A radiatively-quiet glitch and anti-glitch in the magnetar 1E 2259+586. (arXiv:2006.04854v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Younes_G/0/1/0/all/0/1">G. Younes</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Ray_P/0/1/0/all/0/1">P. S. Ray</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Baring_M/0/1/0/all/0/1">M. G. Baring</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Kouveliotou_C/0/1/0/all/0/1">C. Kouveliotou</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Fletcher_C/0/1/0/all/0/1">C. Fletcher</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Wadiasingh_Z/0/1/0/all/0/1">Z. Wadiasingh</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Harding_A/0/1/0/all/0/1">A. K. Harding</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Goldstein_A/0/1/0/all/0/1">A. Goldstein</a> (4) ((1) George Washington University, (2) Naval Research Lab, (3) Rice University, (4) USRA/NASA/MSFC, (5) NASA/GSFC)
We report on the timing and spectral properties of the soft X-ray emission
from the magnetar 1E 2259+586 from January 2013, $sim 8$ months after the
detection of an anti-glitch, until September 2019, using the Neil Gehrels Swift
and NICER observatories. During this time span, we detect two timing
discontinuities. The first, occurring around 5 years after the April 2012
anti-glitch, is a relatively large spin-up glitch with a fractional amplitude
$Deltanu/nu=1.24(2)times10^{-6}$. We find no evidence for flux enhancement
or change in the spectral or pulse profile shape around the time of this
glitch. This is consistent with the picture that a significant number of
magnetar spin-up glitches are radiatively-quiet. Approximately 1.5 years later
in April 2019, 1E 2259+586 exhibited an anti-glitch with spin-down of a
fractional amplitude $Deltanu/nu=-5.8(1)times10^{-7}$; similar to the
fractional change detected in 2012. We do not, however, detect any change to
the pulse-profile shape or increase in the rms pulsed flux of the source, nor
do we see any possible bursts from its direction around the time of the
anti-glitch; all of which occurred during the 2012 event. Hence, similar to
spin-up glitches, anti-glitches can occur silently. This may suggest that these
phenomena originate in the neutron star interior, and that their locale and
triggering mechanism do not necessarily have to be connected to the
magnetosphere. Lastly, our observations suggest that the occurrence rate of
spin-up and spin-down glitches is about the same in 1E 2259+586, with the
former having a larger net fractional change.
We report on the timing and spectral properties of the soft X-ray emission
from the magnetar 1E 2259+586 from January 2013, $sim 8$ months after the
detection of an anti-glitch, until September 2019, using the Neil Gehrels Swift
and NICER observatories. During this time span, we detect two timing
discontinuities. The first, occurring around 5 years after the April 2012
anti-glitch, is a relatively large spin-up glitch with a fractional amplitude
$Deltanu/nu=1.24(2)times10^{-6}$. We find no evidence for flux enhancement
or change in the spectral or pulse profile shape around the time of this
glitch. This is consistent with the picture that a significant number of
magnetar spin-up glitches are radiatively-quiet. Approximately 1.5 years later
in April 2019, 1E 2259+586 exhibited an anti-glitch with spin-down of a
fractional amplitude $Deltanu/nu=-5.8(1)times10^{-7}$; similar to the
fractional change detected in 2012. We do not, however, detect any change to
the pulse-profile shape or increase in the rms pulsed flux of the source, nor
do we see any possible bursts from its direction around the time of the
anti-glitch; all of which occurred during the 2012 event. Hence, similar to
spin-up glitches, anti-glitches can occur silently. This may suggest that these
phenomena originate in the neutron star interior, and that their locale and
triggering mechanism do not necessarily have to be connected to the
magnetosphere. Lastly, our observations suggest that the occurrence rate of
spin-up and spin-down glitches is about the same in 1E 2259+586, with the
former having a larger net fractional change.
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