Detection of a Quiescent Low Mass X-Ray Binary Companion in 47 Tucanae

Abstract

We present the results of a search for optical counterparts to the two quiescent low mass X-ray binaries (X5 and X7) in the globular cluster 47 Tucanae, using high quality Chandra and HST images. A faint blue (V=21.7; U-V=0.9) star within 0.03" of the eclipsing system X5 shows variability on both short and long timescales, and is the counterpart of the X-ray source. The colors and variability of this object are consistent with the combination of light from an accretion disk and a red main sequence star (possibly somewhat larger than a normal MS star with similar luminosity). No evidence is found for a star showing either variability or unusual colors near the position of X7, but a probable chance superposition of a star with V=20.25 limits the depth of our search.

4 pages, 3 figures, accepted for ApJ Letters

References in corpus (8)

• High Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
• The Frequency of Binary Stars in the Core of 47 Tucanae
• Chandra Exposes the Core Collapsed Globular Cluster NGC 6397
• The bright optical companion to the eclipsing millisecond pulsar in NGC 6397
• Timing the millisecond pulsars in 47 Tucanae
• The ages and colours of cool helium-core white dwarf stars
• Optical Detection of a Variable Millisecond Pulsar Companion in 47 Tucanae
• Identification of the LMXB and Faint X-ray Sources in NGC 6652

Cited by in corpus (24)

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• Analysis of the Quiescent Low-Mass X-ray Binary Population in Galactic Globular Clusters
• Neutron Star Mass-Radius Constraints of the Quiescent Low-mass X-ray Binaries X7 and X5 in the Globular Cluster 47 Tuc
• An Extensive Census of HST Counterparts to Chandra X-ray Sources in the Globular Cluster 47 Tucanae. I. Astrometry and Photometry
• An Extensive Census of HST Counterparts to Chandra X-ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis
• X-ray Studies of Two Neutron Stars in 47 Tucanae: Toward Constraints on the Equation of State
• BVI time series data of the Galactic Globular Cluster NGC3201. I. RR Lyrae stars
• A Millisecond Pulsar Optical Counterpart with Large-Amplitude Variability in the Globular Cluster 47 Tucanae
• New constraints on the nuclear equation of state from the thermal emission of neutron stars in quiescent low-mass X-ray binaries
• Chandra X-ray Sources in the Collapsed-Core Globular Cluster M30 (NGC 7099)
• Chandra studies of the globular cluster 47 Tucanae: A deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars, and new constraints to r-mode instability window
• HST/ACS Imaging of Omega Centauri: Optical Counterpart for the Quiescent Low-Mass X-Ray Binary
• Black Holes in Short Period X-ray Binaries and the Transition to Radiatively Inefficient Accretion
• Three Additional Quiescent Low-Mass X-ray Binary Candidates in 47 Tucanae
• X-ray Spectral Identification of Three Candidate Quiescent Low-Mass X-ray Binaries in the Globular Cluster NGC 6304
• The impact of surface temperature inhomogeneities on quiescent neutron star radius measurements
• The X-ray source population of the globular cluster M15: Chandra high resolution imaging
• New possible class of neutron stars: hot and fast non-accreting rotators
• Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters: The Case of 47 Tucanae
• UV-Bright Stellar Populations and Their Evolutionary Implications in the Collapsed-Core Cluster M15
• Far-Ultraviolet Observations of RR Lyrae Stars in the Core of NGC 1851
• Observability of HOFNARs with SRG/eROSITA
• Exploration of faint X-ray and radio sources in the massive globular cluster M14: A UV-bright counterpart to Nova Ophiuchus 1938