scholarly journals The soft X-ray landscape of gamma-ray bursts: thermal components

2011 ◽  
Vol 7 (S279) ◽  
pp. 175-182
Author(s):  
Rhaana Starling ◽  
Kim Page ◽  
Martin Sparre
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Gamma Ray Bursts ◽  
Continuum Emission ◽  
Line Of Sight ◽  
X Ray ◽  
Multiple Components ◽  
The Standard Model ◽  
New Discovery ◽  
The Continuum

AbstractThe repository of GRB (gamma-ray burst) observations made by the Swift X-ray Telescope, now consisting of over 650 bursts, is a valuable and unique resource for the study of GRB X-ray emission. The observed soft X-ray spectrum typically arises from an underlying power law continuum, absorbed by gas along the line-of-sight. However, particularly at early times in a burst's evolution the continuum emission is not always understood and may comprise multiple components including thermal emission unexpected in the standard model. A thermal X-ray component has been discovered in two very unusual GRBs, perhaps suggesting an association only with this subset of events. However, evidence exists for thermal emission from more typical examples and here we present a new discovery of one such case and describe a systematic search for thermal components among all early GRB X-ray spectra.

X-ray probing of NGC 1275 nuclear region with Hitomi, Swift, and Suzaku

2018 ◽  
Vol 14 (S342) ◽  
pp. 118-121
Author(s):  
Yasushi Fukazawa
Keyword(s):  
Gamma Ray ◽  
Seyfert Galaxies ◽  
Continuum Emission ◽  
Line Center ◽  
Nuclear Region ◽  
X Ray ◽  
Line Region ◽  
Flux Increase ◽  
Ngc 1275 ◽  
The Continuum

AbstractNGC 1275 has been known as a ppint-like X-ray source with a continuum and a Fe-K line. Unlike radio and GeV/TeV gamma-ray emissions, origin of X-ray emission is not yet understood; is it a jet emission like blazars or an accretion corona emission like Seyfert galaxies. X-ray emission is important to determine the SED of jet emission to constrain jet parameters and also understand the relation between accretion and jet. Here we report a recent X-ray probing of NGC 1275 nuclear region with Hitomi/SXS, Swift/XRT, and Suzaku/XIS. Hitomi/SXS gave the first opportunity to measure a Fe-K line of AGNs with several eV resolution. The line center is consistent with the neutral iron emission, and the width is constrained to be 500-1600 km/s (FWHM). This ruled out the origin of broad line region and inner accretion disk. A low-covering-fraction molecular torus or a rotating molecular disk around pc scales, illuminated by accretion corona emission, is suggested as a possible origin. For the continuum emission, Suzaku/XIS monitor observations revealed that the X-ray flux has gradually increased as the GeV gamma-ray flux. Swift/XRT showed a several-days flux increase, associated with the GeV gamma-ray flare. These results on the continuum emission suggests a contribution of jet emission to the X-ray emission. Based on the combined results of Fe-K line and continuum, we discuss some scenarios for X-ray emitting region.

The X-ray luminosity function of short gamma-ray bursts

2021 ◽  
Vol 366 (4) ◽  
Author(s):  
Zhi-Ying Liu ◽  
Fu-Wen Zhang ◽  
Si-Yuan Zhu
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
X Ray

scholarly journals Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

2020 ◽  
Vol 499 (4) ◽  
pp. 5986-5992
Author(s):  
Nikhil Sarin ◽  
Paul D Lasky ◽  
Gregory Ashton
Keyword(s):  
Gravitational Wave ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Dipole Radiation ◽  
X Ray ◽  
Radiative Efficiency ◽  
Central Engine ◽  
Radiative Losses ◽  
Wave Emission ◽  
Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

scholarly journals Discovery of recombining plasma inside the extended gamma-ray supernova remnant HB9

2019 ◽  
Vol 489 (3) ◽  
pp. 4300-4310 ◽  
Author(s):  
A Sezer ◽  
T Ergin ◽  
R Yamazaki ◽  
H Sano ◽  
Y Fukui
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Area ◽  
Imaging Spectrometer ◽  
X Ray ◽  
East Region ◽  
X Ray Imaging ◽  
Collisional Ionization

