scholarly journals Sensitivity of gravito-inertial modes to differential rotation in intermediate-mass main-sequence stars

2018 ◽  
Vol 618 ◽  
pp. A24 ◽  
Author(s):  
T. Van Reeth ◽  
J. S. G. Mombarg ◽  
S. Mathis ◽  
A. Tkachenko ◽  
J. Fuller ◽  
...  
Keyword(s):  
Differential Rotation ◽  
Stellar Structure ◽  
Time Base ◽  
Stellar Rotation ◽  
Single Star ◽  
Spacing Pattern ◽  
Surface Rotation ◽  
Long Time ◽  
Core Rotation ◽  
The Impact

Context. While rotation has a major impact on stellar structure and evolution, its effects are not well understood. Thanks to high-quality and long-time base photometric observations obtained with recent space missions, we are now able to study stellar rotation more precisely.Aims. We aim to constrain radial differential rotation profiles inγDoradus (γDor) stars, and to develop new theoretical seismic diagnosis for such stars with rapid and potentially non-uniform rotation.Methods. We have derived a new asymptotic description which accounts for the impact of weak differential near-core rotation on gravity-mode period spacings. The theoretical predictions are illustrated from pulsation computations with the code GYRE and compared with observations ofγDor stars. When possible, we also derived the surface rotation rates in these stars by detecting and analysing signatures of rotational modulation, and computed the core-to-surface rotation ratios.Results. Stellar rotation must be strongly differential before its effects on period spacing patterns can be detected, unless multiple period spacing patterns can be compared. Six stars in our sample exhibit a single unexplained period spacing pattern of retrograde modes. We hypothesise that these are Yanai modes. Finally, we find signatures of rotational spot modulation in the photometric data of eight targets.Conclusions. If only one period spacing pattern is detected and analysed for a star, it is difficult to detect differential rotation. A rigidly rotating model will often provide the best solution. Differential rotation can only be detected when multiple period spacing patterns have been found for a single star or its surface rotation rate is known as well. This is the case for eight of the stars in our sample, revealing surface-to-core rotation ratios between 0.95 and 1.05.

scholarly journals Starspots properties and stellar activity from planetary transits

2016 ◽  
Vol 12 (S328) ◽  
pp. 69-76
Author(s):  
Adriana Valio
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Light Curve ◽  
Physical Properties ◽  
Differential Rotation ◽  
Magnetic Activity ◽  
Stellar Surface ◽  
Stellar Rotation ◽  
Long Time ◽  
Magnetic Cycles

AbstractMagnetic activity of stars manifests itself in the form of dark spots on the stellar surface. This in turn will cause variations of a few percent in the star light curve as it rotates. When an orbiting planet eclipses its host a star, it may cross in front of one of these spots. In this case, a “bump” will be detected in the transit lightcurve. By fitting these spot signatures with a model, it is possible to determine the spots physical properties such as size, temperature, location, magnetic field, and lifetime. Moreover, the monitoring of the spots longitude provides estimates of the stellar rotation and differential rotation. For long time series of transits during multiple years, magnetic cycles can also be determined. This model has been applied successfully to CoRoT-2, CoRoT-4, CoRot-5, CoRoT-6, CoRoT-8, CoRoT-18, Kepler-17, and Kepler-63.

scholarly journals Apsidal motion in the massive binary HD 152248

2020 ◽  
Vol 642 ◽  
pp. A221
Author(s):  
S. Rosu ◽  
A. Noels ◽  
M.-A. Dupret ◽  
G. Rauw ◽  
M. Farnir ◽  
...  
Keyword(s):  
Binary System ◽  
Internal Structure ◽  
Turbulent Diffusion ◽  
Structure Constant ◽  
Orbital Plane ◽  
Apsidal Motion ◽  
Stellar Rotation ◽  
Single Star ◽  
Internal Mixing ◽  
The Impact

