2,179 research outputs found
Rotational Velocities of Individual Components in Very Low Mass Binaries
We present rotational velocities for individual components of 11 very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics system. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s^(â1)), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349â25B and HD 130948C, are rotating at ~30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semimajor axes âŸ3.5 AU, have component v sin i values that differ by greater than 3Ï. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple system HD 130948AâBC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple system in our sample, GJ 569AâBab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349â25AB and 2MASS 0746+20AB, are also known radio sources
Gravity in the Local Universe : density and velocity fields using CosmicFlows-4
This article publicly releases three-dimensional reconstructions of the local
Universe gravitational field below z=0.8 that were computed using the
CosmicFlows-4 catalog of 56,000 galaxy distances and its sub-sample of 1,008
type Ia supernovae distances. The article also provides measurements of the
growth rate of structure using the pairwise correlation of radial peculiar
velocities f sigma8 = 0.38(+/-0.04) (ungrouped CF4), f sigma8 = 0.36(+/-0.05)
(grouped CF4), f sigma8 = 0.30(+/-0.06) (SNIa) and of the bulk flow in the 3D
reconstructed Local Universe of 230 +/- 136 km s-1 at 300 Mpc of distance from
the observer. The exploration of 10,000 reconstructions gives that the
distances delivered by the Cosmicflows-4 catalog are compatible with a Hubble
constant of H0 = 74.5 +/- 0.1 (grouped CF4), H0 = 75.0 +/- 0.35 (ungrouped CF4)
and H0 = 75.5 +/- 0.95 (CF4 SNIa subsample).Comment: Submitted A&A Oct 31st, 2022 / (AA/2022/45331) / Accepted January
2023 All Figures and values updated after the december 2022 major correction
in CF4 catalo
Chronic dermatomycoses of the foot as risk factors for acute bacterial cellulitis of the leg: A case-control study
Objective: To assess the role of foot dermatomycosis ( tinea pedis and onychomycosis) and other candidate risk factors in the development of acute bacterial cellulitis of the leg. Methods: A case-control study, including 243 patients ( cases) with acute bacterial cellulitis of the leg and 467 controls, 2 per case, individually matched for gender, age (+/-5 years), hospital and admission date (+/-2 months). Results: Overall, mycology-proven foot dermatomycosis was a significant risk factor for acute bacterial cellulitis (odds ratio, OR: 2.4; p < 0.001), as were tinea pedis interdigitalis (OR: 3.2; p < 0.001), tinea pedis plantaris (OR: 1.7; p = 0.005) and onychomycosis (OR: 2.2; p < 0.001) individually. Other risk factors included: disruption of the cutaneous barrier, history of bacterial cellulitis, chronic venous insufficiency and leg oedema. Conclusions: Tinea pedis and onychomycosis were found to be significant risk factors for acute bacterial cellulitis of the leg that are readily amenable to treatment with effective pharmacological therapy. Copyright (C) 2004 S. Karger AG, Basel
Deep search for companions to probable young brown dwarfs
We have obtained high contrast images of four nearby, faint, and very low
mass objects 2MASSJ04351455-1414468, SDSSJ044337.61+000205.1,
2MASSJ06085283-2753583 and 2MASSJ06524851-5741376 (here after 2MASS0435-14,
SDSS0443+00, 2MASS0608-27 and 2MASS0652-57), identified in the field as
probable isolated young brown dwarfs. Our goal was to search for binary
companions down to the planetary mass regime. We used the NAOS-CONICA adaptive
optics instrument (NACO) and its unique capability to sense the wavefront in
the near-infrared to acquire sharp images of the four systems in Ks, with a
field of view of 28"*28". Additional J and L' imaging and follow-up
observations at a second epoch were obtained for 2MASS0652-57. With a typical
contrast DKs= 4.0-7.0 mag, our observations are sensitive down to the planetary
mass regime considering a minimum age of 10 to 120 Myr for these systems. No
additional point sources are detected in the environment of 2MASS0435-14,
SDSS0443+00 and 2MASS0608-27 between 0.1-12" (i.e about 2 to 250 AU at 20 pc).
