Context. In meteor physics, the luminous efficiency τ is used to convert the meteor’s magnitude to the corresponding meteoroid’s mass. However, a lack of sufficiently accurate verification methods or ...adequate laboratory tests mean that discussions around this parameter are a subject of controversy. Aims. In this work, we aim to use meteor data obtained by the Fireball Recovery and InterPlanetary Observation to calculate the luminous efficiencies of the recorded meteors. We also show the limitations of the methods presented herein. Methods. Deceleration-based formulas were used to calculate the masses of the pre-atmospheric meteoroids. These can in turn be compared to the meteor brightnesses to assess the luminous efficiencies of the recorded objects. Fragmentation of the meteoroids is not considered within this model. Good measurements of the meteor deceleration are required. Results. We find τ -values, as well as the shape change coefficients, of 294 meteors and fireballs with determined masses in the range of 10 −6 –100 kg. The derived τ -values have a median of τ median = 2.17%. Most of them are of the order of 0.1–10%. We present how our values are obtained, compare them with data reported in the literature, and discuss several methods. A dependence of τ on the pre-atmospheric velocity of the meteor, v e , is noticeable with a relation of τ = 0.0023⋅ v e 2.3 . Furthermore, a dependence of τ on the initial meteoroid mass, M e , is found with negative linear behaviour in log–log space: τ = 0.48⋅ M e −0.47 . Conclusions. The higher luminous efficiency of fast meteors could be explained by the higher amount of energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, the negative dependence of τ on M e implies that the radiation of smaller meteoroids is more efficient. The results of this study also show the limitations of the ablation-based model for the determination of the luminous efficiency.
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Context.
The luminous efficiency,
τ
, can be used to compute the pre-atmospheric masses of meteoroids from corresponding recorded meteor brightnesses. The derivation of the luminous efficiency is ...non-trivial and is subject to biases and model assumptions. This has led to greatly varying results in the last decades of studies.
Aims.
The present paper aims to investigate how a reduction in various observational biases can be achieved to derive (more) reliable values for the luminous efficiency.
Methods.
A total of 281 meteors observed by the Fireball Recovery and InterPlanetary Observation Network (FRIPON) are studied. The luminous efficiencies of the events are computed using an ablation-based model. The relations of
τ
as a function of the pre-atmospheric meteoroid velocity,
v
e
, and mass,
M
e
, are studied. Various aspects that could render the method less valid, cause inaccuracies, or bias the results are investigated. On this basis, the best suitable meteors were selected for luminous efficiency computations.
Results.
The presented analysis shows the limits of the used method. The most influential characteristics that are necessary for reliable results for the
τ
computation were identified. We study the dependence of
τ
on the assumed meteoroid’s density,
ρ
, and include improved
ρ
-values for objects with identified meteoroid stream association. Based on the discovered individual biases and constraints we create a pre-debiased subset of 54 well-recorded events with a relative velocity change >80%, a final height <70 km, and a Knudsen number Kn < 0.01; this last value indicates that the events were observed in the continuum-flow regime. We find
τ
-values in the range between 0.012% and 1.1% for this pre-debiased subset and relations of
τ
to
v
e
and
M
e
of:
τ
=7.33⋅
v
e
−1.10
and
τ
=0.28⋅
M
e
−0.33
.
Conclusions.
The derived luminous efficiency of meteoroids depends on the assumed material density. Our results indicate that the applied debiasing method improves the analysis of
τ
from decelerated meteoroids. The underlying method is only valid for meteors in the continuum-flow regime. These events tend to have low end heights, large masses, and high deceleration.
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On May 30, 2017, at about 21 h 09 min 17 s UTC a green bright fireball crossed the sky of northeastern Italy. The fireball path was observed from some all-sky cameras starting from a mean altitude of
...81.1
±
0.2
km (Lat.
44
.
369
∘
±
0
.
002
∘
N; Long.
11
.
859
∘
±
0
.
002
∘
E) and extinct at
23.3
±
0.2
km (Lat.
45
.
246
∘
±
0
.
002
∘
N; Long.
12
.
046
∘
±
0
.
