PSR J1907+0602: a radio-faint gamma-ray pulsar powering a bright TeV pulsar wind nebula

Abstract

We present multiwavelength studies of the 106.6 ms γ-ray pulsar PSR J1907+06 near the TeV source MGRO J1908+06. Timing observations with Fermi result in a precise position determination for the pulsar of R.A. = 19h07m54fs7(2), decl. = +06°02'16(2)'' placing the pulsar firmly within the TeV source extent, suggesting the TeV source is the pulsar wind nebula of PSR J1907+0602. Pulsed γ-ray emission is clearly visible at energies from 100 MeV to above 10 GeV. The phase-averaged power-law index in the energy range E > 0.1 GeV is Γ = 1.76 ± 0.05 with an exponential cutoff energy Ec = 3.6 ± 0.5 GeV. We present the energy-dependent γ-ray pulsed light curve as well as limits on off-pulse emission associated with the TeV source. We also report the detection of very faint (flux density of sime 3.4 μJy) radio pulsations with the Arecibo telescope at 1.5 GHz having a dispersion measure DM = 82.1 ± 1.1 cm–3 pc. This indicates a distance of 3.2 ± 0.6 kpc and a pseudo-luminosity of L 1400 sime 0.035 mJy kpc2. A Chandra ACIS observation revealed an absorbed, possibly extended, compact (lesssim4'') X-ray source with significant nonthermal emission at R.A. = 19h07m54fs76, decl. = +06°02'14farcs6 with a flux of 2.3+0.6 –1.4 × 10–14 erg cm–2 s–1. From archival ASCA observations, we place upper limits on any arcminute scale 2-10 keV X-ray emission of ~1 × 10–13 erg cm–2 s–1. The implied distance to the pulsar is compatible with that of the supernova remnant G40.5 – 0.5, located on the far side of the TeV nebula from PSR J1907+0602, and the S74 molecular cloud on the nearer side which we discuss as potential birth sites