PSR J2021+4026 IN THE GAMMA CYGNI REGION: THE FIRST VARIABLE gamma-RAY PULSAR SEEN BY THE Fermi LAT
2013 (English)In: ASTROPHYS J LETT, ISSN 2041-8205, Vol. 777, no 1, L2- p.Article in journal (Refereed) Published
Long-term monitoring of PSR J2021+4026 in the heart of the Cygnus region with the Fermi Large Area Telescope unveiled a sudden decrease in flux above 100 MeV over a timescale shorter than a week. The jump was near MJD 55850 (2011 October 16), with the flux decreasing from (8.33+/-0.08) x 10(-10) erg cm(-2) s(-1) to (6.86+/-0.13) x 10(-10) erg cm(-2) s(-1). Simultaneously, the frequency spindown rate increased from (7.8 +/- 0.1) x 10(-13) Hz s(-1) to (8.1 +/- 0.1) x 10(-13) Hz s(-1). Significant (>5 sigma) changes in the pulse profile and marginal (<3 sigma) changes in the emission spectrum occurred at the same time. There is also evidence for a small, steady flux increase over the 3 yr preceding MJD 55850. This is the first observation at gamma-ray energies of mode changes and intermittent behavior, observed at radio wavelengths for other pulsars. We argue that the change in pulsed gamma-ray emission is due to a change in emission beaming and we speculate that it is precipitated by a shift in the magnetic field structure, leading to a change of either effective magnetic inclination or effective current.
Place, publisher, year, edition, pages
2013. Vol. 777, no 1, L2- p.
gamma rays: stars, pulsars: individual (PSR J2021+4026), stars: neutron
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-96870DOI: 10.1088/2041-8205/777/1/L2ISI: 000326187400002OAI: oai:DiVA.org:su-96870DiVA: diva2:668277
FunderSwedish Research CouncilKnut and Alice Wallenberg Foundation
NASA in the United States; DOE in the United States; CEA/Irfu in France; IN2P3/CNRS in France: ASI in Italy; INFN in Italy; MEXT in Japan; KEK in Japan; JAXA in Japan; K.A. Wallenberg Foundation in Sweden; Swedish Research Council in Sweden; National Space Board in Sweden; INAF in Italy; CNES in France 2013-11-292013-11-282013-11-29Bibliographically approved