Context. Apsidal motion in massive eccentric binaries offers precious information about the internal structure of the stars. This is especially true for twin binaries consisting of two nearly identical stars. Aims. We make use of the tidally induced apsidal motion in the twin binary HD 152248 to infer constraints on the internal structure of the O7.5 III-II stars composing this system. Methods. We build stellar evolution models with the code Clés assuming different prescriptions for the internal mixing occurring inside the stars. We identify the models that best reproduce the observationally determined present-day properties of the components of HD 152248, as well as their internal structure constants, and the apsidal motion rate of the system. We analyse the impact on the results of some poorly constrained input parameters in the models, including overshooting, turbulent diffusion, and metallicity. We further build “single” and “binary” GENEC models that account for stellar rotation to investigate the impacts of binarity and rotation. We discuss some effects that could bias our interpretation of the apsidal motion in terms of the internal structure constant. Results. The analysis of the Clés models reveals that reproducing the observed k2 value and rate of apsidal motion simultaneously with the other stellar parameters requires a significant amount of internal mixing (either turbulent diffusion, overshooting, or rotational mixing) or enhanced mass-loss. The results obtained with the GENEC models suggest that a single-star evolution model is sufficient to describe the physics inside this binary system. We suggest that, qualitatively, the high turbulent diffusion required to reproduce the observations could be partly attributed to stellar rotation. We show that higher-order terms in the apsidal motion are negligible. Only a very severe misalignment of the rotation axes with respect to the normal to the orbital plane could significantly impact the rate of apsidal motion, but such a high misalignment is highly unlikely in such a binary system. Conclusions. We infer an age estimate of 5.15 ± 0.13 Myr for the binary system and initial masses of 32.8 ± 0.6 M⊙ for both stars.

scholarly journals Hyperons and quarks in proto-neutron stars

2019 ◽  
Vol 486 (4) ◽  
pp. 5441-5447 ◽  
Author(s):  
J Roark ◽  
X Du ◽  
C Constantinou ◽  
V Dexheimer ◽  
A W Steiner ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Finite Temperature ◽  
Degrees Of Freedom ◽  
Mean Field ◽  
Large Mass ◽  
Stellar Structure ◽  
Stellar Rotation ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
The Impact

ABSTRACT In this work, we study matter in the cores of proto-neutron stars, focusing on the impact of their composition on the stellar structure. We begin by examining the effects of finite temperature (through a fixed entropy per baryon) and lepton fraction on purely nucleonic matter by making use of the DSH (Du, Steiner & Holt) model. We then turn our attention to a relativistic mean-field model containing exotic degrees of freedom, the Chiral Mean Field (CMF) model, again, under the conditions of finite temperature and trapped neutrinos. In the latter, since both hyperons and quarks are found in the cores of large-mass stars, their interplay and the possibility of mixtures of phases is taken into account and analysed. Finally, we discuss how stellar rotation can affect our results.

The role of stellar rotation in Tidal Disruption Events

2018 ◽  
Vol 14 (S342) ◽  
pp. 272-274
Author(s):  
Andrea Sacchi ◽  
Giuseppe Lodato
Keyword(s):  
Black Hole ◽  
Galactic Nuclei ◽  
High Energy ◽  
Stellar Structure ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Smoothed Particle ◽  
The Impact

AbstractTidal Disruption Events (TDEs) are highly variable high energy phenomena originating from Galactic Nuclei (Komossa & Bade 1999). TDEs are thus powerful tools to study quiescent Galactic Nuclei given their extreme brightness (several times super-Eddington) and the possibility of being seen in non-AGN galaxies. A TDE is the violent disruption of a star passing by a Super Massive Black Hole (SMBH); after the disruption, roughly half of the star mass gains enough energy to escape from the Black Hole, while the other half is bound to the Hole, falls back and eventually accretes onto it. Early works, (Rees 1988), pointed out a t−5/3 behaviour for the light curves of this event and since then such a time dependency became the signature of these events. Strong deviations are however introduced when one considers the internal stellar structure or if one considers partial disruptions. One feature that has never been taken into account is the effect of stellar rotation in the resulting fallback rate, which is the aim of the present work. Firstly, we will show analytical estimates of the impact of stellar rotation on the TDE and we will then present a set of Smoothed Particle Hydrodynamic simulations of the tidal disruption of rotating stars, performed in order to test these analytical estimates.

