657 research outputs found
Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR
We present spectral analysis of NuSTAR and Swift observations of Cep X-4
during its outburst in 2014. We observed the source once during the peak of the
outburst and once during the decay, finding good agreement in the spectral
shape between the observations. We describe the continuum using a powerlaw with
a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron
resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line
with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to
describe the shape of the CRSF accurately, leaving significant deviations at
the red side of the line. We characterize this asymmetry with a second
absorption feature around 19 keV. The line energy of the CRSF, which is not
influenced by the addition of this feature, shows a small but significant
positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep
X-4 is below the theoretical limit where such a correlation is expected. This
behavior is similar to Vela X-1 and we discuss parallels between the two
systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter
A Sino-German 6\ cm polarization survey of the Galactic plane VI. Discovery of supernova remnants G178.2-4.2 and G25.1-2.3
Supernova remnants (SNRs) were often discovered in radio surveys of the
Galactic plane. Because of the surface-brightness limit of previous surveys,
more faint or confused SNRs await discovery. The Sino-German 6\ cm
Galactic plane survey is a sensitive survey with the potential to detect new
low surface-brightness SNRs. We want to identify new SNRs from the 6\
cm survey map of the Galactic plane. We searched for new shell-like objects in
the 6\ cm survey maps, and studied their radio emission, polarization,
and spectra using the 6\ cm maps together with the 11\ cm and
21\ cm Effelsberg observations. Extended polarized objects with
non-thermal spectra were identified as SNRs. We have discovered two new, large,
faint SNRs, G178.2-4.2 and G25.1-2.3, both of which show shell structure.
G178.2-4.2 has a size of 72 arcmin x 62 arcmin with strongly polarized emission
being detected along its northern shell. The spectrum of G178.2-4.2 is
non-thermal, with an integrated spectral index of . Its
surface brightness is , which makes G178.2-4.2 the second faintest known Galactic SNR.
G25.1-2.3 is revealed by its strong southern shell which has a size of 80
arcmin x 30\arcmin. It has a non-thermal radio spectrum with a spectral index
of . Two new large shell-type SNRs have been detected at
6\ cm in an area of 2200 deg^2 along the the Galactic plane. This
demonstrates that more large and faint SNRs exist, but are very difficult to
detect.Comment: 8 pages, 8 figures, accepted by Astronomy and Astrophysics. For the
version with high resolution figures, please go to
http://zmtt.bao.ac.cn/6cm/papers/2newSNR.pd
A Sino-German 6 cm polarization survey of the Galactic plane II. The region from 129 degree to 230 degree longitude
Linearly polarized Galactic synchrotron emission provides valuable
information about the properties of the Galactic magnetic field and the
interstellar magneto-ionic medium, when Faraday rotation along the line of
sight is properly taken into account. We aim to survey the Galactic plane at 6
cm including linear polarization. At such a short wavelength Faraday rotation
effects are in general small and the Galactic magnetic field properties can be
probed to larger distances than at long wavelengths. The Urumqi 25-m telescope
is used for a sensitive 6 cm survey in total and polarized intensities. WMAP
K-band (22.8 GHz) polarization data are used to restore the absolute zero-level
of the Urumqi U and Q maps by extrapolation. Total intensity and polarization
maps are presented for a Galactic plane region of 129 degree < l < 230 degree
and |b| < 5 degree in the anti-centre with an angular resolution of 9'5 and an
average sensitivity of 0.6 mK and 0.4 mK Tb in total and polarized intensity,
respectively. We briefly discuss the properties of some extended Faraday
Screens detected in the 6 cm polarization maps. The Sino-German 6 cm
polarization survey provides new information about the properties of the
magnetic ISM. The survey also adds valuable information for discrete Galactic
objects and is in particular suited to detect extended Faraday Screens with
large rotation measures hosting strong regular magnetic fields.Comment: 17 pages, 20 figures, accepted by A&A. Resolutions of the figures
have been significantly reduced. For version with full resolution, see
http://159.226.88.6/zmtt/6cm/papers/gao.paper2.pd
A Sino-German 6\ cm polarization survey of the Galactic plane. V. Large supernova remnants
Observations of large supernova remnants (SNRs) at high frequencies are rare,
but provide valuable information about their physical properties. The total
intensity and polarization properties of 16 large SNRs in the Galactic plane
were investigated based on observations of the Urumqi 6\ cm
polarization survey of the Galactic plane with an angular resolution of
9\farcm5. We extracted total intensity and linear polarization maps of large
SNRs from the Urumqi 6\ cm survey, obtained their integrated flux
densities, and derived the radio spectra in context with previously published
flux densities at various frequencies. In particular, Effelsberg 11\
cm and 21\ cm survey data were used for calculating integrated flux
densities. The 6\ cm polarization data also delineate the magnetic
field structures of the SNRs. We present the first total intensity maps at
6\ cm for SNRs G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO
42.05.01), G205.5+0.5 (Monoceros Nebula) and G206.9+2.3 (PKS 0646+06) and the
first polarization measurements at 6\ cm for SNRs G82.2+5.3 (W63),
G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO 42.05.01), G205.5+0.5
(Monoceros Nebula) and G206.9+2.3 (PKS 0646+06). Most of the newly derived
integrated radio spectra are consistent with previous results. The new flux
densities obtained from the Urumqi 6\ cm, Effelsberg 11\ cm
and 21\ cm surveys are crucial to determine the spectra of SNR
