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. = 19h07m547(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 ≃ 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 L1400 ≃ 0.035 mJy kpc2. A Chandra ACIS observation revealed an absorbed, possibly extended, compact (≲4'') X-ray source with significant nonthermal emission at R.A. = 19h07m5476, decl. = +06°02'146 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.