The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars

Context. The method of gyrochronology relates the age of its star to its rotation period. However, recent evidence of deviations from gyrochronology relations has been reported in the literature. Aims. We study the influence of tidal interaction between a star and its companion on the rotation velocity of the star to explain peculiar stellar rotation velocities. Methods. We followed the interaction of a star and its planet using a comprehensive numerical framework that combines tidal friction, magnetic braking, planet migration, and detailed stellar evolution models from the GARSTEC grid. We focus on close-in companions from 1 to 20 MJup orbiting low-mass (0.8 − 1 M⊙) main-sequence stars with a broad metallicity of [Fe/H] = − 1 up to solar. Results. Our simulations suggest that the dynamical interaction between a star and its companion can have different outcomes that depend on the initial semi-major axis and the mass of the planet, as well as on the mass and metallicity of its host star. In most cases, especially in the case of planet engulfment, we find a catastrophic increase in stellar rotation velocity from 1 kms−1 to over 40 kms−1 while the star is still on the main-sequence. The main prediction of our model is that low-mass main-sequence stars with abnormal rotation velocities should be more common at low-metallicity, as lower [Fe/H] favours faster planet engulfment, based on the assumption that the occurrence rate of close-in massive planets is similar at all metallicities. Conclusions. Our scenario explains peculiar rotation velocities of low-mass main-sequence stars by the tidal interaction between the star and its companion. Current observational samples are too narrow and incomplete, and, thus, they are not sufficient for our model to be tested.

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Age-related observations of low mass pre-main and young main sequence stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031731 ◽

2008 ◽

Vol 4 (S258) ◽

pp. 81-94 ◽

Cited By ~ 1

Author(s):

Lynne A. Hillenbrand

Keyword(s):

Main Sequence ◽

Rotation Period ◽

Age Dating ◽

Main Sequence Stars ◽

Solar Mass ◽

Age Related ◽

Stellar Ages ◽

Dating Methods ◽

Low Mass ◽

Lithium Depletion

AbstractThis overview summarizes the age dating methods available for young sub-solar mass stars. Pre-main sequence age diagnostics include the Hertzsprung-Russell (HR) diagram, spectroscopic surface gravity indicators, and lithium depletion; asteroseismology is also showing recent promise. Near and beyond the zero-age main sequence, rotation period or vsiniand activity (coronal and chromospheric) diagnostics along with lithium depletion serve as age proxies. Other authors in this volume present more detail in each of the aforementioned areas. Herein, I focus on pre-main sequence HR diagrams and address the questions: Do empirical young cluster isochrones match theoretical isochrones? Do isochrones predict stellar ages consistent with those derived via other independent techniques? Do the observed apparent luminosity spreads at constant effective temperature correspond to true age spreads? While definitive answers to these questions are not provided, some methods of progression are outlined.

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Long rotation period main-sequence stars from Kepler SAP light curves

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2432 ◽

2019 ◽

Vol 489 (4) ◽

pp. 5513-5529 ◽

Cited By ~ 3

Author(s):

Kaiming Cui ◽

Jifeng Liu ◽

Shuhong Yang ◽

Qing Gao ◽

Huiqin Yang ◽

...

Keyword(s):

Light Curve ◽

Main Sequence ◽

Rotation Period ◽

Light Curves ◽

Stellar Rotation ◽

Main Sequence Stars ◽

Found Objects ◽

Period Detection ◽

Search Data

ABSTRACT Stellar rotation plays a key role in stellar activity. The rotation period could be detected through light curve variations caused by star-spots. Kepler provides two types of light curves: one is the Pre-search Data Conditioning (PDC) light curves, and the other is the Simple Aperture Photometer (SAP) light curves. Compared with the PDC light curves, the SAP light curves keep the long-term trend, relatively suitable for searches of long-period signals. However, SAP data are inflicted by some artefacts such as quarterly rolls and instrumental errors, making it difficult to find the physical periods in the SAP light curves. We explore a systematic approach based on the light curve pre-processing, period detection, and candidate selection. We also develop a simulated light curve test to estimate our detection limits for the SAP-like LCs. After applying our method to the raw SAP light curves, we found more than 1000 main-sequence stars with periods longer than 30 d; 165 are newly discovered. Considering the potential flaw of the SAP, we also inspect the newly found objects with photometry methods, and most of our periodical signals are confirmed.

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Revisiting the connection between magnetic activity, rotation period, and convective turnover time for main-sequence stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833498 ◽

2018 ◽

Vol 618 ◽

pp. A48 ◽

Cited By ~ 12

Author(s):

M. Mittag ◽

J. H. M. M. Schmitt ◽

K.-P. Schröder

Keyword(s):

Main Sequence ◽

Rotation Period ◽

Magnetic Activity ◽

Turnover Time ◽

Rossby Number ◽

Stellar Rotation ◽

Main Sequence Stars ◽

Rotation Periods ◽

Period Distribution ◽

Cool Stars

The connection between stellar rotation, stellar activity, and convective turnover time is revisited with a focus on the sole contribution of magnetic activity to the Ca II H&K emission, the so-called excess flux, and its dimensionless indicator R+HK in relation to other stellar parameters and activity indicators. Our study is based on a sample of 169 main-sequence stars with directly measured Mount Wilson S-indices and rotation periods. The R+HK values are derived from the respective S-indices and related to the rotation periods in various B–V-colour intervals. First, we show that stars with vanishing magnetic activity, i.e. stars whose excess flux index R+HK approaches zero, have a well-defined, colour-dependent rotation period distribution; we also show that this rotation period distribution applies to large samples of cool stars for which rotation periods have recently become available. Second, we use empirical arguments to equate this rotation period distribution with the global convective turnover time, which is an approach that allows us to obtain clear relations between the magnetic activity related excess flux index R+HK, rotation periods, and Rossby numbers. Third, we show that the activity versus Rossby number relations are very similar in the different activity indicators. As a consequence of our study, we emphasize that our Rossby number based on the global convective turnover time approaches but does not exceed unity even for entirely inactive stars. Furthermore, the rotation-activity relations might be universal for different activity indicators once the proper scalings are used.

