10,567 research outputs found
A photometric and spectroscopic study of the brightest northern Cepheids. III. A high-resolution view of Cepheid atmospheres
We present new high-resolution (R=40000) spectroscopic observations of 18
bright northern Cepheids carried out at David Dunlap Observatory, in 1997. The
measurements mainly extend those of presented in Paper I adding three more
stars (AW Per, SV Vul, T Mon). The spectra were obtained in the interval of
5900 A and 6660 A. New radial velocities determined with the cross-correlation
technique and the bisector technique are presented. We found systematic
differences between the spectroscopic and CORAVEL-type measurements as large as
1-3 km/s in certain phases. We performed Baade-Wesselink analysis for CK Cam
discovered by the Hipparcos satellite. The resulting radius is 31+/-1 Ro, which
is in very good agreement with recent period-radius relation by Gieren et al.
(1999). Observational pieces of evidence of possible velocity gradient
affecting the individual line profiles are studied. The FWHM of the metallic
lines, similarly to the velocity differences, shows a very characteristic phase
dependence, illustrating the effect of global compression in the atmosphere.
The smallest line widths always occur around the maximal radius, while the
largest FWHM is associated with the velocity reversal before the minimal
radius. Three first overtone pulsators do not follow the general trend: the
largest FWHM in SU Cas and SZ Tau occurs after the smallest radius, during the
expansion, while in V1334 Cyg there are only barely visible FWHM-variations.
The possibility of a bright yellow companion of V1334 Cyg is briefly discussed.
The observed line profile asymmetries can be partly associated with the
velocity gradient, which is also supported by the differences between
individual line velocities of different excitation potentials.Comment: 13 pages, 9 figures, accepted for publication in MNRA
Mass and orbit constraints of the gamma-ray binary LS 5039
We present the results of space-based photometric and ground-based
spectroscopic observing campaigns on the gamma-ray binary LS 5039. The new
orbital and physical parameters of the system are similar to former results,
except we found a lower eccentricity. Our MOST-data show that any broad-band
optical photometric variability at the orbital period is below the 2 mmag
level. Light curve simulations support the lower value of eccentricity and
imply that the mass of the compact object is higher than 1.8 solar masses.Comment: 2 pages, 1 figure (with 2 panels); to be published in the
Proceedings: From Interacting Binaries to Exoplanets: Essential Modeling
Tools, IAU Symposium 282 (18-22 July, 2011, Tatranska Lomnica, Slovakia
Characterisation and textural analysis of Middle Bronze Age Transdanubian inlaid wares of the Encrusted Pottery Culture, Hungary: a preliminary study
Inlaid ceramics belonging to the Encrusted Pottery Culture and dated to the Middle Bronze Age (2000–1500 BC) are highly distinctive vessels with complex decorative motifs found in large numbers in the Transdanubia region of Hungary. Despite this considerable corpus of material there has been little systematic investigation of the composition of the inlays. Micro-analysis of Transdanubian inlaid wares by X-ray diffraction (XRD), micro-Fourier transform infrared microscopy (FT-IR), and scanning electron microscopy (SEM) provides new compositional, structural and textural information on the inlays. In contrast to common statements in the literature regarding the materials used to make inlays, these new data show that the majority of inlays are composed of hydroxyapatite (bone) that was previously ashed, although some of the inlays are composed of calcium carbonate. Additional compositional and textural variation in the bone inlays suggests that bone material from different skeletal elements and/or of different age may have been used, and that contrasting recipes for inlay preparation were employed during fabrication. These results suggest that the production of inlaid vessels of the Encrusted Pottery Culture was more complex than has hitherto been thought
Node counting in wireless ad-hoc networks
We study wireless ad-hoc networks consisting of small microprocessors with
limited memory, where the wireless communication between the processors can be highly unreliable. For this setting, we propose a number of algorithms to estimate the number of nodes in the network, and the number of direct neighbors of each node. The algorithms are simulated, allowing comparison of their performance
Selecting molecules in the vibrational and rotational ground state by deflection
A beam of diatomic molecules scattered off a standing wave laser mode splits
according to the rovibrational quantum state of the molecules. Our numerical
calculation shows that single state resolution can be achieved by properly
tuned, monochromatic light. The proposed scheme allows for selecting
non-vibrating and non-rotating molecules from a thermal beam, implementing a
laser Maxwell's demon to prepare a rovibrationally cold molecular ensemble.Comment: 11 pages, LaTeX. To appear in the European Physical Journal
Generalized Kac's Lemma for Recurrence Time in Iterated Open Quantum Systems
We consider recurrence to the initial state after repeated actions of a
quantum channel. After each iteration a projective measurement is applied to
check recurrence. The corresponding return time is known to be an integer for
the special case of unital channels, including unitary channels. We prove that
for a more general class of quantum channels the expected return time can be
given as the inverse of the weight of the initial state in the steady state.
This statement is a generalization of the Kac lemma for classical Markov
chains
Dynamical Equations from a First-Order Perturbative Superspace Formulation of 10D N=1 String-Corrected Supergravity (I)
Utilizing a first-order perturbative superspace approach, we derive the
bosonic equations of motion for the 10D, N = 1 supergravity fields. We give the
Lagrangian corresponding to these equations derived from superspace geometry.
Moreover, the equivalence of this Lagrangian to the first-order perturbative
component level Lagrangian of anomaly-free supergravity is proven. Our
treatment covers both the two-form and six-form formulations.Comment: 20 pages, no figures, references and note in proof adde
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