12,219 research outputs found
A Pre-Merger Stage Galaxy Cluster: Abell 3733
The galaxy cluster Abell 3733 (A3733) is a very suitable candidate in
addressing dynamical processes throughout galaxy cluster mergers. This study
shows structural analysis results of A3733 (z = 0.038) based on X-ray and
optical data. According to X-ray luminosity map, A3733 hosts two sub-structures
separated in the sky by 0.25 Mpc, and the two distinct clumps are
located in the East (A3733E) and the West (A3733W) directions. Both
sub-structures are centred on two different brightest cluster galaxies (BCGs),
and the X-ray and optical centroids of both BCGs substantially coincide with
each other. The intracluster medium (ICM) temperatures of the sub-structures
are estimated to be 2.79 keV for A3733E and 3.28 keV for A3733W. Both
sub-structures are found to be hosting cool central gas (kT 1.5-2.5
keV) surrounded by hotter gas (kT 3.0-3.5 keV). Besides, the X-ray
concentration parameters are found to be c 0.3 for each sub-structure.
These results indicate the existence of cool centres for both sub-structures.
The optical density map reveals a crowded galaxy population within the vicinity
of A3733W. The high probable (% 88.2) dynamical binding model of A3733 suggests
that the cores of sub-structures have a 3D separation of 0.27 Mpc and will
collide in 0.14 Gyr with the relative in-falling velocity of 1936 km s.
As a conclusion, this study demonstrates some evidence suggesting that the
A3733 system is in the pre-merger state.Comment: 9 pages, 7 Figures, published by MNRA
Thermal QCD Sum Rules Study of Vector Charmonium and Bottomonium States
We calculate the masses and leptonic decay constants of the heavy vector
quarkonia, and mesons at finite temperature. In particular,
considering the thermal spectral density as well as additional operators coming
up at finite temperature, the thermal QCD sum rules are acquired. Our numerical
calculations demonstrate that the masses and decay constants are insensitive to
the variation of temperature up to , however after this point,
they start to fall altering the temperature. At deconfinement temperature, the
decay constants attain roughly to 45% of their vacuum values, while the masses
are diminished about 12%, and 2.5% for and states,
respectively. The obtained results at zero temperature are in good consistency
with the existing experimental data as well as predictions of the other
nonperturbative models. Considerable decreasing in the values of the decay
constants can be considered as a sign of the quark gluon plasma phase
transition.Comment: 14 Pages, 8 Figures and 2 Table
Stabilization of Extra Dimensions at Tree Level
By considering the effects of string winding and momentum modes on a time
dependent background, we find a method by which six compact dimensions become
stabilized naturally at the self-dual radius while three dimensions grow large.Comment: 15 pages, 2 figures, minor typos correcte
Spectral and Rotational Changes in the Isolated Neutron Star RX J0720.4-3125
RX J0720.4-3125 is an isolated neutron star that, uniquely in its class, has
shown changes in its thermal X-ray spectrum. We use new spectra taken with
Chandra's Low Energy Transmission Grating Spectrometer, as well as archival
observations, to try to understand the timescale and nature of these changes.
We construct lightcurves, which show both small, slow variations on a timescale
of years, and a larger event that occurred more quickly, within half a year.
From timing, we find evidence for a `glitch' coincident with this larger
event, with a fractional increase in spin frequency of 5x10^{-8}. We compare
the `before' and `after' spectra with those from RX J1308.6+2127, an isolated
neutron star with similar temperature and magnetic field strength, but with a
much stronger absorption feature in its spectrum. We find that the `after'
spectrum can be represented remarkably well by the superposition of the
`before' spectrum, scaled by two thirds, and the spectrum of RX J1308.6+2127,
thus suggesting that the event affected approximately one third of the surface.
We speculate the event reflects a change in surface composition caused by,
e.g., an accretion episode.Comment: 4 pages, 2 figures, 2 tables, emulateapj format. ApJL, accepte
Feeding habits of garfish, Belone belone euxini Günther, 1866 in autumn and winter in Turkey’s south–east coast of the Black Sea
Hábitos alimentarios de la aguja, Belone belone auxini Günther, 1866 en otoño e invierno en la costa suroriental del Mar Negro, en TurquÃa En el estudio se examinó el contenido estomacal de Belone belone en la costa suroriental del Mar Negro durante los meses de otoño e invierno de 2010 y 2011. Las hormigas voladoras constituyeron la presa más frecuente de la dieta en otoño, mientras que en invierno fueron los peces. Otras presas que aparecen en la dieta son moluscos, crustáceos e isópodos. Las hormigas voladoras son consumidas básicamente por los machos, en especial por los más pequeños, durante el otoño.Hábitos alimentarios de la aguja, Belone belone auxini Günther, 1866 en otoño e invierno en la costa suroriental del Mar Negro, en TurquÃa En el estudio se examinó el contenido estomacal de Belone belone en la costa suroriental del Mar Negro durante los meses de otoño e invierno de 2010 y 2011. Las hormigas voladoras constituyeron la presa más frecuente de la dieta en otoño, mientras que en invierno fueron los peces. Otras presas que aparecen en la dieta son moluscos, crustáceos e isópodos. Las hormigas voladoras son consumidas básicamente por los machos, en especial por los más pequeños, durante el otoño.We studied the stomach content of Belone belone in the south–east Black Sea during autumn and winter months in 2010–2011. The most frequent feeding items in the diet were insects in autumn and fish in winter. Other items in the diet were mollusks, crustaceans and isopods. Flying ants were mostly consumed by male garfish, particularly the smaller fish, in autumn
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