scholarly journals Rotation Periods of Nearby, Mid-to-late M Dwarfs from the MEarth Project

2015 ◽  
Vol 10 (S314) ◽  
pp. 124-125
Author(s):  
Elisabeth R. Newton ◽  
Jonathan Irwin ◽  
David Charbonneau ◽  
Zachary K. Berta-Thomspon ◽  
Andrew A. West
Keyword(s):  
Angular Momentum ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Galactic Kinematics ◽  
Proper Motions ◽  
M Dwarfs ◽  
Rotation Periods ◽  
Velocity Dispersions ◽  
Late Stages

AbstractField stars provide important constraints for the late stages of stars' angular momentum evolution. We measured rotation periods ranging from 0.1 to 150 days for approximately 450 mid-to-late M dwarfs using photometry from the MEarth transiting planet survey. We use parallaxes, proper motions, and radial velocities to calculate galactic kinematics for these solar neighborhood M dwarfs. The velocity dispersions increase towards longer rotation periods, indicating that there is a relationship between rotation and age for these stars.

scholarly journals A large catalog of young active RAVE stars in the Solar neighborhood

2016 ◽  
Vol 12 (S328) ◽  
pp. 143-145
Author(s):  
Maruša Žerjal ◽  
Tomaž Zwitter ◽  
Gal Matijevič ◽  
Keyword(s):  
Main Sequence ◽  
Classification Algorithm ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Solar Neighbourhood ◽  
Proper Motions ◽  
Active Stars ◽  
Single Field ◽  
Infrared Triplet

AbstractThe catalog of 38,000 chromospherically active RAVE dwarfs represents one of the largest samples of young active solar-like and later-type single field stars in the Solar neighbourhood. It was established from the unbiased magnitude limited RAVE Survey using an unsupervised stellar classification algorithm based merely on stellar fluxes (Ca II infrared triplet). Using a newly-calibrated age-activity relation, ~15,000 active stars are estimated to be younger than 1 Gyr. Almost 2000 stars are presumably younger than ~100 Myr and possibly still in the pre-main sequence phase, the latter being supported by their significant offset from the main sequence in the NUV − V versus J − K space. 16,000 stars from the sample have positional and velocity vectors available (using TGAS parallaxes and proper motions and radial velocities from RAVE).

scholarly journals Measuring the Stellar Halo Velocity Anisotropy With 3D Kinematics

2015 ◽  
Vol 11 (S317) ◽  
pp. 288-289
Author(s):  
Emily C. Cunningham ◽  
Alis J. Deason ◽  
Puragra Guhathakurta ◽  
Constance M. Rockosi ◽  
Roeland P. van der Marel ◽  
...  
Keyword(s):  
Milky Way ◽  
Anisotropy Parameter ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Line Of Sight ◽  
Proper Motions ◽  
Velocity Anisotropy ◽  
Halo Stars ◽  
Stellar Halo ◽  
Kinematic Information

AbstractWe present the first measurement of the anisotropy parameter β using 3D kinematic information outside of the solar neighborhood. Our sample consists of 13 Milky Way halo stars with measured proper motions and radial velocities in the line of sight of M31. Proper motions were measured using deep, multi-epoch HST imaging, and radial velocities were measured from Keck II/DEIMOS spectra. We measure β = −0.3−0.9+0.4, which is consistent with isotropy, and inconsistent with measurements in the solar neighborhood. We suggest that this may be the kinematic signature of a relatively early, massive accretion event, or perhaps several such events.

scholarly journals Kinematics and Ages of UV Ceti Stars

1995 ◽  
Vol 151 ◽  
pp. 57-60
Author(s):  
A. Poveda ◽  
C. Allen ◽  
M.A. Herrera
Keyword(s):  
Velocity Dispersion ◽  
Space Velocity ◽  
Solar Neighborhood ◽  
Proper Motions ◽  
Contact Binaries ◽  
Flare Stars ◽  
Velocity Dispersions ◽  
Halo Population ◽  
Kinematic Properties ◽  
Total Velocity

