A Chandra X-ray Observatory Study of PSR J1740--5340 and Candidate Millisecond Pulsars in the Globular Cluster NGC 6397

Abstract

We present a deep Chandra X-ray Observatory study of the peculiar binary radio millisecond pulsar PSR J1740--5340 and candidate millisecond pulsars (MSPs) in the globular cluster NGC 6397. The X-rays from PSR J1740--5340 appear to be non-thermal and exhibit variability at the binary period. These properties suggest the presence of a relativistic intrabinary shock formed due to interaction of a relativistic rotation-powered pulsar wind and outflow from the unusual "red-straggler/sub-subgiant" companion. We find the X-ray source U18 to show similar X-ray and optical properties to those of PSR J1740--5340, making it a strong MSP candidate. It exhibits variability on timescales from hours to years, also consistent with an intrabinary shock origin of its X-ray emission. The unprecedented depth of the X-ray data allows us to conduct a complete census of MSPs in NGC 6397. Based on the properties of the present sample of X-ray--detected MSPs in the Galaxy we find that NGC 6397 probably hosts no more than 6 MSPs.

10 pages, 6 figures, 3 tables; accepted for publication in The Astrophysical Journal

References in corpus (16)

• A Radio Pulsar/X-ray Binary Link
• The White Dwarf Cooling Sequence of NGC6397
• Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae
• Dynamical Formation of Close Binaries in Globular Clusters II: Cataclysmic Variables
• Faint X-ray Sources in the Globular Cluster Terzan 5
• Deep XMM-Newton Spectroscopic and Timing Observations of the Isolated Radio Millisecond Pulsar PSR J0030+0451
• Thermal X-rays from Millisecond Pulsars: Constraining the Fundamental Properties of Neutron Stars
• The light curve of the companion to PSR B1957+20
• Studying Millisecond Pulsars in X-rays
• Helium-Core White Dwarfs in the Globular Cluster NGC 6397
• X-ray and optical observations of M55 and NGC 6366: evidence for primordial binaries
• Searches for diffuse X-ray emission around millisecond pulsars: An X-ray nebula associated with PSR J2124-3358
• Chandra X-Ray Observatory Observations of the Globular Cluster M71
• X-Ray Binaries and the Current Dynamical States of Galactic Globular Clusters
• X-ray emission from the planet pulsar B1257+12
• An X-ray View of Radio Millisecond Pulsars

Cited by in corpus (55)

• Improved Mass and Radius Constraints for Quiescent Neutron Stars in Omega Cen and NGC 6397
• The Correlation between Dispersion Measure and X-ray Column Density from Radio Pulsars
• A Chandra X-ray Observation of the Binary Millisecond Pulsar PSR J1023+0038
• Surface Emission from Neutron Stars and Implications for the Physics of their Interiors
• 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
• X-ray Variability and Evidence for Pulsations from the Unique Radio Pulsar/X-ray Binary Transition Object FIRST J102347.6+003841
• Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: a case for Caustic Radio Emission?
• X-ray Observations of XSS J12270-4859 in a New Low State: A Transformation to a Disk-Free Rotation-Powered Pulsar Binary
• Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems
• On the Origin of Sub-subgiant Stars. I. Demographics
• Chandra X-ray Observations of 12 Millisecond Pulsars in the Globular Cluster M28
• 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
• X-ray Through Very-High-Energy Intrabinary Shock Emission from Black Widows and Redbacks
• A Deep X-ray Survey of the Globular Cluster Omega Centauri
• On the Origin of Sub-Subgiant Stars II: Binary Mass Transfer, Envelope Stripping, and Magnetic Activity
• Pressure Balance and Intrabinary Shock Stability in Rotation-Powered State Redback and Transitional Millisecond Pulsar Binary Systems
• A Chandra Look at the X-ray Faint Millisecond Pulsars in the Globular Cluster NGC 6752
• The NuSTAR view of the non-thermal emission from PSR J0437-4715
• 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
• A Census of X-ray Millisecond Pulsars in Globular Clusters
• X-ray and $\gamma$-ray Studies of the Millisecond Pulsar and Possible X-ray Binary/Radio Pulsar Transition Object PSR J1723-2837
• HST/ACS Imaging of Omega Centauri: Optical Counterparts of Chandra X-Ray Sources
• X-ray Binaries in the Ultrahigh Encounter Rate Globular Cluster NGC 6388
• A millisecond pulsar candidate in a 21-hr orbit: 3FGL J0212.1+5320
• A Chandra X-ray study of the interacting binaries in the old open cluster NGC6791
• A Deep Chandra X-ray Observatory Study of the Millisecond Pulsar Population in the Globular Cluster Terzan 5
• An Examination of the X-ray Sources in the Globular Cluster NGC 6652
• Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6752
• X-ray emissivity of old stellar populations: a local group census
• The MAVERIC survey: A hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397
• High-Energy Emission of the First Millisecond Pulsar
• The X-ray Emissivity of Low-Density Stellar Populations
• Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397
• Far-Ultraviolet Observation of the Globular Cluster NGC 6397
• Death Line of Gamma-ray Pulsars with Outer Gaps
• A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and searches for optical and radio counterparts
• A Deep Search for Faint Chandra X-ray Sources, Radio Sources, and Optical Counterparts in NGC 6752
• A complete census of $H\alpha$ emitters in NGC 6397
• Light-element abundance variations in globular clusters
• A comparison of millisecond pulsar populations between globular clusters and the Galactic field
• On the vanishing orbital X-ray variability of the eclipsing binary millisecond pulsar 47 Tuc W
• Exotica in the Globular Cluster M4, Studied with Chandra, HST, and the VLA
• A 2 day orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397
• A candidate magnetic helium core white dwarf in the globular cluster NGC 6397
• Searching for exotic object companions in the dense core of NGC 362: a multi-wavelength and multi-epoch photometric analysis
• Orbital variation of the X-ray emission from the double neutron star binary J1537+1155
• X-rays from Radio Millisecond Pulsars
• A second neutron star in M4?
• Hydrodynamical simulations of wind interaction in spider systems : A step toward understanding transitional millisecond pulsars
• A search for dormant binaries with degenerate components in omega Centauri and NGC 6397
• Exploration of faint X-ray and radio sources in the massive globular cluster M14: A UV-bright counterpart to Nova Ophiuchus 1938
• Reevaluating the Origin of Detectable Cataclysmic Variables in Globular Clusters: Testing the Importance of Dynamics