146 research outputs found
Electron-positron pairs in hot plasma of accretion column in bright X-ray pulsars
The luminosity of X-ray pulsars powered by accretion onto magnetized neutron
stars covers a wide range over a few orders of magnitude. The brightest X-ray
pulsars recently discovered as pulsating ultraluminous X-ray sources reach
accretion luminosity above which exceeds the
Eddington value more than by a factor of ten. Most of the energy is released
within small regions in the vicinity of magnetic poles of accreting neutron
star - in accretion columns. Because of the extreme energy release within a
small volume accretion columns of bright X-ray pulsars are ones of the hottest
places in the Universe, where the internal temperature can exceed 100 keV.
Under these conditions, the processes of creation and annihilation of
electron-positron pairs can be influential but have been largely neglected in
theoretical models of accretion columns. In this letter, we investigate
properties of a gas of electron-positron pairs under physical conditions
typical for accretion columns. We argue that the process of pairs creation can
crucially influence both the dynamics of the accretion process and internal
structure of accretion column limiting its internal temperature, dropping the
local Eddington flux and increasing the gas pressure.Comment: 5 pages, 5 figures, accepted for publication in MNRAS Letter
Bright X-ray pulsars as sources of MeV neutrinos in the sky
High mass accretion rate onto strongly magnetised neutron stars results in
the appearance of accretion columns supported by the radiation pressure and
confined by the strong magnetic field of a star. At mass accretion rates above
, accretion columns are expected to be
advective. Under such conditions, a noticeable part of the total energy release
can be carried away by neutrinos of a MeV energy range. Relying on a simple
model of the neutrino luminosity of accreting strongly magnetised neutron
stars, we estimate the neutrino energy fluxes expected from six ULX pulsars
known up to date and three brightest Be X-ray transits hosting magnetised
neutron stars. Despite the large neutrino luminosity expected in ULX pulsars,
the neutrino energy flux from the Be X-ray transients of our Galaxy, SMC and
LMC is dominant. However, the neutrino flux from the brightest X-ray transients
is estimated to be below the isotropic background by two orders of magnitude at
least, which makes impossible direct registration of neutrino emission from
accreting strongly magnetised neutron stars nowadays.Comment: 7 pages, 6 figures, submitted to MNRA
On the Possible Enhancement of the Magnetic Field by Neutrino Reemission Processes in the Mantle of a Supernova
URCA neutrino reemission processes under the conditions in the mantle of a
supernova with a strong toroidal magnetic field are investigated. It is shown
that parity violation in these processes can be manifested macroscopically as a
torque that rapidly spins up the region of the mantle occupied by such a field.
Neutrino spin-up of the mantle can strongly affect the mechanism of further
generation of the toroidal field, specifically, it can enhance the field in a
small neighborhood of the rigid-body-rotating core of the supernova remnant.Comment: 8 pages, late
Efficiency of Electron-Positron Pair Productionby Neutrino Flux from Accretion Disk of a Kerr Black Hole
Dominant processes of neutrino production and neutrino-induced \ep-pair
production are examined in the model of a disk hyper-accreting onto a Kerr
black hole. The efficiency of plasma production by a neutrino flux from the
disk, obtained for the both cases of presence and absence of a magnetic field,
is found to be no more than several tenths of percent and, therefore, not
enough for the origin of cosmological gamma-ray bursts.Comment: 8 pages, 1 figur
Minimally invasive surgery parenchymal cysts abdominal children
Retrospectively and prospectively studied 53 clinical cases of surgical treatment of cystic formations of parenchpal abdominal organs in children. Experience in treatment of cysts various minimally invasive techniques. The most efficient and optimal results are achieved with laparoscopic fenestration of cysts in conjunction with argon plasma deepitelizatsii inner lining.Π Π΅ΡΡΠΎΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΠΎ ΠΈ ΠΏΡΠΎΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΠΎ ΠΈΠ·ΡΡΠ΅Π½ΠΎ 53 ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ»ΡΡΠ°Ρ ΠΎΠΏΠ΅ΡΠ°ΡΠΈΠ²Π½ΠΎΠ³ΠΎ Π»Π΅ΡΠ΅Π½ΠΈΡ ΠΊΠΈΡΡΠΎΠ·Π½ΡΡ
ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΠΉ ΠΏΠ°ΡΠ΅Π½Ρ
ΠΈΠΌΠ°ΡΠΎΠ·Π½ΡΡ
ΠΎΡΠ³Π°Π½ΠΎΠ² Π±ΡΡΡΠ½ΠΎΠΉ ΠΏΠΎΠ»ΠΎΡΡΠΈ Ρ Π΄Π΅ΡΠ΅ΠΉ. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½ ΠΎΠΏΡΡ Π»Π΅ΡΠ΅Π½ΠΈΡ ΠΊΠΈΡΡ ΡΠ°Π·Π»ΠΈΡΠ½ΡΠΌΠΈ ΠΌΠ°Π»ΠΎΠΈΠ½Π²Π°Π·ΠΈΠ²Π½ΡΠΌΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ°ΠΌΠΈ. ΠΠ°ΠΈΠ±ΠΎΠ»Π΅Π΅ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΡΠ΅ ΠΈ ΠΎΠΏΡΠΈΠΌΠ°Π»ΡΠ½ΡΠ΅ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ Π΄ΠΎΡΡΠΈΠ³Π½ΡΡΡ ΠΏΡΠΈ Π»Π°ΠΏΠ°ΡΠΎΡΠΊΠΎΠΏΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅Π½Π΅ΡΡΡΠ°ΡΠΈΠΈ ΠΊΠΈΡΡ Π² ΡΠΎΡΠ΅ΡΠ°Π½ΠΈΠΈ Ρ Π°ΡΠ³ΠΎΠ½ΠΎΠΏΠ»Π°Π·ΠΌΠ΅Π½Π½ΠΎΠΉ Π΄Π΅ΡΠΏΠΈΡΠ΅Π»ΠΈΠ·Π°ΡΠΈΠ΅ΠΉ Π²Π½ΡΡΡΠ΅Π½Π½Π΅ΠΉ Π²ΡΡΡΠΈΠ»ΠΊΠΈ
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