Possible New γ-Ray Pulsar Detections by the [ITAL]AGILE[/ITAL] and [ITAL]GLAST[/ITAL] Missions: An Outer Gap Model Look at the Parkes Pulsar Catalog

Torres, D. F.; Nuza, Sebastián E.

doi:10.1086/367815

Cited by 11 publications

(11 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some unidentified EGRET -ray sources could be the mature pulsars predicted by this model, with ages between 0.3 and 3 Myr. In fact, a Parkes Observatory survey has discovered a large number of radio pulsars on the error boxes of EGRET unidentified -ray point sources (Torres & Nuza 2003). (5) The previous works on death lines based on the outer-gap model (e.g., Chen & Ruderman 1993) did not give detailed physical motivations; rather, they used a phenomenological approach.…”

Section: Discussionmentioning

confidence: 99%

Gamma‐Ray Luminosity and Death Lines of Pulsars with Outer Gaps

Zhang¹,

Cheng²,

Jiang³

et al. 2004

ApJ

147

View full text Add to dashboard Cite

We reexamine the outer-gap size by taking the geometry of the dipole magnetic field into account. Furthermore, we also consider that instead of taking the gap size at half of the light cylinder radius to represent the entire outer gap, it is more appropriate to average the entire outer-gap size over the distance. When these two factors are considered, the derived outer-gap size f ðP; B; hriðÞÞ is a function not only of the period P and magnetic field B of the neutron star but also of the average radial distance to the neutron star, hri, which depends on the magnetic inclination angle . We use this new outer-gap model to study the -ray luminosity of pulsars, which is given by L ¼ f 3 ðP; B; hriðÞÞL sd , where L sd is the pulsar spin-down power, and to study the death lines of -ray emission of the pulsars. Our model can predict the -ray luminosity of an individual pulsar if its P, B, and are known. Since different pulsars have different , this explains why some -ray pulsars have very similar P and B but very different -ray luminosities. In determining the death line of -ray pulsars, we have used a new criterion based on a concrete physical property, i.e., that the fractional size of the outer gap at the null-charge surface for a given pulsar cannot be larger than unity. In an estimate of the fractional size of the outer gap, two possible X-ray fields are considered: (1) X-rays produced by neutron star cooling and polar-cap heating, and (2) X-rays produced by the bombardment of relativistic particles from the outer gap onto the stellar surface (the outer gap is called a ''self-sustained outer gap''). Since it is very difficult to measure in general, we use a Monte Carlo method to simulate the properties of -ray pulsars in our Galaxy. We find that this new outer-gap model predicts many more weak -ray pulsars, which have a typical age between 0.3 and 3 Myr, than does the old model. For all simulated -ray pulsars with self-sustained outer gaps, the -ray luminosity L satisfies L / L sd , where the value of depends on the sensitivity of the -ray detector. For EGRET, $ 0:38, whereas $ 0:46 for GLAST. For -ray pulsars with L sd P L crit sd , $ 1, and L crit sd ¼ 1:5 Â 10 34 P 1=3 ergs s À1 is determined by f ðhri $ r L Þ ¼ 1. These results are roughly consistent with the observed luminosity of -ray pulsars. These predictions are very different from those of the previous outer-gap model, which predicts a very flat relation between L and L sd .

show abstract

Section: Discussionmentioning

confidence: 99%

Gamma‐Ray Luminosity and Death Lines of Pulsars with Outer Gaps

Zhang¹,

Cheng²,

Jiang³

et al. 2004

ApJ

147

View full text Add to dashboard Cite

show abstract

“…However, as the corresponding flux on Earth, F ∼ L γ /4π d 2 , is ∼2 × 10 −13 erg cm −2 s, which is even below the sensitivity of, and unobservable with, the new γ‐ray telescope GLAST. On the other hand, the middle age pulsars (τ∼ 10 6 yr) will have a gap in which both the pair creation and the γ‐ray radiation processes take place and are interesting candidates for GLAST (Torres & Nuza 2003).…”

