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.

PSR J2021+4026 IN THE GAMMA CYGNI REGION: THE FIRST VARIABLE gamma-RAY PULSAR SEEN BY THE Fermi LAT

D'AMMANDO, FILIPPO;
2013

Abstract

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.
2013
Allafort A; Baldini L; Ballet J; Barbiellini G; Baring MG; Bastieri D; Bellazzini R; Bonamente E; Bottacini E; Brandt TJ; Bregeon J; Bruel P; Buehler R; Buson S; Caliandro GA; Cameron RA; Caraveo PA; Cecchi C; Chaves RCG; Chekhtman A; Chiang J; Chiaro G; Ciprini S; Claus R; DAmmando F; de Palma F; Digel SW; Di Venere L; Drell PS; Favuzzi C; Ferrara EC; Franckowiak A; Fusco P; Gargano F; Gasparrini D; Giglietto N; Giroletti M; Glanzman T; Godfrey G; Grenier IA; Guiriec S; Hadasch D; Harding AK; Hayashida M; Hayashi K; Hays E; Hewitt J; Hill AB; Horan D; Hou X; Jogler T; Johnson AS; Johnson TJ; Kerr M; Knodlseder J; Kuss M; Lande J; Larsson S; Latronico L; Lemoine-Goumard M; Longo F; Loparco F; Lubrano P; Malyshev D; Marelli M; Mayer M; Mazziotta MN; Mehault J; Mizuno T; Monzani ME; Morselli A; Murgia S; Nemmen R; Nuss E; Ohsugi T; Omodei N; Orienti M; Orlando E; Paneque D; Pesce-Rollins M; Pierbattista M; Piron F; Pivato G; Porter TA; Raino S; Rando R; Ray PS; Razzano M; Reimer O; Reposeur T; Romani RW; Sartori A; Parkinson PMS; Sgro C; Siskind EJ; Smith DA; Spinelli P; Strong AW; Takahashi H; Thayer JB; Thompson DJ; Tibaldo L; Tinivella M; Torres DF; Tosti G; Uchiyama Y; Usher TL; Vandenbroucke J; Vasileiou V; Venter C; Vianello G; Vitale V; Winer BL; Wood KS
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/595726
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