2,768 research outputs found
SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud
In this paper we report new radio-continuum detection of an extragalactic PN:
SMC SMP 24. We show the radio-continuum image of this PN and present the
measured radio data. The newly reduced radio observations are consistent with
the multi-wavelength data and derived parameters found in the literature. SMC
SMP 24 appear to be a young and compact PN, optically thick at frequencies
below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa
Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys
We present an updated and newly compiled radio-continuum data-base for MASH
PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS,
SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and
detected in targeted radio-continuum observations. We found radio counterparts
for approximately 250 MASH PNe. In comparison with the percentage of previously
known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and
according to their position on the flux density-angular diameter and the radio
brightness temperature evolutionary diagrams we conclude, unsurprisingly, that
the MASH sample presents the radio-faint end of the known Galactic PNe
population. Also, we present radio-continuum spectral properties of a small
sub-sample of MASH PNe located in the strip between declinations -30arcdeg and
-40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA
An XMM-Newton view of Planetary Nebulae in the Small Magellanic Cloud. The X-ray luminous central star of SMP SMC 22
During an X-ray survey of the Small Magellanic Cloud, carried out with the
XMM-Newton satellite, we detected significant soft X-ray emission from the
central star of the high-excitation planetary nebula SMP SMC 22. Its very soft
spectrum is well fit with a non local thermodynamical equilibrium model
atmosphere composed of H, He, C, N, and O, with abundances equal to those
inferred from studies of its nebular lines. The derived effective temperature
of 1.5x10^5 K is in good agreement with that found from the optical/UV data.
The unabsorbed flux in the 0.1-0.5 keV range is about 3x10^{-11} erg cm^-2
s^-1, corresponding to a luminosity of 1.2x10^37 erg/s at the distance of 60
kpc. We also searched for X-ray emission from a large number of SMC planetary
nebulae, confirming the previous detection of SMP SMC 25 with a luminosity of
(0.2-6)x10^35 erg/s (0.1-1 keV). For the remaining objects that were not
detected, we derived flux upper limits corresponding to luminosity values from
several tens to hundreds times smaller than that of SMP SMC 22. The
exceptionally high X-ray luminosity of SMP SMC 22 is probably due to the high
mass of its central star, quickly evolving toward the white dwarf's cooling
branch, and to a small intrinsic absorption in the nebula itself.Comment: Accepted for publication on Astronomy and Astrophysic
An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud
The local correlation between far-infrared (FIR) emission and radio-continuum
(RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales
from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc.
The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is
shown to be greatest in the most active star forming regions with a power law
slope of ~1.14 indicating that the RC emission increases faster than the FIR
emission. The slope of the other regions and the SMC are much flatter and in
the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the
regions which range from 0.5 to 0.95. The thermal fraction of the RC emission
alone can provide the expected FIR/RC correlation. The results are consistent
with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray
electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s
appear to escape the SMC so readily, the results here may not provide support
for coupling between the local gas density and the magnetic field intensity.Comment: 19 pages, 7 Figure
Ecological taxes in some European countries
Production and consumption of fossil fuels is one of the major causes of the green house effect, which is in economics known as a form of ecological externality. Fiscal solution, as one way of internalization of externalities, is based on polluters-pay principle and the imposition of tax on emission. Although the implementation of ecological tax was intensified during the previous decade, fiscal revenues are modest and account for only 5% of the total fiscal revenues of the European Union. Taxes on energetic products, accounting for 76%, are dominant among ecological taxes. Since the EU Directive 82/92 imposes minimum excise rates on oil products, during the last decade Central Eastern European countries have increased excise rates on fossil fuels and fully engaged in the field of ecological policy
Evidence of molecular adaptation to extreme environments and applicability to space environments
This is initial study of a gene signatures responsible for adapting
microscopic life to the life in extreme Earth environments. We present a
results on ID of the clusters of COGs common to several hyperthermophiles and
exclusion of those common to a mesophile: E.coli.K12, will yield a group of
proteins possibly involved in adaptation to life under extreme T. Methanogens
stand out as the only group of organisms that have species capable of growth at
0C (M.frigidum and M.burtonii) and 110C (M.kandleri). Not all the components of
