scholarly journals NGTS clusters survey – I. Rotation in the young benchmark open cluster Blanco 1

2020 ◽  
Vol 492 (1) ◽  
pp. 1008-1024 ◽  
Author(s):  
Edward Gillen ◽  
Joshua T Briegal ◽  
Simon T Hodgkin ◽  
Daniel Foreman-Mackey ◽  
Floor Van Leeuwen ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Open Cluster ◽  
Rotation Period ◽  
High Mass ◽  
Single Star ◽  
Multiple Systems ◽  
Rotation Periods ◽  
M Stars ◽  
Photometric Monitoring ◽  
Rotation Sequence

ABSTRACT We determine rotation periods for 127 stars in the ∼115-Myr-old Blanco 1 open cluster using ∼200 d of photometric monitoring with the Next Generation Transit Survey. These stars span F5–M3 spectral types (1.2 M⊙ ≳ M ≳ 0.3 M⊙) and increase the number of known rotation periods in Blanco 1 by a factor of four. We determine rotation periods using three methods: Gaussian process (GP) regression, generalized autocorrelation function (G-ACF), and Lomb–Scargle (LS) periodogram, and find that the GP and G-ACF methods are more applicable to evolving spot modulation patterns. Between mid-F and mid-K spectral types, single stars follow a well-defined rotation sequence from ∼2 to 10 d, whereas stars in photometric multiple systems typically rotate faster. This may suggest that the presence of a moderate-to-high mass ratio companion inhibits angular momentum loss mechanisms during the early pre-main sequence, and this signature has not been erased at ∼100 Myr. The majority of mid-F to mid-K stars display evolving modulation patterns, whereas most M stars show stable modulation signals. This morphological change coincides with the shift from a well-defined rotation sequence (mid-F to mid-K stars) to a broad rotation period distribution (late-K and M stars). Finally, we compare our rotation results for Blanco 1 to the similarly aged Pleiades: the single-star populations in both clusters possess consistent rotation period distributions, which suggests that the angular momentum evolution of stars follows a well-defined pathway that is, at least for mid-F to mid-K stars, strongly imprinted by ∼100 Myr.

scholarly journals A Rotational Period Study of a Large Sample of Pre-Main Sequence stars in NGC 2264

2004 ◽  
Vol 215 ◽  
pp. 125-126 ◽  
Author(s):  
M. Lamm ◽  
C.A.L. Bailer-Jones ◽  
R. Mundt ◽  
W. Herbst
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Monitoring Program ◽  
Bimodal Distribution ◽  
Main Sequence Stars ◽  
Lower Mass ◽  
Rotation Periods ◽  
Photometric Monitoring ◽  
Pms Stars ◽  
Mass Dependent

We present the results of a photometric monitoring program of pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC 2264 (d=700 pc). We find that the rotation periods are mass dependent and show a bimodal distribution for higher mass stars with M ≳ 0.3 M⊙ and a unimodal distribution for lower mass stars with M ≲ 0.3 M⊙.

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

2004 ◽  
Vol 215 ◽  
pp. 113-122 ◽  
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.

scholarly journals Rotation periods for cool stars in the open cluster Ruprecht 147 (NGC 6774)

2020 ◽  
Vol 644 ◽  
pp. A16
Author(s):  
D. Gruner ◽  
S. A. Barnes
Keyword(s):  
Open Cluster ◽  
Rotation Period ◽  
Principal Component ◽  
Mass Region ◽  
Open Clusters ◽  
Light Curves ◽  
Rotating Stars ◽  
Rotation Periods ◽  
Periodicity Analysis ◽  
Cool Stars

Context. Gyrochronology allows the derivation of ages for cool main sequence stars based on their observed rotation periods and masses, or a suitable proxy thereof. It is increasingly well-explored for FGK stars, but requires further measurements for older ages and K – M-type stars. Aims. We study the 2.7 Gyr-old open cluster Ruprecht 147 to compare it with the previously-studied, but far more distant, NGC 6819 cluster, and especially to measure cooler stars than was previously possible there. Methods. We constructed an inclusive list of 102 cluster members from prior work, including Gaia DR2, and for which light curves were also obtained during Campaign 7 of the Kepler/K2 space mission. We placed them in the cluster color-magnitude diagram and checked the related information against appropriate isochrones. The light curves were then corrected for data systematics using Principal Component Analysis on all observed K2 C07 stars and subsequently subjected to periodicity analysis. Results. Periodic signals are found for 32 stars, 21 of which are considered to be both highly reliable and to represent single, or effectively single, Ru 147 stars. These stars cover the spectral types from late-F to mid-M stars, and they have periods ranging from 6 d – 33 d, allowing for a comparison of Ruprecht 147 to both other open clusters and to models of rotational spindown. The derived rotation periods connect reasonably to, overlap with, and extend to lower masses the known rotation period distribution of the 2.5 Gyr-old cluster NGC 6819. Conclusions. The data confirm that cool stars lie on a single surface in rotation period-mass-age space, and they simultaneously challenge its commonly assumed shape. The shape at the low mass region of the color-period diagram at the age of Ru 147 favors a recently-proposed model which requires a third mass-dependent timescale in addition to the two timescales required by a former model, suggesting that a third physical process is required to model rotating stars effectively.

