4,996 research outputs found
Post-outburst X-ray flux and timing evolution of Swift J1822.3-1606
Swift J1822.3-1606 was discovered on 2011 July 14 by the Swift Burst Alert
Telescope following the detection of several bursts. The source was found to
have a period of 8.4377 s and was identified as a magnetar. Here we present a
phase-connected timing analysis and the evolution of the flux and spectral
properties using RXTE, Swift, and Chandra observations. We measure a spin
frequency of 0.1185154343(8) s and a frequency derivative of
at MJD 55761.0, in a timing analysis that include
significant non-zero second and third frequency derivatives that we attribute
to timing noise. This corresponds to an estimated spin-down inferred dipole
magnetic field of G, consistent with previous estimates
though still possibly affected by unmodelled noise. We find that the
post-outburst 1--10 keV flux evolution can be characterized by a
double-exponential decay with decay timescales of and
days. We also fit the light curve with a crustal cooling model which suggests
that the cooling results from heat injection into the outer crust. We find that
the hardness-flux correlation observed in magnetar outbursts also characterizes
the outburst of Swift J1822.3-1606. We compare the properties of Swift
J1822.3-1606 with those of other magnetars and their outbursts.Comment: 12 pages, 8 figures, accepted for publication in Ap
Red Noise in Anomalous X-ray Pulsar Timing Residuals
Anomalous X-ray Pulsars (AXPs), thought to be magnetars, exhibit poorly
understood deviations from a simple spin-down called "timing noise". AXP timing
noise has strong low-frequency components which pose significant challenges for
quantification. We describe a procedure for extracting two quantities of
interest, the intensity and power spectral index of timing noise. We apply this
procedure to timing data from three sources: a monitoring campaign of five
AXPs, observations of five young pulsars, and the stable rotator PSR B1937+21.Comment: submitted to the proceedings of the "40 Years of Pulsars" conferenc
No detectable radio emission from the magnetar-like pulsar in Kes 75
The rotation-powered pulsar PSR J1846-0258 in the supernova remnant Kes 75
was recently shown to have exhibited magnetar-like X-ray bursts in mid-2006.
Radio emission has not yet been observed from this source, but other
magnetar-like sources have exhibited transient radio emission following X-ray
bursts. We report on a deep 1.9 GHz radio observation of PSR J1846-0258 with
the 100-m Green Bank Telescope in late 2007 designed to search for radio
pulsations or bursts from this target. We have also analyzed three shorter
serendipitous 1.4 GHz radio observations of the source taken with the 64-m
Parkes telescope during the 2006 bursting period. We detected no radio emission
from PSR J1846-0258 in either the Green Bank or Parkes datasets. We place an
upper limit of 4.9 \mu Jy on coherent pulsed emission from PSR J1846-0258 based
on the 2007 November 2 observation, and an upper limit of 27 \mu Jy around the
time of the X-ray bursts. Serendipitously, we observed radio pulses from the
nearby RRAT J1846-02, and place a 3\sigma confidence level upper limit on its
period derivative of 1.7 * 10^{-13}, implying its surface dipole magnetic field
is less than 2.6 * 10^{13} G.Comment: 15 pages, 2 figures, submitted to Ap
All click, no action? Online action, efficacy perceptions, and prior experience combine to affect future collective action
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordSocial media is increasingly used for social protest, but does internet-enabled action lead to ‘slacktivism’ or promote increased activism? We show that the answer to this question depends on prior level of activism, and on beliefs about the effectiveness of individual contribution to the collective campaign. Internet-enabled action was varied quasi-experimentally, with participants (n = 143) choosing whether or not to share a campaign on social media. Participants were then informed that sharing on social media had a big (high action efficacy) or small (low action efficacy) impact on achieving the campaign's goal. Prior levels of activism were measured before the experiment, and general levels of collective action were measured one week after the experiment. Taking internet-enabled action for one campaign increased future activism for other campaigns – but only in individuals who were already active and who perceived their actions to be an effective contribution to the campaign.This work was supported by the Defence Science and Technology Laboratory [grant number DSTLX-100074625]
Magnetar-like Emission from the Young Pulsar in Kes 75
We report detection of magnetar-like X-ray bursts from the young pulsar PSR
J1846-0258, at the center of the supernova remnant Kes 75. This pulsar, long
thought to be rotation-powered, has an inferred surface dipolar magnetic field
of 4.9x10^13 G, higher than those of the vast majority of rotation-powered
pulsars, but lower than those of the ~12 previously identified magnetars. The
bursts were accompanied by a sudden flux increase and an unprecedented change
in timing behavior. These phenomena lower the magnetic and rotational
thresholds associated with magnetar-like behavior, and suggest that in neutron
stars there exists a continuum of magnetic activity that increases with
inferred magnetic field strength.Comment: 17 pages, 2 figures, accepted for publication in Science. Note: The
content of this paper is embargoed until February 21, 200
Long-term timing and emission behavior of the young Crab-like pulsar PSR B0540-69
We present timing solutions and spin properties of the young pulsar PSR B0540-69 from analysis of 15.8 years of data from the Rossi X-Ray Timing Explorer. We perform a partially phase-coherent timing analysis in order to mitigate the pronounced effects of timing noise in this pulsar. We also perform fully coherent timing over large subsets of the data set in order to arrive at a more precise solution. In addition to the previously reported first glitch undergone by this pulsar, we find a second glitch, which occurred at MJD 52927 +/- 4, with fractional changes in spin frequency Delta nu/nu = (1.64 +/- 0.05) x 10(-9) and spin-down rate Delta(nu) over dot/(nu) over dot = (0.930 +/- 0.011) x 10(-4) (taken from our fully coherent analysis). We measure a braking index that is consistent over the entire data span, with a mean value n = 2.129 +/- 0.012, from our partially coherent timing analysis. We also investigated the emission behavior of this pulsar, and have found no evidence for significant flux changes, flares, burst-type activity, or pulse profile shape variations. While there is strong evidence for the much-touted similarity of PSR B0540-69 to the Crab pulsar, they nevertheless differ in several aspects, including glitch activity, where PSR B0540-69 can be said to resemble certain other very young pulsars. It seems clear that the specific processes governing the formation, evolution, and interiors of this population of recently born neutron stars can vary significantly, as reflected in their observed properties
Timing behavior of the Magnetically Active Rotation-Powered Pulsar in the Supernova Remnant Kestevan 75
We report a large spin-up glitch in PSR J1846-0258 which coincided with the
onset of magnetar-like behavior on 2006 May 31. We show that the pulsar
experienced an unusually large glitch recovery, with a recovery fraction of
Q=8.7+/- 2.5, resulting in a net decrease of the pulse frequency. Such a glitch
recovery has never before been observed in a rotation-powered pulsar, however,
similar but smaller glitch over-recovery has been recently reported in the
magnetar AXP 4U~0142+61 and may have occurred in the SGR 1900+14. We also
report a large increase in the timing noise of the source. We discuss the
implications of the unusual timing behavior in PSR J1846-0258 on its status as
the first identified magnetically active rotation-powered pulsar.Comment: 14 pages, 5 figures, Accepted for publication in the Astrophysical
Journal. Incorporates changes from an anonymous referee; additional analysis
and discussion include
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