Abstract–Data of our compiled catalog containing the positions , velocities , and metallicities of 415 RR Lyrae variable stars and the relative abundances [ el/Fe ] of 12 elements for 101 RR Lyrae stars , including four \alpha  elements ( Mg , Ca , Si , and Ti ) , are used to study the relationships between the chemical and spatial–kinematic properties of these stars .
In general , the dependences of the relative abundances of \alpha  elements on metallicity and velocity for the RR Lyrae stars are approximately the same as those for field dwarfs .
Despite the usual claim that these stars are old , among them are representatives of the thin disk , which is the youngest subsystem of the Galaxy .
Attention is called to the problem of low-metallicity RRÂ Lyrae stars .
Most RRÂ Lyrae stars that have the kinematic properties of thick disk stars have metallicities { [ Fe / H ] } < -1.0 and high ratios [ \alpha /Fe ] \approx 0.4 , whereas only about 10 % of field dwarfs belonging to the so-called “ low-metallicity tail ” have this chemical composition .
At the same time , there is a sharp change in [ \alpha /Fe ] in RRÂ Lyrae stars belonging just to the thick disk , providing evidence for a long period of formation of this subsystem .
The chemical compositions of SDSS J1707+58 , V455 Oph , MACHO 176.18833.411 , V456 Ser , and BPS CS 30339–046 do not correspond to their kinematics .
While the first three of these stars belong to the halo , according to their kinematics , the last two belong to the thick disk .
It is proposed that they are all most likely extragalactic , but the possible appearance of some of them in the solar neighborhood as a result of the gravitational action of the bar on field stars can not be ruled out .