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The Rotation of Low-Mass Pre-Main-Sequence Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900195385 ◽

2004 ◽

Vol 215 ◽

pp. 113-122 ◽

Cited By ~ 5

Author(s):

Robert D. Mathieu

Keyword(s):

Angular Momentum ◽

Main Sequence ◽

Rotation Period ◽

Rotating Stars ◽

Stellar Rotation ◽

Main Sequence Stars ◽

Star Forming ◽

Rotation Periods ◽

Order Of Magnitude ◽

Critical Velocities

Major photometric monitoring campaigns of star-forming regions in the past decade have provided rich rotation period distributions of pre-main-sequence stars. The rotation periods span more than an order of magnitude in period, with most falling between 1 and 10 days. Thus the broad rotation period distributions found in 100 Myr clusters are already established by an age of 1 Myr. The most rapidly rotating stars are within a factor of 2-3 of their critical velocities; if angular momentum is conserved as they evolve to the ZAMS, these stars may come to exceed their critical velocities. Extensive efforts have been made to find connections between stellar rotation and the presence of protostellar disks; at best only a weak correlation has been found in the largest samples. Magnetic disk-locking is a theoretically attractive mechanism for angular momentum evolution of young stars, but the links between theoretical predictions and observational evidence remain ambiguous. Detailed observational and theoretical studies of the magnetospheric environments will provide better insight into the processes of pre-main-sequence stellar angular momentum evolution.

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Evolution of star–planet systems under magnetic braking and tidal interaction

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833314 ◽

2019 ◽

Vol 621 ◽

pp. A124 ◽

Cited By ~ 9

Author(s):

M. Benbakoura ◽

V. Réville ◽

A. S. Brun ◽

C. Le Poncin-Lafitte ◽

S. Mathis

Keyword(s):

Ab Initio ◽

Stellar Wind ◽

Structural Changes ◽

Rotation Period ◽

Major Axis ◽

Orbital Evolution ◽

Open Clusters ◽

Stellar Rotation ◽

Semi Major Axis ◽

Tidal Interaction

Context.With the discovery over the last two decades of a large diversity of exoplanetary systems, it is now of prime importance to characterize star–planet interactions and how such systems evolve.Aims.We address this question by studying systems formed by a solar-like star and a close-in planet. We focus on the stellar wind spinning down the star along its main-sequence phase and tidal interaction causing orbital evolution of the systems. Despite recent significant advances in these fields, all current models use parametric descriptions to study at least one of these effects. Our objective is to introduce ab initio prescriptions of the tidal and braking torques simultaneously, so as to improve our understanding of the underlying physics.Methods.We develop a one-dimensional (1D) numerical model of coplanar circular star–planet systems taking into account stellar structural changes, wind braking, and tidal interaction and implement it in a code called ESPEM. We follow the secular evolution of the stellar rotation and of the semi-major axis of the orbit, assuming a bilayer internal structure for the former. After comparing our predictions to recent observations and models, we perform tests to emphasize the contribution of ab initio prescriptions. Finally, we isolate four significant characteristics of star–planet systems: stellar mass, initial stellar rotation period, planetary mass and initial semi-major axis; and browse the parameter space to investigate the influence of each of them on the fate of the system.Results.Our secular model of stellar wind braking accurately reproduces the recent observations of stellar rotation in open clusters. Our results show that a planet can affect the rotation of its host star and that the resulting spin-up or spin-down depends on the orbital semi-major axis and on the joint influence of magnetic and tidal effects. The ab initio prescription for tidal dissipation that we used predicts fast outward migration of massive planets orbiting fast-rotating young stars. Finally, we provide the reader with a criterion based on the characteristics of the system that allows us to assess whether or not the planet will undergo orbital decay due to tidal interaction.

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Chromospheric Emission and Rotation of Main Sequence Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100095956 ◽

1983 ◽

Vol 71 ◽

pp. 71-73

Author(s):

S. Catalano ◽

E. Marilli

Keyword(s):

Main Sequence ◽

Rotation Period ◽

Total Power ◽

Published Data ◽

Physical Parameters ◽

Stellar Rotation ◽

Main Sequence Stars ◽

Lithium Abundance ◽

Stellar Ages ◽

Chromospheric Emission

Here we present a quatitative approach to the problem of the chromospheric emission and rotation in main sequence stars based on a consistent analysis of recent published data of stars from F8 to K5. This analysis has been performed using the following physical parameters:a) total power emission in the Call K line, Lk;b) stellar rotation period, Prot, from chromospheric emission variability;c) stellar ages from lithium abundance.

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Are sdAs helium core stars?

Open Astronomy ◽

10.1515/astro-2017-0433 ◽

2017 ◽

Vol 26 (1) ◽

Cited By ~ 4

Author(s):

Ingrid Pelisoli ◽

S. O. Kepler ◽

Detlev Koester

Keyword(s):

Main Sequence ◽

Galactic Disk ◽

Physical Nature ◽

Sloan Digital Sky Survey ◽

Distance Modulus ◽

Main Sequence Stars ◽

Sky Survey ◽

Balmer Lines ◽

Low Mass ◽

Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

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