Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of  ∼1100 km s⁻¹  , which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of  10⁶– 10⁷ stars pc⁻³  . Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.     

Lava flow simulations using discharge rates from thermal infrared satellite imagery during the 2006 Etna eruption

Techniques capable of measuring lava discharge rates during an eruption are important for hazard prediction, warning, and mitigation. To this end, we developed an automated system that uses thermal infrared satellite MODIS data to estimate time-averaged discharge rate. MODIS-derived time-varying discharge rates were used to drive lava flow simulations calculated using the MAGFLOW cellular automata model, allowing us to simulate the discharge rate-dependent spread of lava as a function of time. During the July 2006 eruption of Mount Etna (Sicily, Italy), discharge rates were estimated at regular intervals (i.e., up to 2 times/day) using the MODIS data. The eruption lasted 10 days and produced a ~3-km-long lava flow field. Time-averaged discharge rates extracted from 13 MODIS images were utilized to produce a detailed chronology of lava flow emplacement, demonstrating how infrared satellite data can be used to drive numerical simulations of lava flow paths during an ongoing eruptive event. The good agreement between simulated and mapped flow areas indicates that model-based inundation predictions, driven by time-varying discharge rate data, provide an excellent means for assessing the hazard posed by ongoing effusive eruptions.     

On the origin of high-velocity runaway stars

We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary  50–100 M_⊙  star or a more massive one, formed through runaway mergers of ordinary stars in the core of a young massive star cluster). In this process, one of the binary components becomes gravitationally bound to the very massive star, while the second one is ejected, sometimes with a high speed. We performed three-body scattering experiments and found that early B-type stars (the progenitors of the majority of neutron stars) can be ejected with velocities of  ≳200–400 km s⁻¹  (typical of pulsars), while  3–4 M_⊙  stars can attain velocities of  ≳300–400 km s⁻¹  (typical of the bound population of halo late B-type stars). We also found that the ejected stars can occasionally attain velocities exceeding the Milky Ways's escape velocity.     

Reply to Comment on “Hydrodynamics of karst aquifers in metamorphic carbonate rocks: results from spring monitoring in the Apuan Alps (Tuscany,Italy)”: report published in Hydrogeology Journal (2023) 31:241–255, by Leonardo Piccini,Alessia Nannoni,and Emilio Poggetti

Hydrogeology Journal -     

Dynamics and mass balance of the 2007 Cima Una rockfall (Eastern Alps, Italy)

On October 12th, 2007 about 40,000 m³ of dolomitic rock detached from the northern wall of the peak known as “Cima Una” (Val Fiscalina, Sesto Dolomites, Bolzano, Italy), and fell 900 m to Fiscalina Valley below. The event generated a dense dust cloud, which traveled up to 4 km from the source area. The failure surface was formed by two near-vertical surfaces, almost perpendicular to each other. The orientation of these surfaces is consistent with two of the main regional tectonic sets. Only a small portion of the fallen material appeared to be preserved as blocks deposited at the base of the rock wall. About a fifth of the fallen mass was deposited on a colluvial cone. The missing mass, estimated to be about 80 %, may be represented by highly fragmented rock in part deposited as sand on the valley floor and in part dispersed as a dense dust cloud generated during the rockfall. There appears to be a deficit of deposited material, which could lead underestimation in the calculation of rock–cliff recession rates. The dynamics of the rockfall, strongly conditioned by the local topography, partially explains the intense rock breakage and the generation of the dust cloud. The rockfall was not caused by an external trigger, such as an earthquake or heavy rainfall; the failure was most likely progressive due to mechanical and physical degradation along highly stressed failure surfaces, possibly promoted by permafrost degradation and freeze and thaw processes.     

Removal of Lead, Copper, Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb2 ,Cu~(2 ),Zn~(2 )and Cd~(2 )from aqueous solutions by sorption on a natural phosphate rock(FAP)was investigated.The effects of the contact time and initial metal concentration were examined in the batch method.The percentage sorption of heavy metals from solution ranges generally between 50% and 99%.The amount of sorbed metal ions follows the order Cu>Pb>Cd>Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate.The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb~(2 ),Cu~(2 ),Zn~(2 )and Cd~(2 )from polluted waters.     

The ground-based InSAR monitoring system at Stromboli volcano: linking changes in displacement rate and intensity of persistent volcanic activity

Stromboli volcano (Aeolian Archipelago, Southern Italy) experienced an increase in its volcanic activity from late December 2012 to March 2013, when it produced several lava overflows, major Strombolian explosions, crater-wall collapses pyroclastic density currents and intense spatter activity. An analysis of the displacement of the NE portion of the summit crater terrace and the unstable NW flank of the volcano (Sciara del Fuoco depression) has been performed with a ground-based interferometric synthetic aperture radar (GBInSAR) by dividing the monitored part of the volcano into five sectors, three in the summit vents region and two in the Sciara del Fuoco. Changes in the displacement rate were observed in sectors 2 and 3. Field and thermal surveys revealed the presence of an alignment of fumaroles confirming the existence of an area of structural discontinuity between sectors 2 and 3. High displacement rates in sector 2 are interpreted to indicate the increase in the magmastatic pressure within the shallow plumbing systems, related to the rise of the magma level within the conduits, while increased displacement rates in sector 3 are connected to the lateral expansion of the shallow plumbing system. The increases and decreases in the displacement rate registered by the GBInSAR system in the upper part of the volcano have been used as a proxy for changes in the pressure conditions in the shallow plumbing system of Stromboli volcano and hence to forecast the occurrence of phases of higher-intensity volcanic activity.     

Hydraulic failure of diaphragm walls: a possible methodology for safety improvement

The paper presents a methodology aimed at reducing—or even avoiding—the risk of heave and uplift failures of reinforced concrete diaphragm walls. The method is based on the simple concept of increasing the drainage capacity of the embedded portion of the retaining walls. The behaviour of a strutted excavation in a cohesionless soil below groundwater is examined by means of two distinct series of numerical analyses, respectively focused on the hydraulic and mechanical behaviour of the retaining system. It is shown that, for some frequent cases, such methodology is capable to improve the safety of the retaining system with respect to both hydraulic and geotechnical limit states.