scholarly journals Broad-line type Ic SN 2020bvc

2020 ◽  
Vol 639 ◽  
pp. L11 ◽  
Author(s):  
L. Izzo ◽  
K. Auchettl ◽  
J. Hjorth ◽  
F. De Colle ◽  
C. Gall ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Optical Spectra ◽  
Gamma Ray Bursts ◽  
Archival Data ◽  
Broad Line ◽  
X Ray ◽  
Long Duration ◽  
Gamma Ray Emission ◽  
Very High ◽  
Line Type

Long-duration gamma-ray bursts (GRBs) are almost unequivocally associated with very energetic, broad-line supernovae of Type Ic-BL. While the gamma-ray emission is emitted in narrow jets, the SN emits radiation isotropically. Therefore, it has been hypothesized that some SN Ic-BL not associated with GRBs arise from events with inner engines such as off-axis GRBs or choked jets. Here we present observations of the nearby (d = 120 Mpc) SN 2020bvc (ASAS-SN 20bs) that support this scenario. Swift-UVOT observations reveal an early decline (up to two days after explosion), while optical spectra classify it as a SN Ic-BL with very high expansion velocities (≈70 000 km s−1), similar to that found for the jet-cocoon emission in SN 2017iuk associated with GRB 171205A. Moreover, the Swift X-Ray Telescope and CXO X-ray Observatory detected X-ray emission only three days after the SN and decaying onward, which can be ascribed to an afterglow component. Cocoon and X-ray emission are both signatures of jet-powered GRBs. In the case of SN 2020bvc, we find that the jet is off axis (by ≈23 degrees), as also indicated by the lack of early (≈1 day) X-ray emission, which explains why no coincident GRB was detected promptly or in archival data. These observations suggest that SN 2020bvc is the first orphan GRB detected through its associated SN emission.

scholarly journals X-ray and Gamma-ray Variability of NGC 1275

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 63
Author(s):  
Varsha Chitnis ◽  
Amit Shukla ◽  
K. P. Singh ◽  
Jayashree Roy ◽  
Sudip Bhattacharyya ◽  
...  
Keyword(s):  
Time Scales ◽  
Gamma Ray ◽  
Radio Galaxy ◽  
Cluster Emission ◽  
X Ray ◽  
Gamma Ray Emission ◽  
High Degree ◽  
Ngc 1275 ◽  
Perseus Cluster ◽  
Very High

Gamma-ray emission from the bright radio source 3C 84, associated with the Perseus cluster, is ascribed to the radio galaxy NGC 1275 residing at the centre of the cluster. Study of the correlated X-ray/gamma-ray emission from this active galaxy, and investigation of the possible disk-jet connection, are hampered because the X-ray emission, particularly in the soft X-ray band (2–10 keV), is overwhelmed by the cluster emission. Here we present a method to spectrally decouple the cluster and active galactic nucleus (AGN) emission in imaging X-ray detectors. We use three sets of simultaneous Niel Gehrels Swift XRT and NuStar data. These observations were made during the period 2015 November to 2017 February, when a huge increase in the gamma-ray emission was observed. We find that the gamma-ray emission shows a very high degree of variability (40%–50%) on time scales of 1–10 days, whereas the hard X-ray emission, associated with the AGN, shows a low variability (∼15%–30%), on various time scales in the range of 0.01–60 days.

scholarly journals Supernovae and Gamma-ray Bursts

2011 ◽  
Vol 7 (S279) ◽  
pp. 75-82
Author(s):  
Paolo A. Mazzali
Keyword(s):  
Black Hole ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Observational Evidence ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Broad Absorption ◽  
X Ray ◽  
Long Duration

