Abstract At 327 MHz, the observed emission of PSR B1937+21 is greatly affected by scattering in the interstellar medium, on a timescale of order the pulse period. We use the bright impulsive giant ...pulses emitted by the pulsar to measure the impulse response of the interstellar medium and then recover the intrinsic emission of the pulsar by deconvolution—revealing fine structure on timescales not normally observable. We find that the intrinsic widths of the main pulse and interpulse in the pulse profile are similar to those measured at higher frequencies. We detect 60,270 giant pulses, which typically appear as narrow, ∼100 ns bursts consisting of one to a few nanoshots with widths ≲ 10 ns. However, about 10% of the giant pulses exhibit multiple bursts that seem to be causally related to each other. We also report the first detection of giant micropulses in PSR B1937+21, primarily associated with the regular main pulse emission. These are distinct from giant pulses not only in the phases at which they occur, but also in their larger widths, of order a microsecond, and steeper energy distribution. These measurements place useful observational constraints on emission mechanisms for giant pulses as well as the regular radio emission of millisecond pulsars.
Abstract We explore the implications of the light curve of the early TeV gamma-ray afterglow of GRB 221009A reported by the LHAASO Collaboration. We show that the reported offset of the reference ...time, T * , allows the determination of the activation time of the main jet component, which occurs approximately 200 s after the Gamma-ray Burst Monitor (GBM) trigger time and closely precedes the moment at which GBM was saturated. We find that while the LHAASO data do not exclude the homogeneous circumburst medium scenario, the progenitor wind scenario looks preferable, finding excellent agreement with the expected size of the stellar bubble. We conclude that the initial growth of the light curve is dominated by processes internal to the jet or by gamma-gamma attenuation on the photons emitted during the prompt phase. Namely, either the activation of the acceleration process or the decrease of internal gamma-gamma absorption can naturally explain the initial rapid flux increase. The subsequent slow flux growth phase observed up to T * + 18 s can be related to the process of particle accumulation in the production region. The duration of this phase allows an almost parameter-independent determination of the jet’s initial Lorentz factor, Γ 0 ≈ 600, and magnetic field strength, B ′ ∼ 0.3 G . These values appear to match well those previously revealed through spectral modeling of the GRB emission.
Abstract The High Altitude Detection of Astronomical Radiation (HADAR) is a novel wide-field Cherenkov Telescope. It is designed for gamma-ray astronomy in the energy range of 10 GeV to 100 TeV, with ...gamma-ray bursts (GRBs) being one of its primary research focuses. To assess its complementary capabilities, this study first presents the Crab sensitivity of HADAR. Then, to compare the sensitivity of GRBs, the observation time for all experiments is standardized to 100 s. To clearly demonstrate HADAR’s advantages, we estimate its observational results with a 221009A-like GRB. The study found that HADAR is capable of more comprehensively recording the bending and absorption of self-Compton radiation, which is expected to fill observational gaps in space- and ground-based experiments. We anticipate that this facility will ensure a large statistical GRB sample and advance our understanding of GRBs.
Gamma-Ray Burst Pulses and Lateral Jet Motion Hakkila, Jon; Pendleton, Geoffrey N.; Preece, Robert D. ...
The Astrophysical journal,
05/2024, Letnik:
966, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract We propose that gamma-ray burst (GRB) pulses are produced when highly relativistic jets sweep across an observer’s line of sight. We hypothesize that axisymmetric jet profiles, coupled with ...special relativistic effects, produce the time-reversed properties of GRB pulses. Curvature resulting from rapid jet expansion is responsible for much of the observed pulse asymmetry and hard-to-soft evolution. The relative obliqueness with which the jet crosses the line of sight explains the known GRB pulse morphological types. We explore two scenarios: one in which a rigid/semirigid jet moves laterally and another in which a ballistic jet sprays material from a laterally moving nozzle. The ballistic jet model is favored based upon its consistency with standard emission mechanisms.
Abstract
GRB 230307A is the second brightest gamma-ray burst detected in more than 50 years of observations and is located in the direction of the Magellanic Bridge. Despite its long duration, it is ...most likely the result of the merger of a compact binary ejected from a galaxy in the local universe (redshift
z
= 0.065). Our XMM-Newton observation of its afterglow at 4.5 days shows a power-law spectrum with photon index Γ = 1.73 ± 0.10, unabsorbed flux
F
0.3−10 keV
= (8.8 ± 0.5) × 10
−14
erg cm
−2
s
−1
, and no absorption in excess of that produced in our Galaxy and in the Magellanic Bridge. We derive a limit of
N
H
HOST
<
5
×
10
20
cm
−2
on the absorption at the GRB redshift, which is a factor ∼5 below the value measured during the prompt phase. We searched for the presence of dust scattering rings with negative results and set an upper limit of the order of
A
V
< 0.05 on the absorption from dust in the Magellanic Bridge.
