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Title: Detection of a white dwarf companion to a blue straggler star in the outskirts of globular cluster NGC 5466 with the ultraviolet imaging telescope (UVIT)
Authors: Snehalata Sahu
Subramaniam, A
Simunovic, Mirko
Postma, J
Cote, Patrick
Kameswara Rao, N
Geller, Aaron M
Leigh, Nathan
Shara, Michael
Puzia, Thomas H
Stetson, Peter B
Keywords: Blue stragglers;Globular clusters: individual (NGC 5466);Binaries: general;Ultraviolet: stars;White dwarfs
Issue Date: 1-May-2019
Publisher: IOP Publishing
Citation: The Astrophysical Journal, Vol. 876, No. 1, 34
Abstract: We report the discovery of a hot white dwarf (WD) companion to a blue straggler star (BSS) in the globular cluster (GC) NGC 5466, based on observations from the Ultra-Violet Imaging Telescope (UVIT) on board AstroSat. The Spectral Energy Distribution (SED) of the Far-UV detected BSS NH 84 was constructed by combining the flux measurements from four filters of UVIT, with GALEX, GAIA, and other ground-based observations. The SED of NH 84 reveals the presence of a hot companion to the BSS. The temperature and radius of the BSS (T ${}_{\mathrm{eff}}={8000}_{-250}^{+1000}$ K, R/R ${}_{\odot }=1.44\pm 0.05$) derived from Gemini spectra and SED fitting using Kurucz atmospheric models are consistent with each other. The temperature and radius of the hotter companion of NH 84 (T ${}_{\mathrm{eff}}={\rm{32,000}}\pm 2000$ K, R/R ${}_{\odot }=0.021\pm 0.007$) derived by fitting Koester WD models to the SED suggest that it is likely to be a hot WD. The radial velocity derived from the spectra along with the proper motion from GAIA DR2 confirms NH 84 to be a kinematic member of the cluster. This is the second detection of a BSS-WD candidate in a GC, and the first in the outskirts of a low-density GC. The location of this BSS in NGC 5466 along with its dynamical age supports the mass-transfer pathway for BSS formation in low-density environments.
Description: Restricted Access
ISSN: 0004-637X
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Appears in Collections:IIAP Publications

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