scholarly journals Unexpectedly strong effect of supergranulation on the detectability of Earth twins orbiting Sun-like stars with radial velocities

2019 ◽  
Vol 625 ◽  
pp. L6 ◽  
Author(s):  
N. Meunier ◽  
A.-M. Lagrange
Keyword(s):  
Detection Rate ◽  
Current Knowledge ◽  
Magnetic Activity ◽  
Radial Velocities ◽  
The Other ◽  
Habitable Zone ◽  
Velocity Measurements ◽  
Surface Flows ◽  
Earth Like Planets ◽  
Low Mass

Context. Magnetic activity and surface flows at different scales pertub radial velocity measurements. This affects the detectability of low-mass exoplanets. Aims. In these flows, the effect of supergranulation is not as well characterized as the other flows, and we wish to estimate its effect on the detection of Earth-like planets in the habitable zone of Sun-like stars. Methods. We produced time series of radial velocities due to oscillations, granulation, and supergranulation, and estimated the detection limit for a G2 star and a period of 300 days. We also studied in detail the behavior of the power when the signal of a 1 MEarth planet was superposed on the signal from the stellar flows. Results. We find that the detection rate does not reach 100% except for the supergranulation level we assume, which is still optimistic, and for an excellent sampling. Conclusions. We conclude that with current knowledge, it is a very challenging task to find Earth twins around Sun-like stars with our current capabilities.

scholarly journals How the planetary research helps to the stellar dynamo understanding

2012 ◽  
Vol 8 (S294) ◽  
pp. 471-475
Author(s):  
I. Boisse ◽  
M. Oshagh ◽  
C. Lovis ◽  
N. C. Santos ◽  
X. Dumusque ◽  
...  
Keyword(s):  
Planetary System ◽  
Magnetic Activity ◽  
Doppler Imaging ◽  
Habitable Zone ◽  
Stellar Activity ◽  
Term Variation ◽  
Solar Type ◽  
Low Mass ◽  
Stellar Dynamo

AbstractMost of the exoplanet science is dependent on the stellar knowledge. One of them that has to be understood is the magnetic activity when we search for planets with radial velocity or photometry measurements. The main shape of stellar activity and spots properties have to be understood, for example, to choose the best targets to search for low-mass planets in the habitable zone or to derive the accurate parameters of a planetary system. With that aim, we show in this presentation how these studies lead to give clues on spots latitudes and on the long term variation of stellar activity. The properties of magnetic activity on the low rotators solar-type stars are not easily reachable by other techniques (spectropolarimetry or Doppler imaging) and these studies should be used to constrain theories of stellar dynamo.

scholarly journals Search for Low-Mass Planets Around Late-M Dwarfs Using IRD

2012 ◽  
Vol 8 (S293) ◽  
pp. 201-203
Author(s):  
Masashi Omiya ◽  
Bun'ei Sato ◽  
Hiroki Harakawa ◽  
Masayuki Kuzuhara ◽  
Teruyuki Hirano ◽  
...  
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Near Infrared ◽  
Frequency Comb ◽  
Habitable Zone ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
Low Mass ◽  
Rocky Planets ◽  
Theoretical Simulations

AbstractWe have a plan to conduct a Doppler planet search for low-mass planets around nearby middle-to-late M dwarfs using IRD. IRD is the near-infrared high-precision radial velocity instrument for the Subaru 8.2-m telescope. We expect to achieve the accuracy of the radial velocity measurements of 1 m/s using IRD with a frequency comb as a wavelengh calibrator. Thus, we would detect super-Earths in habitable zone and low-mass rocky planets in close-in orbits around late-M dwarfs. In this survey, we aim to understand and discuss statistical properties of low-mass planets around low-mass M dwarfs compared with those derived from theoretical simulations.

