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تسجيل مستخدم جديدLocal Stellar Kinematics and Oort Constants from the LAMOST A-type Stars
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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 fitted by using a non-axisymmetric model. The best-fitting result yields the solar peculiar velocities $(U_odot,V_odot,W_odot)=(11.69pm0.68, 10.16pm0.51, 7.67pm0.10),rm km,s^{-1}$ and Oort constants $A=16.31pm0.89,rm km,s^{-1},kpc^{-1}$, $B=-11.99pm0.79,rm km,s^{-1},kpc^{-1}$, $C=-3.10pm0.48,rm km,s^{-1},kpc^{-1}$, $K=-1.25pm1.04,rm km,s^{-1},kpc^{-1}$, respectively. $|K+C|>4,rm km,s^{-1},kpc^{-1}$ means that there is a radial velocity gradient in the extended local disk, implying the local disk is in a non-asymmetric potential. Using the derived Oort constants, we derive the local angular velocity $Omega,{approx},A-B=28.30pm1.19,rm km,s^{-1},kpc^{-1}$. By using A-type star sample of different volumes, we further try to evaluate the impacts of the ridge pattern in $R$-$V_{phi}$ plane on constraining the solar motions and Oort constants. As the volume becomes larger toward the anti-center direction, the values of $A$ and $B$ become larger (implying a steeper slope of the local rotation curve) and the value of $V_odot$ becomes smaller probably caused by the ridge structure and its signal increasing with distance.
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