We search for gravitational-wave transients associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the first part of the third observing run of Advanced LIGO and ...Advanced Virgo (2019 April 1 15:00 UTC–2019 October 1 15:00 UTC). A total of 105 GRBs were analyzed using a search for generic gravitational-wave transients; 32 GRBs were analyzed with a search that specifically targets neutron star binary mergers as short GRB progenitors. We find no significant evidence for gravitational-wave signals associated with the GRBs that we followed up, nor for a population of unidentified subthreshold signals. We consider several source types and signal morphologies, and report for these lower bounds on the distance to each GRB.
We report the detection of eight bright X-ray bursts from the 6.5 s magnetar 1E 1048.1-5937, during a 2013 July observation campaign with the Nuclear Spectroscopic Telescope Array. We study the ...morphological and spectral properties of these bursts and their evolution with time. The bursts resulted in count rate increases by orders of magnitude, sometimes limited by the detector dead time, and showed blackbody spectra with kT ~ 6-8 keV in the T sub(90) duration of 1-4 s, similar to earlier bursts detected from the source. We find that the spectra during the tail of the bursts can be modeled with an absorbed blackbody with temperature decreasing with flux. The burst flux decays followed a power law of index 0.8-0.9. In the burst tail spectra, we detect a ~13 keV emission feature, similar to those reported in previous bursts from this source as well as from other magnetars observed with the Rossi X-ray Timing Explorer. We explore possible origins of the spectral feature such as proton cyclotron emission, which implies a magnetic field strength of B ~ 2 x 10 super(15) G in the emission region. However, the consistency of the energy of the feature in different objects requires further explanation.
ABSTRACT
We consider the optimization of the observing strategy (cadence, exposure time, and filter choice) using medium-size (2-m-class) optical telescopes in the follow-up of kilonovae localized ...with arcminute accuracy to be able to distinguish among various kilonova models and viewing angles. To develop an efficient observation plan, we made use of the synthetic light curves obtained with the Monte Carlo radiative transfer code POlarization Spectral Synthesis In Supernovae for different kilonova models and as a function of different viewing angles and distances. By adding the appropriate photon counting noise to the synthetic light curves, we analysed four alternative sequences having the same total time exposure of 8 h, with different time windows (0.5, 1, 2, and 4 h), each with i, r, and u filters, to determine the observing sequence that maximizes the chance of a correct identification of the model parameters. We suggest to avoid u filter and to avoid the use of colour curves. We also found that, if the error on distance is ≤$2~{{\ \rm per\ cent}}$, 0.5, 1, and 2-h time window sequences are equivalent, so we suggest to use 2-h one, because it has 1-d cadence, so it can be easily realized. When the distance of the source is unknown, 0.5-h time window sequence is preferable.
Abstract
For a subpopulation of energetic gamma-ray bursts (GRBs), a moderate baryonic loading may suffice to power ultra-high-energy cosmic rays (UHECRs). Motivated by this, we study the radiative ...signatures of cosmic-ray protons in the prompt phase of energetic GRBs. Our framework is the internal shock model with multicollision descriptions of the relativistic ejecta (with different emission regions along the jet), plus time-dependent calculations of photon and neutrino spectra. Our GRB prototypes are motivated by Fermi-Large Area Telescope-detected GRBs (including GRB 221009A) for which further, owing to the large energy flux, neutrino nonobservation of single events may pose a strong limit on the baryonic loading. We study the feedback of protons on electromagnetic spectra in synchrotron- and inverse Compton-dominated scenarios to identify the multiwavelength signatures, to constrain the maximally allowed baryonic loading, and to point out the differences between hadronic and inverse Compton signatures. We find that hadronic signatures appear as correlated flux increases in the optical-UV to soft X-ray and GeV–TeV gamma-ray ranges in the synchrotron scenarios, whereas they are difficult to identify in inverse Compton-dominated scenarios. We demonstrate that baryonic loadings around 10, which satisfy the UHECR energetic requirements, do not distort the predicted photon spectra in the Fermi Gamma-Ray Burst Monitor range and are consistent with constraints from neutrino data if the collision radii are large enough (i.e., the time variability is not too short). It therefore seems plausible that under the condition of large dissipation radii a population of energetic GRBs can be the origin of the UHECRs.
Abstract
We present the catalog of InterPlanetary Network (IPN) localizations for 199 short-duration gamma-ray bursts (sGRBs) detected by the Konus-Wind (KW) experiment between 2011 January 1 and ...2021 August 31, which extends the initial sample of IPN-localized KW sGRBs to 495 events. We present the most comprehensive IPN localization data on these events, including probability sky maps in Hierarchical Equal Area isoLatitude Pixelization format.
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