4,323 research outputs found
Photometric Analysis of the Optical Counterpart of the Black Hole HMXB M33 X-7
Aims: Study the high-mass X-ray binary X-7 in M33 using broad-band optical
data.
Methods: We used recently published CFHT r' and i' data for variable stars in
M33 to extract the light curve of the optical counterpart of X-7. We combined
these data with DIRECT B and V measurements in order to search for an
independent optical modulation with the X-ray periodicity. The periodic
modulation is modelled with the ellipsoidal effect. We used UBVRr'i' magnitudes
of the system to constrain the temperature and radius of the optical component.
Results: The optical data revealed a periodicity of 3.4530 +- 0.0014 days,
which is consistent with the known X-ray period. Double modulation, which we
attributed to ellipsoidal modulation, is clearly seen in four different optical
bands. The absolute magnitude in six optical bands is most consistent with a
stellar counterpart with 33000 < T_{eff} < 47000 K and 15 < R < 20 R_{\sun}. We
modelled the optical periodic modulation and derived the masses of the two
components as a function of the orbital inclination and the radius of the
stellar component. The resulting mass range for the compact object is 1.3 < M <
23 M_{\sun}.
Conclusions: The system is probably a black hole HMXB, similar to Cyg X-1,
LMC X-1 and LMC X-3.Comment: Accepted for publication in A&
Plant biomass nitrogen and effects on the risk of nitrate leaching of intercrops under organic farming in Eastern Austria
Data on the potential of intercrops to reduce soil nitrate contents, on their N accumulation and biological nitrogen fixation (BNF) are lacking for organic farming in the dry, pannonic region of Eastern Austria. The effect of legumes, non-legumes, and legumes + non-legumes used as intercrops on inorganic soil nitrogen, crop yield and biomass N, and BNF were tested in comparison to bare fallow. Non-legumes and legumes + non-legumes were more efficient than legumes in reducing inorganic soil N contents in autumn and nitrate contents in soil solution from the subsoil in winter. This reduction in inorganic soil N did not last until March of the following year due to an N mineralisation from the mulch. The legume + non-legume mixture contained a larger amount of crop N than both legumes and non-legumes. This was due to the combined effect of soil-N uptake by the non-legumes and BNF by the legumes in the mixture
Испытание изоляции вакуумного выключателя на трекингостойкость
Выпускная квалификационная работа содержит 146 с., 45 рисунков, 17 таблиц, 36 источников, 7 приложений.
Ключевые слова: трекингостойкость, полиэтилен, стеклотекстолит, полистирол, оргстекло, винипласт, фторопласт, фарфор
Объектом исследования являются электроизоляционные материалы подверженные трекингом.
Цель работы – определение трекингостойкости различных электроизоляционных материалов.
В процессе работы проводились экспериментальные испытания на трекингостойкость различных электроизоляционных материалов, согласно ГОСТ 27473.
В результате выполнения работы была сконструирована установка для проведения испытаний на трекингостойкость, проведены эксперименты по определению трекингостойкости, оргстекла, фторопласта-4, фарфора, твердого поливинилхлорида ПВХ, полиэтилена низкого давления.Finale qualifiziert Arbeit enthält 146 p . , 45 Abbildungen, Tabellen 17, 36 Quellen 7-Anwendungen .
Stichwort: -verfolgung , Polyethylen, Glasfaser , Polystyrol, Acryl, Vinyl -Liner , Teflon, Porzellan
Die Aufgabe der Studie sind Isoliermaterialien anfällig für Verfolgung.
Ziel - Definieren Verfolgung verschiedenen Dämmstoffen .
In dem Prozess , ein Pilottest- Tracking von verschiedenen elektrischen Isoliermaterialien nach GOST 27473. der Durchführung Als ein Ergebnis der Arbeit für die Installation der on- Tracking- Tests entwickelt wurde, durchgeführten Experimente zu bestimmen -tracking , Plexiglas, PTFE -4 , Porzellan, aus Hart-Polyvinylchlorid PVC , HDPE, eine vergleichende Analyse von Dämmstoffen -tracking
Multi-frequency study of Local Group Supernova Remnants The curious case of the Large Magellanic Cloud SNR J0528-6714
Aims. Recent ATCA, XMM-Newton and MCELS observations of the Magellanic Clouds
(MCs) cover a number of new and known SNRs which are poorly studied, such as
SNR J0528-6714 . This particular SNR exhibits luminous radio-continuum
emission, but is one of the unusual and rare cases without detectable optical
and very faint X-ray emission (initially detected by ROSAT and listed as object
[HP99] 498). We used new multi-frequency radio-continuum surveys and new
optical observations at H{\alpha}, [S ii] and [O iii] wavelengths, in
combination with XMM-Newton X-ray data, to investigate the SNR properties and
to search for a physical explanation for the unusual appearance of this SNR.
Methods. We analysed the X-ray and Radio-Continuum spectra and present
multi-wavelength morphological studies of this SNR.