002
∘
E), between the Italian cities of Venice and Padua. In this paper, on the basis of simple physical models, we will compute the atmospheric trajectory, analyze the meteoroid atmospheric dynamics, the dark flight phase (with the strewn field) and compute the best heliocentric orbit of the progenitor body. Search for meteorites on the ground has not produced any results so far.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ABSTRACT
Two meteorite pieces have been recovered in Italy, near the town of Cavezzo (Modena), on 2020 January 4th. The associated fireball was observed on the evening of New Year’s Day 2020 by eight ...all-sky cameras of the PRISMA fireball network, a partner of FRIPON. The computed trajectory had an inclination angle of approximately 68° and a velocity at infinity of 12.8 km s−1. Together with the relatively low terminal height, estimated as 21.5 km, those values were indicating the significant possibility of a meteorite dropping event, as additionally confirmed by the non-zero residual total mass. The strewn-field was computed taking into account the presence of two bright light flashes, revealing that the meteoroid had been very likely subject to fragmentation. Three days after the event, two samples, weighing 3.1 and 52.2 g, were collected as a result of a dedicated field search and thanks to the involvement of the local people. The two pieces were immediately recognized as freshly fallen fragments of meteorite. The computed orbital elements, compared with the ones of known Near-Earth Asteroids from the NEODyS database, are compatible with one asteroid only; 2013 VC10. The estimated original mass of the meteoroid, 3.5 kg, and size, approximately 13 cm, is so far the smallest among the current 35 cases in which meteorites were recovered from precise strewn-field computation thanks to observational data. This result demonstrates the effectiveness of accurate processing of fireball network data even on challenging events generated by small size meteoroids.
The INAF Radio Data Archive: towards a modern Science Gateway Zanichelli, A.; Knapic, C.; Londero, E. ...
2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS),
2021-Aug.-28
Conference Proceeding
In the Big Data era, the amount and complexity of astronomical data more and more often prevents the scientist from locally store and process her/his data. As a consequence, the geographically ...distributed approach to data archiving and processing is rapidly becoming a requisite. To fulfill this need, we are realizing a prototype of Science Gateway (SG) for the Italian radio telescopes. The huge amount of significantly complex and resource-demanding datasets delivered by the Italian radio telescopes and the variety of use cases from the different observing modes represent an ideal test bed for the implementation and verification of a SG environment where the scientists can exploit, manage and analyse data. To this aim, we are exploiting our previous experience in the realization of a geographically-distributed radio data archive and processing tools as well as in the design of SG prototypes. Such a coordinated approach and harmonization of resources will maximize the return for the Italian observing facilities and, moreover, will match the requirements of the international community for a state-of-the-art, highly-performant environment in which to conduct successful science.
Before about 500 million years ago, most probably our planet experienced temporary snowball conditions, with continental and sea ices covering a large fraction of its surface. This points to a ...potential bistability of Earth's climate, that can have at least two different (statistical) equilibrium states for the same external forcing (i.e., solar radiation). Here we explore the probability of finding bistable climates in earth-like exoplanets, and consider the properties of planetary climates obtained by varying the semi-major orbital axis (thus, received stellar radiation), eccentricity and obliquity, and atmospheric pressure. To this goal, we use the Earth-like planet surface temperature model (ESTM), an extension of 1D Energy Balance Models developed to provide a numerically efficient climate estimator for parameter sensitivity studies and long climatic simulations. After verifying that the ESTM is able to reproduce Earth climate bistability, we identify the range of parameter space where climate bistability is detected. An intriguing result of the present work is that the planetary conditions that support climate bistability are remarkably similar to those required for the sustainance of complex, multicellular life on the planetary surface. The interpretation of this result deserves further investigation, given its relevance for the potential distribution of life in exoplanetary systems.
Superparamagnetic Fe
3
O
4
/SiO
2
/TiO
2
peapod-like nanostructures have been successfully synthesized by using Fe
3
O
4
/SiO
2
core/shell particles as building blocks and TiO
2
as the adhesive ...without the need of any hard or soft templates. The fabrication process involves chaining the Fe
3
O
4
/SiO
2
cores during magnetic stirring and subsequent fixing of the chain structure during TiO
2
coating. The number of Fe
3
O
4
/SiO
2
cores arranged linearly in the chains could be effectively controlled by tuning the amount of titanium precursor or the magnetic stirring rate. The double layer coating of SiO
2
and TiO
2
enhances thermal and chemical stability of the nanopeapods, and the one-dimensional chain structure produces interesting properties that enable applications not possible with conventional magnetite materials. As a demonstration, we show here the use of these superparamagnetic peapod-like nanostructures for low-frequency optical modulation.
Superparamagnetic Fe
3
O
4
/SiO
2
/TiO
2
peapod-like nanostructures with controllable numbers of magnetite cores arranged in a line have been successfully synthesized and then used for low frequency optical modulation.
Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on ...SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.
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