Globular clusters as gamma ray sources

1992 ◽  
Vol 13 (4) ◽  
pp. 287-291 ◽  
Author(s):  
V. B. Bhatia ◽  
S. Mishra ◽  
N. Panchapakesan
Keyword(s):  
Globular Clusters ◽  
Gamma Ray

scholarly journals The dynamic ejecta of compact object mergers and eccentric collisions

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120272 ◽  
Author(s):  
Stephan Rosswog
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Compact Object ◽  
Solar Mass ◽  
Abundance Pattern ◽  
Compact Binary ◽  
Hydrodynamical Simulations ◽  
Rich Material ◽  
R Process

Compact object mergers eject neutron-rich matter in a number of ways: by the dynamical ejection mediated by gravitational torques, as neutrino-driven winds, and probably also a good fraction of the resulting accretion disc finally becomes unbound by a combination of viscous and nuclear processes. If compact binary mergers indeed produce gamma-ray bursts, there should also be an interaction region where an ultra-relativistic outflow interacts with the neutrino-driven wind and produces moderately relativistic ejecta. Each type of ejecta has different physical properties, and therefore plays a different role for nucleosynthesis and for the electromagnetic (EM) transients that go along with compact object encounters. Here, we focus on the dynamic ejecta and present results for over 30 hydrodynamical simulations of both gravitational wave-driven mergers and parabolic encounters as they may occur in globular clusters. We find that mergers eject approximately 1 per cent of a Solar mass of extremely neutron-rich material. The exact amount, as well as the ejection velocity, depends on the involved masses with asymmetric systems ejecting more material at higher velocities. This material undergoes a robust r-process and both ejecta amount and abundance pattern are consistent with neutron star mergers being a major source of the ‘heavy’ ( A >130) r-process isotopes. Parabolic collisions, especially those between neutron stars and black holes, eject substantially larger amounts of mass, and therefore cannot occur frequently without overproducing gala- ctic r-process matter. We also discuss the EM transients that are powered by radioactive decays within the ejecta (‘macronovae’), and the radio flares that emerge when the ejecta dissipate their large kinetic energies in the ambient medium.

scholarly journals Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

2018 ◽  
Vol 475 (4) ◽  
pp. 5313-5321 ◽  
Author(s):  
Giacomo Fragione ◽  
Fabio Antonini ◽  
Oleg Y Gnedin
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Galactic Centre

scholarly journals Gamma-ray emission from globular clusters 2MS-GC01, IC 1257, FSR 1735, NGC 5904 and 6656

2015 ◽  
Vol 448 (4) ◽  
pp. 3215-3220 ◽  
Author(s):  
J. N. Zhou ◽  
P. F. Zhang ◽  
X. Y. Huang ◽  
X. Li ◽  
Y. F. Liang ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Gamma Ray Emission

scholarly journals Timing of PSR J2055+3829, an eclipsing black widow pulsar discovered with the Nançay Radio Telescope

2019 ◽  
Vol 629 ◽  
pp. A92 ◽  
Author(s):  
L. Guillemot ◽  
F. Octau ◽  
I. Cognard ◽  
G. Desvignes ◽  
P. C. C. Freire ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Globular Clusters ◽  
Gamma Ray ◽  
Radio Signal ◽  
Galactic Disk ◽  
Mass Function ◽  
Large Area ◽  
Black Widow ◽  
Low Mass ◽  
Mass Functions

