scholarly journals The Galactic Millisecond Pulsar Population

2012 ◽  
Vol 8 (S291) ◽  
pp. 237-242 ◽  
Author(s):  
Duncan R. Lorimer
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Millisecond Pulsar ◽  
Radio Pulsars ◽  
Complete Understanding ◽  
Parent Population ◽  
Millisecond Pulsars ◽  
The Galaxy ◽  
Current Sample ◽  
First Time

AbstractAmong the current sample of over 2000 radio pulsars known primarily in the disk of our Galaxy, millisecond pulsars now number almost 200. Due to the phenomenal success of blind surveys of the Galactic field, and targeted searches of Fermi gamma-ray sources, for the first time in over a decade, Galactic millisecond pulsars now outnumber their counterparts in globular clusters! In this paper, I briefly review earlier results from studies of the Galactic millisecond pulsar population and present new constraints based on a sample of 60 millisecond pulsars discovered by 20 cm Parkes multibeam surveys. I present a simple model of the population containing ~ 30,000 potentially observable millisecond pulsars with a luminosity function, radial distribution and scale height that matches the observed sample of objects. This study represents only a first step towards a more complete understanding of the parent population of millisecond pulsars in the Galaxy and I conclude with some suggestions for further study in this area.

scholarly journals Radio counterparts of gamma-ray pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 87-92
Author(s):  
L. Guillemot
Keyword(s):  
Gamma Ray ◽  
Population Studies ◽  
Radio Observations ◽  
Large Area ◽  
Millisecond Pulsars ◽  
Follow Up Studies ◽  
First Time

AbstractObservations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.

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 The luminosity function and formation rate of a complete sample of long gamma-ray bursts

2019 ◽  
Vol 488 (4) ◽  
pp. 4607-4613 ◽  
Author(s):  
Guang-Xuan Lan ◽  
Hou-Dun Zeng ◽  
Jun-Jie Wei ◽  
Xue-Feng Wu
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Formation Rate ◽  
Gamma Ray Bursts ◽  
Likelihood Method ◽  
Complete Sample ◽  
Empirical Density ◽  
Power Law Function ◽  
Current Sample ◽  
First Time

ABSTRACT We study the luminosity function and formation rate of long gamma-ray bursts (GRBs) by using a maximum likelihood method. This is the first time this method is applied to a well-defined sample of GRBs that is complete in redshift. The sample is composed of 99 bursts detected by the Swift satellite, 81 of them with measured redshift and luminosity for a completeness level of $82\, {\rm per\, cent}$. We confirm that a strong redshift evolution in luminosity (with an evolution index of $\delta =2.22^{+0.32}_{-0.31}$) or in density ($\delta =1.92^{+0.20}_{-0.21}$) is needed in order to reproduce the observations well. But since the predicted redshift and luminosity distributions in the two scenarios are very similar, it is difficult to distinguish between these two kinds of evolutions only on the basis of the current sample. Furthermore, we also consider an empirical density case in which the GRB rate density is directly described as a broken power-law function and the luminosity function is taken to be non-evolving. In this case, we find that the GRB formation rate rises like $(1+z)^{3.85^{+0.48}_{-0.45}}$ for $z\lesssim 2$ and is proportional to $(1+z)^{-1.07^{+0.98}_{-1.12}}$ for $z\gtrsim 2$. The local GRB rate is $1.49^{+0.63}_{-0.64}$ Gpc−3 yr−1. The GRB rate may be consistent with the cosmic star formation rate (SFR) at $z\lesssim 2$, but shows an enhancement compared to the SFR at $z\gtrsim 2$.

scholarly journals A Review of Galactic Millisecond Pulsar Searches

1996 ◽  
Vol 165 ◽  
pp. 225-234
Author(s):  
A. G. Lyne
Keyword(s):  
Globular Clusters ◽  
Binary Systems ◽  
High Sensitivity ◽  
Millisecond Pulsar ◽  
Present Generation ◽  
Short Period ◽  
The Galaxy ◽  
Evolutionary Phase ◽  
Massive Binary Systems ◽  
Statistical Trends

