21,936 research outputs found
Mode visibilities in radial velocity and intensity Sun-as-a-star helioseismic measurements
We analyze more than 5000 days of Sun-as-a-star radial velocity GOLF and
intensity VIRGO observations to measure the visibilities of the l=0, 1, 2, and
3 modes and the m-amplitude ratios of the l=2 and 3 modes in the solar acoustic
spectrum. We provide observational values that we compare to theoretical
predictions.Comment: SOHO 24 / GONG 2010 conference, to be published in JPC
Towards Syntactic Iberian Polarity Classification
Lexicon-based methods using syntactic rules for polarity classification rely
on parsers that are dependent on the language and on treebank guidelines. Thus,
rules are also dependent and require adaptation, especially in multilingual
scenarios. We tackle this challenge in the context of the Iberian Peninsula,
releasing the first symbolic syntax-based Iberian system with rules shared
across five official languages: Basque, Catalan, Galician, Portuguese and
Spanish. The model is made available.Comment: 7 pages, 5 tables. Contribution to the 8th Workshop on Computational
Approaches to Subjectivity, Sentiment and Social Media Analysis (WASSA-2017)
at EMNLP 201
The influence of binarity on the morpho-kinematics of planetary nebulae
The role of central star binarity in the shaping of planetary nebulae (PNe)
has been the subject of much debate, with single stars believed to be incapable
of producing the most highly collimated morphologies. However, observational
support for binary-induced shaping has been sadly lacking. Here, we highlight
the results of a continuing programme to spatio-kinematically model the
morphologies of all PNe known to contain a close binary central star.
Spatio-kinematical modelling is imperative for these objects, as it circumvents
the degeneracy between morphology and orientation which can adversely affect
determinations of morphology based on imaging alone. Furthermore,
spatio-kinematical modelling accurately determines the orientation of the
nebular shell, allowing the theoretically predicted perpendicular alignment,
between nebular symmetry axis and binary orbital plane, to be tested. To date,
every PN subjected to this investigation has displayed the predicted alignment,
indicating that binarity has played an important role in the formation and
evolution of these nebulae. The further results from this programme will be
key, not only in determining whether binary interaction is responsible for
shaping the studied PNe, but also in assessing the importance of binarity in
the formation and evolution of all PNe in general.Comment: 2 pages, 2 tables, proceedings of the IAU Symposium No. 283,
Planetary Nebulae: An Eye to the Futur
Geometric Morphometrics of Gary Dart Points from the Davy Crockett National Forest
Three-dimensional scans of Gary dart points recovered from the Davy Crockett National Forest are employed in tests of basal morphology by site, size (allometry), and asymmetry. Variability in basal morphology for Gary points from sites on the Davy Crockett National Forest is presented and compared to specimens from the published type books. The hypothesis that Gary basal morphology differs between sites containing Woodland-era sand temped ceramics and those where no sand tempered ceramics were recovered is then tested and the results discussed
High-Resolution Optical Spectroscopy of DY Cen: Diffuse Interstellar Bands in a Proto-Fullerene Circumstellar Environment?
We search high-resolution and high-quality VLT/UVES optical spectra of the hot R Coronae Borealis star DY Cen for electronic transitions of the C-60 molecule and diffuse interstellar bands (DIBs). We report the non-detection of the strongest C-60 electronic transitions (e. g., those at similar to 3760, 3980, and 4024 angstrom). The absence of C-60 absorption bands may support recent laboratory results, which show that the similar to 7.0, 8.5, 17.4, and 18.8 mu m emission features seen in DY Cen-and other similar objects with polycyclic-aromatic-hydrocarbon-like dominated IR spectra-are attributable to proto-fullerenes or fullerene precursors rather than to C-60. DIBs toward DY Cen are normal for its reddening; the only exception is the DIB at 6284 angstrom (possibly also the 7223 angstrom DIB) which is found to be unusually strong. We also report the detection of a new broad (FWHM similar to 2 angstrom) and unidentified feature centered at similar to 4000 angstrom. We suggest that this new band may be related to the circumstellar proto-fullerenes seen at infrared wavelengths.Director's Discretionary Time (DDT) program 284.D-5048Spanish Ministry of Economy and Competitiveness AYA-2011-27754Robert A. Welch Foundation of Houston, Texas F-634McDonald Observator
Detailed Spectral Modeling of a 3-D Pulsating Reverse Detonation Model: Too Much Nickel
We calculate detailed NLTE synthetic spectra of a Pulsating Reverse
Detonation (PRD) model, a novel explosion mechanism for Type Ia supernovae.
While the hydro models are calculated in 3-D, the spectra use an angle averaged
hydro model and thus some of the 3-D details are lost, but the overall average
should be a good representation of the average observed spectra. We study the
model at 3 epochs: maximum light, seven days prior to maximum light, and 5 days
after maximum light. At maximum the defining Si II feature is prominent, but
there is also a prominent C II feature, not usually observed in normal SNe Ia
near maximum. We compare to the early spectrum of SN 2006D which did show a
prominent C II feature, but the fit to the observations is not compelling.
Finally we compare to the post-maximum UV+optical spectrum of SN 1992A. With
the broad spectral coverage it is clear that the iron-peak elements on the
outside of the model push too much flux to the red and thus the particular PRD
realizations studied would be intrinsically far redder than observed SNe Ia. We
briefly discuss variations that could improve future PRD models.Comment: 15 pages, 4 figures, submitted to Ap
- …