X-ray Burst Emission Research Articles

The confrontation of the shock-powered synchrotron maser model with the Galactic FRB 200428

ABSTRACT The association of FRB 200428 with an X-ray burst (XRB) from the Galactic magnetar SGR 1935+2154 offers important implications for the physical processes responsible for the fast radio burst (FRB) phenomena. By assuming that the XRB emission is produced in the magnetosphere, we investigate the possibility that the FRB emission is produced by shock-powered synchrotron maser (SM), which is phenomenologically described with a number of free parameters. The observational constraints on the model parameters indicate that the model can in principle be consistent with the FRB 200428 observations, if the ejecta lunched by magnetar activities can have appropriate ingredients and structures and the shock processes occur on the line of sight. To be specific, a complete burst ejecta should consist of an ultra-relativistic and extremely highly collimated e± component and a sub-relativistic and wide-spreading baryonic component. The internal shocks producing the FRB emission arise from a collision between the e± ejecta and the remnant of a previous baryonic ejecta at the same direction. The parameter constraints depend on the uncertain spectrum and efficiency of the SM emission. While the spectrum is tentatively described by a spectral index of −2, we estimate the emission efficiency to be around 10−4 by requiring that the synchrotron emission of the shocked material cannot be much brighter than the magnetosphere XRB emission.

X-ray burst-induced spectral variability in 4U 1728–34

Aims. INTEGRAL has been monitoring the Galactic center region for more than a decade. Over this time INTEGRAL has detected hundreds of type-I X-ray bursts from the neutron star low-mass X-ray binary 4U 1728-34, a.k.a. "the slow burster". Our aim is to study the connection between the persistent X-ray spectra and the X-ray burst spectra in a broad spectral range. Methods. We performed spectral modeling of the persistent emission and the X-ray burst emission of 4U 1728-34 using data from the INTEGRAL JEM-X and IBIS/ISGRI instruments. Results. We constructed a hardness intensity diagram to track spectral state variations. In the soft state the energy spectra are characterized by two thermal components - likely from the accretion disc and the boundary/spreading layer - together with a weak hard X-ray tail that we detect in 4U 1728-34 for the first time in the 40 to 80 keV range. In the hard state the source is detected up to 200 keV and the spectrum can be described by a thermal Comptonization model plus an additional component: either a powerlaw tail or reflection. By stacking 123 X-ray bursts in the hard state, we detect emission up to 80 keV during the X-ray bursts. We find that during the bursts the emission above 40 keV decreases by a factor of about three with respect to the persistent emission level. Conclusions. Our results suggest that the enhanced X-ray burst emission changes the spectral properties of the accretion disc in the hard state. The likely cause is an X-ray burst induced cooling of the electrons in the inner hot flow near the neutron star.

HIGH-ENERGY NEUTRINO AND GAMMA-RAY TRANSIENTS FROM TRANS-RELATIVISTIC SUPERNOVA SHOCK BREAKOUTS

Relativistic shocks that accompany supernovae (SNe) produce X-ray burst emissions as they break out in the dense circumstellar medium around the progenitors. This phenomenon is sometimes associated with peculiar low-luminosity gamma-ray bursts (LL GRBs). Here, we investigate the high energy neutrino and gamma-ray counterparts of such a class of SNe. Just beyond the shock breakout radius, particle acceleration in the collisionless shock starts to operate in the presence of breakout photons. We show that protons may be accelerated to sufficiently high energies and produce high energy neutrinos and gamma rays via the photomeson interaction. These neutrinos and gamma rays may be detectable from 10 Mpc away by IceCube/KM3Net as multi-TeV transients almost simultaneously with the X-ray burst emission, and even from 100 Mpc away with follow-up observations by CTA using a wide-field sky monitor like Swift as a trigger. A statistical technique using a stacking approach could also be possible for the detection, with the aid of the SN optical/infrared counterparts. Such multi-messenger observations offer the possibility to probe the transition of relativistic shocks from radiation-mediated to collisionless ones, and would also constrain the mechanisms of particle acceleration and emission in LL GRBs.

Photospheric radius expansion X-ray bursts as standard candles

We examined the maximum bolometric peak luminosities during type I X-ray bursts from the persistent or transient luminous X-ray sources in globular clusters. We show that for about two thirds of the sources the maximum peak luminosities during photospheric radius expansion X-ray bursts extend to a critical value of (3.79+/-0.15)x10^{38} erg/s, assuming the total X-ray burst emission is entirely due to black-body radiation and the recorded maximum luminosity is the actual peak luminosity. This empirical critical luminosity is consistent with the Eddington luminosity limit for hydrogen poor material. Since the critical luminosity is more or less always reached during photospheric radius expansion X-ray bursts (except for one source), such bursts may be regarded as empirical standard candles. However, because significant deviations do occur, our standard candle is only accurate to within 15%. We re-evaluated the distances to the twelve globular clusters in which the X-ray bursters reside.