AbstractThe properties of the Supernovae discovered in coincidence with long-duration Gamma-ray Bursts and X-Ray Flashes are reviewed, and compared to those of SNe for which GRBs are not observed. The SNe associated with GRBs are of Type Ic, they are brighter than the norm, and show very broad absorption lines in their spectra, indicative of high expansion velocities and hence of large explosion kinetic energies. This points to a massive star origin, and to the birth of a black hole at the time of core collapse. There is strong evidence for gross asymmetries in the SN ejecta. The observational evidence seems to suggest that GRB/SNe are more massive and energetic than XRF/SNe, and come from more massive stars. While for GRB/SNe the collapsar model is favoured, XRF/SNe may host magnetars.

scholarly journals Constraints on Very High Energy Gamma‐Ray Emission from Gamma‐Ray Bursts

2005 ◽  
Vol 630 (2) ◽  
pp. 996-1002 ◽  
Author(s):  
R. Atkins ◽  
W. Benbow ◽  
D. Berley ◽  
E. Blaufuss ◽  
D. G. Coyne ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Gamma Ray Emission ◽  
Very High

scholarly journals On the Relation Between GRB Classes and X-ray Flashes

10.14311/1496 ◽  
2012 ◽  
Vol 52 (1) ◽  
Author(s):  
Z. Bagoly ◽  
P. Veres ◽  
I. Horváth ◽  
A. Mészáros ◽  
L. G. Balázs
Keyword(s):  
Physical Properties ◽  
Short Duration ◽  
Classification Scheme ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
The Other ◽  
X Ray ◽  
Intermediate Group ◽  
Long Duration

Gamma-ray bursts are usually classified into either short-duration or long-duration bursts. Going beyond the short-long classification scheme, it has been shown on statistical grounds that a third, intermediate population is needed in this classification scheme. We are looking for physical properties which discriminate the intermediate duration bursts from the other two classes. As the intermediate group is the softest, we argue that we have related them with X-ray flashes among the GRBs. We give a new, probabilistic definition for this class of events.

scholarly journals Searching for Gravitationally Lensed Gamma-Ray Bursts with Their Afterglows

2022 ◽  
Vol 924 (2) ◽  
pp. 49
Author(s):  
Shengnan Chen ◽  
Xudong Wen ◽  
He Gao ◽  
Kai Liao ◽  
Liangduan Liu ◽  
...  
Keyword(s):  
Time Delay ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Archival Data ◽  
Potential Candidate ◽  
X Ray ◽  
Gamma Ray Detectors ◽  
Sky Survey ◽  
Lensing Effect ◽  
Recent Claim

Abstract Gamma-ray bursts (GRBs) at high redshifts are expected to be gravitationally lensed by objects of different mass scales. Other than a single recent claim, no lensed GRB has been detected so far by using gamma-ray data only. In this paper, we suggest that multiband afterglow data might be an efficient way to search for lensed GRB events. Using the standard afterglow model, we calculate the characteristics of the lensed afterglow lightcurves under the assumption of two popular analytic lens models: the point-mass and singular isothermal sphere models. In particular, when different lensed images cannot be resolved, their signals would be superimposed together with a given time delay. In this case, the X-ray afterglows are likely to contain several X-ray flares of similar width in linear scale and similar spectrum, and the optical afterglow lightcurve will show re-brightening signatures. Since the lightcurves from the image arriving later would be compressed and deformed in the logarithmic timescale, the larger time delay (i.e., the larger mass of the lens), the easier it is to identify the lensing effect. We analyzed the archival data of optical afterglows and found one potential candidate of the lensed GRB (130831A) with time delay ∼500 s; however, observations of this event in gamma-ray and X-ray bands seem not to support the lensing hypothesis. In the future, with the cooperation of the all-sky monitoring gamma-ray detectors and multiband sky survey projects, the method proposed in this paper would be more efficient in searching for strongly lensed GRBs.

scholarly journals Gamma-ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 459-466
Author(s):  
Alberto J. Castro-Tirado
Keyword(s):  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Compact Objects ◽  
X Ray ◽  
Long Duration ◽  
Multi Wavelength ◽  
New Generation ◽  
Short Grbs