scholarly journals The evolution of ‘the moment of inertia’ of stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 117-118 ◽  
Author(s):  
Y.-C. Kim ◽  
S. Barnes
Keyword(s):  
Stellar Evolution ◽  
Convection Zone ◽  
Open Cluster ◽  
Rotation Period ◽  
Stellar Mass ◽  
Turnover Time ◽  
Moment Of Inertia ◽  
The Core ◽  
Rotation Periods ◽  
The Moment

AbstractObservations of the rotation periods of cool open cluster stars display a distinctive dichotomy when plotted against stellar mass/color. Other measures of stellar activity are also known to be dependent on stellar mass and structure, especially the onset and characteristics of convection zones. One proposal for understanding the observed rotation period dichotomy suggested dependencies on the moment of inertia of either the whole star or that of only the outer convection zone (Barnes 2003).The moment of inertia of stars with the mass between 0.1Msun and 3.0Msun have been calculated using a version of Yale Stellar evolution code (aka YREC). Each star has been evolved from stellar birthline to the onset of the core He burning. For easy comparison to observations, we have calculated the isochrones of these quantities as well as the convective turnover time, of interest to the activity community.

scholarly journals Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity

2020 ◽  
Vol 638 ◽  
pp. A20 ◽  
Author(s):  
E. Magaudda ◽  
B. Stelzer ◽  
K. R. Covey ◽  
St. Raetz ◽  
S. P. Matt ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Rotation Period ◽  
Break Point ◽  
Rotating Stars ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
X Ray ◽  
Uniform Sample ◽  
M Stars ◽  
M Dwarf Stars

The relation of activity to rotation in M dwarfs is of high astrophysical interest because it provides observational evidence of the stellar dynamo, which is poorly understood for low-mass stars, especially in the fully convective regime. Previous studies have shown that the relation of X-ray activity to rotation consists of two different regimes: the saturated regime for fast-rotating stars and the unsaturated regime for slowly rotating stars. The transition between the two regimes lies at a rotation period of ∼10 d. We present here a sample of 14 M dwarf stars observed with XMM-Newton and Chandra, for which we also computed rotational periods from Kepler Two-Wheel (K2) Mission light curves. We compiled X-ray and rotation data from the literature and homogenized all data sets to provide the largest uniform sample of M dwarfs (302 stars) for X-ray activity and rotation studies to date. We then fit the relation between Lx − Prot using three different mass bins to separate partially and fully convective stars. We found a steeper slope in the unsaturated regime for fully convective stars and a nonconstant Lx level in the saturated regime for all masses. In the Lx/Lbol − RO space we discovered a remarkable double gap that might be related to a discontinuous period evolution. Then we combined the evolution of Prot predicted by angular momentum evolution models with our new results on the empirical Lx − Prot relation to provide an estimate for the age decay of X-ray luminosity. We compare predictions of this relationship with the actual X-ray luminosities of M stars with known ages from 100 Myr to a few billion years. We find remarkably good agreement between the predicted Lx and the observed values for partially convective stars. However, for fully convective stars at ages of a few billion years, the constructed Lx-age relation overpredicts the X-ray luminosity because the angular momentum evolution model underpredicts the rotation period of these stars. Finally, we examine the effect of different parameterizations for the Rossby number (RO) on the shape of the activity-rotation relation in Lx/Lbol − RO space, and we find that the slope in the unsaturated regime and the location of the break point of the dual power-law depend sensitively on the choice of RO.

scholarly journals Let the Great World Spin: Revealing the Stormy, Turbulent Nature of Young Giant Exoplanet Analogs with the Spitzer Space Telescope

