1,599 research outputs found
Data Reduction and Control Software for Meteor Observing Stations Based on CCD Video Systems
The SPanish Meteor Network (SPMN) is performing a continuous monitoring of meteor activity over Spain and neighbouring countries. The huge amount of data obtained by the 25 video observing stations that this network is currently operating made it necessary to develop new software packages to accomplish some tasks, such as data reduction and remote operation of autonomous systems based on high-sensitivity CCD video devices. The main characteristics of this software are described here
Orbital characterization of superbolides observed from space: dynamical association with near-Earth objects, meteoroid streams and identification of hyperbolic meteoroids
There is an unceasing incoming flux of extraterrestrial materials reaching
the Earth's atmosphere. Some of these objects produce luminous columns when
they ablate during the hypersonic encounter with air molecules. A few fireballs
occur each year bright enough to be detected from space. The source of these
events is still a matter of debate, but it is generally accepted that they are
of sporadic origin. We studied the NASA-JPL Center for NEOs Studies (CNEOS)
fireball database to infer the dynamic origin of large bolides produced by
meter-sized projectiles that impacted our planet. These likely
meteorite-dropping events were recorded by the US Government satellite sensors.
We estimated the false-positive rate and analyzed the time evolution of
multiple orbit dissimilarity criteria concerning potential associations with
near-Earth objects and meteoroid streams. We found that at least 16% of the
large bolides could be associated with meteoroid streams, about 4% are likely
associated with near-Earth asteroids, and 4% may be linked to near-Earth
comets. This implies that a significant fraction of meter-sized impactors
producing large bolides may have an asteroidal or cometary origin. In addition,
we found at least three bolides having hyperbolic orbits with high tensile
strength values. Meter-sized meteoroids of interstellar origin could be more
common than previously thought, representing about 1% of the flux of large
bolides. The inferred bulk physical properties suggest that the interstellar
medium could bias these projectiles towards high strength rocks with the
ability to survive prolonged exposure to the harsh interstellar space
conditions.Comment: Accepted for publication in The Astronomical Journal (AAS38905R1
Extreme summer temperatures in Iberia: health impacts and associated synoptic conditions
This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal) and Madrid (Spain). Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34&deg;C in Lisbon and 36&deg;C in Madrid). The impact of most intense heat events is very similar for both cities, with significant mortality values occurring up to 3 days after the temperature threshold has been surpassed. This impact is measured as the percentual increase of mortality associated to a 1&deg;C increase above the threshold temperature. In this respect, Lisbon shows a higher impact, 31%, as compared with Madrid at 21%. The difference can be attributed to demographic and socio-economic factors. Furthermore, the longer life span of Iberian women is critical to explain why, in both cities, females are more susceptible than males to heat effects, with an almost double mortality impact value. <P style="line-height: 20px;"> The analysis of Sea Level Pressure (SLP), 500hPa geopotential height and temperature fields reveals that, despite being relatively close to each other, Lisbon and Madrid have relatively different synoptic circulation anomalies associated with their respective extreme summer temperature days. The SLP field reveals higher anomalies for Lisbon, but extending over a smaller area. Extreme values in Madrid seem to require a more western location of the Azores High, embracing a greater area over Europe, even if it is not as deep as for Lisbon. The origin of the hot and dry air masses that usually lead to extreme heat days in both cities is located in Northern Africa. However, while Madrid maxima require&nbsp;wind blowing directly from the south, transporting heat from Southern Spain and Northern Africa, Lisbon maxima occur under more easterly conditions, when Northern African air flows over the central Iberian plateau, which had been previously heated
Simultaneous detection of an intrinsic absorber and a compact jet emission in the X-ray binary IGR J17091-3624 during a hard accretion state
We present a detailed analysis of three XMM-Newton observations of the black
hole low-mass X-ray binary IGR~J17091-3624 taken during its 2016 outburst.
Radio observations obtained with the Australia Telescope Compact Array (ATCA)
indicate the presence of a compact jet during all observations. From the best
X-ray data fit results we concluded that the observations were taken during a
transition from a hard accretion state to a hard-intermediate accretion state.
