Publication Date:
2019-07-13
Description:
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 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.
Keywords:
Astronomy
Type:
GSFC-E-DAA-TN15968
,
The Astrophysical Journal Letters (ISSN 0004-637X) (e-ISSN 1538-4357); 777; 1; L2
Format:
text
Permalink
