263 research outputs found
Low State of the X-ray Burster SLX 1732-304 in the Globular Cluster Terzan 1 According to RXTE Data
Observations of the X-ray burster SLX 1732-304 in the globular cluster Terzan
1 with the PCA/RXTE instrument in April 1997 are presented. The source was in a
low state; its flux in the standard X-ray band was half the flux recorded by
the ART-P/Granat telescope also during its low state. At the same time, its
spectrum was softer than the ART-P spectrum; it was well described by a power
law with a photon index of 2.3 without any evidence of a high-energy cutoff.Comment: 8 pages, 3 figures. Accepted to publication in Astronomy Letter
First results from TOO observations of the Aql X-1 field with INTEGRAL
We present results of observations of the Aql X-1 field performed in
March-April 2003 with the INTEGRAL observatory. This TOO (Target Of
Opportunity) INTEGRAL observations was initiated upon receiving an indication
from the ASM/RXTE that the source started an outburst. Thirteen X-ray sources
were detected by the INTEGRAL imagers, JEM-X and IBIS, during these
observations. We present a preliminary spectral and timing analysis for several
bright sources in the field, Aql X-1, X1901+03, 4U1907+097, XTE J1908+094 and
X1908+075. We also detected two X-ray bursts from Aql X-1 near the end of the
general outburst episode.Comment: 5 pages, 7 figures, accepted for publication in the A&
Optical Identifications of Five INTEGRAL Hard X-ray Sources in the Galactic Plane Region
The results of optical identifications of five hard X-ray sources in the
Galactic plane region from the INTEGRAL all-sky survey are presented. The X-ray
data on one source (IGRJ20216+4359) are published for the first time. The
optical observations were performed with 1.5-m RTT-150 telescope (TUBITAK
National Observatory, Antalya, Turkey) and 6-m BTA telescope (Special
Astrophysical Observatory, Nizhny Arkhyz, Russia). A blazar, three Seyfert
galaxies, and a high-mass X-ray binary are among the identified sources.Comment: 7 pages, 10 figures, Astronomy Letters, v. 34, p. 65
Arctic polar vortex dynamics during winters 2014/2015 and 2020/2021
The dynamic barrier of the polar vortex contributes to lowering the temperature inside the vortex in the lower stratosphere and prevents the penetration of air masses into the vortex. The presence of a dynamic barrier during winter is one of the criteria determining the possibility of ozone depletion from late winter to spring. We considered the dynamics of the Arctic polar vortex in the winters of 2014/2015 and 2020/2021 at the 50, 30 and 10 hPa levels by the vortex delineation method using the geopotential. In early January 2015 and 2021, sudden stratospheric warmings were recorded as a result of the splitting (4 January 2015) and the significant displacement (5 January 2021) of the polar vortex. In both cases, the weakening of the dynamic barrier of the polar vortex was observed. The polar vortex is characterized by the presence of a dynamic barrier, when the wind speed along the entire edge of the vortex is more than 20, 24 and 30 m/s at the 50, 30 and 10 hPa levels, respectively. A decrease in the average wind speed along the vortex edge below 30, 36 and 45 m/s, at the 50, 30 and 10 hPa levels, respectively, usually indicates a local decrease in the wind speed below 20, 24 and 30 m/s at these levels, i.e., indirectly indicates a weakening of the dynamic barrier.The dynamic barrier of the polar vortex contributes to lowering the temperature inside the vortex in the lower stratosphere and prevents the penetration of air masses into the vortex. The presence of a dynamic barrier during winter is one of the criteria determining the possibility of ozone depletion from late winter to spring. We considered the dynamics of the Arctic polar vortex in the winters of 2014/2015 and 2020/2021 at the 50, 30 and 10 hPa levels by the vortex delineation method using the geopotential. In early January 2015 and 2021, sudden stratospheric warmings were recorded as a result of the splitting (4 January 2015) and the significant displacement (5 January 2021) of the polar vortex. In both cases, the weakening of the dynamic barrier of the polar vortex was observed. The polar vortex is characterized by the presence of a dynamic barrier, when the wind speed along the entire edge of the vortex is more than 20, 24 and 30 m/s at the 50, 30 and 10 hPa levels, respectively. A decrease in the average wind speed along the vortex edge below 30, 36 and 45 m/s, at the 50, 30 and 10 hPa levels, respectively, usually indicates a local decrease in the wind speed below 20, 24 and 30 m/s at these levels, i.e., indirectly indicates a weakening of the dynamic barrier
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