564 research outputs found
Search for a circum-planetary material and orbital period variations of short-period Kepler exoplanet candidates
A unique short-period Mercury-size Kepler exoplanet candidate KIC012557548b
has been discovered recently by Rappaport et al. (2012). This object is a
transiting disintegrating exoplanet with a circum-planetary material -
comet-like tail. Close-in exoplanets, like KIC012557548b, are subjected to the
greatest planet-star interactions. This interaction may have various forms. In
certain cases it may cause formation of the comet-like tail. Strong interaction
with the host star, and/or presence of an additional planet may lead to
variations in the orbital period of the planet. Our main aim is to search for
comet-like tails similar to KIC012557548b and for long-term orbital period
variations. We are curious about frequency of comet-like tail formation among
short-period Kepler exoplanet candidates. We concentrate on a sample of 20
close-in candidates with a period similar to KIC012557548b from the Kepler
mission.Comment: 19 pages, 75 figures, AN accepte
A 10-way power divider based on a transducer and a radial junction operating in the circular TM01 mode
This work presents a 10-way Ku-band power divider using a mode transducer and a radial junction connected by an overmoded circular waveguide operating in the TM 01 mode. The circular symmetry of this mode has been exploited to obtain a power divider with the rectangular output ports radially distributed along the broad wall of the waveguides in H-plane configuration. This topology provides the same amplitude and phase for all the output ports. At the same time, a compact profile has been obtained, introducing a simple manufacturing for the two components of the divider. The first component is a mode transducer converting the TE 10 mode in the rectangular waveguide to the TM 01 mode in the circular waveguide. It is based on a novel topology providing a very high purity in the mode conversion with an attenuation for the other propagating mode, the TE 11c , higher than 60 dB. The second component is a 10-way radial junction that must work under the excitation of the TM 01 , whose special features, since this mode is not the fundamental one of the circular waveguide, will be highlighted. The final design has been validated with an experimental prototype, proposing a manufacturing based on four simple parts. This has been the key to obtain an experimental prototype with specifications in the state-of-the-art. The measured efficiency is better than 96.5% in a 16.7% relative frequency bandwidth from 11 GHz to 13 GHz, with return losses better than 25 dB in the common port. The measured difference between the signals at the output ports of the prototype is ±0.3 dB for the amplitudes and ±0.45° for the phases. A comparison of the obtained results with another divider based on the TE 01 mode shows the potential of the presented design for becoming an alternative to the more extended TE 01 -based power dividersThis work was supported by the Spanish Government through the Agencia Estatal de Investigacion, Fondo Europeo de Desarrollo Regional
(AEI/FEDER, UE), under Grant TEC2016-76070-C3-1/2-R (ADDMATE
High-performance 16-way Ku-band radial power combiner based on the TE01-circular waveguide mode
This work presents a 16-way Ku-band radial power combiner for high power and high frequency
applications, using the very low loss TE01 circular waveguide mode. The accomplished design shows
an excellent performance: the experimental prototype has a return loss better than 30 dB, with a balance
for the amplitudes of ( 0.15 dB) and ( 2.5 ) for the phases, in a 16.7% fractional bandwidth (2 GHz
centered at 12 GHz). For obtaining these outstanding specifications, required, for instance, in highfrequency
amplification or on plasma systems, a rigorous step-by-step procedure is presented. First, a
high-purity mode transducer has been designed, from the TE10 mode in the rectangular waveguide to
the TE01 mode in the circularwaveguide, with very high attenuation (>50 dB) for the other propagating
and evanescent modes in the circularwaveguide. This transducer has been manufactured and measured
in a back-to-back configuration, validating the design process. Second, an E-plane 16-way radial
power divider has been designed, where the power is coupled from the 16 non-reduced-height radial
standardwaveguides into the TE01 circularwaveguide mode, improving the insertion loss response and
removing the usual tapered transformers of previous designs limiting the power handling. Finally, both
the transducer and the divider have been assembled to make the final radial combiner. The prototype
has been carefully manufactured, showing very good agreement between the measurements and the
full-wave simulationsThe authors would like to thank INMEPRE S.A., the diligence
in the manufacturing process. This work was supported
by the Spanish government under Grant (ADDMATE) No.
