Abstract Details
| Name: Priyanka Chaturvedi Affiliation: Physical Research Laboratory Conference ID: ASI2016_433 Title : Detection of two M dwarfs in F+M detached eclipsing binary systems with radial velocity measurements from PARAS Authors and Co-Authors : Abhijit Chakraborty (PRL, Ahmedabad) B.G. Anandarao (PRL, Ahmedabad) Abstract Type : Poster Abstract Category : Stars, The Milky Way Galaxy and its neighbours Abstract : Stellar systems gravitationally bound to each other where the orbital plane is inclined in a way that one component passes in front of the other causing variations in brightness are known as eclipsing binaries (EBs). Accurate determination of masses, radii, age and chemical composition of stars is possible to be studied in EBs which is important to study stellar structure and evolution. M dwarfs (having masses less than 0.6 M_sun) are studied poorly due to their relative faintness in the visible bands. A vast majority of M dwarfs have reported a higher value for radius determined observationally by 10 - 20 % in comparison with the theoretical models, an issue termed as 'M dwarf radius problem'. This discrepancy is more prevalent in the mass range of 0.3 - 0.4 M_sun, which forms a boundary between completely convective and partially radiative stars. M dwarfs which occur as companions to bright F, G and K type stars can be studied with radial velocity (RV) and transit photometry for determination of masses and radii at high accuracies with an aim to resolve the M dwarf radius problem. We report one such study of two EBs (STEREO-PARAS 2 and SWASP-PARAS 2) shortlisted from STEREO and SuperWasp (SW) photometry catalogues consisting of F type main sequence primaries and putative M dwarf secondaries. The RV measurements for both the sources have been made by the indigenously built spectrograph, PARAS (Physical Research Laboratory Advanced Radial velocity Abu Sky search), an optical fiber-fed high-resolution spectrograph coupled with the 1.2 m telescope at Mt. Abu, India. The photometry data for STEREO-PARAS 2 have been retrieved from SW. Based on high resolution spectroscopy and photometry measurements, the mass and radius for the M dwarf secondary is 0.393 M_sun and 0.449 R_sun respectively derived at an accuracy of 7 - 8 % indicating that the secondary is a M3 dwarf. The value of radius determined from observation is around 15% higher than the value predicted from theoretical models. For the second EB, SWASP-PARAS 2, the mass of the M dwarf is 0.254 M_sun. The estimated radius value based on SW photometry is 0.12 R_sun which is half the value from theoretical predictions. Noisy SW photometry may have led to erroneous determination of radius. We aim to follow this source in future for accurate determination of radius. The F+M EBs, STEREO-PARAS 2 and SWASP-PARAS 2 have periodicity of 1.686 days and 4.242 days respectively and peculiar eccentricity of around 0.25 and 0.3 respectively which are atypical for EBs in short orbital periods. The observations, analysis methods and interpretation of results for this EB system will be presented along. |