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"Zhang, B."
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A peculiar low-luminosity short gamma-ray burst from a double neutron star merger progenitor
Double neutron star (DNS) merger events are promising candidates of short gamma-ray burst (sGRB) progenitors as well as high-frequency gravitational wave (GW) emitters. On August 17, 2017, such a coinciding event was detected by both the LIGO-Virgo gravitational wave detector network as GW170817 and Gamma-Ray Monitor on board NASA’s
Fermi
Space Telescope as GRB 170817A. Here, we show that the fluence and spectral peak energy of this sGRB fall into the lower portion of the distributions of known sGRBs. Its peak isotropic luminosity is abnormally low. The estimated event rate density above this luminosity is at least
19
0
-
160
+
440
Gpc
−3
yr
−1
, which is close to but still below the DNS merger event rate density. This event likely originates from a structured jet viewed from a large viewing angle. There are similar faint soft GRBs in the
Fermi
archival data, a small fraction of which might belong to this new population of nearby, low-luminosity sGRBs.
A short-duration gamma-ray burst was detected along with a double neutron start merger gravitational wave by LIGO-Virgo on August 17th 2017. Here, the authors show that the fluence and spectral peak energy of this event fall into the lower portion of the distribution of known short-duration gamma-ray bursts.
Journal Article
The best American science & nature writing. 2023
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A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
Mergers of neutron stars are known to be associated with short γ-ray bursts
1
–
4
. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magnetic field
5
–
8
(that is, a magnetar). Such a magnetar signature may have been observed in the form of the X-ray plateau that follows up to half of observed short γ-ray bursts
9
,
10
. However, it has been expected that some X-ray transients powered by binary neutron-star mergers may not be associated with a short γ-ray burst
11
,
12
. A fast X-ray transient (CDF-S XT1) was recently found to be associated with a faint host galaxy, the redshift of which is unknown
13
. Its X-ray and host-galaxy properties allow several possible explanations including a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at high redshift, or a tidal disruption event involving an intermediate-mass black hole and a white dwarf
13
. Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift
z
= 0.738 (ref.
14
). The measured light curve is fully consistent with the X-ray transient being powered by a millisecond magnetar. More intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host galaxy with a moderate offset from the galaxy centre, as short γ-ray bursts often do
15
,
16
. The estimated event-rate density of similar X-ray transients, when corrected to the local value, is consistent with the event-rate density of binary neutron-star mergers that is robustly inferred from the detection of the gravitational-wave event GW170817.
Observations of an X-ray transient associated with a galaxy at redshift 0.738 suggest that the X-ray transient is powered by a millisecond magnetar and that it is the remnant of a merger between two neutron stars.
Journal Article
No pulsed radio emission during a bursting phase of a Galactic magnetar
Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances
1
–
3
. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources
4
–
13
, but no convincing evidence has been collected so far
14
. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts
15
. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare
18
–
21
. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB–SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.
An 8-hour radio observational campaign of the Galactic magnetar SGR 1935+2154, assisted by multi-wavelength data, indicates that associations between fast radio bursts and soft γ-ray bursts are rare.
Journal Article
A fast radio burst source at a complex magnetized site in a barred galaxy
Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts
1
–
3
. Recent observations of a Galactic FRB
4
–
8
suggest that at least some FRBs originate from magnetars, but the origin of cosmological FRBs is still not settled. Here we report the detection of 1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref.
9
). These observations show irregular short-time variation of the Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (
au
; Earth–Sun distance) of the source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy
10
–
12
show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.
Analysis of a set of 1,863 bursts from the repeating source FRB 20201124A provides evidence of a complicated magnetized site within about an astronomical unit from the source in a barred galaxy.
