Related papers: The Oort Constants Measured from Proper Motions
The spatial variations of the velocity field of local stars provide direct evidence of Galactic differential rotation. The local divergence, shear, and vorticity of the velocity field---the traditional Oort constants---can be measured based…
The local stellar kinematics of the Milky Way offer a useful tool for studying the rotation curve of the Galaxy. These kinematics -- usually parameterized by the Oort constants A and B -- depend on the local gradient of the rotation curve…
The local stellar kinematics of the Milky Way, parameterized by the Oort constants A and B, depend on the local gradient of the rotation curve, its absolute value (Theta_0), and the distance to the Galactic center (R_0). The surface density…
We estimate the solar peculiar velocities and Oort constants using a sample of 5,627 A-type stars with $d<0.6\,\rm kpc$ and $|z|<0.1\,\rm kpc$, selected from the LAMOST surveys. The radial and tangential velocities of these A-type stars are…
Truly, kinematics in the Solar neighborhood has provided important information both for the structure and for the evolution of the Galaxy since the early 20th century. The relationship between Oort constants and the ratio of the velocity…
From multi-epoch WFPC2/HST observations we present astrometric measurements of the absolute motion of the bulge stars. The presence of an extragalactic point-source candidate allows us to measure the difference between the Oort constants,…
We have studied a sample of more than 25 000 young stars with proper motions and trigonometric parallaxes from the Gaia DR2 catalogue. The relative errors of their parallaxes do not exceed 10\%. The selection of stars belonging to active…
We report a measurement of the streaming motion of the stars in the Galactic bar with the Red Clump Giants (RCGs) using the data of the Optical Gravitational Lensing Experiment II (OGLE-II). We measure the proper motion of 46,961 stars and…
We perform test-particle simulations in a 2D, differentially rotating stellar disk, subjected to a two-armed steady state spiral density wave perturbation in order to estimate the influence of spiral structure on the local velocity field.…
A proper motion study of a field of 20' x 20' inside Plaut's low extinction window (l,b)=(0 deg,-8 deg), has been completed. Relative proper motions and photographic BV photometry have been derived for ~21,000 stars reaching to V~20.5 mag,…
Previous work has related the Galactic bar to structure in the local stellar velocity distribution. Here we show that the bar also influences the spatial gradients of the velocity vector via the Oort constants. By numerical integration of…
Using multi-epoch VLA observations, covering a time baseline of 29.1 years, we have measured the proper motions of 88 young stars with compact radio emission in the core of the Orion Nebula Cluster (ONC) and the neighboring BN/KL region.…
After their initial formation, disk galaxies are observed to be rotationally stable over periods of >6 Gyr, implying that any large velocity disturbances of stars and gas clouds are damped rapidly on the timescale of their rotation.…
Variability and mass-loss are common phenomena in massive OB-type stars. It is argued that they are caused by violent strange mode instabilities identified in corresponding stellar models. We present a systematic linear stability analysis…
In the context of the space-based mission CoRoT, devoted to asteroseismology and search for planet transits, we analyse the accuracy of fundamental stellar parameters (mass, radius, luminosity) that can be obtained from asteroseismological…
The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with…
As a planet transits the face of a star, it accelerates along the line-of-sight. The changing delay in the propagation of photons produces an apparent deceleration of the planet across the sky throughout the transit. This persistent…
The Oort cloud, a collection of icy bodies orbiting the sun at roughly $10^{3}$ AU to $10^{5}$ AU, is believed to be the source of the long-period comets observed in the inner solar system. Although its existence was predicted nearly 70…
We consider two previously studied samples of OB stars with different distance scales. The first one consists of 98 massive spectroscopic binary stars with photometric distances, and the second one consists on 140 OB stars with the…
We derive the stellar rotation curve of the Galaxy in the range of Galactocentric radii of R=4-16 kpc at different vertical heights from the Galactic plane of z between -2 and +2 kpc. We used the PPMXL survey, which contains the USNO-B1…