AbstractThe kinematic properties of 93 UV Ceti stars of the solar neighborhood are studied, based on a list of flares within 25 pc of the Sun (π ≥ 0".04). With updated values for their distances, proper motions and radial velocities (Gliese & Jahreiss 1991) space velocity dispersions are calculated for these stars. It is found that the total velocity dispersion of the flare stars (σ=30±3 km s−1) is similar to that of the F5 V stars from the same catalogue, for which the conventionally estimated mean age is about 3 · 109 years. A number of flare stars are identified as members of the Hyades, Sirius or Pleiades groups. The velocity dispersions found for the nearby flare stars, as well as their scale height and the membership of some of them to young kinematic groups, indicate that they belong to the young disk population. A small number (7) of UV Ceti stars have kinematics corresponding to the thick disk or halo population. Their long-lived chromospheric activity is interpreted as due to coalescence of old contact binaries. The question of the age of Proxima Centauri is examined in the context of our results, and found to be compatible with the ages of a Centauri A and B.

scholarly journals Astrometric Distances of Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 523-524
Author(s):  
Kyle Cudworth ◽  
Ruth C. Peterson
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Proper Motion ◽  
Globular Clusters ◽  
Small Distance ◽  
Radial Velocities ◽  
Proper Motions ◽  
Velocity Dispersions

With high-precision radial velocities and proper motions, one can equate the proper motion and radial velocity dispersions to obtain astrometric distances independent of any standard candles. We discuss the method and the small distance it yields to M 22.

scholarly journals The relation between velocity dispersions and chemical abundances in RAVE giants

2017 ◽  
Vol 12 (S330) ◽  
pp. 259-260
Author(s):  
Rodolfo Smiljanic ◽  
Rafael Silva de Souza
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Bayesian Framework ◽  
Radial Velocities ◽  
Proper Motions ◽  
Chemical Abundances ◽  
Gaia Dr1 ◽  
Velocity Dispersions ◽  
Kinematic Properties ◽  
Robust Result

AbstractWe developed a Bayesian framework to determine in a robust way the relation between velocity dispersions and chemical abundances in a sample of stars. Our modelling takes into account the uncertainties in the chemical and kinematic properties. We make use of RAVE DR5 radial velocities and abundances together with Gaia DR1 proper motions and parallaxes (when possible, otherwise UCAC4 data is used). We found that, in general, the velocity dispersions increase with decreasing [Fe/H] and increasing [Mg/Fe]. A possible decrease in velocity dispersion for stars with high [Mg/Fe] is a property of a negligible fraction of stars and hardly a robust result. At low [Fe/H] and high [Mg/Fe] the sample is incomplete, affected by biases, and likely not representative of the underlying stellar population.

scholarly journals A spectroscopic survey of late-type giants in the Milky Way disk and local halo substructure

2007 ◽  
Vol 3 (S248) ◽  
pp. 506-507
Author(s):  
A. A. Sheffield ◽  
S. R. Majewski ◽  
A. M. Cheung ◽  
C. M. Hampton ◽  
J. D. Crane ◽  
...  
Keyword(s):  
High Velocity ◽  
Milky Way ◽  
Stellar Populations ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
Proper Motions ◽  
Late Type ◽  
Halo Stars ◽  
Medium Resolution ◽  
Galactic Stellar Populations

AbstractWe report the results of a survey of late-type giants aimed at understanding the nature of the disk and nearby halo Galactic stellar populations. We have obtained medium resolution (2–4 Å) spectra for 749 late K and early M giants at mid-latitudes selected from the 2MASS catalog with the FOBOS system at Fan Mountain Observatory. These spectra provide radial velocities (RVs) at the 5 km s−1 level, spectroscopic [Fe/H] good to σ[Fe/H] = 0.25 dex, and information on the relative abundances of Mg/Fe and Na/Fe in these stars. Proper motions from UCAC2 are used to search for local substructures, in particular the leading arm of the Sagittarius tidal streamer passing through the solar neighborhood. The combined proper motions and RVs yield full 6D stellar space motions. We have, by way of kinematics, relatively cleanly isolated the thick disk from the typically high velocity substructures that compose the nearby halo.We find evidence for substructure in the kinematics and metallicities of local halo stars.

scholarly journals THE ROTATION AND GALACTIC KINEMATICS OF MID M DWARFS IN THE SOLAR NEIGHBORHOOD

2016 ◽  
Vol 821 (2) ◽  
pp. 93 ◽  
Author(s):  
Elisabeth R. Newton ◽  
Jonathan Irwin ◽  
David Charbonneau ◽  
Zachory K. Berta-Thompson ◽  
Jason A. Dittmann ◽  
...  
Keyword(s):  
Solar Neighborhood ◽  
Galactic Kinematics ◽  
M Dwarfs

scholarly journals ON THE ANGULAR MOMENTUM EVOLUTION OF FULLY CONVECTIVE STARS: ROTATION PERIODS FOR FIELD M-DWARFS FROM THE MEarth TRANSIT SURVEY

