Issue |
A&A
Volume 525, January 2011
|
|
---|---|---|
Article Number | A94 | |
Number of page(s) | 12 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/201015317 | |
Published online | 03 December 2010 |
PSRs J0248+6021 and J2240+5832: young pulsars in the northern Galactic plane
Discovery, timing, and gamma-ray observations
1
Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, LPC2E
UMR 6115 CNRS, 45071 Orléans Cedex 02, and Station de radioastronomie de Nançay,
Observatoire de Paris, CNRS/INSU, 18330
Nançay, France
e-mail: theureau@cnrs-orleans.fr
2
Space Science Division, Naval Research Laboratory,
Washington, DC
20375,
USA
e-mail: dparent@ssd5.nrl.navy.mil
3
George Mason University, Fairfax, VA
22030,
USA
4
Université Bordeaux 1, CNRS/IN2P3, Centre d’Études Nucléaires de
Bordeaux, Gradignan, CENBG, Chemin
du Solarium, BP
120, 33175
Gradignan,
France
e-mail: smith@cenbg.in2p3.fr
5
Department of Astronomy and Radio Astronomy Laboratory, University
of California, Berkeley, CA
94720,
USA
6
Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service
d’Astrophysique, CEA Saclay, 91191
Gif-sur-Yvette,
France
7
National Research Council Research Associate, National Academy of
Sciences, Washington,
DC
20001,
USA
8
W. W. Hansen Experimental Physics Laboratory, Kavli Institute for
Particle Astrophysics and Cosmology, Department of Physics and SLAC National
Accelerator Laboratory, Stanford University, Stanford, CA
94305,
USA
9
Center for Research and Exploration in Space Science and
Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD
20771,
USA
10
Department of Physics and Department of Astronomy, University of
Maryland, College
Park, MD
20742,
USA
11
High Performance Technologies, Inc., 11955
Freedom Drive, Reston, VA
20190-5673,
USA
12
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69, 53121
Bonn,
Germany
13
NASA Goddard Space Flight Center, Greenbelt, MD
20771,
USA
14
Observatoire de Paris-CNRS/LERMA, 77 Av. Denfert Rochereau, 75014
Paris,
France
15
Department of Physics and Astronomy, University of
Calgary, Calgary,
AB, T2N 1N4, Canada
16
National Astronomical Observatories of China,
Beijing
100012, PR
China
Received: 1 July 2010
Accepted: 7 October 2010
Context. Pulsars PSR J0248+6021 (with a rotation period P = 217 ms and spin-down power Ė = 2.13 × 1035 erg s-1) and PSR J2240+5832 (P = 140 ms, Ė = 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 Lγ = (2.2 ± 1.7) ×
1034 erg s-1 for the Perseus arm. These luminosities are
consistent with an rule. 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.
Key words: gamma rays: stars / pulsars: individual: J0248+6021 / pulsars: individual: J2240+5832
© ESO, 2010
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