2022 ◽  
Vol 924 (2) ◽  
pp. 68
Author(s):  
Johanna M. Vos ◽  
Jacqueline K. Faherty ◽  
Jonathan Gagné ◽  
Mark Marley ◽  
Stanimir Metchev ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Spectral Type ◽  
Brown Dwarfs ◽  
High Mass ◽  
Occurrence Rate ◽  
Spitzer Space Telescope ◽  
Photometric Variability ◽  
Space Telescope ◽  
Rotation Periods ◽  
Low Mass

Abstract We present a survey for photometric variability in young, low-mass brown dwarfs with the Spitzer Space Telescope. The 23 objects in our sample show robust signatures of youth and share properties with directly imaged exoplanets. We present three new young objects: 2MASS J03492367+0635078, 2MASS J09512690−8023553, and 2MASS J07180871−6415310. We detect variability in 13 young objects, and find that young brown dwarfs are highly likely to display variability across the L2–T4 spectral type range. In contrast, the field dwarf variability occurrence rate drops for spectral types >L9. We examine the variability amplitudes of young objects and find an enhancement in maximum amplitudes compared to field dwarfs. We speculate that the observed range of amplitudes within a spectral type may be influenced by secondary effects such as viewing inclination and/or rotation period. We combine our new rotation periods with the literature to investigate the effects of mass on angular momentum evolution. While high-mass brown dwarfs (>30M Jup) spin up over time, the same trend is not apparent for lower-mass objects (<30M Jup), likely due to the small number of measured periods for old, low-mass objects. The rotation periods of companion brown dwarfs and planetary-mass objects are consistent with those of isolated objects with similar ages and masses, suggesting similar angular momentum histories. Within the AB Doradus group, we find a high-variability occurrence rate and evidence for common angular momentum evolution. The results are encouraging for future variability searches in directly imaged exoplanets with facilities such as the James Webb Space Telescope and 30 m telescopes.

scholarly journals Planetary tidal interactions and the rotational evolution of low-mass stars

2018 ◽  
Vol 619 ◽  
pp. A80 ◽  
Author(s):  
F. Gallet ◽  
E. Bolmont ◽  
J. Bouvier ◽  
S. Mathis ◽  
C. Charbonnel
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Open Cluster ◽  
Rotation Period ◽  
Rotational Period ◽  
Low Mass Stars ◽  
General Behaviour ◽  
Period Distribution ◽  
Rotational Evolution ◽  
Low Mass

Context. The surface angular velocity evolution of low-mass stars is now globally understood and the main physical mechanisms involved in it are observationally quite constrained. However, while the general behaviour of these mechanisms is grasped, their theoretical description is still under ongoing work. This is the case, for instance, about the description of the physical process that extracts angular momentum from the radiative core, which could be described by several theoretical candidates. Additionally, recent observations showed anomalies in the rotation period distribution of open cluster, main sequence, early K-type stars that cannot be reproduced by current angular momentum evolution models. Aims. In this work, we study the parameter space of star-planet system’s configurations to investigate if including the tidal star-planet interaction in angular momentum evolution models could reproduce the anomalies of this rotation period distribution. Methods. To study this effect, we use a parametric angular momentum evolution model that allows for core-envelope decoupling and angular momentum extraction by magnetized stellar wind that we coupled to an orbital evolution code where we take into account the torque due to the tides raised on the star by the planet. We explore different stellar and planetary configurations (stellar mass from 0.5 to 1.0 M⊙ and planetary mass from 10 M⊕ to 13 Mjup) to study their effect on the planetary orbital and stellar rotational evolution. Results. The stellar angular momentum is the most impacted by the star-planet interaction when the planet is engulfed during the early main sequence phase. Thus, if a close-in Jupiter-mass planet is initially located at around 50% of the stellar corotation radius, a kink in the rotational period distribution opens around late and early K-type stars during the early main sequence phase. Conclusions. Tidal star-planet interactions can create a kink in the rotation period distribution of low-mass stars, which could possibly account for unexpected scatter seen in the rotational period distribution of young stellar clusters.

scholarly journals Competing effect of wind braking and interior coupling in the rotational evolution of solar-like stars

2020 ◽  
Vol 636 ◽  
pp. A76 ◽  
Author(s):  
F. Spada ◽  
A. C. Lanzafame
Keyword(s):  
Angular Momentum ◽  
General Pattern ◽  
Rotation Period ◽  
Open Clusters ◽  
Mass Dependence ◽  
Low Mass Stars ◽  
Rotation Periods ◽  
Rotational Evolution ◽  
Low Mass ◽  
Rotational Coupling

