We present timing and time-integrated spectral analysis of 127 bursts from SGR J1935+2154. These bursts were observed with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope and the ...Burst Alert Telescope on the Neil Gehrels Swift Observatory during the source's four active episodes from 2014 to 2016. This activation frequency makes SGR J1935+2154 the most burst prolific transient magnetar. We find the average duration of all the detected bursts to be much shorter than the typical, anticipated value. We fit the burst time-integrated spectra with two blackbody functions, a Comptonized model and three other simpler models. Bursts from SGR J1935+2154 exhibit similar spectral properties to other magnetars, with the exception of the power-law index from the Comptonized model, which correlates with burst fluence. We find that the durations and both blackbody temperatures of the bursts have significantly evolved across the four active episodes. We also find that the burst time history exhibits two trends, which are strongly correlated with the decay of the persistent emission in each outburst.
GRB 221009A: The BOAT Burns, Eric; Svinkin, Dmitry; Fenimore, Edward ...
Astrophysical journal. Letters,
03/2023, Volume:
946, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract GRB 221009A has been referred to as the brightest of all time (BOAT). We investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst ...observations. This burst is the brightest ever detected by the measures of peak flux and fluence. Unexpectedly, GRB 221009A has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ∼99th percentile of the known distribution. We explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. By geometric extrapolation of the total fluence and peak flux distributions, GRB 221009A appears to be a once-in-10,000-year event. Thus, it is almost certainly not the BOAT over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began.
Background Educational interventions are increasingly used to promote peritoneal dialysis (PD), the most common form of home therapy for end-stage renal disease. A systematic review of the evidence ...in support of dialysis modality education is needed to inform the design of patient-targeted interventions to increase selection of PD. We performed a systematic review and meta-analysis to characterize the relationship between patient-targeted educational interventions and choosing and receiving PD. Study Design Systematic review and meta-analysis. Setting & Population Published original studies and abstracts. Selection Criteria for Studies We searched MEDLINE, EMBASE, CINAHL and EBMR. We included controlled observational studies and randomized trials of educational interventions designed to increase PD selection. Intervention Predialysis educational interventions. Outcomes The primary outcome was choosing PD, defined as intention to use PD regardless of whether PD was ever used. The secondary outcome, receiving PD, was defined as an individual receiving PD as his or her treatment. Results Of 3,540 citations, 15 studies met our inclusion criteria, including 1 randomized trial. In the single randomized trial (N = 70), receipt of an educational intervention was associated with a more than 4-fold increase in the odds of choosing PD (OR, 4.60; 95% CI, 1.19-17.74). Based on results from 4 observational studies (N = 7,653), patient-targeted educational interventions were associated with a 2-fold increase in the odds of choosing PD (pooled OR, 2.15; 95% CI, 1.07-4.32; I2 = 76.7%). Based on results from 9 observational studies (N = 8,229), patient-targeted educational intervention was associated with a 3-fold increase in the odds of receiving PD as the initial treatment modality (OR, 3.50; 95% CI, 2.82-4.35; I2 = 24.9%). Limitations Most studies were observational studies, which can establish an association between education and choosing PD or receiving PD, but does not establish causality. Conclusions This systematic review demonstrates a strong association between patient-targeted education interventions and the subsequent choice and receipt of PD.
We present temporal and time-integrated spectral analyses of 148 bursts from the latest activation of SGR J1935+2154, observed with the Fermi/Gamma-ray Burst Monitor from 2019 October 4 through 2020 ...May 20, excluding an ∼130 s segment with a very high burst density on 2020 April 27. The 148 bursts presented here are slightly longer and softer than bursts from earlier activations of SGR J1935+2154, as well as from other magnetars. The long-term spectral evolution trend is interpreted as being associated with an increase in the average plasma loading of the magnetosphere during bursts. We also find a trend of increased burst activity from SGR J1935+2154 since its discovery in 2014. Finally, we find no association of typical radio bursts with X-ray bursts from the source. This contrasts the association of FRB 200428 with an SGR J1935+2154 X-ray burst, which is to-date unique among the magnetar population.
Radio emissions continue to provide insight into the production of terrestrial gamma ray flashes (TGFs) by thunderstorms, including the critical question of the conditions under which they are ...generated. We have identified several TGF‐associated lightning radio emissions in which the altitudes of in‐cloud lightning leader pulses that precede and follow the TGF can be measured. We combine these with high absolute timing accuracy TGF observations from the Fermi satellite to determine the development of the lightning channel before, during, and after the TGF production. All of these TGFs were produced several milliseconds after the leader had initiated and when the leaders reached 1–2 km in length. After the TGFs, the leaders all continued to ascend for several more kilometers with no dramatic change in their characteristics, although they all exhibited high average velocities of 0.8–1.0 × 106 m/s. Implications in the context of TGF models are discussed. These results paint the first clear picture of the lightning processes that occur before, during, and after TGF production.