G65.1+0.6, G69.0+2.7 (CTB 80), G93.7-0.2 and G114.3+0.3. We find that
G192.81.1 (PKS 0607+17) consists of background sources, \ion{H}{II} regions
and the extended diffuse emission of thermal nature, and conclude that
G192.81.1 is not a SNR.Comment: 15 pages, 10 figures, accepted by A&\amp;A. Language improved. For
the version with high resolution figures, please go to:
http://zmtt.bao.ac.cn/6cm/paper/gxy_largeSNR.pd
A Sino-German 6cm polarization survey of the Galactic plane VII. Small supernova remnants
We study the spectral and polarization properties of supernova remnants
(SNRs) based on our 6cm survey data. The observations were taken from the
Sino-German 6cm polarization survey of the Galactic plane. By using the
integrated flux densities at 6cm together with measurements at other
wavelengths from the literature we derive the global spectra of 50 SNRs. In
addition, we use the observations at 6cm to present the polarization images of
24 SNRs. We derived integrated flux densities at 6cm for 51 small SNRs with
angular sizes less than 1 degree. Global radio spectral indices were obtained
in all the cases except for Cas A. For SNRs G15.1-1.6, G16.2-2.7, G16.4-0.5,
G17.4-2.3, G17.8-2.6, G20.4+0.1, G36.6+2.6, G43.9+1.6, G53.6-2.2, G55.7+3.4,
G59.8+1.2, G68.6-1.2, and G113.0+0.2, the spectra have been significantly
improved. From our analysis we argue that the object G16.8-1.1 is probably an
HII region instead of a SNR. Cas A shows a secular decrease in total intensity,
and we measured a flux density of 688+/-35 Jy at 6cm between 2004 and 2008.
Polarized emission from 25 SNRs were detected. For G16.2-2.7, G69.7+1.0,
G84.2-0.8 and G85.9-0.6, the polarized emission is detected for the first time
confirming them as SNRs. High frequency observations of SNRs are rare but
important to establish their spectra and trace them in polarization in
particular towards the inner Galaxy where Faraday effects are important.Comment: 14 pages, 4 figures, 2 tables, accepted for publication in A&
Clar Sextet Analysis of Triangular, Rectangular and Honeycomb Graphene Antidot Lattices
Pristine graphene is a semimetal and thus does not have a band gap. By making
a nanometer scale periodic array of holes in the graphene sheet a band gap may
form; the size of the gap is controllable by adjusting the parameters of the
lattice. The hole diameter, hole geometry, lattice geometry and the separation
of the holes are parameters that all play an important role in determining the
size of the band gap, which, for technological applications, should be at least
of the order of tenths of an eV. We investigate four different hole
configurations: the rectangular, the triangular, the rotated triangular and the
honeycomb lattice. It is found that the lattice geometry plays a crucial role
for size of the band gap: the triangular arrangement displays always a sizable
gap, while for the other types only particular hole separations lead to a large
gap. This observation is explained using Clar sextet theory, and we find that a
sufficient condition for a large gap is that the number of sextets exceeds one
third of the total number of hexagons in the unit cell. Furthermore, we
investigate non-isosceles triangular structures to probe the sensitivity of the
gap in triangular lattices to small changes in geometry
Psychosocial environment for the integrated education opportunities of the disabled in Lithuania
BACKGROUND: The policy of the diminution of the social isolation of the disabled is the main objective of the strategy of the EU new policy concerning the disabled. Lithuanian society faces this objective as well. For this reason, this study aiming at providing the theoretical basis for and predicting the possible psycho-social environment in an integrated education system, as well as at the evaluation of the reasons for the formation of a positive approach to the disabled, is especially relevant, since it creates the prerequisites for the optimisation of the process of the integration of disabled schoolchildren into the general system of education. METHOD: The sample of the study consisted of 2471 children from the same schools: not integrated (1958), integrated (126) and special schools (382). Empirical methods: questionnaire poll, comparative analysis. The statistical analysis was carried out using SAS. RESULTS: Our study showed that the majority of schoolchildren without disabilities and disabled schoolchildren have positive intentions for interpersonal interactions (>82%) and positive emotions (>69%) independently of the discrepant character of interpersonal contacts, different conditions of education and family life, and despite of low level of knowledge. CONCLUSION: The results of the study confirmed positive intentions for interpersonal interaction between disabled schoolchildren and schoolchildren without disabilities, as well as a positive character of emotions, and disprove the unsound myth of the opponents of the social integration of the disabled stating that disabled children in comprehensive schools would undoubtedly experience offence from their peers without disabilities
A Double-peaked Outburst of A 0535+26 Observed with INTEGRAL, RXTE, and Suzaku
The Be/X-ray binary A 0535+26 showed a normal (type I) outburst in 2009 August. It is the fourth in a series of normal outbursts associated with the periastron, but is unusual because it presented a double-peaked light curve. The two peaks reached a flux of ~450 mCrab in the 15-50 keV range. We present results of the timing and spectral analysis of INTEGRAL, RXTE, and Suzaku observations of the outburst. The energy-dependent pulse profiles and their evolution during the outburst are studied. No significant differences with respect to other normal outbursts are observed. The centroid energy of the fundamental cyclotron line shows no significant variation during the outburst. A spectral hardening with increasing luminosity is observed. We conclude that the source is accreting in the sub-critical regime. We discuss possible explanations for the double-peaked outburst
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