A 2-d orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397

Manuel Pichardo Marcano; Liliana E. Rivera Sandoval; Thomas J. MacCarone; Yue Zhao; Craig O. Heinke

doi:10.1093/mnrasl/slab024

A 2-d orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397

Manuel Pichardo Marcano, Liliana E. Rivera Sandoval, Thomas J. MacCarone, Yue Zhao, Craig O. Heinke

Physics

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2 Scopus citations

Abstract

We report optical modulation of the companion to the X-ray source U18 in the globular cluster NGC 6397. U18, with combined evidence from radio and X-ray measurements, is a strong candidate as the second redback in this cluster, initially missed in pulsar searches. This object is a bright variable star with an anomalous red colour and optical variability (∼0.2 mag in amplitude) with a periodicity ∼1.96 d that can be interpreted as the orbital period. This value corresponds to the longest orbital period for known redback candidates and confirmed systems in Galactic globular clusters and one of the few with a period longer than 1 d.

Original language	English
Pages (from-to)	L51-L55
Journal	Monthly Notices of the Royal Astronomical Society: Letters
Volume	503
Issue number	1
DOIs	https://doi.org/10.1093/mnrasl/slab024
State	Published - May 1 2021

Keywords

X-rays: binaries pulsars
globular clusters: general
globular clusters: individual (NGC 6397)

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10.1093/mnrasl/slab024

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title = "A 2-d orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397",

abstract = "We report optical modulation of the companion to the X-ray source U18 in the globular cluster NGC 6397. U18, with combined evidence from radio and X-ray measurements, is a strong candidate as the second redback in this cluster, initially missed in pulsar searches. This object is a bright variable star with an anomalous red colour and optical variability (∼0.2 mag in amplitude) with a periodicity ∼1.96 d that can be interpreted as the orbital period. This value corresponds to the longest orbital period for known redback candidates and confirmed systems in Galactic globular clusters and one of the few with a period longer than 1 d.",

keywords = "X-rays: binaries pulsars, globular clusters: general, globular clusters: individual (NGC 6397)",

author = "Marcano, {Manuel Pichardo} and {Rivera Sandoval}, {Liliana E.} and MacCarone, {Thomas J.} and Yue Zhao and Heinke, {Craig O.}",

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T1 - A 2-d orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397

AU - Marcano, Manuel Pichardo

AU - Rivera Sandoval, Liliana E.

AU - MacCarone, Thomas J.

AU - Zhao, Yue

AU - Heinke, Craig O.

PY - 2021/5/1

Y1 - 2021/5/1

N2 - We report optical modulation of the companion to the X-ray source U18 in the globular cluster NGC 6397. U18, with combined evidence from radio and X-ray measurements, is a strong candidate as the second redback in this cluster, initially missed in pulsar searches. This object is a bright variable star with an anomalous red colour and optical variability (∼0.2 mag in amplitude) with a periodicity ∼1.96 d that can be interpreted as the orbital period. This value corresponds to the longest orbital period for known redback candidates and confirmed systems in Galactic globular clusters and one of the few with a period longer than 1 d.

AB - We report optical modulation of the companion to the X-ray source U18 in the globular cluster NGC 6397. U18, with combined evidence from radio and X-ray measurements, is a strong candidate as the second redback in this cluster, initially missed in pulsar searches. This object is a bright variable star with an anomalous red colour and optical variability (∼0.2 mag in amplitude) with a periodicity ∼1.96 d that can be interpreted as the orbital period. This value corresponds to the longest orbital period for known redback candidates and confirmed systems in Galactic globular clusters and one of the few with a period longer than 1 d.

KW - X-rays: binaries pulsars

KW - globular clusters: general

KW - globular clusters: individual (NGC 6397)

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DO - 10.1093/mnrasl/slab024

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JO - Monthly Notices of the Royal Astronomical Society: Letters

JF - Monthly Notices of the Royal Astronomical Society: Letters

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A 2-d orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397

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