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We present the UV photometry of the globular cluster NGC 1261 using imagesacquired with the Ultraviolet Imaging Telescope (UVIT) on-board ASTROSAT. Weperformed PSF photometry on four near-UV (NUV) and two far-UV (FUV) images andconstructed UV colour-magnitude diagrams (CMDs), in combination with HST, Gaia,and ground-based optical photometry for member stars. We detected the fullhorizontal branch (HB) in NUV, blue HB in the FUV and identified two extreme HB(EHB) stars. HB stars have a tight sequence in UV-optical CMDs well-fitted withisochrones generated (12.6 Gyr age, [Fe/H] = -1.27 metallicity) using updatedBaSTI-IAC models. Effective temperatures (Teff), luminosities and radii ofbright HB stars were estimated using spectral energy distribution. As we detectthe complete sample of UV bright HB stars, the hot end of the HB distributionis found to terminate at the G-jump (Teff ~ 11500 K). The two EHB stars, fittedwell with single spectra, have Teff= 31,000 K and a mass = 0.495Msun and followthe same Teff-Radius relation of the blue HB stars. We constrain the formationpathways of these EHB stars to extreme mass loss in the RGB phase (either dueto rotation or enhanced Helium), OR early hot-flash scenario.

Study of UV bright stellar populations in the globular cluster NGC 1261 using AstroSat