Solar-like stars (M ≲ 1.3 M⊙) lose angular momentum through their magnetized winds. The resulting evolution of the surface rotation period, which can be directly measured photometrically, has the potential to be an accurate indicator of stellar age, and is constrained by observations of rotation periods of coeval stars, such as members of Galactic open clusters. A prominent observational feature of the mass–rotation period diagrams of open clusters is a sequence of relatively slower rotators. The formation and persistence of this slow-rotator sequence across several billion years imply an approximately coherent spin-down of the stars that belong to it. In particular, the sequence is observed to evolve coherently toward longer periods in progressively older clusters. Recent observations of the ≈700 Myr Praesepe and the 1 Gyr NGC 6811 clusters, however, are not fully consistent with this general pattern. While the stars of 1 M⊙ on the slow-rotator sequence of the older NGC 6811 have longer periods than their counterparts in the younger Praesepe, as expected, the two sequences essentially merge at lower masses (≲0.8 M⊙). In other words, it seems that low-mass stars have not been spinning down in the intervening 300 Myr. Here we show that this behavior is a manifestation of the variable rotational coupling in solar-like stars. The resurfacing of angular momentum from the interior can temporarily compensate for that lost at the surface due to wind braking. In our model the internal redistribution of angular momentum has a steep mass dependence; as a result, the re-coupling occurs at different ages for stars of different masses. The semi-empirical mass dependence of the rotational coupling timescale included in our model produces an evolution of the slow-rotator sequence in very good agreement with the observations. Our model, in particular, explains the stalled surface spin-down of low-mass stars between Praesepe and NGC 6811, and predicts that the same behavior should be observable at other ages in other mass ranges.

scholarly journals Reconstruction of asteroid spin states from Gaia DR2 photometry

2018 ◽  
Vol 620 ◽  
pp. A91 ◽  
Author(s):  
J. Ďurech ◽  
J. Hanuš
Keyword(s):  
Rotation Period ◽  
Inversion Method ◽  
Triaxial Ellipsoid ◽  
Independent Data ◽  
Rotation Periods ◽  
Shape Models ◽  
Pole Parameter ◽  
Data Points ◽  
Sidereal Rotation ◽  
Gaia Dr2

Context. In addition to stellar data, Gaia Data Release 2 (DR2) also contains accurate astrometry and photometry of about 14 000 asteroids covering 22 months of observations. Aims. We used Gaia asteroid photometry to reconstruct rotation periods, spin axis directions, and the coarse shapes of a subset of asteroids with enough observations. One of our aims was to test the reliability of the models with respect to the number of data points and to check the consistency of these models with independent data. Another aim was to produce new asteroid models to enlarge the sample of asteroids with known spin and shape. Methods. We used the lightcurve inversion method to scan the period and pole parameter space to create final shape models that best reproduce the observed data. To search for the sidereal rotation period, we also used a simpler model of a geometrically scattering triaxial ellipsoid. Results. By processing about 5400 asteroids with at least 10 observations in DR2, we derived models for 173 asteroids, 129 of which are new. Models of the remaining asteroids were already known from the inversion of independent data, and we used them for verification and error estimation. We also compared the formally best rotation periods based on Gaia data with those derived from dense lightcurves. Conclusions. We show that a correct rotation period can be determined even when the number of observations N is less than 20, but the rate of false solutions is high. For N > 30, the solution of the inverse problem is often successful and the parameters are likely to be correct in most cases. These results are very promising because the final Gaia catalogue should contain photometry for hundreds of thousands of asteroids, typically with several tens of data points per object, which should be sufficient for reliable spin reconstruction.

scholarly journals Interpretation of the Radio Rotation Period of Jupiter in Terms of the Cyclotron Theory

1968 ◽  
Vol 21 (3) ◽  
pp. 409 ◽  
Author(s):  
PM McCulloch
Keyword(s):  
Angular Momentum ◽  
Solid Body ◽  
Rotation Rate ◽  
Rotation Period ◽  
Intense Source

Since 1961 the most intense source of Jovian decametric emission has drifted with respect to system III longitude by about + 100 per year (Douglas and Smith 1963; Smith et al. 1965). Interpreted as a change in the rotation rate, this would imply that the period increased by approximately 1�1 sec around 1960. Runcorn (1967) and Hide (1967) have interpreted this as a change in the rotation rate of the solid body of Jupiter, in which angular momentum is exchanged between Jupiter's core and the Great Red Spot.

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