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Vol 49, No 2 (2023)
Articles
New Active Galactic Nuclei Detected by the ART-XС and eROSITA Telescopes during the First Five SRG All-Sky X-ray Surveys
Abstract
We present the results of our identification of 14 X-ray sources detected in the eastern Galactic sky (0
with 90% confidence). This paper continues our series of publications on the identification of hard X-ray sources detected during the all-sky survey with the SRG orbital X-ray observatory.
97-121
Second Maximum of SN 2019stc: Collision with a Circumstellar Shell?
Abstract
We consider scenario of a supernova interaction with a circumstellar shell proposed earlier to account for the second maximum in the light curve of the superluminous supernova (SLSN-I) SN 2019stc. It is shown that this mechanism is able to describe the secondary maximum at a circumstellar envelope mass of about 0.3 M@. An important consequence of this scenario is the hard X-ray emission with a luminosity of @(0,5-5)*1042 erg s-1 during the secondary maximum. An X-ray flash coeval with a secondary maximum in SLSNe-I is proposed as a crucial test of the circumstellar interaction scenario.
122-129
On the Nature of the Bar-Shaped X-ray Feature in the Lee Jet of the Vela Pulsar Wind Nebula
Abstract
X-ray morphology of pulsar wind nebulae (PWNe) reflects the structure of underlying plasma outflows. This study aims to reveal the nature of one fine X-ray feature in images of the Vela nebula. The feature is shaped like a narrow bar, oriented across the south-eastern jet of the nebula. It is located in the jet at the beginning of its bright middle section (stretching from
to
from the pulsar) and has an angular size of
. Within the framework of relativistic MHD modeling, we show that such a bar may be a characteristic feature of Vela-like objects-transonic PWNe with a double-torus X-ray structure seen from the leeward side. Our modeling indicates the shock-wave origin for the bar. The shock is formed in the jet due to its dynamical interaction with two regular toroidal vortices in the lee hemisphere of the nebula. Namely, with large-scale circulation at middle latitudes, and with smaller-scale recirculation within the polar funnel of the pulsar wind termination shock. The former vortex almost dams the lee jet in its far downstream (so the bright middle section of the jet is limited in length by the axial size of the vortex) and the latter chokes the jet at its very beginning. The shock underlying the bar feature occurs immediately after the breakthrough of the supersonic jet through the recirculation. The shock is strong, so it propagates from the jet’s body into the surrounding plasma, and it is quasi-stationary–it can disappear and reappear again at the same place.
130-139
On the Origin of Knots in the Vela Nebula
Abstract
Pulsar wind nebulae (PWNe) show complex multiscale X-ray morphology with a wide variety of structures in form of tori, jets, rings, arcs, and knots. The global torus-jet morphology of PWNe is well described in terms of modern relativistic MHD models. Meanwhile, the nature of some of the finer features remains to be elucidated. These include the chain of knots in the ‘‘inner ring’’ in the Crab PWN and the chain of knots around the southeastern jet in the Vela PWN. Recently, the knots in Crab have been interpreted as giant plasmoids. These arise due to magnetic reconnection in the equatorial current sheet just after the shock wave terminating the pulsar wind and responsible for the appearance of the ‘‘inner ring’’ feature. In this work, we aim to find out whether the knots in Vela could have been formed in the same way. Within the frame of numerical relativistic MHD model, we show that in Vela-type nebulae—double-torus objects in transonic motion relative to their surroundings—conditions for strong reconnection and hence for giant plasmoids are formed at the outskirts of the X-ray nebula, where compact regions of high magnetization occur regularly on both sides of the equatorial belt. In the projection onto the celestial plane, these regions line up along two narrow coaxial ‘‘outer rings,’’ of which the windward is larger than the leeward. Due to the difference in size of the rings, their far halves must be very close to each other if the nebula is seen from its leeward side at the same angle as Vela. In this case, giant plasmoids from the far side of the nebula should be concentrated in the vicinity a narrow arcuate stripe bounded by these halves.
140-154