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    • Keywords


      Galaxy: globular clusters: individual: NGC 4147; stars: horizontal-branch; stars: blue straggler; stars: Hertzsprung–Russell and colour-magnitude diagrams.

    • Abstract


      We present far ultraviolet (FUV) observations of globular cluster NGC 4147 using three FUV filters, BaF2 (F154W), sapphire (F169M), and silica (F172M) of Ultra-Violet Imaging Telescope (UVIT) onboard the AstroSat satellite. We confirmed the cluster membership of the UVIT observed sources usingproper motions from Gaia data release 2 (GAIA DR2). We identified 37 blue horizontal branch stars (BHBs), one blue straggler star (BSS) and 15 variable stars using UV-optical color magnitude diagrams (CMDs). We find that all the FUV bright BHBs are second generation population stars. Using UV-optical CMDs, weidentify two sub-populations, BHB1 and BHB2, among the UV-bright BHBs in the cluster with stars count ratio of 24:13 for BHB1 and BHB2. The effective temperatures ($T_{\rm eff}$) of BHB1 and BHB2 were derived using color-temperature relation of BaSTI-IAC zero-age horizontal branch (ZAHB). We found that BHB1 stars are more centrally concentrated than BHB2 stars. We also derive physical parameters of the detected FUV bright BSS by fitting younger age BaSTI-IAC isochrones on optical and UV-optical CMDs.

    • Author Affiliations



      1. Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha 769 008, India.
      2. Indian Institute of Astrophysics, Koramangala II-Block, Bangalore 560 034, India.
      3. Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005, India.
      4. INAF - Astronomical Observatory of Abruzzo, Via M. Maggini, sn. 64100 Teramo, Italy.
      5. INFN - Sezione di Pisa, Universita` di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy.
    • Dates

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