A Survey for Hα Pulsar Bow Shocks
Abstract
We report on a survey for Hα bow shock emission around nearby γ-detected energetic pulsars. This survey adds three Balmer-dominated neutron star bow shocks to the six previously confirmed examples. In addition to the shock around Fermi pulsar PSR J1741-2054, we now report Hα structures around two additional γ-ray pulsars, PSR J2030+4415 and PSR J1509-5850. These are the first known examples of Hα nebulae with pre-ionization halos. With new measurements, we show that a simple analytic model can account for the angular size and flux of the bow shocks' apices. The latter, in particular, provides a new pulsar probe and indicates large moments of inertia and smaller distances than previously assumed in several cases. In particular, we show that the re-measured PSR J0437-4715 shock flux implies I = (1.7 ± 0.2) × 1045/(f H I sin i) g cm2. We also derive a distance d ≈ 0.72 kpc for the γ-ray only pulsar PSR J2030+4415 and revised distances for PSRs J1959+2048 (1.4 kpc) and J2555+6535 (~1 kpc), smaller than the conventional DM-estimated values. Finally, we report upper limits for 94 additional LAT pulsars. An estimate of the survey sensitivity indicates that for a warm neutral medium filling factor phiWNM ~ 0.3 there should be a total of approximately nine Hα bow shocks in our LAT-targeted survey; given that seven such objects are now known, a much larger phiWNM seems problematic.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2014
- DOI:
- 10.1088/0004-637X/784/2/154
- arXiv:
- arXiv:1402.5465
- Bibcode:
- 2014ApJ...784..154B
- Keywords:
-
- gamma rays: stars;
- pulsars: individual: PSR J2040+4415 PSR J1509-5850;
- shock waves;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 14 pages, 7 figures