Asteroid Rotation Rates: Comparison between Theory and Observations

I review the advantages, techniques, and results of measurement of magnetic fields on cool stars in the infrared (IR). These measurements have generated several important results, including the following: the first data on the magnetic parameters of dMe and RS CVn variables; evidence for field strength confinement by photospheric gas pressure; support for the correlation between magnetic flux and rotation, with possible saturation at high rotation rates; indications of horizontal and/or vertical magnetic field structure; and evidence of spatial variations in B over a stellar surface. I discuss these results in detail, and suggest future directions for IR magnetic field research.

Download Full-text

The Rotation Rates of White Dwarfs and Pulsars

The Astrophysical Journal ◽

10.1086/306153 ◽

1998 ◽

Vol 505 (1) ◽

pp. 339-343 ◽

Cited By ~ 42

Author(s):

Mario Livio ◽

J. E. Pringle

Keyword(s):

White Dwarfs ◽

Rotation Rates

Download Full-text

The most massive white dwarfs in the solar neighbourhood

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab767 ◽

2021 ◽

Vol 503 (4) ◽

pp. 5397-5408

Author(s):

Mukremin Kilic ◽

P Bergeron ◽

Simon Blouin ◽

A Bédard

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Transverse Velocity ◽

Maximum Mass ◽

Model Calculations ◽

Rapid Rotation ◽

Rotation Rates ◽

Binary Mergers ◽

Chandrasekhar Limit

ABSTRACT We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $1.3\, {\rm M}_{\odot }$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M⊙, which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm−3. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.

Download Full-text

Analysis of the Accuracy of Ten Algorithms for Orientation Estimation Using Inertial and Magnetic Sensing Under Optimal Conditions: One Size Does Not Fit All

Sensors ◽

10.3390/s21072543 ◽

2021 ◽

Vol 21 (7) ◽

pp. 2543

Author(s):

Marco Caruso ◽

Angelo Maria Sabatini ◽

Daniel Laidig ◽

Thomas Seel ◽

Marco Knaflitz ◽

...

Keyword(s):

Inertial Measurement Unit ◽

Motion Tracking ◽

Recent Literature ◽

Human Motion ◽

Measurement Unit ◽

Optimal Conditions ◽

Inertial Measurement ◽

Rotation Rates ◽

Significant Performance ◽

Parameter Values

The orientation of a magneto and inertial measurement unit (MIMU) is estimated by means of sensor fusion algorithms (SFAs) thus enabling human motion tracking. However, despite several SFAs implementations proposed over the last decades, there is still a lack of consensus about the best performing SFAs and their accuracy. As suggested by recent literature, the filter parameters play a central role in determining the orientation errors. The aim of this work is to analyze the accuracy of ten SFAs while running under the best possible conditions (i.e., their parameter values are set using the orientation reference) in nine experimental scenarios including three rotation rates and three commercial products. The main finding is that parameter values must be specific for each SFA according to the experimental scenario to avoid errors comparable to those obtained when the default parameter values are used. Overall, when optimally tuned, no statistically significant differences are observed among the different SFAs in all tested experimental scenarios and the absolute errors are included between 3.8 deg and 7.1 deg. Increasing the rotation rate generally leads to a significant performance worsening. Errors are also influenced by the MIMU commercial model. SFA MATLAB implementations have been made available online.

Download Full-text

Origin of asteroid rotation rates in catastrophic impacts

Nature ◽

10.1038/386154a0 ◽

1997 ◽

Vol 386 (6621) ◽

pp. 154-156 ◽

Cited By ~ 17

Author(s):

Stanley G. Love ◽

Thomas J. Ahrens

Keyword(s):

Rotation Rates

Download Full-text

Parameterization of Mixed Layer Eddies. Part I: Theory and Diagnosis

Journal of Physical Oceanography ◽

10.1175/2007jpo3792.1 ◽

2008 ◽

Vol 38 (6) ◽

pp. 1145-1165 ◽

Cited By ~ 353

Author(s):

Baylor Fox-Kemper ◽

Raffaele Ferrari ◽

Robert Hallberg

Keyword(s):

Mixed Layer ◽

Mixed Layer Depth ◽

Baroclinic Instability ◽

Finite Amplitude ◽

Climate Impacts ◽

Surface Mixed Layer ◽

Rotation Rates ◽

Wide Range ◽

Horizontal Density Gradient ◽

Mixed Layers

Abstract Ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean. In this paper a parameterization for the restratification driven by finite-amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal. The streamfunction is proportional to the product of the horizontal density gradient, the mixed layer depth squared, and the inertial period. Hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence. In this paper the parameterization is theoretically motivated, confirmed to perform well for a wide range of mixed layer depths, rotation rates, and vertical and horizontal stratifications. It is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification. Two companion papers discuss the numerical implementation and the climate impacts of this parameterization.

Download Full-text