, and then dug trenches across them to learn their original structures and recover meteorites preserved within them. Structures of these penetration funnels indicate very low angles of impact, i.e., 9–16° relative to horizontal. This supports the idea that the parent meteoroid traversed the atmosphere at a low angle. Data given here for the four penetration funnels include projectile masses, lengths, widths, depths, and estimates of impact angles and azimuths. One of the penetration funnels described here (No. 6) can almost be classified as an explosion analog crater.     

Improved Resolution of Ambient Flow through Fractured Rock with Temperature Logs

In contaminant hydrogeology, investigations at fractured rock sites are typically undertaken to improve understanding of the fracture networks and associated groundwater flow that govern past and/or future contaminant transport. Conventional hydrogeologic, geophysical, and hydrophysical techniques used to develop a conceptual model are often implemented in open boreholes under conditions of cross-connected flow. A new approach using high-resolution temperature (±0.001°C) profiles measured within static water columns of boreholes sealed using continuous, water-inflated, flexible liners (FLUTe™) identifies hydraulically active fractures under ambient (natural) groundwater flow conditions. The value of this approach is assessed by comparisons of temperature profiles from holes (100 to 200 m deep) with and without liners at four contaminated sites with distinctly different hydrogeologic conditions. The results from the lined holes consistently show many more hydraulically active fractures than the open-hole profiles, in which the influence of vertical flow through the borehole between a few fractures masks important intermediary flow zones. Temperature measurements in temporarily sealed boreholes not only improve the sensitivity and accuracy of identifying hydraulically active fractures under ambient conditions but also offer new insights regarding previously unresolvable flow distributions in fractured rock systems, while leaving the borehole available for other forms of testing and monitoring device installation.     

The galaxy luminosity–size relation and selection biases in the Hubble Ultra Deep Field

We use the Hubble Ultra Deep Field to study the galaxy luminosity–size  ( M – R _e )  distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability, we identify bias-free regions in the   M – R _e   plane for a series of volume-limited samples. By comparison to a nearby survey also having well-defined selection limits, namely the Millennium Galaxy Catalogue, we present clear evidence for evolution in surface brightness since   z ∼ 0.7  . Specifically, we demonstrate that the mean, rest-frame B -band  〈μ〉 _e   for galaxies in a sample spanning 8 mag in luminosity between   M _B =−22  and −14 mag increases by ∼1.0 mag arcsec⁻² from   z ∼ 0.1  to 0.7. We also highlight the importance of considering surface brightness-dependent measurement biases in addition to incompleteness biases. In particular, the increasing, systematic underestimation of Kron fluxes towards low surface brightnesses may cause diffuse, yet luminous, systems to be mistaken for faint, compact objects.     

Precipitation — elevation relationships over Sri Lanka

Summary The change of rainfall totals with height has been the subject of much investigation in many parts of the world. The rates of increase or decrease vary with the climatic regime experienced. This study of Sri Lankan rainfall shows that the relationship between height and mean annual rainfall is complex. Examples of increases and decreases of rainfall with height are found. The climatic regime of the area is important in controlling the level of maximum rainfall.With 7 Figures     

Discovery of a coherent oscillation with a 1.07 h period in the suspected cataclysmic variable FBS 1220+753 (Dra 7)

We report results of extensive photometry of the suspected cataclysmic variable FBS 1220+753. The observations were obtained over 28 nights in 2010, 2011 and 2012. The total duration of the observations was 160 h. We clearly detected the highly coherent oscillation with a period of 1.0712887±0.0000013 h and a stable semi-amplitude of 0.03 mag. In a time scale of years, the oscillation period is very stable (dP/dt<(4.1±1.4)×10^?10). The light curves of FBS 1220+753 show no obvious flickering. The significant brightness changes on large time intervals are also absent. Therefore, it is unlikely that FBS 1220+753 is a cataclysmic variable. The period is compatible with oscillations seen in δ Sct variables. But its high stability and the unchangeable oscillation amplitude suggest that the oscillation cannot be caused by multiperiodic stellar pulsations. The average pulse shape of the oscillation is very sinusoidal with slightly sharper maxima compared with minima, but it is somewhat changeable from year to year. The light curves obtained in 2011 and folded with the doubled oscillation period reveal that the adjacent oscillation cycles have slightly different depths of the minima and different steepness of the rise and decline. This behaviour resembles the behaviour of the binary subdwarf–white dwarf systems, in which the variability is caused by ellipsoidal variations. However, the folded light curve obtained from the data of 2010 reveal nearly equal shapes of the adjacent oscillation cycles, and this does not conform to such an interpretation. Thus, the nature of the oscillation seen in FBS 1220+753 remains puzzling. To solve this puzzle, detailed spectroscopic observations are needed.     

Orbital periods of the binary sdB stars PG 0940+068 and PG 1247+554

We have used the radial velocity variations of two sdB stars previously reported to be binaries to establish their orbital periods. They are PG 0940+068 ( P =8.33 d) and PG 1247+554 ( P =0.599 d). The minimum masses of the unseen companions, assuming a mass of 0.5 M_⊙ for the sdB stars, are 0.090±0.003 M. for PG 1247+554 and 0.63±0.02 M_⊙ for PG 0940+068. The nature of the companions is not constrained further by our data.     

Correlation of longitudinal currents with Alfvén wave generation in the solar atmosphere

Current instability of Alfvén waves in coronal loops is considered. Such a mechanism of Alfvén wave generation is shown to be very efficient, and it can give rise to low-frequency perturbations even in the case of very weak currents, thus fostering the reconnection of magnetic fields and development of a flare. The low-frequency turbulence which arises in the process can be favorable to the heating and acceleration of particles.