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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 observed the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-ray Observatory to study its faint X-ray populations. Five X-ray sources were found inside the cluster core radius, including the known eclipsing binary…

It is expected that specific globular clusters can contain up to a hundred of millisecond pulsars. These pulsars can accelerate leptons at the shock waves originated in collisions of the pulsar winds and/or inside the pulsar magnetospheres.…

Astrophysics · Physics 2013-06-21 W. Bednarek , J. Sitarek

We report the detection of ionized intracluster gas in the globular cluster 47 Tucanae. Pulsars in this cluster with a negative period derivative, which must lie in the distant half of the cluster, have significantly higher measured…

Astrophysics · Physics 2009-10-05 P. C. Freire , M. Kramer , A. G. Lyne , F. Camilo , R. N. Manchester , N. D'Amico

We study the process of dynamical capture of a millisecond pulsar (MSP) by a single or binary IMBH, simulating various types of single-binary and binary-binary encounters. It is found that [IMBH,MSP] binaries form over cosmic time in a…

Astrophysics · Physics 2009-11-13 B. Devecchi , M. Colpi , M. Mapelli , A. Possenti

Theoretical models predict that intermediate-mass black holes (IMBHs) exist in globular clusters (GCs), but observational evidence remains elusive. Millisecond pulsars (MSPs), which are abundant in GCs and have served as precise probes for…

High Energy Astrophysical Phenomena · Physics 2025-07-15 Xian Chen , Verónica Vázquez-Aceves , Siyuan Chen , Kejia Lee , Yanjun Guo , Kuo Liu

This paper reports recent discoveries from the Globular Clusters GMRT Pulsar Search (GCGPS) survey, which aims to uncover pulsars in the globular clusters (GCs) of the Milky Way using the upgraded Giant Metrewave Radio Telescope (uGMRT).…

This paper describes the new Globular Clusters GMRT Pulsar Search (GCGPS) survey. This survey aims to find MSPs in the globular clusters (GCs) of the Milky Way using uGMRT. The observations use the uGMRT's Band-4 (550$-$750 MHz) and Band-3…

Two energetic millisecond pulsars (MSPs) within globular clusters (GC), J1823-3021A in NGC 6624 and PSR B1821-24 in M28, have been recently discovered to emit pulsed GeV gamma-rays. These MSPs are expected to eject energetic leptons.…

High Energy Astrophysical Phenomena · Physics 2016-02-24 W. Bednarek , J. Sitarek , T. Sobczak

Multi-decade observing campaigns of the globular clusters 47 Tucanae and M15 have led to an outstanding number of discoveries. Here, we report on the latest results of the long-term observations of the pulsars in these two clusters. For…

Diffuse X-ray emission has recently been detected from the globular cluster (GC) Terzan 5, extending out to ~2.5' from the cluster centre. This emission may arise from synchrotron radiation (SR) by energetic leptons being injected into the…

High Energy Astrophysical Phenomena · Physics 2012-10-05 I. Buesching , C. Venter , A. Kopp , O. C. de Jager , A. C. Clapson

Globular clusters (GCs) with their ages of the order of several billion years contain many final products of evolution of stars such as: neutron stars, white dwarfs and probably also black holes. These compact objects can be at present…

High Energy Astrophysical Phenomena · Physics 2015-05-19 W. Bednarek

We present a Chandra X-ray Observatory investigation of the millisecond pulsars (MSPs) in the globular cluster M28 (NGC 6626). In what is one of the deepest X-ray observations of a globular cluster, we firmly detect seven and possibly…

We estimate the contribution of Galactic pulsars, both ordinary and millisecond pulsars (MSPs), to the high-energy (>100 MeV) gamma-ray background. We pay particular attention to the high-latitude part of the background that could be…

High Energy Astrophysical Phenomena · Physics 2010-01-15 C. -A. Faucher-Giguere , Abraham Loeb

The X-ray and $\gamma$-ray emission of globular clusters (GCs) is attributed to their large fraction of compact binary systems, especially those with millisecond pulsars (MSPs). We analyze a population of 124 Galactic GCs to investigate how…

High Energy Astrophysical Phenomena · Physics 2023-06-14 Raniere de Menezes , Federico Di Pierro , Andrea Chiavassa

The X-ray and gamma-ray spectrum of rotation-powered millisecond pulsars is investigated in a model for acceleration and pair cascades on open field lines above the polar caps. Although these pulsars have low surface magnetic fields, their…

Astrophysics · Physics 2016-08-30 Alice K. Harding , Vladimir V. Usov , Alex G. Muslimov

Using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, we have searched for the gamma-ray pulsations from the direction of globular cluster M28 (NGC 6626). We report the discovery of a signal with the…

High Energy Astrophysical Phenomena · Physics 2015-06-12 J. H. K. Wu , C. Y. Hui , E. M. H. Wu , A. K. H. Kong , R. H. H. Huang , P. H. T. Tam , J. Takata , K. S. Cheng

We present spectra of pulsed gamma-ray emission expected from millisecond pulsars within the framework of polar-cap models. The spectra are a superposition of three components due to curvature (CR), synchrotron (SR), and Compton…

Astrophysics · Physics 2007-05-23 Tomasz Bulik , Bronislaw Rudak

We review the properties of the 22 millisecond radio pulsars currently known in the globular cluster 47 Tucanae, and their implications for the mass and gas content of the cluster. Further details can be found in the publications from this…

Astrophysics · Physics 2007-05-23 D. R. Lorimer , F. Camilo , P. Freire , M. Kramer , A. G. Lyne , R. N. Manchester , & N. D'Amico

Globular clusters (GCs) are the ideal environment for the formation of neutron stars (NSs) and millisecond pulsars (MSPs). NSs origin and evolution provide a useful information on stellar dynamics and evolution in star clusters, and are…

Astrophysics of Galaxies · Physics 2018-08-29 Giacomo Fragione , Václav Pavlík , Sambaran Banerjee