SIMBAD references

We performed multicolor photometric and spectroscopic observations of four new low-mass M-type eclipsing binaries (HAT 225-03429, CRTS J085623.0+282620, CRTS J110302.4+201611, 2MASS J16344899+3716423) in 2017. We obtained new VRI light curves and minimum times of these four systems. Based on our minimum times, we updated the orbital periods and the linear ephemerides using the least squares method. We analyzed these four systems using the Wilson-Devinney program, and obtained the orbital and starspot parameters. The results of our analysis of the light curves indicate that HAT 225-03429 and CRTS J085623.0+282620 are detached eclipsing binaries, CRTS J110302.4+201611 is a semi-detached eclipsing binary, and 2MASS J16344899+3716423 is a contact binary. We performed LAMOST spectroscopic studies of chromospheric activity indicators (H_α, H_β, H_γ, H_δ, and Ca II H&K lines) for these four systems for the first time. We first determined their spectral types and calculated the equivalent widths of their chromospheric active indicators. These indicators show that the four low-mass M-type eclipsing binaries are active. Furthermore, the radii of these stars are notably larger than model predictions for their masses, except for the secondary component of HAT 225-03429 and the primary component of CRTS J110302.4+201611.