2MASS0652-57 is resolved as a \sim230 mas binary. Follow-up observations reject
a background contaminate, resolve the orbital motion of the pair, and confirm
with high confidence that the system is physically bound. The J, Ks and L'
photometry suggest a q\sim0.7-0.8 mass ratio binary with a probable semi-major
axis of 5-6 AU. Among the four systems, 2MASS0652-57 is probably the less
constrained in terms of age determination. Further analysis would be necessary
to confirm its youth. It would then be interesting to determine its orbital and
physical properties to derive the system's dynamical mass and to test
evolutionary model predictions.Comment: Research note, 5 pages, 2 tables and 3 figures, accepted to A&
A focus on L dwarfs with trigonometric parallaxes
This is an author-created, un-copyedited version of an article published in Publications of the Astronomical Society of the Pacific. Under embargo until 14 May 2019. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1538-3873/aaacc5.We report new parallax measurements for ten L and early T type dwarfs, five of which have no previous published values, using observations over 3 years at the robotic Liverpool Telescope. The resulting parallaxes and proper motions have median errors of 2\,mas and 1.5\,mas/year respectively. Their space motions indicate they are all Galactic disk members. We combined this sample with other objects with astrometry from the Liverpool Telescope and with published literature astrometry to construct a sample of 260 L and early T type dwarfs with measured parallaxes, designated the Astrometry Sample. We study the kinematics of the Astrometry Sample, and derived a solar motion of \,\kms~ with respect to the local standard of rest, in agreement with recent literature. We derive a kinematic age of 1.5-1.7\,Gyr for the Astrometry Sample assuming the age increases monotonically with the total velocity for a given disk sample. This kinematic age is less than half literature values for other low mass dwarf samples. We believe this difference arises for two reasons (1) the sample is mainly composed of mid to late L dwarfs which are expected to be relatively young and (2) the requirement that objects have a measured parallax biases the sample to the brighter examples which tend to be younger.Peer reviewedFinal Accepted Versio
Low temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers
We report on a detailed analysis of the superconducting properties of
boron-doped silicon films grown along the 001 direction by Gas Immersion Laser
Doping. The doping concentration cB has been varied up to approx. 10 at.% by
increasing the number of laser shots to 500. No superconductivity could be
observed down to 40mK for doping level below 2.5 at.%. The critical temperature
Tc then increased steeply to reach 0.6K for cB = 8 at%. No hysteresis was found
for the transitions in magnetic field, which is characteristic of a type II
superconductor. The corresponding upper critical field Hc2(0) was on the order
of 1000 G, much smaller than the value previously reported by Bustarret et al.
in Nature (London) 444, 465 (2006).Comment: 4 pages including 4 figures, submitted to PRB-Rapid Communicatio
Human rights and ethical reasoning : capabilities, conventions and spheres of public action
This interdisciplinary article argues that human rights must be understood in terms of opportunities for social participation and that social and economic rights are integral to any discussion of the subject. We offer both a social constructionist and a normative framework for a sociology of human rights which reaches beyond liberal individualism, combining insights from the work of Amartya Sen and from French convention theory. Following Sen, we argue that human rights are founded on the promotion of human capabilities as ethical demands shaped by public reasoning. Using French convention theory, we show how the terms of such deliberation are shaped by different constructions of collectively held values and the compromises reached between them. We conclude by demonstrating how our approach offers a new perspective on spheres of public action and the role these should play in promoting social cohesion, individual capabilities and human rights
The Young L Dwarf 2MASS J11193254-1137466 Is a Planetary-mass Binary
We have discovered that the extremely red, low-gravity L7 dwarf 2MASS
