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Millisecond Pulsars (MSPs) are fast rotating, highly magnetized neutron stars. According to the "canonical recycling scenario", MSPs form in binary systems containing a neutron star which is spun up through mass accretion from the evolving…

Solar and Stellar Astrophysics · Physics 2014-05-14 Cristina Pallanca

The millisecond pulsar PSR J1740-5340 in the globular cluster NGC 6397 shows radio eclipses over ~40% of its binary orbit. A first Chandra observation revealed indications for the X-ray flux being orbit dependent as well. In this work we…

High Energy Astrophysical Phenomena · Physics 2015-05-14 R. H. H. Huang , W. Becker

We report our analysis of a Chandra X-ray observation of the rich globular cluster M80, in which we detect some 19 sources to a limiting 0.5-2.5 keV X-ray luminosity of 7*10^30 ergs/s within the half-mass radius. X-ray spectra indicate that…

In re-analyzing the archival Chandra data of the globular cluster 47 Tucanae, we have detected a new diffuse X-ray emission feature within the half-mass radius of the cluster. The spectrum of the diffuse emission can be described by a…

High Energy Astrophysical Phenomena · Physics 2015-06-19 E. M. H. Wu , C. Y. Hui , A. K. H. Kong , P. H. T. Tam , K. S. Cheng , V. A. Dogiel

We report the discovery of peculiar X-ray spectral variability in the binary radio millisecond pulsar PSR J0024--7204W in the globular cluster 47 Tucanae. The observed emission consists of a dominant non-thermal component, which is eclipsed…

Astrophysics · Physics 2009-11-11 Slavko Bogdanov , Jonathan E. Grindlay , Maureen van den Berg

We report on the Chandra X-ray Observatory ACIS-S3 imaging observation of the Galactic globular cluster M4 (NGC 6121). We detect 12 X-ray sources inside the core and 19 more within the cluster half-mass radius. The limiting luminosity of…

We report the results of pulsar searches in ten globular clusters using the Robert C. Byrd Green Bank Telescope. One new binary millisecond pulsar has been discovered in NGC 5986 with P=2.6 ms, P_orb=1.3 d, and a minimum companion mass of…

Astrophysics of Galaxies · Physics 2011-06-13 Ryan S. Lynch , Scott M. Ransom

We present a detailed analysis of the kinematics of the Galactic globular cluster NGC 6397 based on more than ~18,000 spectra obtained with the novel integral field spectrograph MUSE. While NGC 6397 is often considered a core collapse…

We have searched for millisecond pulsars (MSPs) in two globular clusters detected by the Fermi Large Area Telescope. These clusters contained no known MSPs prior to their detections in gamma rays. The discovery of gamma ray emission from…

High Energy Astrophysical Phenomena · Physics 2011-11-03 Megan E. DeCesar , Scott M. Ransom , Paul S. Ray

We have used the central 44 antennas of the new 64-dish MeerKAT radio telescope array to conduct a deep search for new pulsars in the core of nine globular clusters. This has led to the discovery of eight new millisecond pulsars in six…

We present a comprehensive census of X-ray millisecond pulsars (MSPs) in 29 Galactic globular clusters (GCs), including 68 MSPs with confirmed X-ray luminosities and 107 MSPs with X-ray upper limits. We compile previous X-ray studies of GC…

High Energy Astrophysical Phenomena · Physics 2022-03-02 Jiaqi Zhao , Craig O. Heinke

Using results from radio and X-ray observations of millisecond pulsars in 47 Tucanae, and extensive HST U, V, I imaging of the globular cluster core, we have derived a common astrometric solution good to < 0.1". A close positional…

We study the gamma-ray spectra of 30 globular clusters (GCs) thus far detected with the Fermi Gamma-ray Space Telescope. Presuming that gamma-ray emission of a GC comes from millisecond pulsars (MSPs) contained in, a model that generates…

High Energy Astrophysical Phenomena · Physics 2022-03-14 Wei Wu , Zhongxiang Wang , Yi Xing , Pengfei Zhang

We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ,…

Solar and Stellar Astrophysics · Physics 2015-10-14 M. Cadelano , C. Pallanca , F. R. Ferraro , M. Salaris , E. Dalessandro , B. Lanzoni , P. C. C. Freire

Transitional millisecond pulsars are millisecond pulsars that switch between a rotation-powered millisecond pulsar state and an accretion-powered X-ray binary state, and are thought to be an evolutionary stage between neutron star low-mass…

Recent observations of the globular cluster 47 Tuc, made with the Parkes telescope at a wavelength of 20 cm, have resulted in the discovery of nine new millisecond pulsars, all in binary systems. The number of timing solutions available has…

X-ray emission from many rotation-powered millisecond pulsars (MSPs) is observed to be of predominantly thermal nature. In PSR J0437--4715, the nearest MSP known, an additional faint power-law tail is observed above 2.5 keV, commonly…

Astrophysics · Physics 2011-02-11 Slavko Bogdanov , Jonathan E. Grindlay , George B. Rybicki

Using the Hubble Ultraviolet Globular Cluster Survey (HUGS) and additional HST archival data, we have carried out a search for optical counterparts to the low-luminosity Chandra X-ray sources in the globular cluster M4 (NGC 6121). We have…

High Energy Astrophysical Phenomena · Physics 2023-06-28 Phyllis M. Lugger , Haldan N. Cohn , Craig O. Heinke , Jiaqi Zhao , Yue Zhao , Jay Anderson

We report on archival Hubble Space Telescope (HST) observations of the globular cluster M71 (NGC 6838). These observations, covering the core of the globular cluster, were performed by the Advanced Camera for Surveys (ACS) and the Wide…

Solar and Stellar Astrophysics · Physics 2015-05-14 R. H. H. Huang , W. Becker , P. D. Edmonds , R. F. Elsner , C. O. Heinke , B. C. Hsieh

The $13.6\times 13.6$ arcmin$^{2}$ field covering the central part of the globular cluster NGC~6397 was surveyed in a search for short-period variable stars. We obtained light curves for 6 close binaries, 2 SX~Phe stars and 1 RR~Lyrae…

Astrophysics · Physics 2009-10-28 J. Kaluzny