Key Points
TGFs are produced when a lightning leader is near the midpoint of its ascent
Lightning leaders associated with TGFs are fast moving but otherwise ordinary
Why TGFs are not produced at other times in the leader ascent is not clear
Abstract SGR J1935+2154 has truly been the most prolific magnetar over the last decade: it has been entering into burst active episodes once every 1–2 yr since its discovery in 2014, it emitted the ...first Galactic fast radio burst associated with an X-ray burst in 2020, and it has emitted hundreds of energetic short bursts. Here, we present the time-resolved spectral analysis of 51 bright bursts from SGR J1935+2154. Unlike conventional time-resolved X-ray spectroscopic studies in the literature, we follow a two-step approach to probe true spectral evolution. For each burst, we first extract spectral information from overlapping time segments, fit them with three continuum models, and employ a machine-learning-based clustering algorithm to identify time segments that provide the largest spectral variations during each burst. We then extract spectra from those nonoverlapping (clustered) time segments and fit them again with the three models: the cutoff power-law model, the sum of two blackbody functions, and the model considering the emission of a modified blackbody undergoing resonant cyclotron scattering, which is applied systematically at this scale for the first time. Our novel technique allowed us to establish the genuine spectral evolution of magnetar bursts. We discuss the implications of our results and compare their collective behavior with the average burst properties of other magnetars.
Abstract
Magnetars are young neutron stars powered by the strongest magnetic fields in the Universe (10
13–15
G). Their transient X-ray emission usually manifests as short (a few hundred ...milliseconds), bright, energetic (∼10
40–41
erg) X-ray bursts. Since its discovery in 2014, SGR J1935+2154 has become one of the most prolific magnetars, exhibiting very active bursting episodes and other fascinating events, such as pulse timing antiglitches and fast radio bursts. Here we present evidence for possible 42 Hz (24 ms) quasiperiodic oscillations in the
ν
F
ν
spectrum peak energy (
E
p
) identified in a unique burst detected with the Fermi Gamma-ray Burst Monitor in 2022 January. While quasiperiodic oscillations have been previously reported in the intensity of magnetar burst light curves, quasiperiodic oscillations in
E
p
have not. We also find an additional event from the same outburst that appears to exhibit a similar character in
E
p
, albeit of lower statistical quality. For these two exceptional transients, such
E
p
oscillations can be explained by magnetospheric density and pressure perturbations. For burst-emitting plasma consisting purely of
e
+
e
−
pairs, these acoustic modes propagate along a highly magnetized flux tube of length up to around
L
∼ 130 neutron star radii, with
L
being lower if ions are present in the emission zone. Detailed time-resolved analyses of other magnetar bursts are encouraged to evaluate the rarity of these events and their underlying mechanisms.
ABSTRACT Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has triggered and located on average approximately two γ-ray bursts (GRBs) every three days. Here, we present the third of a ...series of catalogs of GRBs detected by GBM, extending the second catalog by two more years through the middle of 2014 July. The resulting list includes 1405 triggers identified as GRBs. The intention of the GBM GRB catalog is to provide information to the community on the most important observables of the GBM-detected GRBs. For each GRB, the location and main characteristics of the prompt emission, the duration, peak flux, and fluence are derived. The latter two quantities are calculated for the 50-300 keV energy band where the maximum energy release of GRBs in the instrument reference system is observed, and also for a broader energy band from 10 to 1000 keV, exploiting the full energy range of GBM's low-energy NaiTl) detectors. Using statistical methods to assess clustering, we find that the hardness and duration of GRBs are better fit by a two-component model with short-hard and long-soft bursts than by a model with three components. Furthermore, information is provided on the settings and modifications of the triggering criteria and exceptional operational conditions during years five and six in the mission. This third catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.
Abstract
The detection of magnetar-like bursts from highly magnetic (
B
> 10
13
G) rotation-powered pulsars (RPPs) opened the magnetar population to yet another group of neutron stars. At the same ...time the question arose as to whether magnetar-like bursts from high-B RPPs have similar characteristics to bursts from known magnetar sources. We present here our analyses of the Fermi Gamma-ray Burst Monitor (GBM) data from two magnetar candidates, Swift J1818.0−1607 (a radio-loud magnetar) and PSR J1846.4−0258. Both sources entered active bursting episodes in 2020 triggering Fermi-GBM in 2020 and in early 2021. We searched for untriggered bursts from both sources and performed temporal and spectral analyses on all events. Here, we present the results of our comprehensive burst search and analyses. We identified 37 and 58 bursts that likely originated from Swift J1818.0−1607 and PSR J1846.4−0258, respectively. We find that the bursts from these sources are shorter on average than typical magnetar bursts. In addition, their spectra are best described with a single blackbody function with
kT
∼ 10–11 keV; several relatively bright events, however, show higher energy emission that could be modeled with a cutoff power-law model. We find that the correlation between the blackbody emitting area and the spectral temperature for the burst ensemble of each pulsar deviates from the ideal Stefan–Boltzmann law, as it does for some burst-active magnetars. We interpret this characteristic as being due to the significant radiation anisotropy expected from optically thick plasmas in very strong magnetic fields.
ABSTRACT Two energetic hard X-ray bursts from the rotation-powered pulsar PSR J1119−6127 recently triggered the Fermi and Swift space observatories. We have performed in-depth spectral and temporal ...analyses of these two events. Our extensive searches in both observatories' data for lower luminosity bursts uncovered 10 additional events from the source. We report here on the timing and energetics of the 12 bursts from PSR J1119−6127 during its burst active phase on 2016 July 26 and 28. We also found a spectral softer X-ray flux enhancement in a post-burst episode, which shows evidence of cooling. Here we discuss the implications of these results on the nature of this unusual high-field radio pulsar, which firmly place it within the typical magnetar population.
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