J11193254-1137466 is a 0.14" (3.6 AU) binary using Keck laser guide star
adaptive optics imaging. 2MASS J11193254-1137466 has previously been identified
as a likely member of the TW Hydrae Association (TWA). Using our updated
photometric distance and proper motion, a kinematic analysis based on the
BANYAN II model gives an 82% probability of TWA membership. At TWA's 103
Myr age and using hot-start evolutionary models, 2MASS J11193254-1137466AB is a
pair of brown dwarfs, making it the
lowest-mass binary discovered to date. We estimate an orbital period of
years. One component is marginally brighter in band but
fainter in band, making this a probable flux-reversal binary, the first
discovered with such a young age. We also imaged the spectrally similar TWA L7
dwarf WISEA J114724.10-204021.3 with Keck and found no sign of binarity. Our
evolutionary model-derived estimate for WISEA J114724.10-204021.3
is 230 K higher than for 2MASS J11193254-1137466AB, at odds with their
spectral similarity. This discrepancy suggests that WISEA J114724.10-204021.3
may actually be a tight binary with masses and temperatures very similar to
2MASS J11193254-1137466AB, or further supporting the idea that near-infrared
spectra of young ultracool dwarfs are shaped by factors other than temperature
and gravity. 2MASS J11193254-1137466AB will be an essential benchmark for
testing evolutionary and atmospheric models in the young planetary-mass regime.Comment: Accepted to ApJ Letters. 8 pages, 3 figures, 2 table
DISCOVERY OF A LOW-LUMINOSITY, TIGHT SUBSTELLAR BINARY AT THE T/Y TRANSITION
We have discovered that the brown dwarf WISEJ014656.66+423410.0 is a close
binary (0.08750.0021 arcsec, 0.93 AU) from Keck laser
guide star adaptive optics imaging. Our photometry for this system reveals that
both components are less luminous than those in any known substellar binary.
Combining a new integrated-light spectrum (T9p) and resolved YJH-band
photometry from Keck allows us to perform spectral decomposition and assign
component types of T9 and Y0. Many of the unusual features in the spectrum
might be explained by high surface gravity: Y-band peak broadened to the blue;
J-band peak broadened to the red; H-band peak shifted slightly to the red; and
red Y-J colors. Interestingly, the very low component luminosities imply that
the T9 primary is unexpectedly cold ( = 34545 K assuming an
age of 10 Gyr), making it 100 K cooler than any other late-T dwarf and
comparable to Y dwarfs. One intriguing explanation for this apparent
discrepancy is that the J- and H-band spectral features that trigger the
transition from T to Y spectral types are highly gravity-dependent. This can be
tested directly in the very near future by orbit monitoring. We constrain the
orbital period to be 10 yr by combining evolutionary model-based mass
estimates for the components (1221 , 1 at 10
Gyr) with a statistical constraint on the semimajor axis (1.3 AU).
Such a period is shorter than any other known T/Y transition binary, meaning
that WISEJ0146+4234AB will likely yield a dynamical mass within the next few
years.Comment: Accepted to ApJ (2015 Feb 14); 24 pages, 4 figures, 5 table
TESTING the BINARY TRIGGER HYPOTHESIS in FUors
We present observations of three FU Orionis objects (hereafter, FUors) with nonredundant aperture-mask interferometry at 1.59 Όm and 2.12 Όm that probe for binary companions on the scale of the protoplanetary disk that feeds their accretion outbursts. We do not identify any companions to V1515 Cyg or HBC 722, but we do resolve a close binary companion to V1057 Cyg that is at the diffraction limit ( mas or 30 ± 5 au) and currently much fainter than the outbursting star ( mag). Given the flux excess of the outbursting star, we estimate that the mass of the companion () is similar to or slightly below that of the FUor itself, and therefore it resembles a typical T Tauri binary system. Our observations only achieve contrast limits of mag, and hence we are only sensitive to companions that were near or above the pre-outburst luminosity of the FUors. It remains plausible that FUor outbursts could be tied to the presence of a close binary companion. However, we argue from the system geometry and mass reservoir considerations that these outbursts are not directly tied to the orbital period (i.e., occurring at periastron passage), but instead must only occur infrequently
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