161 research outputs found
Observation of the electromagnetic doubly OZI-suppressed decay
Using a sample of billion events accumulated with the BESIII
detector at the BEPCII collider, we report the observation of the decay , which is the first evidence for a doubly
Okubo-Zweig-Iizuka suppressed electromagnetic decay. A clear structure
is observed in the mass spectrum around 1.02 GeV/, which can
be attributed to interference between and
decays. Due to this interference, two
possible solutions are found. The corresponding measured values of the
branching fraction of are and .Comment: 7 pages, 4 figures, published in Phys. Rev.
X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT
We investigate the absorption and emission features in observations of GX
301-2 detected with Insight-HXMT/LE in 2017-2019. At different orbital phases,
we found prominent Fe Kalpha, Kbeta and Ni Kalpha lines, as well as Compton
shoulders and Fe K-shell absorption edges. These features are due to the X-ray
reprocessing caused by the interaction between the radiation from the source
and surrounding accretion material. According to the ratio of iron lines Kalpha
and Kbeta, we infer the accretion material is in a low ionisation state. We
find an orbital-dependent local absorption column density, which has a large
value and strong variability around the periastron. We explain its variability
as a result of inhomogeneities of the accretion environment and/or
instabilities of accretion processes. In addition, the variable local column
density is correlated with the equivalent width of the iron Kalpha lines
throughout the orbit, which suggests that the accretion material near the
neutron star is spherically distributed.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in MNRA
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
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