Radiographic and spectroscopic studies of X-pinch plasma implosion dynamics and x-ray burst emission characteristics

Experimental results are presented from studies of the dynamics of X-pinch plasmas, formed using two fine wires that cross and touch at a single point (in the form of an X) as the load of a high current pulser. High-resolution (sub-ns in time and 2–3 μm in space) x-ray radiographs of X pinches driven by current pulses that rise to 200–250 kA peak current in 40 ns show that ⩽300 μm long Z pinches form in the region of the original wire cross-point a few ns prior to the first sub-ns intense x-ray bursts that are characteristic of an X pinch. The Z pinches implode to ⩽10 μm diam and then appear to develop gaps in the radiographic images in one or two places, coincident in time with the x-ray burst(s). The emission spectra of the intense x-ray bursts from different wire materials indicate electron temperatures of 500–1300 eV and densities in excess of 1022/cm3.

Evidence for weak X-ray burst emission from Cygnus X-2 and GX 17 + 2

view Abstract Citations (64) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for weak X-ray burst emission from Cygnus X-2 and GX 17+2. Kahn, S. M. ; Grindlay, J. E. Abstract Events resembling weak X-ray bursts have been detected from the two strong persistent sources, Cygnus X-2 and GX 17+2. Both events exhibit rise times less than 2.56 s and 1.2 - 14.4 keV decay times of approximately 5 - 10 s. The event from Cyg X-2 is similar to a type I burst in terms of blackbody temperature and peak luminosity, and it is shown that it can be plausibly interpreted as a thermonuclear flash from an accreting neutron star. The GX 17+2 event exhibits a considerably harder X-ray spectrum which makes it unlikely to be a thermonuclear flash. This event could arise from an accretion instability as in type II bursts. Publication: The Astrophysical Journal Pub Date: June 1984 DOI: 10.1086/162161 Bibcode: 1984ApJ...281..826K Keywords: Binary Stars; Neutron Stars; Stellar Mass Accretion; X Ray Sources; Black Body Radiation; Bremsstrahlung; Cygnus Constellation; Thermonuclear Explosions; Astrophysics full text sources ADS | data products SIMBAD (9)

Energetics of a compact flare

We study the spatial and spectral characteristics of the 3.5 to 30.0 keV emission in a solar flare of 9 May, 1980. We find that: (a) A classical thick target interpretation of the hard X-ray burst at energies E ≥ 10 keV implies that approximately all the electrons contained within the flare loop(s) have to be accelerated per second. (b) A ‘thermal model’ interpretation does not fit the data, unless its characteristics are such that it does not represent an efficient alternative to the acceleration model. We thus conclude that: (c) Acceleration does take place during the early phase of the impulsive hard X-ray event, but substantial amount of the emission at low (<20 keV) energies is of thermal origin. (d) We show the evolution of the energy content in the flare volume, and find that the energy input requirements are such that ≈ 102 erg cm-3 s-1 have to be released within the flare structure(s), for a period of time comparable to that of the hard X-ray burst emission. We also point out that although the main flare component (≳ 90% of the soft X-ray emission) was confined to a compact magnetic kernel, there are evidences of interaction of this structure with a larger field structure connecting towards the leading portion of the active region, where secondary Hα brightenings were observed.

X-ray bursts from Type II supernovae

view Abstract Citations (190) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray bursts from type II supernovae. Klein, R. I. ; Chevalier, R. A. Abstract X-ray burst emission during the shock breakout phase of a Type II supernova is investigated for a 12-solar-mass red giant at the end of its nuclear evolution. A supernova model based on a one-dimensional spherically symmetric hydrodynamic code with fine zoning is employed, the detailed time-dependent evolution of the supernova is calculated, and the time-dependent development of the emitted spectrum is computed. By using the calculated structure of the model at any given time, a formal solution of the non-LTE equation of radiative transfer is performed frequency by frequency for the mean intensity. Spectra of the emergent radiation near luminosity maximum and at a somewhat later time are plotted and compared with blackbody spectra for temperatures corresponding to a Rosseland optical depth of 0.67. It is found that a precursor burst of soft X radiation (0.2 to 0.5 keV) with a duration of 1000 sec, a peak luminosity corresponding to a blackbody at 230,000 K, and a distinctly non-Planckian spectrum emerges from the photosphere within 75,000 sec of the explosion. The potential observability of such a burst with an X-ray satellite is estimated. Publication: The Astrophysical Journal Pub Date: August 1978 DOI: 10.1086/182740 Bibcode: 1978ApJ...223L.109K Keywords: Astronomical Models; Computerized Simulation; Supernovae; X Ray Sources; Energy Spectra; Hydrodynamics; Shock Waves; Thermodynamic Equilibrium; Astrophysics; Supernovae:Models; Supernovae:X-Ray Bursts full text sources ADS |

Correlations of solar-flare electron events with radio and X-ray emission from the sun

The &gt; 40-keV solar-flare electrons observed by the IMP III and Mariner IV satellites are shown to be closely correlated with solar radio and X-ray burst emission. In particular, intense type III radio bursts are observed to accompany solar electron-event flares. The energies of the electrons, the total number of electrons, and the size of the electron source at the sun can be inferred from radio observations. The characteristics of the electrons observed in interplanetary space are consistent with these radio observations. Therefore these electrons are identified as the exciting agents of the type III emission. It has been noted that the radio and X-ray bursts are part of the flash phase of flares. The observations indicate that a striking feature of the flash phase is the production of electrons of 10–100 keV energies.