scholarly journals Unraveling the Mystery of Exozodiacal Dust

2013 ◽  
Vol 8 (S299) ◽  
pp. 338-339 ◽  
Author(s):  
S. Ertel ◽  
J.-C. Augereau ◽  
P. Thébault ◽  
O. Absil ◽  
A. Bonsor ◽  
...  
Keyword(s):  
Spectral Type ◽  
Detection Rate ◽  
Near Infrared ◽  
Habitable Zone ◽  
Direct Imaging ◽  
Preliminary Results ◽  
Dust Clouds ◽  
Zodiacal Dust ◽  
Earth Like Planets ◽  
Mere Presence

AbstractExozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the Habitable Zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemispheres. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. We focus here on presenting the observational work carried out by our team.

scholarly journals Precision Radial Velocities in the Near Infrared with TEDI

2008 ◽  
Vol 4 (S253) ◽  
pp. 157-161 ◽  
Author(s):  
James P. Lloyd ◽  
Agnieszka Czeszumska ◽  
Jerry Edelstein ◽  
David Erskine ◽  
Michael Feuerstein ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Habitable Zones ◽  
Low Mass ◽  
Transit Method

AbstractThe TEDI (TripleSpec - Exoplanet Discovery Instrument) is a dedicated instrument for the near-infrared radial velocity search for planetary companions to low-mass stars with the goal of achieving meters-per-second radial velocity precision. Heretofore, such planet searches have been limited almost entirely to the optical band and to stars that are bright in this band. Consequently, knowledge about planetary companions to the populous but visibly faint low-mass stars is limited. In addition to the opportunity afforded by precision radial velocity searches directly for planets around low mass stars, transits around the smallest M dwarfs offer a chance to detect the smallest possible planets in the habitable zones of the parent stars. As has been the the case with followup of planet candidates detected by the transit method requiring radial velocity confirmation, the capability to undertake efficient precision radial velocity measurements of mid-late M dwarfs will be required. TEDI has been commissioned on the Palomar 200” telescope in December 2007, and is currently in a science verification phase.

Exoplanets: the quest for Earth twins

2011 ◽  
Vol 369 (1936) ◽  
pp. 572-581 ◽  
Author(s):  
Michel Mayor ◽  
Stephane Udry ◽  
Francesco Pepe ◽  
Christophe Lovis
Keyword(s):  
Planetary Systems ◽  
The Other ◽  
General Interest ◽  
Formation Mechanisms ◽  
Habitable Zone ◽  
Huge Amount ◽  
The Status ◽  
Terrestrial Life ◽  
Low Mass ◽  
The Universe

Today, more than 400 extra-solar planets have been discovered. They provide strong constraints on the structure and formation mechanisms of planetary systems. Despite this huge amount of data, we still have little information concerning the constraints for extra-terrestrial life, i.e. the frequency of Earth twins in the habitable zone and the distribution of their orbital eccentricities. On the other hand, these latter questions strongly excite general interest and trigger future searches for life in the Universe. The status of the extra-solar planets field—in particular with respect to very-low-mass planets—will be discussed and an outlook on the search for Earth twins will be given in this paper.

The pseudomalachite-ludjibaite-reichenbachite conundrum: OD description

2019 ◽  
Vol 57 (5) ◽  
pp. 571-581
Author(s):  
Emil Makovicky
Keyword(s):  
Crystal Structures ◽  
Current Knowledge ◽  
The Other ◽  
Crystal Chemical ◽  
Layer System ◽  
Coordination Polyhedra

Abstract Crystal structures of the three polymorphs of Cu5(PO4)2(OH)4, namely pseudomalachite, ludjibaite, and reichenbachite, can be described as being composed of rods perpendicular to their crystal-chemical layering. Two different sorts of rods can be defined. Type 1 rods share rows of Cu coordination polyhedra, forming a series of slabs. Slab boundaries and slab interiors represent alternating geometric OD layers of two kinds, with layer symmetries close to P21/m and , which make up two different stacking schemes of geometric OD layers in the structures of ludjibaite and pseudomalachite. Such OD layers, however, are not developed in reichenbachite. Type 2 rods are defined as having columns of PO4 tetrahedra in the corners of the rods. In the Type 2 slabs composed of these rods, geometric Pg OD layers of glide-arrayed tetrahedra alternate with more complex OD layers; in ludjibaite this system of layers is oriented diagonally with respect to the Type 1 OD layer system. Two different OD stackings of Type 2 OD layers form the ludjibaite and reichenbachite structures but not that of pseudomalachite. Thus, ludjibaite might form disordered intergrowths with either of the other two members of the triplet but reichenbachite and pseudomalachite should not form oriented intergrowths. Current knowledge concerning formation of the three polymorphs is considered.