SummarySince their discovery in 1967 Gamma-ray bursts (GRBs) have been puzzling to astrophysicists. With the advent of a new generation of X–ray satellites in the late 90’s, it was possible to carry out deep multi-wavelength observations of the counterparts associated with the long duration GRBs class just within a few hours of occurrence, thanks to the observation of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. The fact that this emission (the afterglow) extends at longer wavelengths, led to the discovery of optical/IR/radio counterparts in 1997-2003, greatly improving our understanding of these sources. The classical, long duration GRBs, have been observed to originate at cosmological distances in a range of redshifts with 0.1685 ≤ z ≤ 4.50 implying energy releases of ~ 1051 ergs. The recent results on GRB 021004 and GRB 030329 confirm that the central engines that power these extraordinary events are due to be collapse of massive stars rather than the merging of compact objects as previously also suggested. Short GRBs still remain a mystery as no counterparts have been detected so far.

scholarly journals Can we quickly flag ultra-long gamma-ray bursts?

2019 ◽  
Vol 486 (2) ◽  
pp. 2471-2476 ◽  
Author(s):  
B Gendre ◽  
Q T Joyce ◽  
N B Orange ◽  
G Stratta ◽  
J L Atteia ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Wide Field ◽  
Exact Nature ◽  
X Ray ◽  
Central Engine ◽  
Long Duration ◽  
Limited Coverage

Abstract Ultra-long gamma-ray bursts are a class of high-energy transients lasting several hours. Their exact nature is still elusive, and several models have been proposed to explain them. Because of the limited coverage of wide-field gamma-ray detectors, the study of their prompt phase with sensitive narrow-field X-ray instruments could help in understanding the origin of ultra-long GRBs. However, the observers face a true problem in rapidly activating follow-up observations, due to the challenging identification of an ultra-long GRB before the end of the prompt phase. We present here a comparison of the prompt properties available after a few tens of minutes of a sample of ultra-long GRBs and normal long GRBs, looking for prior indicators of the long duration. We find that there is no such clear prior indicator of the duration of the burst. We also found that statistically, a burst lasting at least 10 and 20 minutes has respectively $28{{\ \rm per\ cent}}$ and $50{{\ \rm per\ cent}}$ probability to be an ultralong event. These findings point towards a common central engine for normal long and ultra-long GRBs, with the collapsar model privileged.

scholarly journals Precessing magnetars as central engines in short gamma-ray bursts

2021 ◽  
Vol 502 (2) ◽  
pp. 2482-2494
Author(s):  
A G Suvorov ◽  
K D Kokkotas
Keyword(s):  
Gamma Ray ◽  
Magnetic Energy ◽  
Information Criterion ◽  
Gamma Ray Bursts ◽  
Internal Stresses ◽  
X Ray ◽  
Compact Binary ◽  
Long Duration ◽  
Hydrodynamic Evolution ◽  
Data Points

ABSTRACT Short gamma-ray bursts that are followed by long-duration X-ray plateaus may be powered by the birth, and hydrodynamic evolution, of magnetars from compact binary coalescence events. If the rotation and magnetic axes of the system are not orthogonal to each other, the star will undergo free precession, leading to fluctuations in the luminosity of the source. In some cases, precession-induced modulations in the spin-down power may be discernible in the X-ray flux of the plateau. In this work, 25 X-ray light curves associated with bursts exhibiting a plateau are fitted to luminosity profiles appropriate for precessing, oblique rotators. Based on the Akaike Information Criterion, 16 $(64{{\ \rm per\ cent}})$ of the magnetars within the sample display either moderate or strong evidence for precession. Additionally, since the precession period of the star is directly tied to its quadrupolar ellipticity, the fits allow for an independent measure of the extent to which the star is deformed by internal stresses. Assuming these deformations arise due to a mixed poloidal–toroidal magnetic field, we find that the distribution of magnetic-energy ratios is bimodal, with data points clustering around energetically equal and toroidally dominated partitions. Implications of this result for gravitational-wave emission and dynamo activity in newborn magnetars are discussed.

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