Multiwavelength study of old open cluster M67

 We investigate the old open cluster M67 using ultraviolet photometric data of Ultra-Violet Imaging Telescope (UVIT) in multi-filter far-UV (FUV) bands and combined with other photometric data from 0.14 - 11.5 μm wavelength range. M67 is a benchmark cluster to study stellar evolution, dynamics and cluster properties due to its proximity, richness, Solar metallicity and presence of exotic stellar populations. A deep UV study of the M67 was performed to reveal the presence of a large number of stars with FUV and/or near-UV (NUV) excess. Some of these stars were found to be in binaries and many are single stars. These indicate that a large number of Sun- like stars in this cluster may be chromospherically active. A few main-sequence + white dwarf (MS+WD) binaries in M67 were detected, which could be progenitors of cataclysmic variables. We created multiwavelength spectral energy distributions (SED)s of 45 interesting candidates and estimated their fundamental parameters. We classified blue straggler stars (BSS)s into three groups and suggest that they are formed between 400 Myr - 2 Gyr, more or less continuously. The multi-filter FUV images of M67 from UVIT were used to study 9 bright BSSs. The SEDs of 6 stars were found not to fit well with single star spectra, but fitted well with a hot + cool composite spectra, consistent with IUE and HST spectra. The estimated parameters suggest the hot companions to be WDs, and this the first confirmed detection of WD companions to BSSs in M67.