scholarly journals Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

scholarly journals NHPP Software Reliability Model with Inflection Factor of the Fault Detection Rate Considering the Uncertainty of Software Operating Environments and Predictive Analysis

Symmetry ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 521 ◽  
Author(s):  
Song ◽  
Chang ◽  
Pham
Keyword(s):  
Fault Detection ◽  
Software Reliability ◽  
Detection Rate ◽  
The Other ◽  
Reliability Model ◽  
New Model ◽  
Software Failures ◽  
Software Failure ◽  
Software Reliability Model ◽  
Operating Environments

The non-homogeneous Poisson process (NHPP) software has a crucial role in computer systems. Furthermore, the software is used in various environments. It was developed and tested in a controlled environment, while real-world operating environments may be different. Accordingly, the uncertainty of the operating environment must be considered. Moreover, predicting software failures is commonly an important part of study, not only for software developers, but also for companies and research institutes. Software reliability model can measure and predict the number of software failures, software failure intervals, software reliability, and failure rates. In this paper, we propose a new model with an inflection factor of the fault detection rate function, considering the uncertainty of operating environments and analyzing how the predicted value of the proposed new model is different than the other models. We compare the proposed model with several existing NHPP software reliability models using real software failure datasets based on ten criteria. The results show that the proposed new model has significantly better goodness-of-fit and predictability than the other models.

EVOLUTION OF SHELL STRUCTURE IN NUCLEI

2011 ◽  
Vol 20 (08) ◽  
pp. 1663-1675 ◽  
Author(s):  
A. BHAGWAT ◽  
Y. K. GAMBHIR
Keyword(s):  
Shell Structure ◽  
Crucial Role ◽  
Field Model ◽  
Mean Field ◽  
Mass Region ◽  
The Other ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
Shell Closures ◽  
Low Mass

Systematic investigations of the pairing and two-neutron separation energies which play a crucial role in the evolution of shell structure in nuclei, are carried out within the framework of relativistic mean-field model. The shell closures are found to be robust, as expected, up to the lead region. New shell closures appear in low mass region. In the superheavy region, on the other hand, it is found that the shell closures are not as robust, and they depend on the particular combinations of neutron and proton numbers. Effect of deformation on the shell structure is found to be marginal.

The habitable zone of Earth-mass planets around 47 UMa: results for land and water worlds

2003 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
S. Franck ◽  
M. Cuntz ◽  
W. von Bloh ◽  
C. Bounama
Keyword(s):  
Surface Water ◽  
System Approach ◽  
Distinct Type ◽  
Integrated System ◽  
Habitable Zone ◽  
Stable Orbit ◽  
The Earth ◽  
Earth Like Planets ◽  
Very High

In a previous paper, we showed that Earth-type habitable planets around 47 UMa are in principle possible if a distinct set of conditions is warranted. These conditions include that the Earth-type planets have successfully formed and are orbitally stable and, in addition, that the 47 UMa star–planet system is relatively young ([lsim ]6 Gyr). We now extend this study by considering Earth-like planets with different land/ocean coverages. This study is again based on the so-called integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical and geodynamical processes. This approach implies a special characterization of the habitable zone defined for a distinct type of planet. We show that the likelihood of finding a habitable Earth-like planet on a stable orbit around 47 UMa critically depends on the percentage of the planetary land/ocean coverage. The likelihood is significantly increased for planets with a very high percentage of ocean surface (‘water worlds’).

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