Since the discovery of the first millisecond pulsar in 1982, the main discoveries of more of these exotic objects have come in two bursts. The first followed the realization late in the decade that they might be formed readily in globular clusters and resulted in the discovery of about two dozen objects in these clusters between 1987 and 1990. The second burst started shortly after this as improved computer technology permitted widespread searches of the Galaxy with high sensitivity and is continuing at the present time. This paper describes the main successful surveys for these galactic millisecond pulsars of which 29 are now known. 21 of these are in circular orbits with low-mass companion stars. The large number of objects now available allows a number of firm statistical trends to be seen which all point to an evolutionary phase of these systems involving the spin-up of old neutron stars during the accretion of matter from less evolved companions during their giant phase. Surveys of the present generation are still very insensitive to short period pulsars or highly accelerated pulsars in close or massive binary systems, limitations which should be removed in future years.

scholarly journals Morphological transformation of NGC 205?

2009 ◽  
Vol 5 (S262) ◽  
pp. 426-427
Author(s):  
Ivo Saviane ◽  
Lorenzo Monaco ◽  
Tony Hallas
Keyword(s):  
Globular Clusters ◽  
Large Scale ◽  
Central Field ◽  
Morphological Transformation ◽  
The Galaxy ◽  
Central Regions ◽  
Radial Orbit ◽  
Specific Frequency ◽  
Stellar Associations ◽  
First Time

NGC 205 is a small galaxy (M/M⊙ = 0.7 × 109; MV = −16.6) currently located 36′ NW of M31. It is classified as dE because in ground-based images it appears as an elliptical body. However past investigations have revealed characteristics that are more typical of a disk galaxy: the specific frequency of globular clusters is 1.8; the large scale dynamics shows partial rotational support; there is a significant amount (106M⊙) of rotating gas (molecular and atomic) and dust; the central regions harbor a fairly complex stellar population, including a 100–500 Myr old nucleus surrounded by 50- and 100-Myr old stellar associations (see references in Monaco et al. 2009; M09). Very recently, thanks to hst/acs imaging we have been able to reveal a young central ‘field’ population (M09), extending out to ~40″ in radius (~160 pc). The luminosity function of the main sequence can be fitted with Saviane et al. (2004) model of continuous star formation (SF) from at least ~600 Myr ago to ~60 Myr ago. We found that 1.5 × 105M⊙ in stars were produced from ~300 Myr to ~60 Myr ago, with a SF rate of 7 × 10−4M⊙ yr−1. A continuous SF seems to support the latest simulations of NGC 205 orbit: Howley et al. (2008) found that the galaxy must be moving with a velocity 300–500 km s−1 (comparable to the escape velocity) along an almost radial orbit, and it should be approaching M31 for the first time. An episodic SF triggered by passages through M31 disk every ~300 Myr in a bound orbit (Cepa & Beckman 1988) is excluded by our data.

scholarly journals Millisecond Pulsar Formation and Evolution

1987 ◽  
Vol 125 ◽  
pp. 393-406 ◽  
Author(s):  
E.P.J. van den Heuvel
Keyword(s):  
Neutron Stars ◽  
Millisecond Pulsar ◽  
Radio Pulsars ◽  
X Ray ◽  
Binary Pulsars ◽  
The Galaxy ◽  
History Of ◽  
Low Mass ◽  
Formation And Evolution ◽  
X Ray Binaries

The evolutionary history of binary radio pulsars, including the two millisecond binary pulsars, is reviewed. There are two groups of binary pulsars, the PSR 1913+16-group, which descended from massive X-ray binaries, and the PSR 1953+29-group, which descended from fairly wide low-mass X-ray binaries. The neutron stars in the second group probably formed by the accretion-induced collapse of a massive white dwarf. The companion stars in both groups of systems are expected to be dead stars, i.e. white dwarfs or neutron stars.The large total number of millisecond binary pulsars in the galaxy (∼ 104), indicates that magnetic fields of neutron stars do not decay below a value of order 109 G. Possible explanations for this phenomenon are discussed.Coalescence with a close degenerate companion provides a viable model for the formation of the single millisecond pulsar.

