A 2 day 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 color and optical variability (\sim 0.2 mag in amplitude) with a periodicity \sim 1.96 days 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 day.

arXiv commentAccepted for publication as a letter in MNRAS

References in corpus (48)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• WFPC2 Stellar Photometry with HSTphot
• Resolved Massive Star Clusters in the Milky Way and its Satellites: Brightness Profiles and a Catalogue of Fundamental Parameters
• A Radio Pulsar/X-ray Binary Link
• Swings between rotation and accretion power in a millisecond binary pulsar
• Assessing statistical significance of periodogram peaks
• Distances and ages of NGC 6397, NGC 6752 and 47 Tuc
• Re-examining the X-Ray versus Spin-Down Luminosity Correlation of Rotation Powered Pulsars
• A state change in the low-mass X-ray binary XSS J12270-4859
• Detectability of Extrasolar Planets in Radial Velocity Surveys
• Formation of black widows and redbacks -- two distinct populations of eclipsing binary millisecond pulsars
• Improved Mass and Radius Constraints for Quiescent Neutron Stars in Omega Cen and NGC 6397
• An X-ray Nebula Associated with the Millisecond Pulsar B1957+20
• Chandra Exposes the Core Collapsed Globular Cluster NGC 6397
• A Chandra X-ray Observation of the Binary Millisecond Pulsar PSR J1023+0038
• Discovery of short-period binary millisecond pulsars in four globular clusters
• Surrounded by Spiders! New Black Widows and Redbacks in the Galactic Field
• MUSE crowded field 3D spectroscopy of over 12,000 stars in the globular cluster NGC 6397 - I. The first comprehensive spectroscopic HRD of a globular cluster
• Intra-Binary Shock Heating of Black Widow Companions
• Optical spectroscopy and demographics of redback millisecond pulsar binaries
• The bright optical companion to the eclipsing millisecond pulsar in NGC 6397
• Is FIRST J102347.6+003841 Really a Cataclysmic Binary?
• X-ray Radiation from the Millisecond Pulsar J0437-4715
• Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function
• An X-ray Variable Millisecond Pulsar in the Globular Cluster 47 Tucanae: Closing the Link to Low Mass X-ray Binaries
• Understanding the evolution of close binary systems with radio pulsars
• Probing the Faintest Stars in a Globular Star Cluster
• Atmospheric Circulation on Black Widow Companions
• Cataclysmic Variables and a New Class of Faint UV Stars in the Globular Cluster NGC 6397
• A Chandra X-ray Observatory Study of PSR J1740--5340 and Candidate Millisecond Pulsars in the Globular Cluster NGC 6397
• Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6397: Evidence for a Bimodal Cataclysmic Variable Population
• New Cataclysmic Variables and other Exotic Binaries in the Globular Cluster 47 Tucanae
• 1FGL J1417.7-4407: A likely gamma-ray bright binary with a massive neutron star and a giant secondary
• Variable Heating and Flaring of Three Redback Millisecond Pulsar Companions
• Discovery of a millisecond pulsar in the 5.4 day binary 3FGL J1417.5-4402: observing the late phase of pulsar recycling
• A multi-wavelength view of the neutron star binary 1FGL J1417.7--4402: A progenitor to canonical millisecond pulsars
• Exploring the intrabinary shock from the redback millisecond pulsar PSR J2129-0429
• 2FGL J0846.0+2820: A new neutron star binary with a giant secondary and variable $\gamma$-ray emission
• Different twins in the millisecond pulsar recycling scenario: optical polarimetry of PSR J1023+0038 and XSS J12270-4859
• The MAVERIC survey: A hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397
• Photometric study of the variable star population in the globular cluster NGC 6397
• A New Likely Redback Millisecond Pulsar Binary with a Massive Neutron Star: 4FGL J2333.1--5527
• Far-Ultraviolet Observation of the Globular Cluster NGC 6397
• The 26.3-hr orbit and multi-wavelength properties of the "redback" millisecond pulsar PSR J1306-40
• Erupting Cataclysmic Variable Stars in the Nearest Globular Cluster, NGC 6397: Intermediate Polars?
• A complete census of $H\alpha$ emitters in NGC 6397

Cited by in corpus (4)

• A Census of X-ray Millisecond Pulsars in Globular Clusters
• Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397
• A time-series VI study of the variable stars of the globular cluster NGC 6397
• A VLITE Search for Millisecond Pulsars in Globular Clusters: Discovery of a Pulsar in GLIMPSE-C01