For Observations 1 and 2 a local absorber can be identified in the EPIC-pn
spectra but not in the RGS spectra, preventing us from distinguishing between
absorption local to the source and that from the hot ISM component. For
Observation 3, on the other hand, we have identified an intrinsic ionized
static absorber in both EPIC-pn and RGS spectra. The absorber, observed
simultaneously with a compact jet emission, is characterized by an ionization
parameter of 1.96< log({\xi}) <2.05 and traced mainly by Ne X, Mg XII, Si XIII
and Fe XVIII.Comment: 13 pages, 10 figure
First record of Caprella mutica from the Iberian Peninsula: expansion southwards in European waters
The caprellid amphipod, Caprella mutica, is a well-known invasive species, originating in the Sea of Japan, which has been rapidly expanding along the coasts of North America, Europe and Oceania for the last forty years. Caprella mutica is frequently associated with man-made structures, especially those dedicated to aquaculture activities, where it can reach high densities of up to 300,000 ind./m2. A well-established population of C. mutica was recently found by SCUBA-divers in Galician waters (north-west Spain) at 6 different man-made floating structures along Ría de Arousa. The record of this species in this location implies a new southernmost limit of distribution, extending the known distribution range in Atlantic European waters and confirming the continuity of the colonization southwards
The Effect of Aqueous Alteration in Antarctic Carbonaceous Chondrites from Comparative ICP-MS Bulk Chemistry
Terrestrial ages of Antarctic carbonaceous chondrites (CC) indicate that these meteorites have been preserved in or on ice for, at least, tens of thousands of years. Due to the porous structure of these chondrites formed by the aggregation of silicate-rich chondrules, refractory inclusions, metal grains, and fine-grained matrix materials, the effect of pervasive terrestrial water is relevant. Our community defends that pristine CC matrices are representing samples of scarcely processed protoplanetary disk materials as they contain stellar grains, but they might also trace parent body processes. It is important to study the effects of terrestrial aqueous alteration in promoting bulk chemistry changes, and creating distinctive alteration minerals. Particularly because it is thought that aqueous alteration has particularly played a key role in some CC groups in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive. With the goal to learn more about terrestrial alteration in Antarctica we are obtaining reflectance spectra of CCs, but also performing ICP-MS bulk chemistry of the different CC groups. A direct comparison with the mean bulk elemental composition of recovered falls might inform us on the effects of terrestrial alteration in finds. With such a goal, in the current work we have analyzed some members representative of CO and CM chondrite groups
Application of an Equilibrium Vaporization Model to the Ablation of Chondritic and Achondritic Meteoroids
We modeled equilibrium vaporization of chondritic and achondritic materials
using the MAGMA code. We calculated both instantaneous and integrated element
abundances of Na, Mg, Ca, Al, Fe, Si, Ti, and K in chondritic and achondritic
meteors. Our results are qualitatively consistent with observations of meteor
spectra.Comment: 8 pages, 4 figures; in press, Earth, Moon, and Planets, Meteoroids
2004 conference proceeding
MAXI J1659-152: the shortest orbital period black-hole binary
Following the detection of a bright new X-ray source, MAXI J1659-152, a
series of observations was triggered with almost all currently flying
high-energy missions. We report here on XMM-Newton, INTEGRAL and RXTE
observations during the early phase of the X-ray outburst of this transient
black-hole candidate. We confirm the dipping nature in the X-ray light curves.
We find that the dips recur on a period of 2.4139+/-0.0005 hrs, and interpret
this as the orbital period of the system. It is thus the shortest period
black-hole X-ray binary known to date. Using the various observables, we derive
the properties of the source. The inclination of the accretion disk with
respect to the line of sight is estimated to be 60-75 degrees. The companion
star to the black hole is possibly a M5 dwarf star, with a mass and radius of
about 0.15 M_sun and 0.23 R_sun, respectively. The system is rather compact
(orbital separation is about 1.35 R_sun) and is located at a distance of
roughly 7 kpc. In quiescence, MAXI J1659-152 is expected to be optically faint,
about 28 mag in the V-band.Comment: 5 pages, 4 figures, to be published in the proceedings of the 4th
International MAXI Workshop `The First Year of MAXI: Monitoring variable
X-ray sources', 2010 Nov 30 - Dec 2, Tokyo, Japa
The collisional evolution of undifferentiated asteroids and the formation of chondritic meteoroids
Most meteorites are fragments from recent collisions experienced in the asteroid belt. In such a hypervelocity collision, the smaller collision partner is destroyed, whereas a crater on the asteroid is formed or it is entirely disrupted, too. The present size distribution of the asteroid belt suggests that an asteroid with a 100 km radius is encountered 1014 times during the lifetime of the solar system by objects larger than 10 cm in radius; the formed craters cover the surface of the asteroid about 100 times. We present a Monte Carlo code that takes into account the statistical bombardment of individual infinitesimally small surface elements, the subsequent compaction of the underlying material, and the formation of a crater and a regolith layer. For the entire asteroid, 10,000 individual surface elements are calculated. We compare the ejected material from the calculated craters with the shock stage of meteorites with low petrologic type and find that these most likely stem from smaller parent bodies that do not possess a significant regolith layer. For larger objects, which accrete a regolith layer, a prediction of the thickness depending on the largest visible crater can be made. Additionally, we compare the crater distribution of an object initially 100 km in radius with the shape model of the asteroid (21) Lutetia, assuming it to be initially formed spherical with a radius that is equal to its longest present ellipsoid length. Here we find the shapes of both objects to show resemblance to each other.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí
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