1,403 research outputs found
In-orbit demonstration of X-ray pulsar navigation with the Insight-HXMT satellite
In this work, we report the in-orbit demonstration of X-ray pulsar navigation
with Insight-Hard X-ray Modulation Telescope (Insight-HXMT), which was launched
on Jun. 15th, 2017. The new pulsar navigation method 'Significance Enhancement
of Pulse-profile with Orbit-dynamics' (SEPO) is adopted to determine the orbit
with observations of only one pulsar. In this test, the Crab pulsar is chosen
and observed by Insight-HXMT from Aug. 31th to Sept. 5th in 2017. Using the
5-day-long observation data, the orbit of Insight-HXMT is determined
successfully with the three telescopes onboard - High Energy X-ray Telescope
(HE), Medium Energy X-ray Telescope (ME) and Low Energy X-ray Telescope (LE) -
respectively. Combining all the data, the position and velocity of the
Insight-HXMT are pinpointed to within 10 km (3 sigma) and 10 m/s (3 sigma),
respectively.Comment: Accepted by the Astrophysical Journal Supplemen
Discovery of delayed spin-up behavior following two large glitches in the Crab pulsar, and the statistics of such processes
Glitches correspond to sudden jumps of rotation frequency () and its
derivative () of pulsars, the origin of which remains not well
understood yet, partly because the jump processes of most glitches are not well
time-resolved. There are three large glitches of the Crab pulsar, detected in
1989, 1996 and 2017, which were found to have delayed spin-up processes before
the normal recovery processes. Here we report two additional glitches of the
Crab pulsar occurred in 2004 and 2011 for which we discovered delayed spin up
processes, and present refined parameters of the largest glitch occurred in
2017. The initial rising time of the glitch is determined as hour. We
also carried out a statistical study of these five glitches with observed
spin-up processes. The two glitches occurred in 2004 and 2011 have delayed
spin-up time scales () of \,days and \,days,
respectively. We find that the vs. relation
of these five glitches is similar to those with no detected delayed spin-up
process, indicating that they are similar to the others in nature except that
they have larger amplitudes. For these five glitches, the amplitudes of the
delayed spin-up process () and recovery process
(), their time scales (, ), and
permanent changes in spin frequency () and total frequency
step () have positive correlations. From these
correlations, we suggest that the delayed spin-up processes are common for all
glitches, but are too short and thus difficult to be detected for most
glitches.Comment: 25 pages, 8 figure
A Variable Ionized Disk Wind in the Black Hole Candidate EXO 1846–031
After 34 yr, the black hole candidate EXO 1846–031 went into outburst again in 2019. We investigate its spectral properties in the hard intermediate and the soft states with NuSTAR and Insight-HXMT. A reflection component has been detected in the two spectral states but possibly originating from different illumination spectra: in the intermediate state, the illuminating source is attributed to a hard coronal component, which has been commonly observed in other X-ray binaries, whereas in the soft state, the reflection is probably produced by disk self-irradiation. Both cases support EXO 1846–031 as a low-inclination system of ~40°. An absorption line is clearly detected at ~7.2 keV in the hard intermediate state, corresponding to a highly ionized disk wind (log} ξ > 6.1) with a velocity of up to 0.06c. Meanwhile, quasi-simultaneous radio emissions have been detected before and after the X-rays, implying the coexistence of disk winds and jets in this system. If only the high-flux segment of the NuSTAR observation is considered, the observed wind appears to be magnetically driven. The absorption line disappeared in the soft state and a narrow emission line appeared at ~6.7 keV on top of the reflection component, which may be evidence for disk winds, but data with higher spectral resolution are required to examine this
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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