151 research outputs found
The binary companion mass ratio distribution: an imprint of the star formation process?
We explore the effects of dynamical evolution in dense clusters on the
companion mass ratio distribution (CMRD) of binary stars. Binary systems are
destroyed by interactions with other stars in the cluster, lowering the total
binary fraction and significantly altering the initial semi-major axis
distribution. However, the shape of the CMRD is unaffected by dynamics; an
equal number of systems with high mass ratios are destroyed compared to systems
with low mass ratios. We might expect a weak dependence of the survivability of
a binary on its mass ratio because its binding energy is proportional to both
the primary and secondary mass components of the system. However, binaries are
broken up by interactions in which the perturbing star has a significantly
higher energy (by a factor of >10, depending on the particular binary
properties) than the binding energy of the binary, or through multiple
interactions in the cluster. We therefore suggest that the shape of the
observed binary CMRD is an outcome of the star formation process, and should be
measured in preference to the distributions of orbital parameters, such as the
semi-major axis distribution.Comment: 8 pages, 4 figures, accepted for publication in MNRA
Imaging the Inner and Outer Gaps of the Pre-Transitional Disk of HD 169142 at 7 mm
We present Very Large Array observations at 7 mm that trace the thermal
emission of large dust grains in the HD 169142 protoplanetary disk. Our images
show a ring of enhanced emission of radius ~25-30 AU, whose inner region is
devoid of detectable 7 mm emission. We interpret this ring as tracing the rim
of an inner cavity or gap, possibly created by a planet or a substellar
companion. The ring appears asymmetric, with the western part significantly
brighter than the eastern one. This azimuthal asymmetry is reminiscent of the
lopsided structures that are expected to be produced as a consequence of
trapping of large dust grains. Our observations also reveal an outer annular
gap at radii from ~40 to ~70 AU. Unlike other sources, the radii of the inner
cavity, the ring, and the outer gap observed in the 7 mm images, which trace
preferentially the distribution of large (mm/cm sized) dust grains, coincide
with those obtained from a previous near-infrared polarimetric image, which
traces scattered light from small (micron- sized) dust grains. We model the
broad-band spectral energy distribution and the 7 mm images to constrain the
disk physical structure. From this modeling we infer the presence of a small
(radius ~0.6 AU) residual disk inside the central cavity, indicating that the
HD 169142 disk is a pre-transitional disk. The distribution of dust in three
annuli with gaps in between them suggests that the disk in HD 169142 is being
disrupted by at least two planets or substellar objects.Comment: Accepted by ApJ Letters, 16 pages, 3 figures, ApJ Letters 201
Binary Formation Mechanisms: Constraints from the Companion Mass Ratio Distribution
We present a statistical comparison of the mass ratio distribution of
companions, as observed in different multiplicity surveys, to the most recent
estimate of the single object mass function (Bochanski et al. 2010). The main
goal of our analysis is to test whether or not the observed companion mass
ratio distribution (CMRD) as a function of primary star mass and star formation
environment is consistent with having been drawn from the field star IMF. We
consider samples of companions for M dwarfs, solar type and intermediate mass
stars, both in the field as well as clusters or associations, and compare them
with populations of binaries generated by random pairing from the assumed IMF
for a fixed primary mass. With regard to the field we can reject the hypothesis
that the CMRD was drawn from the IMF for different primary mass ranges: the
observed CMRDs show a larger number of equal-mass systems than predicted by the
IMF. This is in agreement with fragmentation theories of binary formation. For
the open clusters {\alpha} Persei and the Pleiades we also reject the IMF
random- pairing hypothesis. Concerning young star-forming regions, currently we
can rule out a connection between the CMRD and the field IMF in Taurus but not
in Chamaeleon I. Larger and different samples are needed to better constrain
the result as a function of the environment. We also consider other companion
mass functions (CMF) and we compare them with observations. Moreover the CMRD
both in the field and clusters or associations appears to be independent of
separation in the range covered by the observations. Combining therefore the
CMRDs of M and G primaries in the field and intermediate mass primary binaries
in Sco OB2 for mass ratios, q = M2/M1, from 0.2 to 1, we find that the best
chi-square fit follows a power law dN/dq \propto q^{\beta}, with {\beta} =
-0.50 \pm 0.29, consistent with previous results.Comment: 9 pages, 9 figures, Accepted for publication in The Astrophysical
Journa
Three years of harvest with the vector vortex coronagraph in the thermal infrared
For several years, we have been developing vortex phase masks based on
sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto
diamond substrates, these AGPMs are currently designed to be used in the
thermal infrared (ranging from 3 to 13 {\mu}m). Our AGPMs were first installed
on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and
Keck/NIRC2 in 2015. In this paper, we review the development, commissioning,
on-sky performance, and early scientific results of these new coronagraphic
modes and report on the lessons learned. We conclude with perspectives for
future developments and applications.Comment: To appear in SPIE proceedings vol. 990
Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment
The Deep Underground Neutrino Experiment (DUNE) will produce world-leading
neutrino oscillation measurements over the lifetime of the experiment. In this
work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in
the neutrino sector, and to resolve the mass ordering, for exposures of up to
100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed
uncertainties on the flux prediction, the neutrino interaction model, and
detector effects. We demonstrate that DUNE will be able to unambiguously
resolve the neutrino mass ordering at a 3 (5) level, with a 66
(100) kt-MW-yr far detector exposure, and has the ability to make strong
statements at significantly shorter exposures depending on the true value of
other oscillation parameters. We also show that DUNE has the potential to make
a robust measurement of CPV at a 3 level with a 100 kt-MW-yr exposure
for the maximally CP-violating values \delta_{\rm CP}} = \pm\pi/2.
Additionally, the dependence of DUNE's sensitivity on the exposure taken in
neutrino-enhanced and antineutrino-enhanced running is discussed. An equal
fraction of exposure taken in each beam mode is found to be close to optimal
when considered over the entire space of interest
Long-baseline neutrino oscillation physics potential of the DUNE experiment
The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5σ, for all ΑCP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3σ (5σ) after an exposure of 5 (10) years, for 50% of all ΑCP values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to sin22θ13 to current reactor experiments
First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber with an active volume of 7.2× 6.1× 7.0 m3. It is installed at the CERN Neutrino Platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 GeV/c to 7 GeV/c. Beam line instrumentation provides accurate momentum measurements and particle identification. The ProtoDUNE-SP detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment, and it incorporates full-size components as designed for that module. This paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. It presents the first results on ProtoDUNE-SP\u27s performance, including noise and gain measurements, dE/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. The measured values meet or exceed the specifications for the DUNE far detector, in several cases by large margins. ProtoDUNE-SP\u27s successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design
Long-baseline neutrino oscillation physics potential of the DUNE experiment
The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5σ, for all δ_(CP) values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3σ (5σ) after an exposure of 5 (10) years, for 50% of all δ_(CP) values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to sin²θ₁₃ to current reactor experiments
A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE
This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model
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