1,172 research outputs found
A phenomenological analysis of azimuthal asymmetries in unpolarized semi-inclusive deep inelastic scattering
We present a phenomenological analysis of the cos-phi and cos-2phi
asymmetries in unpolarized semi-inclusive deep inelastic scattering, based on
the recent multidimensional data released by the COMPASS and HERMES
Collaborations. In the TMD framework, valid at relatively low transverse
momenta, these asymmetries arise from intrinsic transverse momentum and
transverse spin effects, and from their correlations. The role of the Cahn and
Boer-Mulders effects in both azimuthal moments is explored up to order 1/Q. As
the kinematics of the present experiments is dominated by the low-Q^2 region,
higher-twist contributions turn out to be important, affecting the results of
our fits.Comment: 18 pages, 5 figures, one paragraph added at the end of Section IV,
one reference added. PRD versio
Geomorphological processes, forms and features in the surroundings of the Melka Kunture Palaeolithic site, Ethiopia
The landscape of the surroundings of the Melka Kunture prehistoric site, Upper Awash Basin, Ethiopia, were studied intensively in the last decades. Nonetheless, the area was mainly characterized under a stratigraphic/geological and archaeological point of view. However, a detailed geomorphological map is still lacking. Hence, in this study, we identify, map and visualize geomorphological forms and processes. The morphology of the forms, as well as the related processes, were remotely sensed with available high-resolution airborne and satellite sources and calibrated and validated through extensive field work conducted in 2013 and 2014. Furthermore, we integrated multispectral satellite imagery to classify areas affected by intensive erosion processes and/or anthropic activities. The Main Map at 1:15,000 scale reveals structural landforms as well as intensive water-related degradation processes in the Upper Awash Basin. Moreover, the map is available as an interactive WebGIS application providing further information and detail (www.roceeh.net/ethiopia_geomorphological_map/)
Measuring track vertical stiffness through dynamic monitoring
[EN] This paper proposes a methodology for the evaluation of the track condition by means of the measurement of the track stiffness. This magnitude is calculated from vertical acceleration data measured at the axle box of trains during their normal operation. From the corresponding vertical acceleration spectra, the dominant vibration frequencies for each track stretch are identified and the combined stiffness is then determined. Then the stiffness without the contribution of the rail is calculated. The results obtained for a High Speed ballasted track in several track stretches are within the range 120-130 kN/mm, a result consistent with direct stiffness measurements taken during previous studies. Therefore, the proposed methodology may be used to obtain a first insight to the track condition by means of a continuous measurement of the track combined stiffness. This offers an alternative to traditional stationary stiffness measuring devices and might be a useful complement to dedicated continuous monitoring vehicles.Cano, MJ.; MartÃnez Fernández, P.; Insa Franco, R. (2016). Measuring track vertical stiffness through dynamic monitoring. Proceedings of the Institution of Civil Engineers - Transport. 169(1). doi:10.1680/jtran.14.00081S169
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A triple protostar system formed via fragmentation of a gravitationally unstable disk
Binary and multiple star systems are a frequent outcome of the star formation process(1,2) and as a result almost half of all stars with masses similar to that of the Sun have at least one companion star(3). Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large-scale fragmentation of turbulent gas cores and filaments(4,5) or smaller-scale fragmentation of a massive protostellar disk due to gravitational instability(6,7). Observational evidence for turbulent fragmentation on scales of more than 1,000 astronomical units has recently emerged(8,9). Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems(10-13). The triple protostar system L1448 IRS3B is an ideal system with which to search for evidence of disk fragmentation as it is in an early phase of the star formation process, it is likely to be less than 150,000 years old(14) and all of the protostars in the system are separated by less than 200 astronomical units. Here we report observations of dust and molecular gas emission that reveal a disk with a spiral structure surrounding the three protostars. Two protostars near the centre of the disk are separated by 61 astronomical units and a tertiary protostar is coincident with a spiral arm in the outer disk at a separation of 183 astronomical units(13). The inferred mass of the central pair of protostellar objects is approximately one solar mass, while the disk surrounding the three protostars has a total mass of around 0.30 solar masses. The tertiary protostar itself has a minimum mass of about 0.085 solar masses. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150 and 320 astronomical units, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars
