181 research outputs found
AX J1749.1-2733 and AX J1749.2-2725 - the close pair of X-ray pulsars behind the Galactic Center: an optical identification
Two faint X-ray pulsars, AX J1749.2-2725 and AX J1749.1-2733, located in the
direction to the Galactic Center, were studied in detail using data of
INTEGRAL, XMM-Newton and Chandra observatories in X-rays, the SOFI/NTT
instrument in infrared and the RTT150 telescope in optics. X-ray positions of
both sources were determined with the uncertainty better than ~1 arcsec, that
allowed us to identify their infrared counterparts. From the subsequent
analysis of infrared and optical data we conclude that counterparts of both
pulsars are likely massive stars of B0-B3 classes located behind the Galactic
Center at distances of 12-20 kpc, depending on the type, probably in further
parts of galactic spiral arms. In addition, we investigated the extinction law
towards the galactic bulge and found that it is significantly different from
standard one.Comment: 6 pages, 7 figures, will be published in MNRA
Accurate Localization and Identification of Six Hard X-ray Sources from Chandra and XMM-Newton data
We present the results of Chandra and XMM-Newton observations for six hard
X-ray sources (IGR J12134-6015, IGR J18293-1213, IGR J18219-1347, IGR
J17350-2045, IGR J18048-1455, XTE J1901+014) from the INTEGRAL all-sky survey.
Based on these observations, we have improved significantly the localization
accuracy of the objects and, therefore, have managed to identify their optical
counterparts. Using data from the publicly available 2MASS and UKIDSS infrared
sky surveys as well as data from the SOFI/NTT telescope (European Southern
Observatory), we have determined the magnitudes of the optical counterparts,
estimated their types and (in some cases) the distances to the program objects.
A triplet of iron lines with energies of 6.4, 6.7, and 6.9 keV has been
detected in the X-ray spectrum of IGR J18048-1455; together with the detection
of pulsations with a period of ~1440 s from this source, this has allowed it to
be classified as a cataclysmic variable, most likely an intermediate polar. In
addition, broadband X-ray spectra of IGR J12134-6015 and IGR J17350-2045 in
combination with infrared and radio observations suggest an extragalactic
nature of these objects. The source IGR J18219-1347 presumably belongs to the
class of high-mass X-ray binaries.Comment: 15 pages, 9 figures. Will be published in Astronomy Letters, 2012,
Vol. 38, No. 10, pp. 629-63
XMM-Newton discovery of transient X-ray pulsar in NGC 1313
We report on the discovery and analysis of the transient X-ray pulsar XMMU
J031747.5-663010 detected in the 2004 November 23 XMM-Newton observation of the
spiral galaxy NGC 1313. The X-ray source exhibits pulsations with a period
P~765.6 s and a nearly sinusoidal pulse shape and pulsed fraction ~38% in the
0.3-7 keV energy range. The X-ray spectrum of XMMU J031747.5-663010 is hard and
is well fitted with an absorbed simple power law of photon index ~1.5 in the
0.3-7 keV energy band. The X-ray properties of the source and the absence of an
optical/UV counterpart brighter than 20 mag allow us to identify XMMU
J031747.5-663010 as an accreting X-ray pulsar located in NGC 1313. The
estimated absorbed 0.3-7 keV luminosity of the source L~1.6\times 10^{39}
ergs/s, makes it one of the brightest X-ray pulsars known. Based on the
relatively long pulse period and transient behaviour of the source, we classify
it as a Be binary X-ray pulsar candidate. XMMU J031747.5-663010 is the second
X-ray pulsar detected outside the Local Group, after transient 18 s pulsating
source CXOU J073709.1+653544 discovered in the nearby spiral galaxy NGC 2403.Comment: 6 pages, 4 figures. Accepted for publication in MNRAS. Updated to
match the accepted versio
XTE J1901+014 - the First Low-Mass Fast X-ray Transient?
We continue to study the fast X-ray transient XTE J1901+014 discovered in
2002 by the RXTE observatory, whose nature has not yet been established. Based
on the XMM-Newton observations of the source in 2006, we have obtained its
energy spectrum, light curves, and power spectrum in the energy range 0.5-12
keV, which are in good agreement with our results obtained previously from the
data of other observatories. In turn, this suggests that the source's emission
is stable in the quiescent state. The XMM-Newton observations also allowed the
source's localization accuracy to be improved to <2", which subsequently
enabled us to search for its optical companion with the RTT-150 and 6-m BTA
(Special Astrophysical Observatory) telescopes. Combining optical, X-ray, and
infrared observations, we have concluded that the optical companion in the
system under study can be either a later-type star at a distance of several kpc
or a very distant red giant or an A or F star. Thus, XTE J1901+014 may be the
first low-mass fast X-ray transient.Comment: 12 pages, 5 figure
Graphene as a quantum surface with curvature-strain preserving dynamics
We discuss how the curvature and the strain density of the atomic lattice
generate the quantization of graphene sheets as well as the dynamics of
geometric quasiparticles propagating along the constant curvature/strain
levels. The internal kinetic momentum of Riemannian oriented surface (a vector
field preserving the Gaussian curvature and the area) is determined.Comment: 13p, minor correction
Cohomologies of the Poisson superalgebra
Cohomology spaces of the Poisson superalgebra realized on smooth
Grassmann-valued functions with compact support on ($C^{2n}) are
investigated under suitable continuity restrictions on cochains. The first and
second cohomology spaces in the trivial representation and the zeroth and first
cohomology spaces in the adjoint representation of the Poisson superalgebra are
found for the case of a constant nondegenerate Poisson superbracket for
arbitrary n>0. The third cohomology space in the trivial representation and the
second cohomology space in the adjoint representation of this superalgebra are
found for arbitrary n>1.Comment: Comments: 40 pages, the text to appear in Theor. Math. Phys.
supplemented by computation of the 3-rd trivial cohomolog
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