scholarly journals Population of Short γ-ray Bursters — Result of Gravitational lensing of “Quiet” γ-ray Sources in Remote Galaxies

1995 ◽  
Vol 151 ◽  
pp. 363-366
Author(s):  
G.M. Beskin
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Neutron Star ◽  
Gravitational Lensing ◽  
Spectral Properties ◽  
Brightness Distribution ◽  
Source Plane ◽  
Critical Curves ◽  
Flux Variability ◽  
Γ Ray

We consider the hypothesis of the existence of a class of short (10−2-10−3s) and weak (10−6-10−7erg/s· cm2) γ-bursts of cosmological origin. These events arise from gravitational microlensing of bright, quiet γ-ray sources (with luminosity about 3·1038erg/s) located in distant (z ≥ 1) galaxies by stars inside foreground galaxies. If the size of the γ-ray sources is 104-106cm, motion with respect to the observer or the intermediate galaxy may bring them close to the neigborhood of cusps along critical curves generated by individual stars (corresponding to caustics in the observer’s plane). In these cases the observed fluxes increase by a factor 1011-1013, the temporal variation of intensity being due to the brightness distribution in the source and to the distance from the cusp (in the source plane). Using standard assumptions for the number and sizes of “quiet” γ-ray sources, the number and characteristics of galaxies, we estimate the observed burst rate to be between 1 and 10 bursts per year (see below). Their temporal and spectral properties are determined by the nature of sources (ejecting pulsar, accreting neutron star with a weak or strong magnetic field, black hole) and by their velocity relative to the cusp. Similar effects have been discussed in the context of flux variability and structure studies of quasars (e.g. Schneider & Weiss 1986, Grieger et al. 1988, Refsdal & Surdej 1994). However, in these cases the source sizes were larger than 1014cm3 and amplification did not exceed 102.

scholarly journals Swift/XRT, Chandra, and XMM–Newton observations of IGR J17091–3624 as it returns into quiescence

2020 ◽  
Vol 497 (1) ◽  
pp. 1115-1126
Author(s):  
M Pereyra ◽  
D Altamirano ◽  
J M C Court ◽  
N Degenaar ◽  
R Wijnands ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Time Scales ◽  
Strong Evidence ◽  
Spectral Properties ◽  
X Ray ◽  
Term Evolution ◽  
Wide Range ◽  
Low Mass

ABSTRACT IGR J17091–3624 is a low-mass X-ray binary (LMXB), which received wide attention from the community thanks to its similarities with the bright black hole system GRS 1915+105. Both systems exhibit a wide range of highly structured X-ray variability during outburst, with time-scales from few seconds to tens of minutes, which make them unique in the study of mass accretion in LMXBs. In this work, we present a general overview into the long-term evolution of IGR J17091–3624, using Swift/XRT observations from the onset of the 2011–2013 outburst in 2011 February till the end of the last bright outburst in 2016 November. We found four re-flares during the decay of the 2011 outburst, but no similar re-flares appear to be present in the latter one. We studied, in detail, the period with the lowest flux observed in the last 10 yr, just at the tail end of the 2011–2013 outburst, using Chandra and XMM-Newton observations. We observed changes in flux as high as a factor of 10 during this period of relative quiescence, without strong evidence of softening in the spectra. This result suggests that the source has not been observed at its true quiescence so far. By comparing the spectral properties at low luminosities of IGR J17091–3624 and those observed for a well-studied population of LMXBs, we concluded that IGR J17091–3624 is most likely to host a black hole as a compact companion rather than a neutron star.

scholarly journals CLOSE BINARY PROGENITORS OF HYPERNOVAE

2012 ◽  
Vol 08 ◽  
pp. 209-219 ◽  
Author(s):  
MAXIM V. BARKOV
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Close Binary ◽  
Transient Event ◽  
Common Envelope ◽  
Starting Point ◽  
The Common ◽  
Rayet Star