TEC2016-76070-C3-1/2-R (AEI/FEDER/UE) and the program
of Comunidad de Madrid S2013/ICE-3000 (SPADERADARCM
Search for the wide-orbit massive companion of XO-7b in the follow-up radial-velocity and transit-timing data: no significant clues
XO-7b is a hot Jupiter transiting a mag G0V-type star. The
planetary system is interesting because the linear slope in the discovery
radial-velocity (RV) data indicated a wide-orbit massive companion. In 2020 we
started an RV campaign for the system with the main scientific goal to
follow-up this linear slope, and to put constraints on the orbital period of
the companion. Furthermore, we aimed at refining the system parameters and we
wanted to probe transit timing variations (TTVs) of XO-7b in order to search
for long-term dynamical signs of the companion of XO-7b in the
observed-minus-calculated (O-C) data of mid-transit times. Apart from the
discovery RVs, we obtained and analyzed 20 follow-up RV observations and TESS
photometric data. The previously observed significant linear RV slope was not
confirmed with the follow-up RV data, where we detected only a marginal linear
slope with the opposite trend. If the announced companion really exists, the
most convincing explanation is that both RV datasets were collected near its
quadrature position. Based on the RVs we estimated the minimum orbital period,
which is d, and the 'minimum'
minimum mass of the companion, which is . We did not find significant evidence of the companion of
XO-7b in the O-C dataset of mid-transit times. We can again conclude that if
the announced companion really exists, this is in agreement with previous
results that distant companions of exoplanets are only known by RV solutions.Comment: Accepted for publication in MNRA
Development of a high-performance W-band duplexer for plasma diagnosis using a single band with dual circular polarization
Discrepancia entre la información que aparece en el artículo que indica que el copyright es de Elsevier, y la información que aparece en la página de la revista y en el Copyright Clearance Center que indican © 2019 The Authors. Published by Elsevier B.V., así como que el artículo está publicado en Open Access under a Creative Commons licenceThis work presents the design and experimental validation of a high performance, compact, waveguide duplexer operating from 91.5 to 96.5 GHz for its integration in diverse W-band microwave equipment as in plasma diagnosis applications. It uses a single frequency band, with two signals discriminated by different orthogonal circular polarization, which is generated by means of a septum orthomode transducer (OMT) polarizer. Moreover, this component is optimized loaded with the horn antenna for improving the overall system performance. It is explained how these two components are integrated into a very compact duplexer, designed using efficient numerical algorithms. The manufacturing process by mean of high precision milling, and including electrical discharge machining (EDM) has led to excellent performances. The measured return loss level and isolation are higher than 30 dB, and the insertion loss level is below 0.3 dB. Finally, the key parameter in this device, which reflects the symmetry in the manufacturing process, i.e., the axial ratio, is lower than 0.6 dB for both polarizations, an excellent result showing the potential of the presented designThis work was supported by the Spanish government under grants (ADDMATE) TEC2016-76070-C3-1/2-R (Agencia Estatal de Investigación, Spain, Fondo Europeo de Desarrollo Regional: AEI/FEDER/UE) and the program of Comunidad de Madrid, Spain S2013/ICE-3000 (SPADERADARCM
The temperature dependence of the isothermal bulk modulus at 1 bar pressure
It is well established that the product of the volume coefficient of thermal
expansion and the bulk modulus is nearly constant at temperatures higher than
the Debye temperature. Using this approximation allows predicting the values of
the bulk modulus. The derived analytical solution for the temperature
dependence of the isothermal bulk modulus has been applied to ten substances.
The good correlations to the experiments indicate that the expression may be
useful for substances for which bulk modulus data are lacking
Design of a Ku-Band High-Purity Transducer for the TM01 Circular Waveguide Mode by Means of T-Type Junctions
© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksA new mode transducer for converting the TE10 rectangular waveguide mode to the TM01 circular waveguide mode is presented. The novel topology is based on two T type junctions with in-phaseexcitation at their input rectangular ports. The first one is an H-plane T-junction in rectangular waveguide. The second one differs from the standard E-plane T-junction in the excitation, which is carried out by modes excited with fields having the same in-phase polarization at the input rectangular ports, and has the output port in circular waveguide. This configuration exploits the symmetry of the modes under consideration to achieve a high-purity conversion, controlling the propagating circular waveguide TE11 mode to a maximum level of -42 dB in the whole operation band. The design bandwidth is 2 GHz centered at 12 GHz with a return loss level higher than 28 dB. In addition, the transducer can be divided in a main body plus a cover for easing the manufacturing. In order to verify the proposed geometry, a back-to-back arrangement has been measured connecting two similar aluminum transducers with four different angles between their rectangular ports (0◦, 45◦, 90◦, and 180◦). The excellent experimental results validate the novel transducer with a measured converting efficiency higher than 98.2% in a 16.7% relative frequency bandwidthThis work was supported by the Spanish Government (Agencia Estatal de Investigación) under Grant (ADDMATE) TEC2016-76070-C3-1/2-R (AEI/FEDER/UE
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