ABSTRACT We present the results from the Suzaku X-ray Imaging Spectrometer observation of the mixed-morphology supernova remnant (SNR) HB9 (G160.9+2.6). We discovered recombining plasma (RP) in the western Suzaku observation region and the spectra here are well described by a model having collisional ionization equilibrium (CIE) and RP components. On the other hand, the X-ray spectra from the eastern Suzaku observation region are best reproduced by the CIE and non-equilibrium ionization model. We discuss possible scenarios to explain the origin of the RP emission based on the observational properties and concluded that the rarefaction scenario is a possible explanation for the existence of RP. In addition, the gamma-ray emission morphology and spectrum within the energy range of 0.2–300 GeV are investigated using 10 yr of data from the Fermi Large Area Telescope (LAT). The gamma-ray morphology of HB9 is best described by the spatial template of radio continuum emission. The spectrum is well fit to a log-parabola function and its detection significance was found to be 25σ. Moreover, a new gamma-ray point source located just outside the south-east region of the SNR’s shell was detected with a significance of 6σ. We also investigated the archival H i and CO data and detected an expanding shell structure in the velocity range of $-10.5$ and $+1.8$ km s−1 that is coinciding with a region of gamma-ray enhancement at the southern rim of the HB9 shell.

scholarly journals UV and X-ray observations of the neutron star LMXB EXO 0748–676 in its quiescent state

2020 ◽  
Vol 501 (1) ◽  
pp. 1453-1462
Author(s):  
A S Parikh ◽  
N Degenaar ◽  
J V Hernández Santisteban ◽  
R Wijnands ◽  
I Psaradaki ◽  
...  
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
Hubble Space Telescope ◽  
Dense Matter ◽  
Continuum Emission ◽  
Quiescent State ◽  
X Ray ◽  
Low Level ◽  
Low Mass ◽  
Different Origins

ABSTRACT The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <1034 erg s−1, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here, we examine ultraviolet (UV) and X-ray data obtained when EXO 0748–676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, C iv. The line is relatively broad (≳3500 km s−1), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM–Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of LX/LUV ≳ 100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748–676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.

scholarly journals Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

2018 ◽  
Vol 614 ◽  
pp. A44 ◽  
Author(s):  
E. S. Kammoun ◽  
E. Nardini ◽  
G. Risaliti
Keyword(s):  
Thermal Emission ◽  
Signal To Noise Ratio ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
High Signal ◽  
X Ray ◽  
Multiple Components ◽  
Spin Parameter ◽  
Partial Covering ◽  
Spin Measurements

Context. X-ray reflection is a very powerful method to assess the spin of supermassive black holes (SMBHs) in active galactic nuclei (AGN), yet this technique is not universally accepted. Indeed, complex reprocessing (absorption, scattering) of the intrinsic spectra along the line of sight can mimic the relativistic effects on which the spin measure is based. Aims. In this work, we test the reliability of SMBH spin measurements that can currently be achieved through the simulations of high-quality XMM-Newton and NuSTAR spectra. Methods. Each member of our group simulated ten spectra with multiple components that are typically seen in AGN, such as warm and (partial-covering) neutral absorbers, relativistic and distant reflection, and thermal emission. The resulting spectra were blindly analysed by the other two members. Results. Out of the 60 fits, 42 turn out to be physically accurate when compared to the input model. The SMBH spin is retrieved with success in 31 cases, some of which (9) are even found among formally inaccurate fits (although with looser constraints). We show that, at the high signal-to-noise ratio assumed in our simulations, neither the complexity of the multi-layer, partial-covering absorber nor the input value of the spin are the major drivers of our results. The height of the X-ray source (in a lamp-post geometry) instead plays a crucial role in recovering the spin. In particular, a success rate of 16 out of 16 is found among the accurate fits for a dimensionless spin parameter larger than 0.8 and a lamp-post height lower than five gravitational radii.

scholarly journals Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special?

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
J. J. Geng ◽  
Y. F. Huang
Keyword(s):  
Black Holes ◽  
Numerical Method ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Shock Model ◽  
Reverse Shock ◽  
X Ray ◽  
Electron Positron ◽  
Forward Shock ◽  
Electron Positron Pair

The detection of optical rebrightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamics of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical rebrightenings would be caused by the fall-back accretion of black holes, while the shallow optical rebrightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines.

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