Pulsed Gamma-rays from PSR J2021+3651 with the Fermi Large Area Telescope

Abstract

We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 +/- 0.002 in phase. The first peak lags the maximum of the 2 GHz radio pulse by 0.162 +/- 0.004 +/- 0.01 in phase. The integral gamma-ray photon flux above 100 MeV is (56 +/- 3 +/- 11) x 10^{-8} /cm2/s. The photon spectrum is well-described by an exponentially cut-off power law of the form dF/dE = kE^{-Γ} e^(-E/E_c) where the energy E is expressed in GeV. The photon index is Γ= 1.5 +/- 0.1 +/- 0.1 and the exponential cut-off is E_c = 2.4 +/- 0.3 +/- 0.5 GeV. The first uncertainty is statistical and the second is systematic. The integral photon flux of the bridge is approximately 10% of the pulsed emission, and the upper limit on off-pulse gamma-ray emission from a putative pulsar wind nebula is <10% of the pulsed emission at the 95% confidence level. Radio polarization measurements yield a rotation measure of RM = 524 +/- 4 rad/m^2 but a poorly constrained magnetic geometry. Re-analysis of Chandra data enhanced the significance of the weak X-ray pulsations, and the first peak is roughly phase-aligned with the first gamma-ray peak. We discuss the emission region and beaming geometry based on the shape and spectrum of the gamma-ray light curve combined with radio and X-ray measurements, and the implications for the pulsar distance. Gamma-ray emission from the polar cap region seems unlikely for this pulsar.

Accepted by the Astrophysical Journal, 25 May 2009

References in corpus (10)

• The ATNF Pulsar Catalogue
• PSRCHIVE and PSRFITS An Open Approach to Radio Pulsar Data Storage and Analysis
• High-Altitude Emission from Pulsar Slot Gaps: The Crab Pulsar
• Fermi LAT Observations of the Vela Pulsar
• An empirical model for the beams of radio pulsars
• Profile morphology and polarization of young pulsars
• Pulsar Timing for the Fermi Gamma-ray Space Telescope
• A Survey of 56 Mid-latitude EGRET Error Boxes for Radio Pulsars
• Discovery of High-Energy Gamma-Ray Pulsations from PSR J2021+3651 with AGILE
• Rings and Jets around PSR J2021+3651: the `Dragonfly Nebula'

Cited by in corpus (14)

• Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT
• The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars
• Spatially Resolving the Very High Energy emission from MGRO J2019+37 with VERITAS
• Discovery of Pulsations from the Pulsar J0205+6449 in SNR 3C 58 with the Fermi Gamma-Ray Space Telescope
• Gamma-ray Observation of the Cygnus Region in the 100 TeV Energy Region
• Six Faint Gamma-ray Pulsars Seen with the Fermi Large Area Telescope -- Towards a Sample Blending into the Background
• Investigating the multiband nonthermal emission of the 100 TeV source eHWC J2019$+$368 with a pulsar wind nebula scenario
• Observations of three young gamma-ray pulsars with the Gran Telescopio Canarias
• Polarization Measurements of Arecibo-Sky Pulsars: Faraday Rotations and Emission-Beam Analyses
• Prospects for the detection of high-energy (E>25 GeV) Fermi pulsars with the Cherenkov Telescope Array
• High-Resolution Radio Study of the Dragonfly Nebula
• Detections of millisecond pulsars with the Fermi Large Area Telescope
• Multi-wavelength study of the MGRO J2019+37
• On the pulsar spin frequency derivatives and the glitch activity