scholarly journals The New Astronomy: Observing Our Universe With Light and Gravity

2019 ◽  
Vol 7 ◽  
Author(s):  
Joey Shapiro Key ◽  
LIGO Scientific Collaboration
Keyword(s):  
Black Holes ◽  
South America ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Distant Galaxy ◽  
The World ◽  
The Galaxy ◽  
First Time

On a summer day in 2017, astronomers around the world received a message about an exciting collision of two stars far, far away. The message was sent by a team of astronomers from the LIGO and Virgo observatories. These new observatories are very different from the telescopes we have used to study our Universe up until now. LIGO and Virgo are gravitational wave observatories, listening for quiet ripples in spacetime created by the collisions of distant black holes and neutron stars. On August 17, 2017 LIGO and Virgo detected a signal that astronomers named GW170817, from the collision of two neutron stars. Less than two seconds later, NASA's Fermi satellite caught a signal, known as a gamma-ray burst, and within minutes, telescopes around the world began searching the sky. Telescopes in South America found the location of the collision in a distant galaxy known as NGC 4993. For the weeks and months that followed, astronomers watched the galaxy and the fading light from the collision. This is a new kind of multi-messenger astronomy where, for the first time, the same event was observed by both gravitational waves and light.

GAMMA-RAY BURSTS FROM HALO NEUTRON STARS CROSSING DARK CLUSTERS

1996 ◽  
Vol 11 (27) ◽  
pp. 2179-2186
Author(s):  
F. DE PAOLIS
Keyword(s):  
Neutron Stars ◽  
Globular Clusters ◽  
Flux Distribution ◽  
Gamma Ray ◽  
Galactic Halo ◽  
Outer Part ◽  
Gamma Ray Bursts ◽  
Halo Neutron ◽  
Peak Flux ◽  
The Galaxy

Two classes of neutron stars may exist in the galactic halo: high velocity neutron stars originating from the disk and injected in the halo and neutron stars originating from globular clusters (via type II supernovae and/or accretion induced collapse of white dwarfs). Moreover, the halo dark matter is likely in the form of dark clusters made of Massive Astrophysical Compact Halo Objects (MACHOs) and cold molecular clouds, expected to be formed in the outer part of the galaxy. We suggest that halo neutron stars may emit gamma-ray bursts crossing dark clusters. This assumption allows us to explain all the observed properties of gamma-ray bursts (rate, isotropy, cumulative peak flux distribution), including the different spectral properties of the two classes of short and long bursts. Several methods to test this model, independently on observations of gamma-ray bursts, are discussed.

scholarly journals Source of circular polarization in radio pulsars

2020 ◽  
Vol 498 (4) ◽  
pp. 5003-5008
Author(s):  
P B Jones
Keyword(s):  
Circular Polarization ◽  
Particle Number ◽  
Millisecond Pulsar ◽  
Radio Pulsars ◽  
Millisecond Pulsars ◽  
Detailed Understanding ◽  
Light Cylinder ◽  
Electron Positron ◽  
Distinct Process ◽  
Ion Proton

ABSTRACT It is known that the concept of limiting polarization introduced 70 yr ago by K. G. Budden has the capacity to explain the magnitude of circular polarization seen in normal pulsars with light-cylinder radii of the order of 109–10 cm under the assumption of a high-multiplicity electron–positron plasma. However, a review of limiting polarization under the same assumption in millisecond pulsars indicates that it is inapplicable there because the region of limiting polarization lies far outside the light cylinder. This paper, using the ion–proton model, evaluates circular polarization both generally and specifically for J2144−3933, and gives a fairly detailed understanding of the observations in normal pulsars including the change of sign as a function of frequency seen in J0908−4913. But it also fails to explain circular polarization in millisecond pulsars owing to the smaller particle number densities and birefringence of the magnetosphere in these objects. However, the review of limiting polarization finds that, within the ion–proton model, this distinct process can describe their circular polarization. It is argued that certain features of millisecond pulsar Stokes profiles are clearly consistent with limiting polarization.

Sign in / Sign up

Export Citation Format

Share Document