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PSR J2021+4026 in the Gamma Cygni Region: The First Variable Gamma-Ray Pulsar Seen by the Fermi LATLong-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 plus or minus 0.08)×10(exp −10) erg cm(exp −2) s(exp −1) to (6.86 plus or minus 0.13)× 10 (exp −1)0 erg cm (exp −2) s(exp −1). Simultaneously, the frequency spindown rate increased from (7.8 plus or minus 0.1) × 10(exp −13) Hz s(exp −1) to (8.1 plus or minus 0.1) × 10(exp −1)3 Hz s(exp −1). Significant (greater than 5 sigma) changes in the pulse profile and marginal (less than 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.
Document ID
20160005795
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Allafort, A.
(Stanford Univ. Stanford, CA, United States)
Baldini, L.
(Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Ballet, J.
(CEA Saclay, Service d'Astrophysique Gif-sur-Yvette, France)
Barbiellini, G.
(Istituto Nazionale di Fisica Nucleare Trieste, Italy)
Baring, M. G.
(Rice Univ. Houston, TX, United States)
Bastieri, D.
(Istituto Nazionale di Fisica Nucleare Padova, Italy)
Bellazzini, R.
(Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Bonamente, E.
(Istituto Nazionale di Fisica Nucleare Perugia, Italy)
Bottacini, E.
(Stanford Univ. Stanford, CA, United States)
Brandt, T. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Bregeon, J.
(Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Bruel, P.
(Ecole Polytechnique Palaiseau, France)
Buehler, R.
(Deutsches Elektronen-Synchrotron Zeuthen, Germany)
Buson, S.
(Istituto Nazionale di Fisica Nucleare Padova, Italy)
Caliandro, G. A.
(institut de Ciencies de l'Espai (Ice-CSIC) Barcelona, Spain)
Cameron, R. A.
(Stanford Univ. Stanford, CA, United States)
Caraveo, P. A.
(Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Milan, Italy)
Cecchi, C.
(Istituto Nazionale di Fisica Nucleare Perugia, Italy)
Chaves, R. C. G.
(CEA Saclay, Service d'Astrophysique Gif-sur-Yvette, France)
Chekhtman, A.
(George Mason Univ. Fairfax, VA, United States)
Chiang, J.
(Stanford Univ. Stanford, CA, United States)
Chiaro, G.
(Padua Univ. Italy)
Ciprini, S.
(Italian Space Agency Matera, Italy)
Claus, R.
(Stanford Univ. Stanford, CA, United States)
D’Ammando, F.
(Istituto di Radioastronomia Bologna, Italy)
Harding, A. K.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hays, E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hewitt, J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Thompson, D. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
May 4, 2016
Publication Date
November 1, 2013
Publication Information
Publication: The Astrophysical Journal Letters
Publisher: The American Astronomical Society
Volume: 777
Issue: 1
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Astronomy
Report/Patent Number
GSFC-E-DAA-TN15968
Distribution Limits
Public
Copyright
Other
Keywords
pulsars: individual
(PSR J2021+4026)
gamma rays: stars

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