In this paper we propose a new plausible mechanism of supernova explosions specific to close binary systems. The starting point is the common envelope phase in the evolution of a binary consisting of a red super giant and a neutron star. As the neutron star spirals towards the center of its companion it spins up via disk accretion. Depending on the specific angular momentum of gas captured by the neutron star via the Bondi-Hoyle mechanism, it may reach millisecond periods either when it is still inside the common envelope or after it has merged with the companion core. The high accretion rate may result in strong differential rotation of the neutron star and generation of a magnetar-strength magnetic field. The magnetar wind can blow away the common envelope if its magnetic field is as strong as 1015 G, and can destroy the entire companion if it is as strong as 1016 G. The total explosion energy can be comparable to the rotational energy of a millisecond pulsar and reach 1052 erg. The result is an unusual type-II supernova with very high luminosity during the plateau phase, followed by a sharp drop in brightness and a steep light-curve tail. The remnant is either a solitary magnetar or a close binary involving a Wolf-Rayet star and a magnetar. When this Wolf-Rayet star explodes this will be a third supernovae explosion in the same binary. A particularly interesting version of the binary progenitor involves merger of a red super giant star with an ultra-compact companion, neutron star or black hole. In the case if a strong magnetic field is not generated on the surface of a neutron star then it will collapse to a black hole. After that we expect the formation of a very long-lived accretion disk around the black hole. The Blandford-Znajek driven jet from this black hole may drive not only hypernovae explosion but produce a bright X-ray transient event on a time scale of 104 s.

A neutron star collapse induced by a primordial black hole as the source of cosmological γ-ray bursts

1998 ◽  
Vol 41 (1) ◽  
pp. 7-15 ◽  
Author(s):  
E. V. Derishev ◽  
V. V. Kocharovsky ◽  
Vl. V. Kocharovsky
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Primordial Black Hole ◽  
Γ Ray

scholarly journals ROSAT Observations of Soft X-ray Transients in Quiescence

1996 ◽  
Vol 165 ◽  
pp. 333-339
Author(s):  
Frank Verbunt
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Neutron Star ◽  
Neutron Stars ◽  
Weak Magnetic Field ◽  
Small Surface ◽  
X Ray ◽  
Surface Areas ◽  
Actual Spectrum ◽  
Small Surface Area

Four soft X-ray transients, two with a neutron star and two with a black hole, have been detected at quiescence with ROSAT. Blackbody fits to their spectra give temperatures of 160–300 eV, and surface areas of <1 km2. The small surface area suggests that the actual spectrum may be optically thin. The companion star does not contribute significantly to the X-ray luminosity, except perhaps in the case of A 0620-00. From the observation that accretion continues at luminosity levels of ∼1033 erg s−1 it is concluded that the neutron stars in Aql X-1 and Cen X-4 have a weak magnetic field and rotate rather slowly.

scholarly journals THE GIANT FLARE FROM SGR 1806–20 AND ITS RADIO AFTERGLOW

2006 ◽  
Vol 21 (29) ◽  
pp. 2171-2188 ◽  
Author(s):  
G. B. TAYLOR ◽  
J. GRANOT
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Cosmic Rays ◽  
Total Energy ◽  
High Energy ◽  
Multi Wavelength ◽  
Γ Ray ◽  
High Energy Neutrinos ◽  
Giant Flare ◽  
The Magnetic Field

The multi-wavelength observations of the 2004 December 27 Giant Flare (GF) from SGR 1806–20 and its long-lived radio afterglow are briefly reviewed. The GF appears to have been produced by a dramatic reconfiguration of the magnetic field near the surface of the neutron star, possibly accompanied by fractures in the crust. The explosive release of over 1046 erg (isotropic equivalent) powered a one-sided mildly relativistic outflow. The outflow produced a new expanding radio nebula that is still visible over a year after the GF. Also considered are the constraints on the total energy in the GF, the energy and mass in the outflow, and on the external density, as well as possible implications for short γ-ray bursts and potential signatures in high energy neutrinos, photons, or cosmic rays. Some possible future observations of this and other GFs are briefly discussed.

scholarly journals Gamma Ray Bursts as Death of Magnetized Neutron Stars

1996 ◽  
Vol 160 ◽  
pp. 361-362
Author(s):  
Hitoshi Hanami
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Neutron Star ◽  
Neutron Stars ◽  
Strong Magnetic Field ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Final Phase ◽  
Poynting Flux ◽  
Free Process

AbstractWe propose magnetic cannon ball mechanism in which the collapse of a magnetosphere onto a black hole can generate strong outward Poynting flux which can drive a baryon-free fireball. This process can occur at the final collapsing phase of a neutron star with strong magnetic field. The magnetic cannon ball can drive a relativistic outflow without the rotation of the central object. This baryon-free process can explain gamma-ray bursts as the final phase of dead pulsars.

Cosmological γ-ray bursts from a neutron star collapse induced by a primordial black hole

JETP Letters ◽  
1999 ◽  
Vol 70 (10) ◽  
pp. 652-658 ◽  
Author(s):  
E. V. Derishev ◽  
V. V. Kocharovsky ◽  
Vl. V. Kocharovsky
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Primordial Black Hole ◽  
Γ Ray
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