heat adaptation can be attributed to novel genes, the chaperones known as heat
shock proteins stabilize the enzymes under elevated temperature. Highly
conserved chaperons found in bacteria and eukaryots are not present in
hyperthermophilic Archea, rather, they have a unique chaperone TF55. Our aim is
to use software which we specifically developed for extremophile genome
comparative analyses in order to search for additional novel genes involved in
hyperthermophile adaptation. The following hyperthermophile genomes
incorporated in our software were used for these studies: M.jannaschii,
M.kandleri, A.fulgidus and 3 species of Pyrococcus. Common genes were annotated
and grouped according to their roles in cellular processes when information was
available and proteins not previously implicated in the heat-adaptation of
hyperthermophiles were identified. Additional experimental data is needed in
order to learn more about these proteins. To address a non-gene based
components of thermal adaptation, all sequenced extremophiles were analysed for
their GC contents and aminoacid hydrophobicity. We develop a prediction model
for optimal growth temperature.Comment: 6 pages, 1 figure, To be published in Serbian Astronomical Journa
XMM-Newton study of 30 Dor C and a newly identified MCSNR J0536-6913 in the Large Magellanic Cloud
Aims: We present a study of the superbubble (SB) 30 Dor C and the newly
identified MCSNR J0536-6913 in the LMC. Methods: All available XMM-Newton data
(exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) were
used to characterise the thermal X-ray emission in the region. An analysis of
the non-thermal X-rays is also presented and discussed in the context of
emission mechanisms previously suggested in the literature. These data are
supplemented by X-ray data from Chandra, optical data from the MCELS, and radio
data from ATCA and MOST. Results: The brightest thermal emission was found to
be associated with a new supernova remnant, MCSNR J0536-6913. X-ray spectral
analysis of MCSNR J0536-6913 suggested an ejecta-dominated remnant with lines
of O, Ne, Mg, and Si, and a total 0.3-10 keV luminosity of ~8E+34 erg/s. Based
on derived ejecta abundance ratios, we determined the mass of the stellar
progenitor to be either ~18 M_sun or as high as >40 M_sun, though the spectral
fits were subject to assumptions (e.g., uniform temperature and well-mixed
ejecta). The thermal emission from the SB exhibited enrichment by alpha-process
elements, evidence for a recent core-collapse SNR interaction with the SB
shell. We detected non-thermal X-ray emission throughout 30 Dor C, with the
brightest regions being highly correlated with the H-alpha and radio shells. We
created a non-thermal spectral energy distribution for the north-eastern shell
of 30 Dor C which was best-fit with an exponentially cut-off synchrotron model.
Conclusions: Thermal X-ray emission from 30 Dor C is very complex, consisting
of a large scale SB emission at the eastern shell wall with the brightest
emission due to MCSNR J0536-6913. The fact that the non-thermal spectral energy
distribution of the SB shell was observed to roll-off is further evidence that
the non-thermal X-rays from 30 Dor C are synchrotron in origin.Comment: 22 pages, 21 figures, accepted for publication in Astronomy and
Astrophysic
"Hiccup" accretion in the swinging pulsar IGR J18245-2452
IGR J18245-2452 is the fifteenth discovered accreting millisecond X-ray
pulsar and the first source of this class showing direct evidence for
transition between accretion and rotational powered emission states. These
swing provided the strongest confirmation of the pulsar recycling scenario
available so far. During the two XMM-Newton observations that were carried out
while the source was in outburst in April 2013, IGR J18245-2452 displayed a
unique and peculiar variability of its X-ray emission. In this work, we report
on a detailed analysis of the XMM- Newton data and focus in particular on the
timing and spectral variability of the source. IGR J18245-2452 continuously
switches between lower and higher intensity states, with typical variations in
flux up to a factor of about 500 in time scales as short as few seconds. These
variations in the source intensity are sometimes associated to a dramatic
spectral hardening, during which the power-law photon index of the source
changes from Gamma=1.7 to Gamma=0.9. The pulse profiles extracted at different
count rates and energies show a complex variability. These phenomena are not
usually observed in accreting millisecond X-ray pulsars, at least not on such a
short time scale. Fast variability was also found in the ATCA radio
observations carried out for about 6 hours during the outburst at a frequency
of 5.5 and 9 GHz. We interpret the variability observed from IGR J18245-2452 in
terms of a "hiccup" accretion phase, during which the accretion of material
from the inner boundary of the Keplerian disk is reduced by the onset of
centrifugal inhibition of accretion, possibly causing the launch of strong
outflows. Changes across accretion and propeller regimes have been long
predicted and reproduced by MHD simulations of accreting millisecond X-ray
pulsars but never observed to produce an extreme variability as that shown by
IGR J18245-2452.Comment: A&A in press. Revised versio
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