Section: Discussionmentioning

confidence: 99%

A pulsar outer gap model with trans-field structure

Takata¹,

Shibata²,

Hirotani³

2004

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We investigate the electrodynamics of an outer gap in the meridional plane of the aligned-rotator. The charge depletion from the Goldreich-Julian charge density causes a large electric field along the magnetic field line. The electrons or the positrons are accelerated by the field-aligned electric field and radiate the $\gamma$-rays tangentially to the local magnetic field line. Some of such $\gamma$-rays collide with $X$-rays to materialize as the electron-positron pairs on different field lines from the field line on which they were emitted. As a result, the electric field structure is expected to change across the field lines. Including these trans-field effects, we solve the formation of the electric field self-consistently with the curvature radiation and the pair creation processes. The $\gamma$-ray emission and the pair creation are treated by use of Monte Carlo technique. We demonstrate that the distribution of the electric field along the field lines is affected by both the gap geometry and the external currents coming into the gap through the boundaries. In the electrodynamical model, it has been known that the solution disappears if the current density carried by the electron-positron pairs produced in the gap exceeds a critical value. We show that the critical current density is significantly increased when the trans-field structure is taken into account. We also find that the location of the inner boundary of the gap shifts toward the stellar surface from the conventional null surface as the current density increases. The reason for the shift is derived from the stability condition of the inner boundary. We also argue that the ideal-MHD condition holds outside of the gap only when the low energy particles coexist with the high energy particles migrating from the gap.Comment: 28 pages, 8 figures. Accepted for publication in MNRA

show abstract

“…Furthermore, the nearby Gould Belt also contributes a significant number of -ray pulsars at high latitude. Torres & Nuza (2003) have predicted that AGILE can detect more -ray pulsars (for a general review of AGILE, cf. Tavani et al 2001).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Gamma‐Ray Emission Properties from Mature Pulsars in the Galaxy and in the Gould Belt

Cheng

Zhang

Leung

et al. 2004

ApJ

View full text Add to dashboard Cite

We study the -ray emission properties of pulsars by using a new self-consistent outer gap model. The outer gap can exist in pulsars older than 1 million yr if the effect of magnetic inclination angle, as well as the average properties of the outer gap, are considered. The mature -ray pulsars, whose ages are between 0.3 and 3 million yr, are able to move up to high Galactic latitude. Moreover, their -ray luminosities are weaker, and their spectra are significantly softer than those of younger -ray pulsars in the Galactic plane. We use a Monte Carlo method to simulate the statistical properties of -ray pulsars in the Galaxy as well as in the Gould Belt. We find that -ray pulsars located at j b j< 5 and j b j > 5 have very different properties. High Galactic latitude -ray pulsars are dominated by mature pulsars with longer periods, weaker fluxes, and softer spectra. If the pulsar birth rates in the Galaxy and the Gould Belt are $10 À2 and $2 ; 10 À5 yr À1 , respectively, there are 42 and 35 radio-quiet -ray pulsars for j b j< 5 and j b j > 5 , respectively. The number of radio-quiet -ray pulsars from the Gould Belt are 2 and 13 for j b j< 5 and j b j > 5 , respectively. We suggest that a good fraction of unidentified EGRET -ray sources may be these radio-quiet -ray pulsars. Furthermore, -ray pulsars located at j b j > 5 satisfy L / L sd , whereas L / L sd for -ray pulsars in the Galactic plane, where $ 0:6 and $ 0:3, respectively.

show abstract

Possible New γ-Ray Pulsar Detections by the [ITAL]AGILE[/ITAL] and [ITAL]GLAST[/ITAL] Missions: An Outer Gap Model Look at the Parkes Pulsar Catalog

Cited by 11 publications

References 18 publications

Gamma‐Ray Luminosity and Death Lines of Pulsars with Outer Gaps

Gamma‐Ray Luminosity and Death Lines of Pulsars with Outer Gaps

A pulsar outer gap model with trans-field structure

Gamma‐Ray Emission Properties from Mature Pulsars in the Galaxy and in the Gould Belt

Contact Info

Product

Resources

About