Results. We present the results of new moderate resolution ATCA observations
of SNR J0528-6714. We found that this object is a typical older SNR with a
radio spectral index of {\alpha}=-0.36 \pm 0.09 and a diameter of D=52.4 \pm
1.0 pc. Regions of moderate and somewhat irregular polarisation were detected
which are also indicative of an older SNR. Using a non-equilibrium ionisation
collisional plasma model to describe the X-ray spectrum, we find temperatures
kT of 0.26 keV for the remnant. The low temperature, low surface brightness,
and large extent of the remnant all indicate a relatively advanced age. The
near circular morphology indicates a Type Ia event.
Conclusions. Our study revealed one of the most unusual cases of SNRs in the
Local Group of galaxies - a luminous radio SNR without optical counterpart and,
at the same time, very faint X-ray emission. While it is not unusual to not
detect an SNR in the optical, the combination of faint X-ray and no optical
detection makes this SNR very unique.Comment: 6 pages, 5 figures, Accepted for publication in A&
Investigation of the Influence of Plastic Evaporation on Pressure Rise due to Fault Arcs in Electrical Installations
Internal arcs in electrical installations cause a sudden pressure rise due to heating of the gas surroundingthe arc. The pressure rise may endanger personnel, the electrical installation and even the switchgearbuilding. Based on the need to design switchgear more compact, plastic materials are used. The interactionof the arc with these materials releases gases by evaporation and thereby influences the pressure risewithin the installation as well as the energy balance of the arc. In order to analyse these effects in detail,some commonly used plastics are exposed to a high current arc. In this contribution the pressure developmentin a closed vessel equipped with different plastic materials, their mass losses and the portion ofelectrical energy causing overpressure, known as thermal transfer coefficient or kp–factor, are determinedat three values of the filling pressure of the vessel. The plastic materials under investigation are epoxy,polyamide 6.6, polybutyleneterephtalate, polycarbonate and silicone rubber. With the information provided,the influence of the different plastics on pressure development can be predicted
Glass transition in Ultrathin Polymer Films : A Thermal Expansion Study
Glass transition process gets affected in ultrathin films having thickness
comparable to the size of the molecules. We observe systematic broadening of
glass transition temperature (Tg) as the thickness of the polymer film reduces
below the radius of gyration but the change in the average Tg was found to be
very small. Existence of reversible negative and positive thermal expansion
below and above Tg increased the sensitivity of our thickness measurements
performed using energy dispersive x-ray reflectivity. A simple model of Tg
variation as a function of depth expected from sliding motion could explain the
results. We observe clear glass transition even for 4 nm polystyrene film that
was predicted to be absent from ellipsometry measurements of thicker films.Comment: 11 pages, 5 figure
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic Cloud
We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the
LMC. The optical counterpart has been identified and appears to exhibit an
eclipsing light curve. We performed follow-up observations to clarify the
eclipsing nature of the system. Energy spectra and time series were extracted
from two XMM-Newton observations to search for pulsations, characterise the
spectrum, and measure spectral and timing changes. Long-term X-ray variability
was studied using archival ROSAT data. The XMM positions were used to identify
the optical counterpart. We obtained UV to NIR photometry to characterise the
companion, along with its 4000 d long I-band light curve. We observed LXP169
with Swift at two predicted eclipse times. We found a spin period of 168.8 s
that did not change between two XMM observations. The X-ray spectrum, well
characterised by a power law, was harder when the source was brighter. The
X-ray flux of LXP169 is found to be variable by a factor of at least 10. The
counterpart is highly variable on short and long timescales, and its photometry
is that of an early-type star with a NIR excess. This classifies the source as
a BeXRB pulsar. We observed a transit in the UV, thereby confirming that the
companion star itself is eclipsed. We give an ephemeris for the transit of MJD
56203.877 + N*24.329. We propose and discuss the scenario where the matter
captured from the companion's equatorial disc creates an extended region of
high density around the neutron star (NS), which partially eclipses the
companion as the NS transits in front of it. This is most likely the first time
the compact object in an XRB is observed to eclipse its companion star. LXP169
would be the first eclipsing BeXRB, and a wealth of important information might
be gained from additional observations, such as a measure of the possible Be
disc/orbital plane misalignment, or the mass of the NS.Comment: Updated version of arXiv 1302.4665v1, accepted for publication in
Astronomy and Astrophysics. 11 pages, 8 figures, 3 table
Massive Coronae of Galaxies
There is reason to suspect that about half of the baryons are in
pressure-supported plasma in the halos of normal galaxies, drawn in by gravity
along with about half of the dark matter. To be consistent with the
observations this baryonic component, the corona, would have to be hotter than
the kinetic temperature of the dark matter in the halo so as to produce
acceptable central electron densities. We ascribe this hotter plasma
temperature to the addition of entropy prior to and during assembly of the
system, in an analogy to cluster formation. The plasma cooling time would be
longer than the gravitational collapse time but, in the inner parts, shorter
than the Hubble time, making the corona thermally unstable to the formation of
a cloudy structure that may be in line with what is indicated by quasar
absorption line systems. The corona of an isolated spiral galaxy would be a
source of soft X-ray and recombination radiation, adding to the more commonly
discussed effects of stars and supernovae. In this picture the mass in the
corona is much larger than the mass in condensed baryons in a spiral galaxy.
The corona thus would be a substantial reservoir of diffuse baryons that are
settling and adding to the mass in interstellar matter and stars, so that star
formation in isolated spirals will continue well beyond the present epoch.Comment: 14 pages, 5 figure
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