PSRs J0248+6021 and J2240+5832: young pulsars in the northern Galactic plane: Discovery, timing, and gamma-ray observations

Journal Article · Fri Dec 03 00:00:00 EST 2010 · Astronomy and Astrophysics

DOI:https://doi.org/10.1051/0004-6361/201015317· OSTI ID:1357267

Theureau, G.; Parent, D.; Cognard, I.; Desvignes, G.; Smith, D. A.; Casandjian, J. M.; Cheung, C. C.; Craig, H. A.; Donato, D.; Foster, R.; Guillemot, L.; Harding, A. K.; Lestrade, J. -F.; Ray, P. S.; Romani, R. W.; Thompson, D. J.; Tian, W. W.; Watters, K.

Context. Pulsars PSR J0248+6021 (with a rotation period P = 217 ms and spin-down power $$\dot{E}$$ = 2.13 × 10³⁵ erg s^-1) and PSR J2240+5832 (P = 140 ms, $$\dot{E}$$ = 2.12 × 10³⁵ erg s^-1) were discovered in 1997 with the Nançay radio telescope during a northern Galactic plane survey, using the Navy-Berkeley Pulsar Processor (NBPP) filter bank. The GeV gamma-ray pulsations from both were discovered using the Fermi Large Area Telescope. Aims. We characterize the neutron star emission using radio and gamma-ray observations, and explore the rich environment of PSR J0248+6021. Methods. Twelve years of radio timing data, including glitches, with steadily improved instrumentation, such as the Berkeley-Orleans-Nançay pulsar backend, and a gamma-ray data set 2.6 times larger than previously published allow detailed investigations of these pulsars. Radio polarization data allow comparison with the geometry inferred from gamma-ray emission models. Results. The two pulsars resemble each other in both radio and gamma-ray data. Both are rare in having a single gamma-ray pulse offset far from the radio peak. The anomalously high dispersion measure for PSR J0248+6021 (DM = 370 pc cm^-3) is most likely due to its being within the dense, giant HII region W5 in the Perseus arm at a distance of 2 kpc, as opposed to being beyond the edge of the Galaxy as obtained from models of average electron distributions. Its large transverse velocity and the low magnetic field along the line-of-sight favor this small distance. Neither gamma-ray, X-ray, nor optical data yield evidence of a pulsar wind nebula surrounding PSR J0248+6021. We report the discovery of gamma-ray pulsations from PSR J2240+5832. We argue that it could be in the outer arm, although slightly nearer than its DM-derived distance, but that it may be in the Perseus arm at half the distance. Conclusions. The energy flux and distance yield a gamma-ray luminosity for PSR J0248+6021 of Lγ = (1.4 ± 0.3) × 10³⁴ erg s^-1. For PSR J2240+5832, we find either Lγ = (7.9 ± 5.2) × 10³⁴ erg s^-1 if the pulsar is in the outer arm, or L_γ = (2.2 ± 1.7) × 10³⁴ erg s^-1 for the Perseus arm. These luminosities are consistent with an L_γ∝ $$\sqrt{\dot{E}}$$ rule. Lastly, comparison of the gamma-ray pulse profiles with model predictions, including the constraints obtained from radio polarization data, implies outer magnetosphere emission. These two pulsars differ mainly in terms of their inclination angles and acceleration gap widths, which in turn explain the observed differences in the gamma-ray peak widths.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE; National Aeronautics and Space Administration (NASA)
• Contributing Organization: The Fermi LAT Collaboration
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1357267
• Journal Information: Astronomy and Astrophysics, Vol. 525; ISSN 0004-6361
• Publisher: EDP Sciences
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
gamma rays
stars
pulsars
J0248+6021
J2240+5832