Euratom and Brexit: Could the United Kingdom Maintain One Foot in the European Union? Current Scenarios and Future Prospects of British withdrawal from the EAEC

2018 ◽  
Vol 18 (2) ◽  
pp. 134-151
Author(s):  
Andrea Circolo ◽  
Ondrej Hamuľák
Keyword(s):  
European Union ◽  
United Kingdom ◽  
Independent Solution ◽  
Legal Regulation ◽  
The European Union ◽  
The United Kingdom ◽  
The Status ◽  
Long Time ◽  
Energy Community ◽  
The Impact

Abstract The paper focuses on the very topical issue of conclusion of the membership of the State, namely the United Kingdom, in European integration structures. The ques­tion of termination of membership in European Communities and European Union has not been tackled for a long time in the sources of European law. With the adop­tion of the Treaty of Lisbon (2009), the institute of 'unilateral' withdrawal was intro­duced. It´s worth to say that exit clause was intended as symbolic in its nature, in fact underlining the status of Member States as sovereign entities. That is why this institute is very general and the legal regulation of the exercise of withdrawal contains many gaps. One of them is a question of absolute or relative nature of exiting from integration structures. Today’s “exit clause” (Art. 50 of Treaty on European Union) regulates only the termination of membership in the European Union and is silent on the impact of such a step on membership in the European Atomic Energy Community. The presented paper offers an analysis of different variations of the interpretation and solution of the problem. It´s based on the independent solution thesis and therefore rejects an automa­tism approach. The paper and topic is important and original especially because in the multitude of scholarly writings devoted to Brexit questions, vast majority of them deals with institutional questions, the interpretation of Art. 50 of Treaty on European Union; the constitutional matters at national UK level; future relation between EU and UK and political bargaining behind such as all that. The question of impact on withdrawal on Euratom membership is somehow underrepresented. Present paper attempts to fill this gap and accelerate the scholarly debate on this matter globally, because all consequences of Brexit already have and will definitely give rise to more world-wide effects.

„Arvīd, uz kurieni Tu aizgāji?”: Arvīda Griguļa personības loma Rakstnieku savienības vēsturē

2020 ◽  
pp. 74-84
Author(s):  
Madara Eversone
Keyword(s):  
20Th Century ◽  
Communist Party ◽  
Central Committee ◽  
State Archive ◽  
National Archives ◽  
Literary Heritage ◽  
Literary Process ◽  
Long Time ◽  
The Impact

The article aims to highlight the role of Arvīds Grigulis’ (1906–1989) personality in the Latvian Soviet literary process in the context of the Latvian Soviet Writers’ Union, attempting to discover the contradictions and significance of Arvīds Grigulis’ personality. Arvīds Grigulis was a long-time member of the Writers’ Union, a member of the Soviet nomenklatura, and an authority of the soviet literary process. His evaluations of pre-soviet literary heritage and writings of his contemporaries were often harsh and ruthless, and also influenced the development of the further literary process. The article is based on the documents of the Central Committee of the Latvian Communist Party, the Latvian Soviet Writers’ Union and the Communist Party local organization of the Latvian Soviet Writers’ Union that are available at the Latvian State Archive of the National Archives of Latvia, as well as memories of Grigulis’ contemporaries. It is concluded that the personality of the writer Arvīds Grigulis, although unfolding less in the context of the Writers’ Union, is essential for the exploration of the soviet literary process and events behind the scenes. The article mainly describes events and episodes taking place until 1965, when Arvīds Grigulis’ influence in the Writers’ Union was more remarkable. Individual and further studies should analyse changes and the impact of his decisions in the cultural process of the 70s and 80s of the 20th century.