We report on the timing observations of the millisecond pulsar PSR J2055+3829 originally discovered as part of the SPAN512 survey conducted with the Nançay Radio Telescope. The pulsar has a rotational period of 2.089 ms and is in a tight 3.1 h orbit around a very low mass (0.023 ≤ mc ≲ 0.053 M⊙, 90% c.l.) companion. Our 1.4 GHz observations reveal the presence of eclipses of the radio signal of the pulsar, caused by the outflow of material from the companion, for a few minutes around superior conjunction of the pulsar. The very low companion mass, the observation of radio eclipses, and the detection of time variations of the orbital period establish PSR J2055+3829 as a “black widow” (BW) pulsar. Inspection of the radio signal from the pulsar during ingress and egress phases shows that the eclipses in PSR J2055+3829 are asymmetric and variable, as is commonly observed in other similar systems. More generally, the orbital properties of the new pulsar are found to be very similar to those of other known eclipsing BW pulsars. No gamma-ray source has been detected at the location of the pulsar in recent Fermi-LAT source catalogs. We used the timing ephemeris to search ten years of Fermi Large Area Telescope (LAT) data for gamma-ray pulsations, but were unable to detect any. This non-detection could be a consequence of the large distance of the pulsar compared to those of known gamma-ray millisecond pulsars outside of globular clusters. We finally compared the mass functions of eclipsing and non-eclipsing BW pulsars and confirmed previous findings that eclipsing BWs have higher mass functions than their non-eclipsing counterparts. Larger inclinations could explain the higher mass functions of eclipsing BWs. On the other hand, the mass function distributions of Galactic disk and globular cluster BWs appear to be consistent, suggesting, despite the very different environments, the existence of common mechanisms taking place in the last stages of evolution of BWs.

EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

1994 ◽  
Vol 435 ◽  
pp. 218 ◽  
Author(s):  
P. F. Michelson ◽  
D. L. Bertsch ◽  
K. Brazier ◽  
J. Chiang ◽  
B. L. Dingus ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
High Energy ◽  
Millisecond Pulsars ◽  
High Energy Gamma ◽  
Upper Limits ◽  
Energy Gamma ◽  
Gamma Ray Emission

scholarly journals A population of gamma-ray emitting globular clusters seen with theFermiLarge Area Telescope

2010 ◽  
Vol 524 ◽  
pp. A75 ◽  
Author(s):  
A. A. Abdo ◽  
M. Ackermann ◽  
M. Ajello ◽  
L. Baldini ◽  
J. Ballet ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray

scholarly journals No velocity-kicks are required to explain large-distance offsets of Ca-rich supernovae and short-GRBs

2021 ◽  
Vol 503 (4) ◽  
pp. 5997-6004
Author(s):  
Hagai B Perets ◽  
Paz Beniamini
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Gamma Ray ◽  
Stellar Populations ◽  
Host Galaxy ◽  
Early Type ◽  
Late Type ◽  
Remote Locations ◽  
Large Velocity ◽  
Short Grbs

ABSTRACT Environments of supernovae (SNe) and gamma-ray bursts (GRBs) link their progenitors to the underlying stellar population, providing critical clues for their origins. However, various transients including Ca-rich SNe and short-GRBs, appear to be located at remote locations, far from the stellar population of their host galaxy, challenging our understanding of their origin and/or physical evolution. These findings instigated models suggesting that either large velocity-kicks were imparted to the transient progenitors, allowing them to propagate to large distances and attain their remote locations; or that they formed in dense globular-clusters residing in the haloes. Here we show that instead, large spatial-offsets of such transients are naturally explained by observations of highly extended stellar populations in (mostly early-type) galaxy haloes, typically missed since they can only be identified through ultra-deep/stacked images. Consequently, no large velocity kicks, nor halo globular–cluster environments are required in order to explain the origin of these transients. These findings support thermonuclear explosions on white-dwarfs, for the origins of Ca-rich SNe progenitors, and the existence of small (or zero) kick-velocities given to short-GRB progenitors. Furthermore, since stacked/ultra-deep imaging show that early-type galaxies are more extended than late-type galaxies, studies of transients’ offset-distribution (e.g. type Ia SNe or FRBs) should account for host galaxy-type. Since early-type galaxies contain older stellar populations, transient arising from older stellar populations would have larger fractions of early-type hosts, and consequently larger fractions of large-offset transients. In agreement with our results for short-GRBs and Ca-rich SNe showing different offset distributions in early versus late-type galaxies.

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