4,562 research outputs found
The 2HWC HAWC Observatory Gamma Ray Catalog
We present the first catalog of TeV gamma-ray sources realized with the
recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the
most sensitive wide field-of-view TeV telescope currently in operation, with a
1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an
instantaneous field of view >1.5 sr and >90% duty cycle, it continuously
surveys and monitors the sky for gamma ray energies between hundreds GeV and
tens of TeV.
HAWC is located in Mexico at a latitude of 19 degree North and was completed
in March 2015. Here, we present the 2HWC catalog, which is the result of the
first source search realized with the complete HAWC detector. Realized with 507
days of data and represents the most sensitive TeV survey to date for such a
large fraction of the sky. A total of 39 sources were detected, with an
expected contamination of 0.5 due to background fluctuation. Out of these
sources, 16 are more than one degree away from any previously reported TeV
source. The source list, including the position measurement, spectrum
measurement, and uncertainties, is reported. Seven of the detected sources may
be associated with pulsar wind nebulae, two with supernova remnants, two with
blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa
Multi-technical approach for the characterization of polychrome decorative surfaces at Spanish Mission Churches in Nueva Vizcaya (Chihuahua, Mexico)
An interdisciplinary and multi-institutional group of science and art conservation specialists has provided new insight into the painting materials used in the polychrome walls and wooden ceilings in four seventeenth century Spanish colonial churches of Nueva Vizcaya (Chihuahua, Mexico). A multi-analytical study of the decorative surfaces was performed in situ using spectroscopic approaches (XRF, FORS), False Colour Infrared Reflectography–IRFC, as well as micro sampling (ATR-FTIR, LM, GC/MS). A survey of natural resources and study (ATR-FTIR, LM) was carried out to elucidate the natural occurrence of a select number of materials in the surrounding areas of the churches. The present paper presents a multi-analytical study and characterization of green, red-orange and black colour pigments and binders selected from the decorative surfaces. The aim of this study is to highlight relationships between local materials and those from the original polychrome ceilings, in order to understand the material and technological influences that converged in the Spanish colonial architecture of northern Mexico
Bright Stars and Recent Star Formation in the Irregular Magellanic Galaxy NGC2366
The stellar content of the Im galaxy NGC 2366 is discussed on the basis of
CCD BVR photometry. The three brightest blue and red stars have been used to
estimate its distance, obtaining a balue of 2.9 Mpc. The spatial distribution
of the young stellar population is discussed in the light of the integrated
color indices and the color-magnitude diagrams of different zones of the
galaxy. A generalized star formation burst seems to have taken place about 50
Myr ago. The youngest stars are preferentially formed in the South-West part of
the bar, where the giant HII complex NGC 2363 is located, being younger and
bluer. The bar seems to play a role favouring star formation in one of its
extremes. Self-propagation however, does not seem to be triggering star
formation at large scale. A small region, populated by very young stars has
also been found at the East of the galaxy.Comment: Astronomical Journal, accepted. This is a uuencoded, compressed, tar
file (102 Kbytes) of 1 text, 1 table postscript files. Figures are retrieved
as a separate file. One single file with all figures and tables (552Kb) also
available from http://www.ast.cam.ac.uk/~etelles/astronomy.htm
LYACOLORE: synthetic datasets for current and future Lyman-alpha forest BAO surveys
The statistical power of Lyman-α forest Baryon Acoustic Oscillation (BAO) measurements is set to increase significantly in the coming years as new instruments such as the Dark Energy Spectroscopic Instrument deliver progressively more constraining data. Generating mock datasets for such measurements will be important for validating analysis pipelines and evaluating the effects of systematics. With such studies in mind, we present LyaCoLoRe: a package for producing synthetic Lyman-α forest survey datasets for BAO analyses. LyaCoLoRe transforms initial Gaussian random field skewers into skewers of transmitted flux fraction via a number of fast approximations. In this work we explain the methods of producing mock datasets used in LyaCoLoRe, and then measure correlation functions on a suite of realisations of such data. We demonstrate that we are able to recover the correct BAO signal, as well as large-scale bias parameters similar to literature values. Finally, we briefly describe methods to add further astrophysical effects to our skewers—high column density systems and metal absorbers—which act as potential complications for BAO analyses
The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in
the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent
a series of upgrades, involving the exchange of the MAGIC-I camera and its
trigger system, as well as the upgrade of the readout system of both
telescopes. We use observations of the Crab Nebula taken at low and medium
zenith angles to assess the key performance parameters of the MAGIC stereo
system. For low zenith angle observations, the standard trigger threshold of
the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources
with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula
flux in 50 h of observations. The angular resolution, defined as the sigma of a
2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while
the energy resolution is 16%. We also re-evaluate the effect of the systematic
uncertainty on the data taken with the MAGIC telescopes after the upgrade. We
estimate that the systematic uncertainties can be divided in the following
components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for
the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle
Physic
Probing the quadrupole transition strength of C15 via deuteron inelastic scattering
Deuteron elastic scattering from C and inelastic scattering reactions to the first excited state of C were studied using a radioactive beam of C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length δd = 1.04(11) fm has been extracted from the differential cross sections of inelastic scattering to the first excited state. The ratio of neutron and proton matrix elements Mn/Mp = 3.6(4) has been determined from this quadrupole transition. Neutron effective charges and core-polarization parameters of C were determined and discussed. Results from ab initio no-core configuration interaction calculations were also compared with the experimental observations. This result supports a moderate core decoupling effect of the valence neutron in C similarly to its isotone O, in line with the interpretation of other neutron-rich carbon isotopes.Deuteron elastic scattering from 15C and inelastic scattering reactions to the first excited state of 15C were studied using a radioactive beam of 15C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length δd = 1.04(11) fm has been extracted from the differential cross sections of inelastic scattering to the first excited state. The ratio of neutron and proton matrix elements Mn/Mp = 3.6(4) has been determined from this quadrupole transition. Neutron effective charges and core-polarization parameters of 15C were determined and discussed. Results from ab-initio no-core configuration interaction calculations were also compared with the experimental observations. This result supports a moderate core decoupling effect of the valence neutron in 15C similarly to its isotone 17O, in line with the interpretation of other neutron-rich carbon isotopes
Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008
The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays
by MAGIC in spring 2007. Before that the source was little studied in different
wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in
spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio
observatory, Bell and KVA optical telescopes and the Swift and AGILE
satellites. MAGIC observations span from March to May, 2008 for a total of 27.9
hours, of which 19.4 hours remained after quality cuts. The light curve showed
no significant variability. The differential VHE spectrum could be described
with a power-law function. Both results were similar to those obtained during
the discovery. Swift XRT observations revealed an X-ray flare, characterized by
a harder when brighter trend, as is typical for high synchrotron peak BL Lac
objects (HBL). Strong optical variability was found during the campaign, but no
conclusion on the connection between the optical and VHE gamma-ray bands could
be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike
concluded in previous work based on nonsimultaneous data, and is well described
by a standard one zone synchrotron self Compton model. We also performed a
study on the source classification. While the optical and X-ray data taken
during our campaign show typical characteristics of an HBL, we suggest, based
on archival data, that 1ES 1011+496 is actually a borderline case between
intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA
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