scholarly journals An extensive photometric study of the Blazhko RR Lyrae star RZ Lyr*

2012 ◽  
Vol 423 (2) ◽  
pp. 993-1005 ◽  
Author(s):  
J. Jurcsik ◽  
Á. Sódor ◽  
G. Hajdu ◽  
B. Szeidl ◽  
Á. Dózsa ◽  
...  
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Stellar Structure ◽  
Time Base ◽  
Photometric Method ◽  
Physical Parameters ◽  
Component Solution ◽  
Rr Lyrae ◽  
Curve Variation ◽  
Type Variable

Abstract The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time base of ∼110 yr, a strict anticorrelation between the pulsation- and modulation-period changes is established. The light curve of RZ Lyr shows a remarkable bump on the descending branch in the small-amplitude phase of the modulation, similarly to the light curves of bump Cepheids. We speculate that the stellar structure temporally suits a 4:1 resonance between the periods of the fundamental and one of the higher order radial modes in this modulation phase. The light-curve variation of RZ Lyr can be correctly fitted with a two-modulation-component solution; the 121-d period of the main modulation is nearly but not exactly four times longer than the period of the secondary modulation component. Using the inverse photometric method, the variations in the pulsation-averaged values of the physical parameters in different phases of both modulation components are determined.

scholarly journals Sexuality and Affection in the Time of Technological Innovation: Artificial Partners in the Japanese Context

Religions ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 296
Author(s):  
Beatriz Yumi Aoki ◽  
Takeshi Kimura
Keyword(s):  
18Th Century ◽  
Human Life ◽  
Human Sexuality ◽  
Sexual Intimacy ◽  
Ancient History ◽  
Human Relationships ◽  
Living Things ◽  
Long Time ◽  
History Of ◽  
The Impact

Recent years have witnessed an increase in the number of academic studies on the impact of technological advancements on human life, including possible transformations and changes in human sexuality following the development of sex-related devices, such as sex robots. In this context, terms such as posthuman sexuality, digisexuality, and techno-sexuality have emerged, signaling possible new understandings of sexual, intimacy, and emotional practices. It is important to note that ancient history shows that humankind has for a long time been fascinated with their relationship to non-living things, mostly human-like figures, such as dolls. The Ningyo (人形, the Japanese term for doll) has a long history of usage, and has deep religious and animistic significance in the Japanese context—there are records of sexual use as early as the 18th century. With this context in mind, this paper focuses on three Japanese examples, aiming to shine a light on beyond-human relationships, which include a Japanese man’s marriage to a digital character, sex dolls, and communicative robots, from both a sexual and emotional perspective. In a new horizon of sexual and romantic possibilities, how will humans respond, and what can emerge from these interactions?

scholarly journals Stock Market Trading Rules Discovery Based on Biclustering Method

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Yun Xue ◽  
Zhiwen Liu ◽  
Jie Luo ◽  
Zhihao Ma ◽  
Meizhen Zhang ◽  
...  
Keyword(s):  
Stock Price ◽  
Historical Data ◽  
Probability Model ◽  
Trading Rules ◽  
Normal Probability ◽  
Long Time ◽  
Local Patterns ◽  
Short Term Prediction ◽  
Stock Market Trading ◽  
The Impact

The prediction of stock market’s trend has become a challenging task for a long time, which is affected by a variety of deterministic and stochastic factors. In this paper, a biclustering algorithm is introduced to find the local patterns in the quantized historical data. The local patterns obtained are regarded as the trading rules. Then the trading rules are applied in the short term prediction of the stock price, combined with the minimum-error-rate classification of the Bayes decision theory under the assumption of multivariate normal probability model. In addition, this paper also makes use of the idea of the stream mining to weaken the impact of historical data on the model and update the trading rules dynamically. The experiment is implemented on real datasets and the results prove the effectiveness of the proposed algorithm.

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