All-sky Search for High-Energy Neutrinos from Gravitational Wave Event GW170104 with the ANTARES Neutrino Telescope
Advanced LIGO detected a significant gravitational wave signal (GW170104)
originating from the coalescence of two black holes during the second
observation run on January 4, 2017. An all-sky high-energy
neutrino follow-up search has been made using data from the ANTARES neutrino
telescope, including both upgoing and downgoing events in two separate
analyses. No neutrino candidates were found within s around the GW
event time nor any time clustering of events over an extended time window of
months. The non-detection is used to constrain isotropic-equivalent
high-energy neutrino emission from GW170104 to less than
erg for a spectrum
The ANTARES Collaboration: Contributions to ICRC 2017 Part I: Neutrino astronomy (diffuse fluxes and point sources)
Papers on neutrino astronomy (diffuse fluxes and point sources, prepared for
the 35th International Cosmic Ray Conference (ICRC 2017, Busan, South Korea) by
the ANTARES Collaboratio
Modest dust settling in the IRAS04302+2247 Class I protoplanetary disk
We present new VLA observations, between 6.8mm and 66mm, of the edge-on
Class~I disk IRAS04302+2247. Observations at 6.8mm and 9.2mm lead to the
detection of thermal emission from the disk, while shallow observations at the
other wavelengths are used to correct for emission from other processes. The
disk radial brightness profile transitions from broadly extended in previous
ALMA 0.9mm and 2.1mm observations to much more centrally brightened at 6.8mm
and 9.2mm, which can be explained by optical depth effects. The radiative
transfer modeling of the 0.9mm, 2.1mm, and 9.2mm data suggests that the grains
are smaller than 1cm in the outer regions of the disk and allows us to obtain
the first lower limit for the scale height of grains emitting at millimeter
wavelengths in a protoplanetary disk. We find that the millimeter dust scale
height is between 1au and 6au at a radius 100au from the central star, while
the gas scale height is estimated to be about 7au, indicating a modest level of
settling. The estimated dust height is intermediate between less evolved Class
0 sources, that are found to be vertically thick, and more evolved Class II
sources, which show a significant level of settling. This suggests that we are
witnessing an intermediate stage of dust settling.Comment: Accepted for publication in the Astrophysical Journa
The ANTARES Collaboration: Contributions to ICRC 2017 Part II: The multi-messenger program
Papers on the ANTARES multi-messenger program, prepared for the 35th
International Cosmic Ray Conference (ICRC 2017, Busan, South Korea) by the
ANTARES Collaboratio
The ANTARES Collaboration: Contributions to ICRC 2017 Part III: Searches for dark matter and exotics, neutrino oscillations and detector calibration
Papers on the searches for dark matter and exotics, neutrino oscillations and
detector calibration, prepared for the 35th International Cosmic Ray Conference
(ICRC 2017, Busan, South Korea) by the ANTARES Collaboratio
Duty cycle of the radio galaxy B2 0258+35
Radio loud Active Galactic Nuclei are episodic in nature, cycling through
periods of activity and quiescence. In this work we investigate the duty cycle
of the radio galaxy B2~0258+35, which was previously suggested to be a
restarted radio galaxy based on its morphology. The radio source consists of a
pair of kpc-scale jets embedded in two large-scale lobes (~240 kpc) with
relaxed shape and very low surface brightness, which resemble remnants of a
past AGN activity. We have combined new LOFAR data at 145 MHz and new SRT data
at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral
properties of the outer lobes and derive their age. Interestingly, the spectrum
of both the outer Northern and Southern lobes is not ultra-steep as expected
for an old ageing plasma with spectral index values equal to and in
the outer Northern lobe, and in the outer
Southern lobe. Moreover, despite the wide frequency coverage available for the
outer Northern lobe (145-6600~MHz), we do not identify a significant spectral
curvature (SPC0.2). While mechanisms such as in-situ particle
reacceleration, mixing or compression can temporarily play a role in preventing
the spectrum from steepening, in no case seem the outer lobes to be compatible
with being very old remnants of past activity as previously suggested (with age
80 Myr). We conclude that either the large-scale lobes are still
fuelled by the nuclear engine or the jets have switched off no more than a few
tens of Myr ago. Our study shows the importance of combining morphological and
spectral properties to reliably classify the evolutionary stage of low surface
brightness, diffuse emission that low frequency observations are revealing
around a growing number of radio sources.Comment: 13 pages, 4 figures, 6 tables, A&A accepte
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