Eclipsing Binaries ( EBs ) with one of the companions as very low mass stars ( VLMS or M dwarfs ) are testbeds to substantiate stellar models and evolutionary theories .
Here , we present four EB candidates with F type primaries , namely , SAO 106989 , HD 24465 , EPIC 211682657 and HD 205403 , identified from different photometry missions , SuperWasp , KELT , Kepler 2 ( K2 ) and STEREO .
Using the high-resolution spectrograph , PARAS , at the 1.2 m telescope at Mount Abu , Rajasthan , India , we hereby report the detection of four VLMS as companions to the four EBs .
We performed spectroscopic analysis and found the companion masses to be 0.256 \pm 0.005 , 0.233 \pm 0.002 , 0.599 \pm 0.017 , and 0.406 \pm 0.005 ~ { } M _ { \odot } for SAO 106989 , HD 24465 , EPIC 211682657 and HD 205403 respectively .
We determined orbital periods of 4.39790 \pm 0.00001 , 7.19635 \pm 0.00002 , 3.142023 \pm 0.000003 and 2.444949 \pm 0.000001 d and eccentricities of 0.248 \pm 0.005 , 0.208 \pm 0.002 , 0.0097 \pm 0.0008 and 0.002 \pm 0.002 for EBs SAO 106989 , HD 24465 , EPIC 211682657 and HD 205403 respectively .
The radius derived by modeling the photometry data are 0.326 \pm 0.012 ~ { } R _ { \odot } for SAO 106989 , 0.244 \pm 0.001 ~ { } R _ { \odot } for HD 24465 , 0.566 \pm 0.005 ~ { } R _ { \odot } for EPIC 211682657 , and 0.444 \pm 0.014 ~ { } R _ { \odot } for HD 205403 .
The radii of HD 24465B and EPIC 211682657B have been measured by precise KEPLER photometry and are consistent with theory within error bars .
However , the radii of SAO 106989B and HD 205403B , measured by KELT and STEREO photometry , are 17 - 20 \% higher than those predicted by theory .
A brief comparison of the results of the current work is made with the M dwarfs already studied in literature .