380 research outputs found
Constraint on the ejecta mass for a black hole-neutron star merger event candidate S190814bv
We derive the upper limit to the ejecta mass of S190814bv, a black
hole-neutron star merger candidate, through the radiative transfer simulations
for kilonovae with the realistic ejecta density profile as well as the detailed
opacity and heating rate models. The limits to the ejecta mass strongly depend
on the viewing angle. For the face-on observations (), the total
ejecta mass should be smaller than for the average distance of
S190814bv ( Mpc), while larger mass is allowed for the edge-on
observations. We also derive the conservative upper limits of the dynamical
ejecta mass to be , , and for the
viewing angle , , and for ,
respectively. We show that the {\it iz}-band observation deeper than mag
within 2 d after the GW trigger is crucial to detect the kilonova with the
total ejecta mass of at the distance of Mpc. We also
show that a strong constraint on the NS mass-radius relation can be obtained if
the future observations put the upper limit of to the dynamical
ejecta mass for a BH-NS event with the chirp mass smaller than and effective spin larger than .Comment: 16 pages, 15 figure
Radiation hydrodynamics simulations of wide-angle outflows from super-critical accretion disks around black holes
By performing two-dimensional radiation hydrodynamics simulations with large
computational domain of 5000 Schwarzschild radius, we revealed that wide-angle
outflow is launched via the radiation force from the super-critical accretion
flows around black holes. The angular size of the outflow, of which the radial
velocity (v_r) is over the escape velocity (v_esc), increases with an increase
of the distance from the black hole. As a result, the mass is blown away with
speed of v_r > v_esc in all direction except for the very vicinity of the
equatorial plane, theta=0-85^circ, where theta is the polar angle. The mass
ejected from the outer boundary per unit time by the outflow is larger than the
mass accretion rate onto the black hole, ~150L_Edd/c^2, where L_Edd and c are
the Eddington luminosity and the speed of light. Kinetic power of such
wide-angle high-velocity outflow is comparable to the photon luminosity and is
a few times larger than the Eddington luminosity. This corresponds to
~10^39-10^40 erg/s for the stellar mass black holes. Our model consistent with
the observations of shock excited bubbles observed in some ultra-luminous X-ray
sources (ULXs), supporting a hypothesis that ULXs are powered by the
super-critical accretion onto stellar mass black holes.Comment: 9 pages, 8 figures, accepted for publication in PAS
Constraining the Age and Distance of the Galactic Supernova Remnant G156.2+5.7 by H-alpha Expansion Measurements
We present deep H-alpha images of portions of the X-ray bright but optically
faint Galactic supernova remnant G156.2+5.7, revealing numerous and delicately
thin nonradiative filaments which mark the location of the remnant's forward
shock. These new images show that these filaments have a complex structure not
visible on previous lower resolution optical images. By comparing H-alpha
images taken in 2004 at the McDonald Observatory and in 2015-2016 at the Kiso
Observatory, we set a stringent 1-sigma upper limit of expansion to be 0.06
arcsec/yr. This proper motion, combined with a shock speed of 500 km/s inferred
from X-ray spectral analyses, gives a distance of > 1.7 kpc. In addition, a
simple comparison of expansion indices of several SNRs allows us to infer the
age of the remnant to be a few 10,000 yr old. These estimates are more
straightforward and reliable than any other previous studies, and clearly rule
out a possibility that G156.2+5.7 is physically associated with part of the
Taurus-Auriga cloud and dust complex at a distance of 200-300 pc.Comment: 16 pages, 5 figures, accepted for publication in The Astrophysical
Journa
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