32 research outputs found
Level of biogenic and organic substances in a water of the Dniprovs’ke reservoir and Samara River in fall-winter period
Вивчено актуальні проблеми впливу евтрофування Дніпровського водосховища органічними та біогенними речовинами господарсько-побутових і промислових стічних вод на рибогосподарські показники. Проведені досліди показали перевищення ГДК за деякими показниками для рибогосподарських водойм.Вивчено актуальні проблеми впливу евтрофування Дніпровського водосховища органічними та біогенними речовинами господарсько-побутових і промислових стічних вод на рибогосподарські показники. Проведені досліди показали перевищення ГДК за деякими показниками для рибогосподарських водойм.Relevant problems of influence of the Dniprovs’ke reservoir eutrophication by the household sewage on the water quality indices in fishing zones were studied. Investigations disclosed the excess of the maximum permissible concentration of some indices developed for a fishing reservoir
Observations of PSR J2021+3651 and its X-ray Pulsar Wind Nebula G75.2+0.1
We present results from X-ray and radio observations of the recently
discovered young Vela-like pulsar PSR J2021+3651, which is coincident with the
EGRET gamma-ray source GeV 2020+3658. A 19.0-ks Chandra ACIS-S observation has
revealed a ~20'' x 10'' pulsar wind nebula that is reminiscent of the
equatorial tori seen around some young pulsars, along with thermal emission
from an embedded point source (kT = 0.15 +/- 0.02 keV). We name the nebula
G75.2+0.1. Its spectrum is well fit by an absorbed power-law model with photon
index 1.7 +/- 0.3, hydrogen column density nH = 7.8 +/- 1.7 x 10^21 cm^-2, and
an unabsorbed 0.3-10.0 keV flux of 1.9 +/- 0.3 x 10^-12 erg cm^-2 s^-1. We have
spatially fit G75.2+0.1 with a model that assumes a toroidal morphology, and
from this we infer that the torus is highly inclined 83 deg +/- 1 deg to the
line of sight. A 20.8-ks Chandra observation in continuous-clocking mode
reveals a possible pulse detection, with a pulsed fraction of ~37% and an
H-test probability of occuring by chance of 1.2 x 10^-4. Timing observations
with the Arecibo radio telescope spanning two years show that PSR J2021+3651
glitched sometime between MJDs 52616 and 52645 with parameters delta(v)/v =
(2.587 +/- 0.002) x 10^-6 and delta(dot(v))/v = (6.2 +/- 0.3) x 10^-3, similar
to those of the largest glitches observed in the Vela pulsar. PSR J2021+3651 is
heavily scattered (T_sc = 17.7 ms +/- 0.9 ms at 1 GHz) and exhibits a
significant amount of timing noise.Comment: 23 pages, 6 figures. Submitted to the Astrophysical Journa
Asymptotics of Eigenvalues and Eigenfunctions for the Laplace Operator in a Domain with Oscillating Boundary. Multiple Eigenvalue Case
We study the asymptotic behavior of the solutions of a spectral problem for
the Laplacian in a domain with rapidly oscillating boundary. We consider the
case where the eigenvalue of the limit problem is multiple. We construct the
leading terms of the asymptotic expansions for the eigenelements and verify the
asymptotics
The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought
We use moderate-resolution optical spectrophotometry and the new MARCS
stellar atmosphere models to determine the effective temperatures of 74
Galactic red supergiants. From these we find a new effective temperature scale
that is significantly warmer than those in the literature. We show that this
temperature scale, along with the newly derived bolometric corrections, gives
much better agreement between our red supergiants and stellar evolutionary
tracks. This agreement provides an independent verification of our new
temperature scale. The combination of effective temperature and bolometric
luminosities allows us to calculate stellar radii; the coolest and most
luminous stars have radii of roughly 1500 solar radii (7 AU), in excellent
accordance with the largest stellar radii predicted from current evolutionary
theory. We find that similar results are obtained for the effective
temperatures and bolometric luminosities using only the de-reddened V-K colors,
providing a powerful demonstration of the self-consistency of the MARCS models.Comment: 32 pages, 16 figures; Accepted by the Astrophysical Journa
Galactic Kinematics from OB3 Stars with Distances determined from Interstellar Ca II Lines
Based on data for 102 OB3 stars with known proper motions and radial
velocities, we have tested the distances derived by Megier et al. from
interstellar Ca II spectral lines. The internal reconciliation of the distance
scales using the first derivative of the angular velocity of Galactic rotation
{\Omega}'0 and the external reconciliation with Humphreys's distance scale for
OB associations refined by Mel'nik and Dambis show that the initial distances
should be reduced by \approx 20%. Given this correction, the heliocentric
distances of these stars lie within the range 0.6-2.6 kpc. A kinematic analysis
of these stars at a fixed Galactocentric distance of the Sun, R0=8 kpc, has
allowed the following parameters to be determined:(1) the solar peculiar
velocity components (U_o,V_o,W_o)=(8.9,10.3,6.8)\pm(0.6,1.0,0.4) km/s;(2) the
Galactic rotation parameters {\Omega}_o=-31.5\pm0.9 km/s/kpc,
{\Omega}'_o=+4.49\pm0.12 km/s/kpc^2, {\Omega}"_o=-1.05\pm0.38 km/s/kpc^3, (the
corresponding Oort constants are A=17.9\pm0.5 km/s/kpc, B=-13.6\pm1.0 km/s/kpc
and the circular rotation velocity of the solar neighborhood is |V_o|=252\pm14
km/s); (3) the spiral density wave parameters, namely: the perturbation
amplitudes for the radial and azimuthal velocity components, respectively, f_R
= -12.5\pm1.1 km/s and f_{\theta}=2.0\pm1.6 km/s; the pitch angle for the
two-armed spiral pattern i=-5.3\pm0.3 degrees, with the wavelength of the
spiral density wave at the solar distance being {\lambda}=2.3\pm0.2 kpc; the
Sun's phase in the spiral wave {\chi}_o=-91\pm4 degrees.Comment: 14 pages, 4 figures, 3 table