Journal Article
A peculiarly short-duration gamma-ray burst from massive star core collapse
Gamma-ray bursts (GRBs) have been phenomenologically classified into long and short populations based on the observed bimodal distribution of duration1. Multi-wavelength and multi-messenger observations in recent years have revealed that in general long GRBs originate from massive star core collapse events2, whereas short GRBs originate from binary neutron star mergers3. It has been known that the duration criterion is sometimes unreliable, and multi-wavelength criteria are needed to identify the physical origin of a particular GRB4. Some apparently long GRBs have been suggested to have a neutron star merger origin5, whereas some apparently short GRBs have been attributed to genuinely long GRBs6 whose short, bright emission is slightly above the detector’s sensitivity threshold. Here, we report the comprehensive analysis of the multi-wavelength data of the short, bright GRB 200826A. Characterized by a sharp pulse, this burst shows a duration of 1 second and no evidence of an underlying longer-duration event. Its other observational properties such as its spectral behaviours, total energy and host galaxy offset are, however, inconsistent with those of other short GRBs believed to originate from binary neutron star mergers. Rather, these properties resemble those of long GRBs. This burst confirms the existence of short-duration GRBs with stellar core-collapse origin4, and presents some challenges to the existing models.A gamma-ray burst (GRB) is reported to show a sharp 1-second spike, characteristic of short GRBs, but with other observational properties resembling those of long GRBs. This burst may belong to a class of core-collapse-origin GRBs with genuinely short durations.
Journal Article
Moderate swimming suppressed the growth and metastasis of the transplanted liver cancer in mice model: with reference to nervous system
Physical activity has been shown to suppress tumor initiation and progression. The neurotransmitter dopamine (DA) is closely related to movement and exhibits antitumor properties. However, whether the suppressive effects of physical activity on tumors was mediated by the nervous system via increased DA level remains unknowns. Here we show that regular moderate swimming (8 min/day, 9 weeks) raised DA levels in the prefrontal cortex, serum and tumor tissue, suppressed growth, reduced lung metastasis of transplanted liver cancer, and prolonged survival in a C57BL/6 mouse model, while overload swimming (16 and 32 min/day, 9 weeks) had the opposite effect. In nude mice that were orthotopically implanted with human liver cancer cell lines, DA treatment significantly suppressed growth and lung metastasis by acting on the D2 receptor (DR2). Furthermore, DR2 blockade attenuated the suppressive effect of moderate swimming on liver cancer. Both moderate swimming and DA treatment suppressed the transforming growth factor-beta (TGF-β1)-induced epithelial–mesenchymal transition of transplanted liver cancer cells. At the molecular level, DR2 signaling inhibited extracellular signal-regulated kinase phosphorylation and expression of TGF-β1
in vitro
. Together, these findings demonstrated a novel mechanism by which the moderate exercise suppressed liver cancer through boosting DR2 activity, while overload exercise had the opposite effect, highlighting the possible importance of the dopaminergic system in tumor growth and metastasis of liver cancer.
Journal Article
Enhanced energy coupling for indirect-drive fast-ignition fusion targets
One of the most promising approaches to reach a high gain in inertial confinement fusion is the fast ignition scheme. In this scheme, a relativistic electron beam is generated; this passes through the imploded plasma and deposits parts of its energy in the core. However, the large angular spread of the relativistic electron beam and the poorly controlled compression of the target affect realization of the fast ignition technique. Here, we demonstrate that indirectly driven (that is, driven by X-rays generated inside a gold hohlraum) implosions with a ‘high-foot’ and a short-coast time of less than 200 ps allow us to tightly compress the shell. Furthermore, we show the ability to optimize the symmetry of the imploding shell by changing the hohlraum length, successfully tuning a suitable tube-shaped shell to compensate for the large angular spread of the relativistic electron beam and to enhance the electron-to-core coupling efficiency via resistive magnetic fields. Benefiting from those experimental techniques, a significant enhancement in neutron yield was achieved in our indirectly driven fast ignition experiments. These results pave the way towards high-coupling fast ignition experiments with indirectly driven targets similar to those at the National Ignition Facility.
Experiments realizing the indirect-drive fast ignition scheme for inertial confinement fusion are reported. Enabled by a tightly compressed target, an increase of neutron yield is observed.
Journal Article
Diverse polarization angle swings from a repeating fast radio burst source
Fast radio bursts (FRBs) are millisecond-duration radio transients
1
,
2
of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star magnetospheres
3
–
5
or relativistic shocks far from the central energy source
6
–
8
. Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters
9
,
10
or variable polarization angles in some other apparently one-off events
11
,
12
. Here we report observations of 15 bursts from FRB 180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks.
Polarization observations of the fast radio burst FRB 180301 with the FAST radio telescope show diverse polarization angle swings, consistent with a magnetospheric origin of the emission.
Journal Article