2011 ◽  
Vol 727 (1) ◽  
pp. 56 ◽  
Author(s):  
Jonathan Irwin ◽  
Zachory K. Berta ◽  
Christopher J. Burke ◽  
David Charbonneau ◽  
Philip Nutzman ◽  
...  
Keyword(s):  
Angular Momentum ◽  
M Dwarfs ◽  
Rotation Periods

scholarly journals Gaia EDR3 Proper Motions of Milky Way Dwarfs. II Velocities, Total Energy, and Angular Momentum

2021 ◽  
Vol 922 (2) ◽  
pp. 93
Author(s):  
Francois Hammer ◽  
Jianling Wang ◽  
Marcel S. Pawlowski ◽  
Yanbin Yang ◽  
Piercarlo Bonifacio ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Total Energy ◽  
Large Scale ◽  
Milky Way ◽  
Radial Velocities ◽  
Proper Motions ◽  
Satellite Systems ◽  
Angular Momenta ◽  
Total Energies ◽  
Mass Profile

Abstract Here we show that precise Gaia EDR3 proper motions have provided robust estimates of 3D velocities, angular momentum, and total energy for 40 Milky Way dwarfs. The results are statistically robust and are independent of the Milky Way mass profile. Dwarfs do not behave like long-lived satellites of the Milky Way because of their excessively large velocities, angular momenta, and total energies. Comparing them to other MW halo populations, we find that many are at first passage, ≤2 Gyr ago, i.e., more recent than the passage of Sagittarius, ∼4–5 Gyr ago. We suggest that this is in agreement with the stellar populations of all dwarfs, for which we find that a small fraction of young stars cannot be excluded. We also find that dwarf radial velocities contribute too little to their kinetic energy when compared to satellite systems with motions only regulated by gravity, and some other mechanism must be at work such as ram pressure. The latter may have preferentially reduced radial velocities when dwarf progenitors entered the halo until they lost their gas. It could also explain why most dwarfs lie near their pericenter. We also discover a novel large-scale structure perpendicular to the Milky Way disk, which is made by 20% of dwarfs orbiting or counter-orbiting with the Sagittarius dwarf.

scholarly journals Infrared effects in the late stages of black hole evaporation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Éanna É. Flanagan
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Planck Scale ◽  
Black Hole Mass ◽  
Order Unity ◽  
Intrinsic Angular Momentum ◽  
Hole Position ◽  
Late Stages ◽  
Shear Tensor

Abstract As a black hole evaporates, each outgoing Hawking quantum carries away some of the black holes asymptotic charges associated with the extended Bondi-Metzner-Sachs group. These include the Poincaré charges of energy, linear momentum, intrinsic angular momentum, and orbital angular momentum or center-of-mass charge, as well as extensions of these quantities associated with supertranslations and super-Lorentz transformations, namely supermomentum, superspin and super center-of-mass charges (also known as soft hair). Since each emitted quantum has fluctuations that are of order unity, fluctuations in the black hole’s charges grow over the course of the evaporation. We estimate the scale of these fluctuations using a simple model. The results are, in Planck units: (i) The black hole position has a uncertainty of $$ \sim {M}_i^2 $$ ∼ M i 2 at late times, where Mi is the initial mass (previously found by Page). (ii) The black hole mass M has an uncertainty of order the mass M itself at the epoch when M ∼ $$ {M}_i^{2/3} $$ M i 2 / 3 , well before the Planck scale is reached. Correspondingly, the time at which the evaporation ends has an uncertainty of order $$ \sim {M}_i^2 $$ ∼ M i 2 . (iii) The supermomentum and superspin charges are not independent but are determined from the Poincaré charges and the super center-of-mass charges. (iv) The supertranslation that characterizes the super center-of-mass charges has fluctuations at multipole orders l of order unity that are of order unity in Planck units. At large l, there is a power law spectrum of fluctuations that extends up to l ∼ $$ {M}_i^2/M $$ M i 2 / M , beyond which the fluctuations fall off exponentially, with corresponding total rms shear tensor fluctuations ∼ MiM−3/2.

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